cadence: go.uber.org/cadence/workflow Index | Files

package workflow

import "go.uber.org/cadence/workflow"

Package workflow contains functions and types used to implement Cadence workflows.

A workflow is an implementation of coordination logic. The Cadence programming framework (aka client library) allows you to write the workflow coordination logic as simple procedural code that uses standard Go data modeling. The client library takes care of the communication between the worker service and the Cadence service, and ensures state persistence between events even in case of worker failures. Any particular execution is not tied to a particular worker machine. Different steps of the coordination logic can end up executing on different worker instances, with the framework ensuring that necessary state is recreated on the worker executing the step.

In order to facilitate this operational model both the Cadence programming framework and the managed service impose some requirements and restrictions on the implementation of the coordination logic. The details of these requirements and restrictions are described in the "Implementation" section below.

Overview

The sample code below shows a simple implementation of a workflow that executes one activity. The workflow also passes the sole parameter it receives as part of its initialization as a parameter to the activity.

package sample

import (
	"time"

	"go.uber.org/cadence/workflow"
)

func init() {
	workflow.Register(SimpleWorkflow)
}

func SimpleWorkflow(ctx workflow.Context, value string) error {
	ao := workflow.ActivityOptions{
		TaskList:               "sampleTaskList",
		ScheduleToCloseTimeout: time.Second * 60,
		ScheduleToStartTimeout: time.Second * 60,
		StartToCloseTimeout:    time.Second * 60,
		HeartbeatTimeout:       time.Second * 10,
		WaitForCancellation:    false,
	}
	ctx = workflow.WithActivityOptions(ctx, ao)

	future := workflow.ExecuteActivity(ctx, SimpleActivity, value)
	var result string
	if err := future.Get(ctx, &result); err != nil {
		return err
	}
	workflow.GetLogger(ctx).Info(“Done”, zap.String(“result”, result))
	return nil
}

The following sections describe what is going on in the above code.

Declaration

In the Cadence programing model a workflow is implemented with a function. The function declaration specifies the parameters the workflow accepts as well as any values it might return.

func SimpleWorkflow(ctx workflow.Context, value string) error

The first parameter to the function is ctx workflow.Context. This is a required parameter for all workflow functions and is used by the Cadence client library to pass execution context. Virtually all the client library functions that are callable from the workflow functions require this ctx parameter. This **context** parameter is the same concept as the standard context.Context provided by Go. The only difference between workflow.Context and context.Context is that the Done() function in workflow.Context returns workflow.Channel instead of the standard go chan.

The second string parameter is a custom workflow parameter that can be used to pass in data into the workflow on start. A workflow can have one or more such parameters. All parameters to an workflow function must be serializable, which essentially means that params can’t be channels, functions, variadic, or unsafe pointer.

Since it only declares error as the return value it means that the workflow does not return a value. The error return value is used to indicate an error was encountered during execution and the workflow should be terminated.

Implementation

In order to support the synchronous and sequential programming model for the workflow implementation there are certain restrictions and requirements on how the workflow implementation must behave in order to guarantee correctness. The requirements are that:

- Execution must be deterministic
- Execution must be idempotent

A simplistic way to think about these requirements is that the workflow code:

- Can only read and manipulate local state or state received as return values
  from Cadence client library functions
- Should really not affect changes in external systems other than through
  invocation of activities
- Should interact with time only through the functions provided by the
  Cadence client library (i.e. workflow.Now(), workflow.Sleep())
- Should not create and interact with goroutines directly, it should instead
  use the functions provided by the Cadence client library. (i.e.
  workflow.Go() instead of go, workflow.Channel instead of chan,
  workflow.Selector instead of select)
- Should do all logging via the logger provided by the Cadence client
  library (i.e. workflow.GetLogger())
- Should not iterate over maps using range as order of map iteration is
  randomized

Now that we laid out the ground rules we can take a look at how to implement some common patterns inside workflows.

Special Cadence client library functions and types

The Cadence client library provides a number of functions and types as alternatives to some native Go functions and types. Usage of these replacement functions/types is necessary in order to ensure that the workflow code execution is deterministic and repeatable within an execution context.

Coroutine related constructs:

- workflow.Go : This is a replacement for the the go statement
- workflow.Channel : This is a replacement for the native chan type. Cadence
  provides support for both buffered and unbuffered channels
- workflow.Selector : This is a replacement for the select statement

Time related functions:

- workflow.Now() : This is a replacement for time.Now()
- workflow.Sleep() : This is a replacement for time.Sleep()

Failing a Workflow

To mark a workflow as failed all that needs to happen is for the workflow function to return an error via the err return value.

Execute Activity

The primary responsibility of the workflow implementation is to schedule activities for execution. The most straightforward way to do that is via the library method workflow.ExecuteActivity:

ao := workflow.ActivityOptions{
	TaskList:               "sampleTaskList",
	ScheduleToCloseTimeout: time.Second * 60,
	ScheduleToStartTimeout: time.Second * 60,
	StartToCloseTimeout:    time.Second * 60,
	HeartbeatTimeout:       time.Second * 10,
	WaitForCancellation:    false,
}
ctx = workflow.WithActivityOptions(ctx, ao)

future := workflow.ExecuteActivity(ctx, SimpleActivity, value)
var result string
if err := future.Get(ctx, &result); err != nil {
	return err
}

Before calling workflow.ExecuteActivity(), ActivityOptions must be configured for the invocation. These are for the most part options to customize various execution timeouts. These options are passed in by creating a child context from the initial context and overwriting the desired values. The child context is then passed into the workflow.ExecuteActivity() call. If multiple activities are sharing the same exact option values then the same context instance can be used when calling workflow.ExecuteActivity().

The first parameter to the call is the required workflow.Context object. This type is an exact copy of context.Context with the Done() method returning workflow.Channel instead of native go chan.

The second parameter is the function that we registered as an activity function. This parameter can also be the a string representing the fully qualified name of the activity function. The benefit of passing in the actual function object is that in that case the framework can validate activity parameters.

The remaining parameters are the parameters to pass to the activity as part of the call. In our example we have a single parameter: **value**. This list of parameters must match the list of parameters declared by the activity function. Like mentioned above the Cadence client library will validate that this is indeed the case.

The method call returns immediately and returns a workflow.Future. This allows for more code to be executed without having to wait for the scheduled activity to complete.

When we are ready to process the results of the activity we call the Get() method on the future object returned. The parameters to this method are the ctx object we passed to the workflow.ExecuteActivity() call and an output parameter that will receive the output of the activity. The type of the output parameter must match the type of the return value declared by the activity function. The Get() method will block until the activity completes and results are available.

The result value returned by workflow.ExecuteActivity() can be retrieved from the future and used like any normal result from a synchronous function call. If the result above is a string value we could use it as follows:

var result string
if err := future.Get(ctx1, &result); err != nil {
	return err
}

switch result {
case “apple”:
	// do something
case “bannana”:
	// do something
default:
	return err
}

In the example above we called the Get() method on the returned future immediately after workflow.ExecuteActivity(). However, this is not necessary. If we wish to execute multiple activities in parallel we can repeatedly call workflow.ExecuteActivity() store the futures returned and then wait for all activities to complete by calling the Get() methods of the future at a later time.

