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package appengine

import ""

Package appengine provides basic functionality for Google App Engine.

For more information on how to write Go apps for Google App Engine, see:


Package Files

appengine.go appengine_vm.go errors.go identity.go namespace.go timeout.go

func APICall Uses

func APICall(ctx context.Context, service, method string, in, out proto.Message) error

APICall performs an API call.

This is not intended for general use; it is exported for use in conjunction with WithAPICallFunc.

func AccessToken Uses

func AccessToken(c context.Context, scopes ...string) (token string, expiry time.Time, err error)

AccessToken generates an OAuth2 access token for the specified scopes on behalf of service account of this application. This token will expire after the returned time.

func AppID Uses

func AppID(c context.Context) string

AppID returns the application ID for the current application. The string will be a plain application ID (e.g. "appid"), with a domain prefix for custom domain deployments (e.g. "").

func BackgroundContext Uses

func BackgroundContext() context.Context

BackgroundContext returns a context not associated with a request. This should only be used when not servicing a request. This only works in App Engine "flexible environment".

func Datacenter Uses

func Datacenter(c context.Context) string

Datacenter returns an identifier for the datacenter that the instance is running in.

func DefaultVersionHostname Uses

func DefaultVersionHostname(c context.Context) string

DefaultVersionHostname returns the standard hostname of the default version of the current application (e.g. ""). This is suitable for use in constructing URLs.

func InstanceID Uses

func InstanceID() string

InstanceID returns a mostly-unique identifier for this instance.

func IsAppEngine Uses

func IsAppEngine() bool

IsAppEngine reports whether the App Engine app is running on App Engine, in either the standard or flexible environment.

func IsDevAppServer Uses

func IsDevAppServer() bool

IsDevAppServer reports whether the App Engine app is running in the development App Server.

func IsFlex Uses

func IsFlex() bool

IsFlex reports whether the App Engine app is running in the flexible environment.

func IsOverQuota Uses

func IsOverQuota(err error) bool

IsOverQuota reports whether err represents an API call failure due to insufficient available quota.

func IsSecondGen Uses

func IsSecondGen() bool

IsSecondGen reports whether the App Engine app is running on the second generation runtimes (>= Go 1.11).

func IsStandard Uses

func IsStandard() bool

IsStandard reports whether the App Engine app is running in the standard environment. This includes both the first generation runtimes (<= Go 1.9) and the second generation runtimes (>= Go 1.11).

func IsTimeoutError Uses

func IsTimeoutError(err error) bool

IsTimeoutError reports whether err is a timeout error.

func Main Uses

func Main()

Main is the principal entry point for an app running in App Engine.

On App Engine Flexible it installs a trivial health checker if one isn't already registered, and starts listening on port 8080 (overridden by the $PORT environment variable).

See for details on how to do your own health checking.

On App Engine Standard it ensures the server has started and is prepared to receive requests.

Main never returns.

Main is designed so that the app's main package looks like this:

package main

import (

        _ "myapp/package0"
        _ "myapp/package1"

func main() {

The "myapp/packageX" packages are expected to register HTTP handlers in their init functions.

func ModuleHostname Uses

func ModuleHostname(c context.Context, module, version, instance string) (string, error)

ModuleHostname returns a hostname of a module instance. If module is the empty string, it refers to the module of the current instance. If version is empty, it refers to the version of the current instance if valid, or the default version of the module of the current instance. If instance is empty, ModuleHostname returns the load-balancing hostname.

func ModuleName Uses

func ModuleName(c context.Context) string

ModuleName returns the module name of the current instance.

func Namespace Uses

func Namespace(c context.Context, namespace string) (context.Context, error)

Namespace returns a replacement context that operates within the given namespace.

func NewContext Uses

func NewContext(req *http.Request) context.Context

NewContext returns a context for an in-flight HTTP request. This function is cheap.

func RequestID Uses

func RequestID(c context.Context) string

RequestID returns a string that uniquely identifies the request.

func ServerSoftware Uses

func ServerSoftware() string

ServerSoftware returns the App Engine release version. In production, it looks like "Google App Engine/X.Y.Z". In the development appserver, it looks like "Development/X.Y".

func ServiceAccount Uses

func ServiceAccount(c context.Context) (string, error)

ServiceAccount returns a string representing the service account name, in the form of an email address (typically

func SignBytes Uses

func SignBytes(c context.Context, bytes []byte) (keyName string, signature []byte, err error)

SignBytes signs bytes using a private key unique to your application.

func VersionID Uses

func VersionID(c context.Context) string

VersionID returns the version ID for the current application. It will be of the form "X.Y", where X is specified in app.yaml, and Y is a number generated when each version of the app is uploaded. It does not include a module name.

func WithAPICallFunc Uses

func WithAPICallFunc(ctx context.Context, f APICallFunc) context.Context

WithAPICallFunc returns a copy of the parent context that will cause API calls to invoke f instead of their normal operation.

