appengine - ActiveState ActiveGo 1.8

Package appengine

import ""

Overview ▾

Package appengine provides basic functionality for Google App Engine.

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

func APICall

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

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

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

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

func Datacenter(c context.Context) string

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

func DefaultVersionHostname

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

func InstanceID() string

InstanceID returns a mostly-unique identifier for this instance.

func IsDevAppServer

func IsDevAppServer() bool

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

func IsOverQuota

func IsOverQuota(err error) bool

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

func IsTimeoutError

func IsTimeoutError(err error) bool

IsTimeoutError reports whether err is a timeout error.

func Main

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

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

func ModuleName(c context.Context) string

ModuleName returns the module name of the current instance.

func Namespace

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

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

func NewContext

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

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

func PublicCertificates

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.

func RequestID

func RequestID(c context.Context) string

RequestID returns a string that uniquely identifies the request.

func ServerSoftware

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

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

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

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

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

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

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

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

type BlobKey

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 BlobKey string

type Certificate

Certificate represents a public certificate for the app.

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

type GeoPoint

GeoPoint represents a location as latitude/longitude in degrees.

type GeoPoint struct {
    Lat, Lng float64

func (GeoPoint) Valid

func (g GeoPoint) Valid() bool

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

type MultiError

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.

type MultiError []error

func (MultiError) Error

func (m MultiError) Error() string


Name Synopsis
aetest Package aetest provides an API for running dev_appserver for use in tests.
blobstore Package blobstore provides a client for App Engine's persistent blob storage service.
capability Package capability exposes information about outages and scheduled downtime for specific API capabilities.
channel Package channel implements the server side of App Engine's Channel API.
cloudsql Package cloudsql exposes access to Google Cloud SQL databases.
aebundler Program aebundler turns a Go app into a fully self-contained tar file.
aedeploy Program aedeploy assists with deploying App Engine "flexible environment" Go apps to production.
datastore Package datastore provides a client for App Engine's datastore service.
delay Package delay provides a way to execute code outside the scope of a user request by using the taskqueue API.
file Package file provides helper functions for using Google Cloud Storage.
image Package image provides image services.
log Package log provides the means of querying an application's logs from within an App Engine application.
mail Package mail provides the means of sending email from an App Engine application.
memcache Package memcache provides a client for App Engine's distributed in-memory key-value store for small chunks of arbitrary data.
module Package module provides functions for interacting with modules.
remote_api Package remote_api implements the /_ah/remote_api endpoint.
runtime Package runtime exposes information about the resource usage of the application.
search Package search provides a client for App Engine's search service.
socket Package socket provides outbound network sockets.
taskqueue Package taskqueue provides a client for App Engine's taskqueue service.
urlfetch Package urlfetch provides an http.RoundTripper implementation for fetching URLs via App Engine's urlfetch service.
user Package user provides a client for App Engine's user authentication service.
xmpp Package xmpp provides the means to send and receive instant messages to and from users of XMPP-compatible services.