To implement more complex wait conditions on the returned future objects, use the workflow.Selector class. Take a look at our Pickfirst sample for an example of how to use of workflow.Selector.

Child Workflow

workflow.ExecuteChildWorkflow enables the scheduling of other workflows from within a workflow's implementation. The parent workflow has the ability to "monitor" and impact the life-cycle of the child workflow in a similar way it can do for an activity it invoked.

cwo := workflow.ChildWorkflowOptions{
	// Do not specify WorkflowID if you want cadence to generate a unique ID for child execution
	WorkflowID:                   "BID-SIMPLE-CHILD-WORKFLOW",
	ExecutionStartToCloseTimeout: time.Minute * 30,
}
ctx = workflow.WithChildOptions(ctx, cwo)

var result string
future := workflow.ExecuteChildWorkflow(ctx, SimpleChildWorkflow, value)
if err := future.Get(ctx, &result); err != nil {
	workflow.GetLogger(ctx).Error("SimpleChildWorkflow failed.", zap.Error(err))
	return err
}

Before calling workflow.ExecuteChildWorkflow(), ChildWorkflowOptions must be configured for the invocation. These are for the most part options to customize various execution timeouts. These options are passed in by creating a child context from the initial context and overwriting the desired values. The child context is then passed into the workflow.ExecuteChildWorkflow() call. If multiple activities are sharing the same exact option values then the same context instance can be used when calling workflow.ExecuteChildWorkflow().

The first parameter to the call is the required workflow.Context object. This type is an exact copy of context.Context with the Done() method returning workflow.Channel instead of the native go chan.

The second parameter is the function that we registered as a workflow function. This parameter can also be a string representing the fully qualified name of the workflow function. What's the benefit? When you pass in the actual function object, the framework can validate workflow parameters.

The remaining parameters are the parameters to pass to the workflow as part of the call. In our example we have a single parameter: value. This list of parameters must match the list of parameters declared by the workflow function.

The method call returns immediately and returns a workflow.Future. This allows for more code to be executed without having to wait for the scheduled workflow to complete.

When we are ready to process the results of the workflow we call the Get() method on the future object returned. The parameters to this method are the ctx object we passed to the workflow.ExecuteChildWorkflow() call and an output parameter that will receive the output of the workflow. The type of the output parameter must match the type of the return value declared by the workflow function. The Get() method will block until the workflow completes and results are available.

The workflow.ExecuteChildWorkflow() function is very similar to the workflow.ExecuteActivity() function. All the patterns described for using the workflow.ExecuteActivity() apply to the workflow.ExecuteChildWorkflow() function as well.

Error Handling

Activities and child workflows can fail. You could handle errors differently based on different error cases. If the activity returns an error as errors.New() or fmt.Errorf(), those errors will be converted to error.GenericError. If the activity returns an error as error.NewCustomError("err-reason", details), that error will be converted to *error.CustomError. There are other types of errors like error.TimeoutError, error.CanceledError and error.PanicError. So the error handling code would look like:

err := workflow.ExecuteActivity(ctx, YourActivityFunc).Get(ctx, nil)
switch err := err.(type) {
case *error.CustomError:
	switch err.Reason() {
	case "err-reason-a":
		// handle error-reason-a
		var details YourErrorDetailsType
		err.Details(&details)
		// deal with details
	case "err-reason-b":
		// handle error-reason-b
	default:
		// handle all other error reasons
	}
case *error.GenericError:
	switch err.Error() {
	case "err-msg-1":
		// handle error with message "err-msg-1"
	case "err-msg-2":
		// handle error with message "err-msg-2"
	default:
		// handle all other generic errors
	}
case *error.TimeoutError:
	switch err.TimeoutType() {
	case shared.TimeoutTypeScheduleToStart:
		// handle ScheduleToStart timeout
	case shared.TimeoutTypeStartToClose:
		// handle StartToClose timeout
	case shared.TimeoutTypeHeartbeat:
		// handle heartbeat timeout
	default:
	}
case *error.PanicError:
	 // handle panic error
case *error.CanceledError:
	// handle canceled error
default:
	// all other cases (ideally, this should not happen)
}

Signals

Signals provide a mechanism to send data directly to a running workflow. Previously, you had two options for passing data to the workflow implementation:

- Via start parameters
- As return values from activities

With start parameters, we could only pass in values before workflow execution begins.

Return values from activities allowed us to pass information to a running workflow, but this approach comes with its own complications. One major drawback is reliance on polling. This means that the data needs to be stored in a third-party location until it's ready to be picked up by the activity. Further, the lifecycle of this activity requires management, and the activity requires manual restart if it fails before acquiring the data.

Signals, on the other hand, provides a fully asynch and durable mechanism for providing data to a running workflow. When a signal is received for a running workflow, Cadence persists the event and the payload in the workflow history. The workflow can then process the signal at any time afterwards without the risk of losing the information. The workflow also has the option to stop execution by blocking on a signal channel.

var signalVal string
signalChan := workflow.GetSignalChannel(ctx, signalName)

s := workflow.NewSelector(ctx)
s.AddReceive(signalChan, func(c workflow.Channel, more bool) {
	c.Receive(ctx, &signalVal)
	workflow.GetLogger(ctx).Info("Received signal!", zap.String("signal", signalName), zap.String("value", signalVal))
})
s.Select(ctx)

if len(signalVal) > 0 && signalVal != "SOME_VALUE" {
	return errors.New("signalVal")
}

In the example above, the workflow code uses workflow.GetSignalChannel to open a workflow.Channel for the named signal. We then use a workflow.Selector to wait on this channel and process the payload received with the signal.

ContinueAsNew Workflow Completion

Workflows that need to rerun periodically could naively be implemented as a big for loop with a sleep where the entire logic of the workflow is inside the body of the for loop. The problem with this approach is that the history for that workflow will keep growing to a point where it reaches the maximum size enforced by the service.

ContinueAsNew is the low level construct that enables implementing such workflows without the risk of failures down the road. The operation atomically completes the current execution and starts a new execution of the workflow with the same workflow ID. The new execution will not carry over any history from the old execution. To trigger this behavior, the workflow function should terminate by returning the special ContinueAsNewError error:

func SimpleWorkflow(workflow.Context ctx, value string) error {
    ...
    return workflow.NewContinueAsNewError(ctx, SimpleWorkflow, value)
}

For a complete example implementing this pattern please refer to the Cron example.

SideEffect API

workflow.SideEffect executes the provided function once, records its result into the workflow history, and doesn't re-execute upon replay. Instead, it returns the recorded result. Use it only for short, nondeterministic code snippets, like getting a random value or generating a UUID. It can be seen as an "inline" activity. However, one thing to note about workflow.SideEffect is that whereas for activities Cadence guarantees "at-most-once" execution, no such guarantee exists for workflow.SideEffect. Under certain failure conditions, workflow.SideEffect can end up executing the function more than once.

