hive

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Published: Apr 25, 2024 License: Apache-2.0 Imports: 15 Imported by: 2

README ΒΆ

🐝 Hive GoDoc

Hive is a dependency injection framework for Go. To build an application in Hive you tell it your object constructors and then ask it to invoke functions that make use of those constructors. Hive figures out what constructors to call and in what order.

Hive is built on top of uber/dig and is similar to uber/fx. The main difference to uber/fx is opinionated way to provide configuration and command-line inspection tooling (go run ./example hive). Hive was built for the needs of the Cilium project to improve modularity of the Cilium codebase.

To get started, see the documentation and explore the example.

Documentation ΒΆ

Overview ΒΆ

Package hive provides the infrastructure for building Cilium applications from modular components (cells).

Hive is implemented using the uber/dig library, which provides the dependency injection for objects in the hive. It is similar to uber/fx, but adds an opinionated approach to configuration.

The configuration for cells is extracted from Viper. By default the field names are assumed to correspond to flag names, e.g. field 'MyOption' corresponds to '--my-option' flag.

The hive constructor, New(), takes the viper instance and the pflag FlagSet as parameters and registers the flags from all cells and binds them to viper variables. Once the FlagSet and viper configuration has been parsed one can call Populate() to pull the values from viper and construct the application. The hive can then be Run().

Example ΒΆ

For a runnable example see pkg/hive/example.

Try running:

example$ go run .
(ctrl-c stops)

example$ go run . --dot-graph | dot -Tx11

Try also commenting out cell.Provide lines and seeing what the dependency errors look like.

Index ΒΆ

Constants ΒΆ

This section is empty.

Variables ΒΆ

This section is empty.

Functions ΒΆ

func AddConfigOverride ΒΆ

func AddConfigOverride[Cfg cell.Flagger](h *Hive, override func(*Cfg))

AddConfigOverride appends a config override function to modify a configuration after it has been parsed.

This method is only meant to be used in tests.

Types ΒΆ

type Hive ΒΆ

type Hive struct {
	// contains filtered or unexported fields
}

Hive is a framework building modular applications.

It implements dependency injection using the dig library.

See pkg/hive/example for a runnable example application.

func New ΒΆ

func New(cells ...cell.Cell) *Hive

New returns a new hive that can be run, or inspected. The command-line flags from the cells are registered as part of this.

The object graph is not constructed until methods of the hive are invoked.

Applications should call RegisterFlags() to register the hive's command-line flags. Likewise if configuration settings come from configuration files, then the Viper() method can be used to populate the hive's viper instance.

func NewWithOptions ΒΆ

func NewWithOptions(opts Options, cells ...cell.Cell) *Hive

func (*Hive) AppendInvoke ΒΆ

func (h *Hive) AppendInvoke(invoke func(*slog.Logger, time.Duration) error)

func (*Hive) Command ΒΆ

func (h *Hive) Command() *cobra.Command

Command constructs the cobra command for hive. The hive command can be used to inspect the dependency graph.

func (*Hive) Populate ΒΆ

func (h *Hive) Populate(log *slog.Logger) error

Populate instantiates the hive. Use for testing that the hive can be instantiated.

func (*Hive) PrintDotGraph ΒΆ

func (h *Hive) PrintDotGraph()

func (*Hive) PrintObjects ΒΆ

func (h *Hive) PrintObjects()

func (*Hive) RegisterFlags ΒΆ

func (h *Hive) RegisterFlags(flags *pflag.FlagSet)

RegisterFlags adds all flags in the hive to the given flag set. Fatals if a flag already exists in the given flag set. Use with e.g. cobra.Command:

cmd := &cobra.Command{...}
h.RegisterFlags(cmd.Flags())

func (*Hive) Run ΒΆ

func (h *Hive) Run(log *slog.Logger) error

Run populates the cell configurations and runs the hive cells. Interrupt signal or call to Shutdowner.Shutdown() will cause the hive to stop.

func (*Hive) Shutdown ΒΆ

func (h *Hive) Shutdown(opts ...ShutdownOption)

Shutdown implements the Shutdowner interface and is provided for the cells to use for triggering a early shutdown.

func (*Hive) Start ΒΆ

func (h *Hive) Start(log *slog.Logger, ctx context.Context) error

Start starts the hive. The context allows cancelling the start. If context is cancelled and the start hooks do not respect the cancellation then after 5 more seconds the process will be terminated forcefully.

func (*Hive) Stop ΒΆ

func (h *Hive) Stop(log *slog.Logger, ctx context.Context) error

Stop stops the hive. The context allows cancelling the stop. If context is cancelled and the stop hooks do not respect the cancellation then after 5 more seconds the process will be terminated forcefully.

func (*Hive) Viper ΒΆ

func (h *Hive) Viper() *viper.Viper

Viper returns the hive's viper instance.

type Options ΒΆ

type Options struct {
	// EnvPrefix is the prefix to use for environment variables, e.g.
	// with prefix "CILIUM" the flag "foo" can be set with environment
	// variable "CILIUM_FOO".
	EnvPrefix string

	// ModuleDecorator is an optional set of decorator functions to use for each
	// module. This can be used to provide module-scoped overrides to objects.
	// For example:
	//
	// 	opts.ModuleDecorators = cell.ModuleDecorators{
	// 		func(foo Foo, id cell.ModuleID) Foo {
	// 			return foo.With("moduleID", id)
	//		},
	//	}
	//
	// The above would give each cell within a module an augmented version of 'Foo'.
	// The object that is being decorated (the return value) must already exist in
	// the object graph.
	ModuleDecorators cell.ModuleDecorators

	// ModulePrivateProvider is an optional set of private provide functions to
	// use for each module. This can be used to provide module-scoped objects.
	// For example:
	//
	// 	opts.ModulePrivateProviders = cell.ModulePrivateProviders{
	// 		func(id cell.ModuleID) Foo {
	// 			return foo.New(id)
	//		},
	//	}
	//
	ModulePrivateProviders cell.ModulePrivateProviders

	// DecodeHooks are optional additional decode hooks to use with cell.Config
	// to decode a configuration flag into a config field. See existing hooks
	// in [cell/config.go] for examples.
	DecodeHooks cell.DecodeHooks

	StartTimeout time.Duration
	StopTimeout  time.Duration

	// LogThreshold is an optional threshold to reduce logging verbosity.
	// When an Invoke or Lifecycle Start/Stop hook takes longer than this
	// threshold, it will be logged at Info level. Otherwise it is logged
	// at Debug level.
	LogThreshold time.Duration
}

func DefaultOptions ΒΆ

func DefaultOptions() Options

type ShutdownOption ΒΆ

type ShutdownOption interface {
	// contains filtered or unexported methods
}

func ShutdownWithError ΒΆ

func ShutdownWithError(err error) ShutdownOption

ShutdownWithError shuts down with an error.

type Shutdowner ΒΆ

type Shutdowner interface {
	Shutdown(...ShutdownOption)
}

Shutdowner provides Shutdown(), which is a way to trigger stop for hive.

To shut down with an error, call Shutdown with ShutdownWithError(err). This error will be returned from Run().

Directories ΒΆ

Path Synopsis
Package hivetest makes testing components using hive easier.
Package hivetest makes testing components using hive easier.

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