Google App Engine

The appengine package

import "appengine"

Introduction

Package appengine provides basic functionality for Google App Engine.

For more information on how to write Go apps for Google App Engine, see: https://developers.google.com/appengine/docs/go/

Index

func AccessToken(c Context, scopes ...string) (token string, expiry time.Time, err error)
func AppID(c Context) string
func BackendHostname(c Context, name string, index int) string
func BackendInstance(c Context) (name string, index int)
func Datacenter() string
func DefaultVersionHostname(c Context) string
func InstanceID() string
func IsCapabilityDisabled(err error) bool
func IsDevAppServer() bool
func IsOverQuota(err error) bool
func IsTimeoutError(err error) bool
func ModuleHostname(c Context, module, version, instance string) (string, error)
func ModuleName(c Context) string
func PublicCertificates(c Context) ([]Certificate, error)
func RequestID(c Context) string
func ServerSoftware() string
func ServiceAccount(c Context) (string, error)
func SignBytes(c Context, bytes []byte) (string, []byte, error)
func VersionID(c Context) string
type BlobKey
type Certificate
type Context
    func Namespace(c Context, namespace string) (Context, error)
    func NewContext(req *http.Request) Context
    func Timeout(c Context, d time.Duration) Context
type GeoPoint
    func (g GeoPoint) Valid() bool
type MultiError
    func (m MultiError) Error() string

func AccessToken

func AccessToken(c 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) 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. "example.com:appid").

func BackendHostname

func BackendHostname(c Context, name string, index int) string

BackendHostname returns the standard hostname of the specified backend. If index is -1, BackendHostname returns the load-balancing hostname for the backend.

func BackendInstance

func BackendInstance(c Context) (name string, index int)

BackendInstance returns the name and index of the current backend instance, or "", -1 if this is not a backend instance.

func Datacenter

func Datacenter() string

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

func DefaultVersionHostname

func DefaultVersionHostname(c Context) string

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

func InstanceID

func InstanceID() string

InstanceID returns a mostly-unique identifier for this instance.

func IsCapabilityDisabled

func IsCapabilityDisabled(err error) bool

IsCapabilityDisabled reports whether err represents an API call failure due to the API being disabled. See the appengine/capability package for a way to detect this condition in advance.

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 ModuleHostname

func ModuleHostname(c 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) string

ModuleName returns the module name of the current instance.

func PublicCertificates

func PublicCertificates(c 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) 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) (string, error)

ServiceAccount returns a string representing the service account name, in the form of an email address (typically app_id@appspot.gserviceaccount.com).

func SignBytes

func SignBytes(c Context, bytes []byte) (string, []byte, error)

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

func VersionID

func VersionID(c 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.

type BlobKey

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

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

Certificate represents a public certificate for the app.

type Context

type Context interface {
    // Debugf formats its arguments according to the format, analogous to fmt.Printf,
    // and records the text as a log message at Debug level.
    Debugf(format string, args ...interface{})

    // Infof is like Debugf, but at Info level.
    Infof(format string, args ...interface{})

    // Warningf is like Debugf, but at Warning level.
    Warningf(format string, args ...interface{})

    // Errorf is like Debugf, but at Error level.
    Errorf(format string, args ...interface{})

    // Criticalf is like Debugf, but at Critical level.
    Criticalf(format string, args ...interface{})

    // Internal use only.
    Call(service, method string, in, out appengine_internal.ProtoMessage, opts *appengine_internal.CallOptions) error
    // Internal use only. Use AppID instead.
    FullyQualifiedAppID() string
    // Internal use only.
    Request() interface{}
}

Context represents the context of an in-flight HTTP request.

func Namespace

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

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

func NewContext

func NewContext(req *http.Request) Context

NewContext returns a context for an in-flight HTTP request. Repeated calls will return the same value.

func Timeout

func Timeout(c Context, d time.Duration) Context

Timeout returns a replacement context that uses d as the default API RPC timeout.

type GeoPoint

type GeoPoint struct {
    Lat, Lng float64
}

GeoPoint represents a location as latitude/longitude in degrees.

func (GeoPoint) Valid

func (g GeoPoint) Valid() bool

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

type MultiError

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

func (m MultiError) Error() string

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