The only way to fail SideEffect is to panic, which causes decision task failure. The decision task after timeout is rescheduled and re-executed giving SideEffect another chance to succeed. Be careful to not return any data from the SideEffect function any other way than through its recorded return value.

encodedRandom := SideEffect(func(ctx workflow.Context) interface{} {
	return rand.Intn(100)
})

var random int
encodedRandom.Get(&random)
if random < 50 {
	....
} else {
	....
}

Query API

A workflow execution could be stuck at some state for longer than expected period. Cadence provide facilities to query the current call stack of a workflow execution. You can use cadence-cli to do the query, for example:

cadence-cli --domain samples-domain workflow query -w my_workflow_id -r my_run_id -qt __stack_trace

The above cli command uses __stack_trace as the query type. The __stack_trace is a built-in query type that is supported by cadence client library. You can also add your own custom query types to support thing like query current state of the workflow, or query how many activities the workflow has completed. To do so, you need to setup your own query handler using workflow.SetQueryHandler in your workflow code:

func MyWorkflow(ctx workflow.Context, input string) error {
   currentState := "started" // this could be any serializable struct
   err := workflow.SetQueryHandler(ctx, "state", func() (string, error) {
	 return currentState, nil
   })
   if err != nil {
	 return err
   }
   // your normal workflow code begins here, and you update the currentState as the code makes progress.
   currentState = "waiting timer"
   err = NewTimer(ctx, time.Hour).Get(ctx, nil)
   if err != nil {
	 currentState = "timer failed"
	 return err
   }
   currentState = "waiting activity"
   ctx = WithActivityOptions(ctx, myActivityOptions)
   err = ExecuteActivity(ctx, MyActivity, "my_input").Get(ctx, nil)
   if err != nil {
	 currentState = "activity failed"
	 return err
   }
   currentState = "done"
   return nil
}

The above sample code sets up a query handler to handle query type "state". With that, you should be able to query with cli:

cadence-cli --domain samples-domain workflow query -w my_workflow_id -r my_run_id -qt state

Besides using cadence-cli, you can also issue query from code using QueryWorkflow() API on cadence Client object.

Registration

For some client code to be able to invoke a workflow type, the worker process needs to be aware of all the implementations it has access to. A workflow is registered with the following call:

workflow.Register(SimpleWorkflow)

This call essentially creates an in memory mapping inside the worker process between the fully qualified function name and the implementation. It is safe to call this registration method from an **init()** function. If the worker receives tasks for a workflow type it does not know it will fail that task. However, the failure of the task will not cause the entire workflow to fail.

Testing

The Cadence client library provides a test framework to facilitate testing workflow implementations. The framework is suited for implementing unit tests as well as functional tests of the workflow logic.

The code below implements the unit tests for the SimpleWorkflow sample.

package sample

import (
	"errors"
	"testing"

	"code.uber.internal/devexp/cadence-worker/activity"

	"github.com/stretchr/testify/mock"
	"github.com/stretchr/testify/suite"

	"go.uber.org/cadence/testsuite"
)

type UnitTestSuite struct {
	suite.Suite
	testsuite.WorkflowTestSuite

	env *testsuite.TestWorkflowEnvironment
}

func (s *UnitTestSuite) SetupTest() {
	s.env = s.NewTestWorkflowEnvironment()
}

func (s *UnitTestSuite) AfterTest(suiteName, testName string) {
	s.env.AssertExpectations(s.T())
}

func (s *UnitTestSuite) Test_SimpleWorkflow_Success() {
	s.env.ExecuteWorkflow(SimpleWorkflow, "test_success")

	s.True(s.env.IsWorkflowCompleted())
	s.NoError(s.env.GetWorkflowError())
}

func (s *UnitTestSuite) Test_SimpleWorkflow_ActivityParamCorrect() {
	s.env.OnActivity(SimpleActivity, mock.Anything, mock.Anything).Return(func(ctx context.Context, value string) (string, error) {
		s.Equal("test_success", value)
		return value, nil
	})
	s.env.ExecuteWorkflow(SimpleWorkflow, "test_success")

	s.True(s.env.IsWorkflowCompleted())
	s.NoError(s.env.GetWorkflowError())
}

func (s *UnitTestSuite) Test_SimpleWorkflow_ActivityFails() {
	s.env.OnActivity(SimpleActivity, mock.Anything, mock.Anything).Return("", errors.New("SimpleActivityFailure"))
	s.env.ExecuteWorkflow(SimpleWorkflow, "test_failure")

	s.True(s.env.IsWorkflowCompleted())

	s.NotNil(s.env.GetWorkflowError())
	_, ok := s.env.GetWorkflowError().(*error.GenericError)
	s.True(ok)
	s.Equal("SimpleActivityFailure", s.env.GetWorkflowError().Error())
}

func TestUnitTestSuite(t *testing.T) {
	suite.Run(t, new(UnitTestSuite))
}

Setup

First, we define a "test suite" struct that absorbs both the basic suite functionality from testify http://godoc.org/github.com/stretchr/testify/suite via suite.Suite and the suite functionality from the Cadence test framework via testsuite.WorkflowTestSuite. Since every test in this suite will test our workflow we add a property to our struct to hold an instance of the test environment. This will allow us to initialize the test environment in a setup method. For testing workflows we use a testsuite.TestWorkflowEnvironment.

We then implement a SetupTest method to setup a new test environment before each test. Doing so ensure that each test runs in it's own isolated sandbox. We also implement an AfterTest function where we assert that all mocks we setup were indeed called by invoking s.env.AssertExpectations(s.T()).

Finally, we create a regular test function recognized by "go test" and pass the struct to suite.Run.

A Simple Test

The simplest test case we can write is to have the test environment execute the workflow and then evaluate the results.

func (s *UnitTestSuite) Test_SimpleWorkflow_Success() {
	s.env.ExecuteWorkflow(SimpleWorkflow, "test_success")

	s.True(s.env.IsWorkflowCompleted())
	s.NoError(s.env.GetWorkflowError())
}

Calling s.env.ExecuteWorkflow(...) will execute the workflow logic and any invoked activities inside the test process. The first parameter to s.env.ExecuteWorkflow(...) is the workflow functions and any subsequent parameters are values for custom input parameters declared by the workflow function. An important thing to note is that unless the activity invocations are mocked or activity implementation replaced (see next section), the test environment will execute the actual activity code including any calls to outside services.

In the example above, after executing the workflow we assert that the workflow ran through to completion via the call to s.env.IsWorkflowComplete(). We also assert that no errors where returned by asserting on the return value of s.env.GetWorkflowError(). If our workflow returned a value, we we can retrieve that value via a call to s.env.GetWorkflowResult(&value) and add asserts on that value.

Activity Mocking and Overriding

When testing workflows, especially unit testing workflows, we want to test the workflow logic in isolation. Additionally, we want to inject activity errors during our tests runs. The test framework provides two mechanisms that support these scenarios: activity mocking and activity overriding. Both these mechanisms allow you to change the behavior of activities invoked by your workflow without having to modify the actual workflow code.