This is intended for advanced users only.

func WithContext Uses

func WithContext(parent context.Context, req *http.Request) context.Context

WithContext returns a copy of the parent context and associates it with an in-flight HTTP request. This function is cheap.

type APICallFunc Uses

type APICallFunc func(ctx context.Context, service, method string, in, out proto.Message) error

APICallFunc defines a function type for handling an API call. See WithCallOverride.

type BlobKey Uses

type BlobKey string

BlobKey is a key for a blobstore blob.

Conceptually, this type belongs in the blobstore package, but it lives in the appengine package to avoid a circular dependency: blobstore depends on datastore, and datastore needs to refer to the BlobKey type.

type Certificate Uses

type Certificate struct {
    KeyName string
    Data    []byte // PEM-encoded X.509 certificate

Certificate represents a public certificate for the app.

func PublicCertificates Uses

func PublicCertificates(c context.Context) ([]Certificate, error)

PublicCertificates retrieves the public certificates for the app. They can be used to verify a signature returned by SignBytes.

type GeoPoint Uses

type GeoPoint struct {
    Lat, Lng float64

GeoPoint represents a location as latitude/longitude in degrees.

func (GeoPoint) Valid Uses

func (g GeoPoint) Valid() bool

Valid returns whether a GeoPoint is within [-90, 90] latitude and [-180, 180] longitude.

type MultiError Uses

type MultiError []error

MultiError is returned by batch operations when there are errors with particular elements. Errors will be in a one-to-one correspondence with the input elements; successful elements will have a nil entry.

func (MultiError) Error Uses

func (m MultiError) Error() string


aetestPackage aetest provides an API for running dev_appserver for use in tests.
blobstorePackage blobstore provides a client for App Engine's persistent blob storage service.
capabilityPackage capability exposes information about outages and scheduled downtime for specific API capabilities.
channelPackage channel implements the server side of App Engine's Channel API.
cloudsqlPackage cloudsql exposes access to Google Cloud SQL databases.
cmd/aebundlerProgram aebundler turns a Go app into a fully self-contained tar file.
cmd/aedeployProgram aedeploy assists with deploying App Engine "flexible environment" Go apps to production.
datastorePackage datastore provides a client for App Engine's datastore service.
datastore/internal/cloudkeyPackage cloudpb is a subset of types and functions, copied from
datastore/internal/cloudpbPackage cloudpb is a subset of protobufs, copied from
delayPackage delay provides a way to execute code outside the scope of a user request by using the taskqueue API.
filePackage file provides helper functions for using Google Cloud Storage.
imagePackage image provides image services.
internalPackage internal provides support for package appengine.
internal/aetestingPackage aetesting provides utilities for testing App Engine packages.
logPackage log provides the means of writing and querying an application's logs from within an App Engine application.
mailPackage mail provides the means of sending email from an App Engine application.
memcachePackage memcache provides a client for App Engine's distributed in-memory key-value store for small chunks of arbitrary data.
modulePackage module provides functions for interacting with modules.
remote_apiPackage remote_api implements the /_ah/remote_api endpoint.
runtimePackage runtime exposes information about the resource usage of the application.
searchPackage search provides a client for App Engine's search service.
socketPackage socket provides outbound network sockets.
taskqueuePackage taskqueue provides a client for App Engine's taskqueue service.
urlfetchPackage urlfetch provides an http.RoundTripper implementation for fetching URLs via App Engine's urlfetch service.
userPackage user provides a client for App Engine's user authentication service.
xmppPackage xmpp provides the means to send and receive instant messages to and from users of XMPP-compatible services.

Package appengine imports 9 packages (graph) and is imported by 1611 packages. Updated 2020-12-09. Refresh now. Tools for package owners.