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Go App Engine packages
This repository supports the Go runtime on App Engine,
including both classic App Engine and Managed VMs.
It provides APIs for interacting with App Engine services.
Its canonical import path is google.golang.org/appengine
.
See https://cloud.google.com/appengine/docs/go/ for more information.
File issue reports and feature requests on the Google App Engine issue tracker.
Directory structure
The top level directory of this repository is the appengine
package. It
contains the
basic APIs (e.g. appengine.NewContext
) that apply across APIs. Specific API
packages are in subdirectories (e.g. datastore
).
There is an internal
subdirectory that contains service protocol buffers,
plus packages required for connectivity to make API calls. App Engine apps
should not directly import any package under internal
.
Updating a Go App Engine app
This section describes how to update a traditional Go App Engine app to use these packages.
1. Update YAML files (Managed VMs only)
The app.yaml
file (and YAML files for modules) should have these new lines added:
vm: true
manual_scaling:
instances: 1
See https://cloud.google.com/appengine/docs/go/modules/#Go_Instance_scaling_and_class for details.
2. Update import paths
The import paths for App Engine packages are now fully qualified, based at google.golang.org/appengine
.
You will need to update your code to use import paths starting with that; for instance,
code importing appengine/datastore
will now need to import google.golang.org/appengine/datastore
.
You can do that manually, or by running this command to recursively update all Go source files in the current directory:
(may require GNU sed)
sed -i '/"appengine/{s,"appengine,"google.golang.org/appengine,;s,appengine_,appengine/,}' \
$(find . -name '*.go')
3. Update code using deprecated, removed or modified APIs
Most App Engine services are available with exactly the same API. A few APIs were cleaned up, and some are not available yet. This list summarises the differences:
appengine.Context
has been replaced with theContext
type fromgolang.org/x/net/context
.- Logging methods that were on
appengine.Context
are now functions ingoogle.golang.org/appengine/log
. appengine.Timeout
has been removed. Usecontext.WithTimeout
instead.appengine.Datacenter
now takes acontext.Context
argument.datastore.PropertyLoadSaver
has been simplified to use slices in place of channels.delay.Call
now returns an error.search.FieldLoadSaver
now handles document metadata.urlfetch.Transport
no longer has a Deadline field; set a deadline on thecontext.Context
instead.aetest
no longer declares its own Context type, and uses the standard one instead.taskqueue.QueueStats
no longer takes a maxTasks argument. That argument has been deprecated and unused for a long time.appengine.BackendHostname
andappengine.BackendInstance
were for the deprecated backends feature. Useappengine.ModuleHostname
andappengine.ModuleName
instead.- Most of
appengine/file
and parts ofappengine/blobstore
are deprecated. Use Google Cloud Storage instead. appengine/socket
is not required on Managed VMs. Use the standardnet
package instead.