Lets first take a look at a test that simulates a test failing via the "activity mocking" mechanism.

func (s *UnitTestSuite) Test_SimpleWorkflow_ActivityFails() {
	s.env.OnActivity(SimpleActivity, mock.Anything, mock.Anything).Return("", errors.New("SimpleActivityFailure"))
	s.env.ExecuteWorkflow(SimpleWorkflow, "test_failure")

	s.True(s.env.IsWorkflowCompleted())

	s.NotNil(s.env.GetWorkflowError())
	_, ok := s.env.GetWorkflowError().(*error.GenericError)
	s.True(ok)
	s.Equal("SimpleActivityFailure", s.env.GetWorkflowError().Error())
}

In this test we want to simulate the execution of the activity SimpleActivity invoked by our workflow SimpleWorkflow returning an error. We do that by setting up a mock on the test environment for the SimpleActivity that returns an error.

s.env.OnActivity(SimpleActivity, mock.Anything, mock.Anything).Return("", errors.New("SimpleActivityFailure"))

With the mock set up we can now execute the workflow via the s.env.ExecuteWorkflow(...) method and assert that the workflow completed successfully and returned the expected error.

Simply mocking the execution to return a desired value or error is a pretty powerful mechanism to isolate workflow logic. However, sometimes we want to replace the activity with an alternate implementation to support a more complex test scenario. For our simple workflow lets assume we wanted to validate that the activity gets called with the correct parameters.

func (s *UnitTestSuite) Test_SimpleWorkflow_ActivityParamCorrect() {
	s.env.OnActivity(SimpleActivity, mock.Anything, mock.Anything).Return(func(ctx context.Context, value string) (string, error) {
		s.Equal("test_success", value)
		return value, nil
	})
	s.env.ExecuteWorkflow(SimpleWorkflow, "test_success")

	s.True(s.env.IsWorkflowCompleted())
	s.NoError(s.env.GetWorkflowError())
}

In this example, we provide a function implementation as the parameter to Return. This allows us to provide an alternate implementation for the activity SimpleActivity. The framework will execute this function whenever the activity is invoked and pass on the return value from the function as the result of the activity invocation. Additionally, the framework will validate that the signature of the "mock" function matches the signature of the original activity function.

Since this can be an entire function, there really is no limitation as to what we can do in here. In this example, to assert that the "value" param has the same content to the value param we passed to the workflow.

Index

Package Files

activity_options.go context.go context_propagator.go deterministic_wrappers.go doc.go error.go session.go workflow.go workflow_options.go

Variables

var ErrCanceled = internal.ErrCanceled

ErrCanceled is the error returned by Context.Err when the context is canceled.

var ErrDeadlineExceeded = internal.ErrDeadlineExceeded

ErrDeadlineExceeded is the error returned by Context.Err when the context's deadline passes.

var ErrSessionFailed = internal.ErrSessionFailed

ErrSessionFailed is the error returned when user tries to execute an activity but the session it belongs to has already failed

func CompleteSession Uses

func CompleteSession(ctx Context)

CompleteSession completes a session. It releases worker resources, so other sessions can be created. CompleteSession won't do anything if the context passed in doesn't contain any session information or the session has already completed or failed.

After a session has completed, user can continue to use the context, but the activities will be scheduled on the normal taskList (as user specified in ActivityOptions) and may be picked up by another worker since it's not in a session.

func GetLastCompletionResult Uses

func GetLastCompletionResult(ctx Context, d ...interface{}) error

GetLastCompletionResult extract last completion result from previous run for this cron workflow. This is used in combination with cron schedule. A workflow can be started with an optional cron schedule. If a cron workflow wants to pass some data to next schedule, it can return any data and that data will become available when next run starts. This GetLastCompletionResult() extract the data into expected data structure. See TestWorkflowEnvironment.SetLastCompletionResult() for unit test support.

func GetLogger Uses

func GetLogger(ctx Context) *zap.Logger

GetLogger returns a logger to be used in workflow's context

func GetMetricsScope Uses

func GetMetricsScope(ctx Context) tally.Scope

GetMetricsScope returns a metrics scope to be used in workflow's context

func Go Uses

func Go(ctx Context, f func(ctx Context))

Go creates a new coroutine. It has similar semantic to goroutine in a context of the workflow.

func GoNamed Uses

func GoNamed(ctx Context, name string, f func(ctx Context))

GoNamed creates a new coroutine with a given human readable name. It has similar semantic to goroutine in a context of the workflow. Name appears in stack traces that include this coroutine.

func HasLastCompletionResult Uses

func HasLastCompletionResult(ctx Context) bool

HasLastCompletionResult checks if there is completion result from previous runs. This is used in combination with cron schedule. A workflow can be started with an optional cron schedule. If a cron workflow wants to pass some data to next schedule, it can return any data and that data will become available when next run starts. This HasLastCompletionResult() checks if there is such data available passing down from previous successful run.

func IsReplaying Uses

func IsReplaying(ctx Context) bool

IsReplaying returns whether the current workflow code is replaying.

Warning! Never make decisions, like schedule activity/childWorkflow/timer or send/wait on future/channel, based on this flag as it is going to break workflow determinism requirement. The only reasonable use case for this flag is to avoid some external actions during replay, like custom logging or metric reporting. Please note that Cadence already provide standard logging/metric via workflow.GetLogger(ctx) and workflow.GetMetricsScope(ctx), and those standard mechanism are replay-aware and it will automatically suppress during replay. Only use this flag if you need custom logging/metrics reporting, for example if you want to log to kafka.

Warning! Any action protected by this flag should not fail or if it does fail should ignore that failure or panic on the failure. If workflow don't want to be blocked on those failure, it should ignore those failure; if workflow do want to make sure it proceed only when that action succeed then it should panic on that failure. Panic raised from a workflow causes decision task to fail and cadence server will rescheduled later to retry.

func MutableSideEffect Uses

func MutableSideEffect(ctx Context, id string, f func(ctx Context) interface{}, equals func(a, b interface{}) bool) encoded.Value

MutableSideEffect executes the provided function once, then it looks up the history for the value with the given id. If there is no existing value, then it records the function result as a value with the given id on history; otherwise, it compares whether the existing value from history has changed from the new function result by calling the provided equals function. If they are equal, it returns the value without recording a new one in history;

otherwise, it records the new value with the same id on history.

Caution: do not use MutableSideEffect to modify closures. Always retrieve result from MutableSideEffect's encoded return value.

The difference between MutableSideEffect() and SideEffect() is that every new SideEffect() call in non-replay will result in a new marker being recorded on history. However, MutableSideEffect() only records a new marker if the value changed. During replay, MutableSideEffect() will not execute the function again, but it will return the exact same value as it was returning during the non-replay run.

One good use case of MutableSideEffect() is to access dynamically changing config without breaking determinism.

func NewDisconnectedContext Uses

func NewDisconnectedContext(parent Context) (ctx Context, cancel CancelFunc)

NewDisconnectedContext returns a new context that won't propagate parent's cancellation to the new child context. One common use case is to do cleanup work after workflow is cancelled.

err := workflow.ExecuteActivity(ctx, ActivityFoo).Get(ctx, &activityFooResult)
if err != nil && cadence.IsCanceledError(ctx.Err()) {
  // activity failed, and workflow context is canceled
  disconnectedCtx, _ := workflow.newDisconnectedContext(ctx);
  workflow.ExecuteActivity(disconnectedCtx, handleCancellationActivity).Get(disconnectedCtx, nil)
  return err // workflow return CanceledError
}

func NewFuture Uses

func NewFuture(ctx Context) (Future, Settable)

NewFuture creates a new future as well as associated Settable that is used to set its value.

func Now Uses

func Now(ctx Context) time.Time

Now returns the current time when the decision is started or replayed. The workflow needs to use this Now() to get the wall clock time instead of the Go lang library one.

func Register Uses

func Register(workflowFunc interface{})

Register - registers a workflow function with the framework. A workflow takes a workflow context and input and returns a (result, error) or just error. Examples:

func sampleWorkflow(ctx workflow.Context, input []byte) (result []byte, err error)
func sampleWorkflow(ctx workflow.Context, arg1 int, arg2 string) (result []byte, err error)
func sampleWorkflow(ctx workflow.Context) (result []byte, err error)
func sampleWorkflow(ctx workflow.Context, arg1 int) (result string, err error)

Serialization of all primitive types, structures is supported ... except channels, functions, variadic, unsafe pointer. This method calls panic if workflowFunc doesn't comply with the expected format.

func RegisterWithOptions Uses

func RegisterWithOptions(workflowFunc interface{}, opts RegisterOptions)

RegisterWithOptions registers the workflow function with options The user can use options to provide an external name for the workflow or leave it empty if no external name is required. This can be used as

client.RegisterWorkflow(sampleWorkflow, RegisterOptions{})
client.RegisterWorkflow(sampleWorkflow, RegisterOptions{Name: "foo"})

A workflow takes a workflow context and input and returns a (result, error) or just error. Examples:

func sampleWorkflow(ctx workflow.Context, input []byte) (result []byte, err error)
func sampleWorkflow(ctx workflow.Context, arg1 int, arg2 string) (result []byte, err error)
func sampleWorkflow(ctx workflow.Context) (result []byte, err error)
func sampleWorkflow(ctx workflow.Context, arg1 int) (result string, err error)

Serialization of all primitive types, structures is supported ... except channels, functions, variadic, unsafe pointer. This method calls panic if workflowFunc doesn't comply with the expected format.

func SetQueryHandler Uses

func SetQueryHandler(ctx Context, queryType string, handler interface{}) error

SetQueryHandler sets the query handler to handle workflow query. The queryType specify which query type this handler should handle. The handler must be a function that returns 2 values. The first return value must be a serializable result. The second return value must be an error. The handler function could receive any number of input parameters. All the input parameter must be serializable. You should call workflow.SetQueryHandler() at the beginning of the workflow code. When client calls Client.QueryWorkflow() to cadence server, a task will be generated on server that will be dispatched to a workflow worker, which will replay the history events and then execute a query handler based on the query type. The query handler will be invoked out of the context of the workflow, meaning that the handler code must not use workflow context to do things like workflow.NewChannel(), workflow.Go() or to call any workflow blocking functions like Channel.Get() or Future.Get(). Trying to do so in query handler code will fail the query and client will receive QueryFailedError. Example of workflow code that support query type "current_state":

func MyWorkflow(ctx workflow.Context, input string) error {
  currentState := "started" // this could be any serializable struct
  err := workflow.SetQueryHandler(ctx, "current_state", func() (string, error) {
    return currentState, nil
  })
  if err != nil {
    currentState = "failed to register query handler"
    return err
  }
  // your normal workflow code begins here, and you update the currentState as the code makes progress.
  currentState = "waiting timer"
  err = NewTimer(ctx, time.Hour).Get(ctx, nil)
  if err != nil {
    currentState = "timer failed"
    return err
  }

  currentState = "waiting activity"
  ctx = WithActivityOptions(ctx, myActivityOptions)
  err = ExecuteActivity(ctx, MyActivity, "my_input").Get(ctx, nil)
  if err != nil {
    currentState = "activity failed"
    return err
  }
  currentState = "done"
  return nil
}

func SideEffect Uses

func SideEffect(ctx Context, f func(ctx Context) interface{}) encoded.Value

SideEffect executes the provided function once, records its result into the workflow history. The recorded result on history will be returned without executing the provided function during replay. This guarantees the deterministic requirement for workflow as the exact same result will be returned in replay. Common use case is to run some short non-deterministic code in workflow, like getting random number or new UUID. The only way to fail SideEffect is to panic which causes decision task failure. The decision task after timeout is rescheduled and re-executed giving SideEffect another chance to succeed.

Caution: do not use SideEffect to modify closures. Always retrieve result from SideEffect's encoded return value. For example this code is BROKEN:

// Bad example:
var random int
workflow.SideEffect(func(ctx workflow.Context) interface{} {
       random = rand.Intn(100)
       return nil
})
// random will always be 0 in replay, thus this code is non-deterministic
if random < 50 {
       ....
} else {
       ....
}

On replay the provided function is not executed, the random will always be 0, and the workflow could takes a different path breaking the determinism.

Here is the correct way to use SideEffect:

// Good example:
encodedRandom := SideEffect(func(ctx workflow.Context) interface{} {
      return rand.Intn(100)
})
var random int
encodedRandom.Get(&random)
if random < 50 {
       ....
} else {
       ....
}

func Sleep Uses

func Sleep(ctx Context, d time.Duration) (err error)

Sleep pauses the current workflow for at least the duration d. A negative or zero duration causes Sleep to return immediately. Workflow code needs to use this Sleep() to sleep instead of the Go lang library one(timer.Sleep()). You can cancel the pending sleep by cancel the Context (using context from workflow.WithCancel(ctx)). Sleep() returns nil if the duration d is passed, or it returns *CanceledError if the ctx is canceled. There are 2 reasons the ctx could be canceled: 1) your workflow code cancel the ctx (with workflow.WithCancel(ctx)); 2) your workflow itself is canceled by external request. The current timer resolution implementation is in seconds and uses math.Ceil(d.Seconds()) as the duration. But is subjected to change in the future.

func UpsertSearchAttributes Uses

func UpsertSearchAttributes(ctx Context, attributes map[string]interface{}) error

UpsertSearchAttributes is used to add or update workflow search attributes. The search attributes can be used in query of List/Scan/Count workflow APIs. The key and value type must be registered on cadence server side; The value has to deterministic when replay; The value has to be Json serializable. UpsertSearchAttributes will merge attributes to existing map in workflow, for example workflow code:

  func MyWorkflow(ctx workflow.Context, input string) error {
	   attr1 := map[string]interface{}{
		   "CustomIntField": 1,
		   "CustomBoolField": true,
	   }
	   workflow.UpsertSearchAttributes(ctx, attr1)

	   attr2 := map[string]interface{}{
		   "CustomIntField": 2,
		   "CustomKeywordField": "seattle",
	   }
	   workflow.UpsertSearchAttributes(ctx, attr2)
  }

will eventually have search attributes:

map[string]interface{}{
	"CustomIntField": 2,
	"CustomBoolField": true,
	"CustomKeywordField": "seattle",
}

This is only supported when using ElasticSearch.

func WithCancel Uses

func WithCancel(parent Context) (ctx Context, cancel CancelFunc)

WithCancel returns a copy of parent with a new Done channel. The returned context's Done channel is closed when the returned cancel function is called or when the parent context's Done channel is closed, whichever happens first.

Canceling this context releases resources associated with it, so code should call cancel as soon as the operations running in this Context complete.

type ActivityOptions Uses

type ActivityOptions = internal.ActivityOptions

ActivityOptions stores all activity-specific invocation parameters that will be stored inside of a context.

type CancelFunc Uses

type CancelFunc = internal.CancelFunc

A CancelFunc tells an operation to abandon its work. A CancelFunc does not wait for the work to stop. After the first call, subsequent calls to a CancelFunc do nothing.

type Channel Uses

type Channel = internal.Channel

Channel must be used instead of native go channel by workflow code. Use workflow.NewChannel(ctx) method to create Channel instance.

func GetSignalChannel Uses

func GetSignalChannel(ctx Context, signalName string) Channel

GetSignalChannel returns channel corresponding to the signal name.

func NewBufferedChannel Uses

func NewBufferedChannel(ctx Context, size int) Channel

NewBufferedChannel create new buffered Channel instance

func NewChannel Uses

func NewChannel(ctx Context) Channel

NewChannel create new Channel instance

func NewNamedBufferedChannel Uses

func NewNamedBufferedChannel(ctx Context, name string, size int) Channel

NewNamedBufferedChannel create new BufferedChannel instance with a given human readable name. Name appears in stack traces that are blocked on this Channel.

func NewNamedChannel Uses

func NewNamedChannel(ctx Context, name string) Channel

NewNamedChannel create new Channel instance with a given human readable name. Name appears in stack traces that are blocked on this channel.

type ChildWorkflowFuture Uses

type ChildWorkflowFuture = internal.ChildWorkflowFuture

ChildWorkflowFuture represents the result of a child workflow execution

func ExecuteChildWorkflow Uses

func ExecuteChildWorkflow(ctx Context, childWorkflow interface{}, args ...interface{}) ChildWorkflowFuture

ExecuteChildWorkflow requests child workflow execution in the context of a workflow. Context can be used to pass the settings for the child workflow. For example: task list that this child workflow should be routed, timeouts that need to be configured. Use ChildWorkflowOptions to pass down the options.

 cwo := ChildWorkflowOptions{
	    ExecutionStartToCloseTimeout: 10 * time.Minute,
	    TaskStartToCloseTimeout: time.Minute,
	}
 ctx := WithChildOptions(ctx, cwo)

Input childWorkflow is either a workflow name or a workflow function that is getting scheduled. Input args are the arguments that need to be passed to the child workflow function represented by childWorkflow. If the child workflow failed to complete then the future get error would indicate the failure and it can be one of CustomError, TimeoutError, CanceledError, GenericError. You can cancel the pending child workflow using context(workflow.WithCancel(ctx)) and that will fail the workflow with error CanceledError. ExecuteChildWorkflow returns ChildWorkflowFuture.

type ChildWorkflowOptions Uses

type ChildWorkflowOptions = internal.ChildWorkflowOptions

ChildWorkflowOptions stores all child workflow specific parameters that will be stored inside of a Context.

type Context Uses

type Context = internal.Context

Context is a clone of context.Context with Done() returning Channel instead of native channel. A Context carries a deadline, a cancellation signal, and other values across API boundaries.

Context's methods may be called by multiple goroutines simultaneously.

func CreateSession Uses

func CreateSession(ctx Context, sessionOptions *SessionOptions) (Context, error)

CreateSession creates a session and returns a new context which contains information of the created session. The session will be created on the tasklist user specified in ActivityOptions. If none is specified, the default one will be used.

CreationSession will fail in the following situations:

1. The context passed in already contains a session which is still open
   (not closed and failed).
2. All the workers are busy (number of sessions currently running on all the workers have reached
   MaxConcurrentSessionExecutionSize, which is specified when starting the workers) and session
   cannot be created within a specified timeout.

If an activity is executed using the returned context, it's regarded as part of the session. All activities within the same session will be executed by the same worker. User still needs to handle the error returned when executing an activity. Session will not be marked as failed if an activity within it returns an error. Only when the worker executing the session is down, that session will be marked as failed. Executing an activity within a failed session will return ErrSessionFailed immediately without scheduling that activity.

The returned session Context will be cancelled if the session fails (worker died) or CompleteSession() is called. This means that in these two cases, all user activities scheduled using the returned session Context will also be cancelled.

If user wants to end a session since activity returns some error, use CompleteSession API below. New session can be created if necessary to retry the whole session.

Example:

   so := &SessionOptions{
	      ExecutionTimeout: time.Minute,
	      CreationTimeout:  time.Minute,
   }
   sessionCtx, err := CreateSession(ctx, so)
   if err != nil {
		    // Creation failed. Wrong ctx or too many outstanding sessions.
   }
   defer CompleteSession(sessionCtx)
   err = ExecuteActivity(sessionCtx, someActivityFunc, activityInput).Get(sessionCtx, nil)
   if err == ErrSessionFailed {
       // Session has failed
   } else {
       // Handle activity error
   }
   ... // execute more activities using sessionCtx

func RecreateSession Uses

func RecreateSession(ctx Context, recreateToken []byte, sessionOptions *SessionOptions) (Context, error)

RecreateSession recreate a session based on the sessionInfo passed in. Activities executed within the recreated session will be executed by the same worker as the previous session. RecreateSession() returns an error under the same situation as CreateSession() or the token passed in is invalid. It also has the same usage as CreateSession().

The main usage of RecreateSession is for long sessions that are splited into multiple runs. At the end of one run, complete the current session, get recreateToken from sessionInfo by calling SessionInfo.GetRecreateToken() and pass the token to the next run. In the new run, session can be recreated using that token.

func WithActivityOptions Uses

func WithActivityOptions(ctx Context, options ActivityOptions) Context

WithActivityOptions adds all options to the copy of the context.

func WithChildOptions Uses

func WithChildOptions(ctx Context, cwo ChildWorkflowOptions) Context

WithChildOptions adds all workflow options to the context.

func WithDataConverter Uses

func WithDataConverter(ctx Context, dc encoded.DataConverter) Context

WithDataConverter adds DataConverter to the context.

func WithExecutionStartToCloseTimeout Uses

func WithExecutionStartToCloseTimeout(ctx Context, d time.Duration) Context

WithExecutionStartToCloseTimeout adds a workflow execution timeout to the context.

func WithHeartbeatTimeout Uses

func WithHeartbeatTimeout(ctx Context, d time.Duration) Context

WithHeartbeatTimeout adds a timeout to the copy of the context.

func WithLocalActivityOptions Uses

func WithLocalActivityOptions(ctx Context, options LocalActivityOptions) Context

WithLocalActivityOptions adds options for local activity to context

func WithScheduleToCloseTimeout Uses

func WithScheduleToCloseTimeout(ctx Context, d time.Duration) Context

WithScheduleToCloseTimeout adds a timeout to the copy of the context.

func WithScheduleToStartTimeout Uses

func WithScheduleToStartTimeout(ctx Context, d time.Duration) Context

WithScheduleToStartTimeout adds a timeout to the copy of the context.

func WithStartToCloseTimeout Uses

func WithStartToCloseTimeout(ctx Context, d time.Duration) Context

WithStartToCloseTimeout adds a timeout to the copy of the context.

func WithTaskList Uses

func WithTaskList(ctx Context, name string) Context

WithTaskList adds a task list to the copy of the context.

func WithValue Uses

func WithValue(parent Context, key interface{}, val interface{}) Context

WithValue returns a copy of parent in which the value associated with key is val.

Use context Values only for request-scoped data that transits processes and APIs, not for passing optional parameters to functions.

func WithWaitForCancellation Uses

func WithWaitForCancellation(ctx Context, wait bool) Context

WithWaitForCancellation adds wait for the cacellation to the copy of the context.

func WithWorkflowDomain Uses

func WithWorkflowDomain(ctx Context, name string) Context

WithWorkflowDomain adds a domain to the context.

func WithWorkflowID Uses

func WithWorkflowID(ctx Context, workflowID string) Context

WithWorkflowID adds a workflowID to the context.

func WithWorkflowTaskList Uses

func WithWorkflowTaskList(ctx Context, name string) Context

WithWorkflowTaskList adds a task list to the context.

func WithWorkflowTaskStartToCloseTimeout Uses

func WithWorkflowTaskStartToCloseTimeout(ctx Context, d time.Duration) Context

WithWorkflowTaskStartToCloseTimeout adds a decision timeout to the context.

type ContextPropagator Uses

type ContextPropagator = internal.ContextPropagator

ContextPropagator is an interface that determines what information from context to pass along

type ContinueAsNewError Uses

type ContinueAsNewError = internal.ContinueAsNewError

ContinueAsNewError can be returned by a workflow implementation function and indicates that the workflow should continue as new with the same WorkflowID, but new RunID and new history.

func NewContinueAsNewError Uses

func NewContinueAsNewError(ctx Context, wfn interface{}, args ...interface{}) *ContinueAsNewError

NewContinueAsNewError creates ContinueAsNewError instance If the workflow main function returns this error then the current execution is ended and the new execution with same workflow ID is started automatically with options provided to this function.

 ctx - use context to override any options for the new workflow like execution timeout, decision task timeout, task list.
	  if not mentioned it would use the defaults that the current workflow is using.
       ctx := WithExecutionStartToCloseTimeout(ctx, 30 * time.Minute)
       ctx := WithWorkflowTaskStartToCloseTimeout(ctx, time.Minute)
	  ctx := WithWorkflowTaskList(ctx, "example-group")
 wfn - workflow function. for new execution it can be different from the currently running.
 args - arguments for the new workflow.

type Execution Uses

type Execution = internal.WorkflowExecution

Execution Details.

type Future Uses

type Future = internal.Future

Future represents the result of an asynchronous computation.

func ExecuteActivity Uses

func ExecuteActivity(ctx Context, activity interface{}, args ...interface{}) Future

ExecuteActivity requests activity execution in the context of a workflow. Context can be used to pass the settings for this activity. For example: task list that this need to be routed, timeouts that need to be configured. Use ActivityOptions to pass down the options.

 ao := ActivityOptions{
	    TaskList: "exampleTaskList",
	    ScheduleToStartTimeout: 10 * time.Second,
	    StartToCloseTimeout: 5 * time.Second,
	    ScheduleToCloseTimeout: 10 * time.Second,
	    HeartbeatTimeout: 0,
	}
	ctx := WithActivityOptions(ctx, ao)

Or to override a single option

ctx := WithTaskList(ctx, "exampleTaskList")

Input activity is either an activity name (string) or a function representing an activity that is getting scheduled. Input args are the arguments that need to be passed to the scheduled activity.

If the activity failed to complete then the future get error would indicate the failure, and it can be one of CustomError, TimeoutError, CanceledError, PanicError, GenericError. You can cancel the pending activity using context(workflow.WithCancel(ctx)) and that will fail the activity with error CanceledError.

ExecuteActivity returns Future with activity result or failure.

func ExecuteLocalActivity Uses

func ExecuteLocalActivity(ctx Context, activity interface{}, args ...interface{}) Future

ExecuteLocalActivity requests to run a local activity. A local activity is like a regular activity with some key differences:

• Local activity is scheduled and run by the workflow worker locally.

• Local activity does not need Cadence server to schedule activity task and does not rely on activity worker.

• No need to register local activity.

• The parameter activity to ExecuteLocalActivity() must be a function.

• Local activity is for short living activities (usually finishes within seconds).

• Local activity cannot heartbeat.

Context can be used to pass the settings for this local activity. For now there is only one setting for timeout to be set:

lao := LocalActivityOptions{
	ScheduleToCloseTimeout: 5 * time.Second,
}
ctx := WithLocalActivityOptions(ctx, lao)

The timeout here should be relative shorter than the DecisionTaskStartToCloseTimeout of the workflow. If you need a longer timeout, you probably should not use local activity and instead should use regular activity. Local activity is designed to be used for short living activities (usually finishes within seconds).

Input args are the arguments that will to be passed to the local activity. The input args will be hand over directly to local activity function without serialization/deserialization because we don't need to pass the input across process boundary. However, the result will still go through serialization/deserialization because we need to record the result as history to cadence server so if the workflow crashes, a different worker can replay the history without running the local activity again.

If the activity failed to complete then the future get error would indicate the failure, and it can be one of CustomError, TimeoutError, CanceledError, PanicError, GenericError. You can cancel the pending activity by cancel the context(workflow.WithCancel(ctx)) and that will fail the activity with error CanceledError.

ExecuteLocalActivity returns Future with local activity result or failure.

func NewTimer Uses

func NewTimer(ctx Context, d time.Duration) Future

NewTimer returns immediately and the future becomes ready after the specified duration d. The workflow needs to use this NewTimer() to get the timer instead of the Go lang library one(timer.NewTimer()). You can cancel the pending timer by cancel the Context (using context from workflow.WithCancel(ctx)) and that will cancel the timer. After timer is canceled, the returned Future become ready, and Future.Get() will return *CanceledError. The current timer resolution implementation is in seconds and uses math.Ceil(d.Seconds()) as the duration. But is subjected to change in the future.

func RequestCancelExternalWorkflow Uses

func RequestCancelExternalWorkflow(ctx Context, workflowID, runID string) Future

RequestCancelExternalWorkflow can be used to request cancellation of an external workflow. Input workflowID is the workflow ID of target workflow. Input runID indicates the instance of a workflow. Input runID is optional (default is ""). When runID is not specified, then the currently running instance of that workflowID will be used. By default, the current workflow's domain will be used as target domain. However, you can specify a different domain of the target workflow using the context like:

ctx := WithWorkflowDomain(ctx, "domain-name")

RequestCancelExternalWorkflow return Future with failure or empty success result.

func SignalExternalWorkflow Uses

func SignalExternalWorkflow(ctx Context, workflowID, runID, signalName string, arg interface{}) Future

SignalExternalWorkflow can be used to send signal info to an external workflow. Input workflowID is the workflow ID of target workflow. Input runID indicates the instance of a workflow. Input runID is optional (default is ""). When runID is not specified, then the currently running instance of that workflowID will be used. By default, the current workflow's domain will be used as target domain. However, you can specify a different domain of the target workflow using the context like:

ctx := WithWorkflowDomain(ctx, "domain-name")

SignalExternalWorkflow return Future with failure or empty success result.

type GenericError Uses

type GenericError = internal.GenericError

GenericError is returned from activity or child workflow when an implementations return error other than from workflow.NewCustomError() API.

type HeaderReader Uses

type HeaderReader = internal.HeaderReader

HeaderReader is an interface to read information from cadence headers

type HeaderWriter Uses

type HeaderWriter = internal.HeaderWriter

HeaderWriter is an interface to write information to cadence headers

type Info Uses

type Info = internal.WorkflowInfo

Info information about currently executing workflow

func GetInfo Uses

func GetInfo(ctx Context) *Info

GetInfo extracts info of a current workflow from a context.

type LocalActivityOptions Uses

type LocalActivityOptions = internal.LocalActivityOptions

LocalActivityOptions doc

type PanicError Uses

type PanicError = internal.PanicError

PanicError contains information about panicked workflow/activity.

type RegisterOptions Uses

type RegisterOptions = internal.RegisterWorkflowOptions

RegisterOptions consists of options for registering a workflow

type Selector Uses

type Selector = internal.Selector

Selector must be used instead of native go select by workflow code. Use workflow.NewSelector(ctx) method to create a Selector instance.

func NewNamedSelector Uses

func NewNamedSelector(ctx Context, name string) Selector

NewNamedSelector creates a new Selector instance with a given human readable name. Name appears in stack traces that are blocked on this Selector.

func NewSelector Uses

func NewSelector(ctx Context) Selector

NewSelector creates a new Selector instance.

type SessionInfo Uses

type SessionInfo = internal.SessionInfo

SessionInfo contains information of a created session. For now, exported fields are SessionID and HostName. SessionID is a uuid generated when CreateSession() or RecreateSession() is called and can be used to uniquely identify a session. HostName specifies which host is executing the session

func GetSessionInfo Uses

func GetSessionInfo(ctx Context) *SessionInfo

GetSessionInfo returns the sessionInfo stored in the context. If there are multiple sessions in the context, (for example, the same context is used to create, complete, create another session. Then user found that the session has failed, and created a new one on it), the most recent sessionInfo will be returned.

This API will return nil if there's no sessionInfo in the context.

type SessionOptions Uses

type SessionOptions = internal.SessionOptions

SessionOptions specifies metadata for a session. ExecutionTimeout: required, no default

Specifies the maximum amount of time the session can run

CreationTimeout: required, no default

Specfifies how long session creation can take before returning an error

type Settable Uses

type Settable = internal.Settable

Settable is used to set value or error on a future. See more: workflow.NewFuture(ctx).

type TerminatedError Uses

type TerminatedError = internal.TerminatedError

TerminatedError returned when workflow was terminated.

type TimeoutError Uses

type TimeoutError = internal.TimeoutError

TimeoutError returned when activity or child workflow timed out.

func NewHeartbeatTimeoutError Uses

func NewHeartbeatTimeoutError(details ...interface{}) *TimeoutError

NewHeartbeatTimeoutError creates TimeoutError instance WARNING: This function is public only to support unit testing of workflows. It shouldn't be used by application level code.

func NewTimeoutError Uses

func NewTimeoutError(timeoutType shared.TimeoutType, details ...interface{}) *TimeoutError

NewTimeoutError creates TimeoutError instance. Use NewHeartbeatTimeoutError to create heartbeat TimeoutError WARNING: This function is public only to support unit testing of workflows. It shouldn't be used by application level code.

type Type Uses

type Type = internal.WorkflowType

Type identifies a workflow type.

type UnknownExternalWorkflowExecutionError Uses

type UnknownExternalWorkflowExecutionError = internal.UnknownExternalWorkflowExecutionError

UnknownExternalWorkflowExecutionError can be returned when external workflow doesn't exist

type Version Uses

type Version = internal.Version

Version represents a change version. See GetVersion call.

const DefaultVersion Version = internal.DefaultVersion

DefaultVersion is a version returned by GetVersion for code that wasn't versioned before

func GetVersion Uses

func GetVersion(ctx Context, changeID string, minSupported, maxSupported Version) Version

GetVersion is used to safely perform backwards incompatible changes to workflow definitions. It is not allowed to update workflow code while there are workflows running as it is going to break determinism. The solution is to have both old code that is used to replay existing workflows as well as the new one that is used when it is executed for the first time. GetVersion returns maxSupported version when is executed for the first time. This version is recorded into the workflow history as a marker event. Even if maxSupported version is changed the version that was recorded is returned on replay. DefaultVersion constant contains version of code that wasn't versioned before. For example initially workflow has the following code:

err = workflow.ExecuteActivity(ctx, foo).Get(ctx, nil)

it should be updated to

err = workflow.ExecuteActivity(ctx, bar).Get(ctx, nil)

The backwards compatible way to execute the update is

v :=  GetVersion(ctx, "fooChange", DefaultVersion, 1)
if v  == DefaultVersion {
    err = workflow.ExecuteActivity(ctx, foo).Get(ctx, nil)
} else {
    err = workflow.ExecuteActivity(ctx, bar).Get(ctx, nil)
}

Then bar has to be changed to baz:

v :=  GetVersion(ctx, "fooChange", DefaultVersion, 2)
if v  == DefaultVersion {
    err = workflow.ExecuteActivity(ctx, foo).Get(ctx, nil)
} else if v == 1 {
    err = workflow.ExecuteActivity(ctx, bar).Get(ctx, nil)
} else {
    err = workflow.ExecuteActivity(ctx, baz).Get(ctx, nil)
}

Later when there are no workflow executions running DefaultVersion the correspondent branch can be removed:

v :=  GetVersion(ctx, "fooChange", 1, 2)
if v == 1 {
    err = workflow.ExecuteActivity(ctx, bar).Get(ctx, nil)
} else {
    err = workflow.ExecuteActivity(ctx, baz).Get(ctx, nil)
}

It is recommended to keep the GetVersion() call even if single branch is left:

GetVersion(ctx, "fooChange", 2, 2)
err = workflow.ExecuteActivity(ctx, baz).Get(ctx, nil)

The reason to keep it is: 1) it ensures that if there is older version execution still running, it will fail here and not proceed; 2) if you ever need to make more changes for “fooChange”, for example change activity from baz to qux, you just need to update the maxVersion from 2 to 3.

Note that, you only need to preserve the first call to GetVersion() for each changeID. All subsequent call to GetVersion() with same changeID are safe to remove. However, if you really want to get rid of the first GetVersion() call as well, you can do so, but you need to make sure: 1) all older version executions are completed; 2) you can no longer use “fooChange” as changeID. If you ever need to make changes to that same part like change from baz to qux, you would need to use a different changeID like “fooChange-fix2”, and start minVersion from DefaultVersion again. The code would looks like:

v := workflow.GetVersion(ctx, "fooChange-fix2", workflow.DefaultVersion, 1)
if v == workflow.DefaultVersion {
  err = workflow.ExecuteActivity(ctx, baz, data).Get(ctx, nil)
} else {
  err = workflow.ExecuteActivity(ctx, qux, data).Get(ctx, nil)
}

type WaitGroup Uses

type WaitGroup = internal.WaitGroup

WaitGroup is used to wait for a collection of coroutines to finish

func NewWaitGroup Uses

func NewWaitGroup(ctx Context) WaitGroup

NewWaitGroup creates a new WaitGroup instance.

Package workflow imports 6 packages (graph) and is imported by 31 packages. Updated 2019-10-15. Refresh now. Tools for package owners.

The go get command cannot install this package because of the following issues: