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100 lines
4.7 KiB
Markdown
100 lines
4.7 KiB
Markdown
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# Go App Engine packages
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[](https://travis-ci.org/golang/appengine)
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This repository supports the Go runtime on *App Engine standard*.
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It provides APIs for interacting with App Engine services.
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Its canonical import path is `google.golang.org/appengine`.
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See https://cloud.google.com/appengine/docs/go/
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for more information.
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File issue reports and feature requests on the [GitHub's issue
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tracker](https://github.com/golang/appengine/issues).
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## Upgrading an App Engine app to the flexible environment
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This package does not work on *App Engine flexible*.
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There are many differences between the App Engine standard environment and
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the flexible environment.
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See the [documentation on upgrading to the flexible environment](https://cloud.google.com/appengine/docs/flexible/go/upgrading).
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## Directory structure
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The top level directory of this repository is the `appengine` package. It
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contains the
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basic APIs (e.g. `appengine.NewContext`) that apply across APIs. Specific API
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packages are in subdirectories (e.g. `datastore`).
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There is an `internal` subdirectory that contains service protocol buffers,
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plus packages required for connectivity to make API calls. App Engine apps
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should not directly import any package under `internal`.
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## Updating from legacy (`import "appengine"`) packages
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If you're currently using the bare `appengine` packages
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(that is, not these ones, imported via `google.golang.org/appengine`),
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then you can use the `aefix` tool to help automate an upgrade to these packages.
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Run `go get google.golang.org/appengine/cmd/aefix` to install it.
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### 1. Update import paths
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The import paths for App Engine packages are now fully qualified, based at `google.golang.org/appengine`.
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You will need to update your code to use import paths starting with that; for instance,
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code importing `appengine/datastore` will now need to import `google.golang.org/appengine/datastore`.
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### 2. Update code using deprecated, removed or modified APIs
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Most App Engine services are available with exactly the same API.
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A few APIs were cleaned up, and there are some differences:
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* `appengine.Context` has been replaced with the `Context` type from `golang.org/x/net/context`.
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* Logging methods that were on `appengine.Context` are now functions in `google.golang.org/appengine/log`.
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* `appengine.Timeout` has been removed. Use `context.WithTimeout` instead.
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* `appengine.Datacenter` now takes a `context.Context` argument.
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* `datastore.PropertyLoadSaver` has been simplified to use slices in place of channels.
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* `delay.Call` now returns an error.
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* `search.FieldLoadSaver` now handles document metadata.
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* `urlfetch.Transport` no longer has a Deadline field; set a deadline on the
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`context.Context` instead.
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* `aetest` no longer declares its own Context type, and uses the standard one instead.
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* `taskqueue.QueueStats` no longer takes a maxTasks argument. That argument has been
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deprecated and unused for a long time.
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* `appengine.BackendHostname` and `appengine.BackendInstance` were for the deprecated backends feature.
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Use `appengine.ModuleHostname`and `appengine.ModuleName` instead.
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* Most of `appengine/file` and parts of `appengine/blobstore` are deprecated.
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Use [Google Cloud Storage](https://godoc.org/cloud.google.com/go/storage) if the
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feature you require is not present in the new
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[blobstore package](https://google.golang.org/appengine/blobstore).
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* `appengine/socket` is not required on App Engine flexible environment / Managed VMs.
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Use the standard `net` package instead.
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## Key Encode/Decode compatibiltiy to help with datastore library migrations
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Key compatibility updates have been added to help customers transition from google.golang.org/appengine/datastore to cloud.google.com/go/datastore.
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The `EnableKeyConversion` enables automatic conversion from a key encoded with cloud.google.com/go/datastore to google.golang.org/appengine/datastore key type.
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### Enabling key conversion
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Enable key conversion by calling `EnableKeyConversion(ctx)` in the `/_ah/start` handler for basic and manual scaling or any handler in automatic scaling.
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#### 1. Basic or manual scaling
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This start handler will enable key conversion for all handlers in the service.
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```
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http.HandleFunc("/_ah/start", func(w http.ResponseWriter, r *http.Request) {
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datastore.EnableKeyConversion(appengine.NewContext(r))
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})
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```
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#### 2. Automatic scaling
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`/_ah/start` is not supported for automatic scaling and `/_ah/warmup` is not guaranteed to run, so you must call `datastore.EnableKeyConversion(appengine.NewContext(r))`
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before you use code that needs key conversion.
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You may want to add this to each of your handlers, or introduce middleware where it's called.
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`EnableKeyConversion` is safe for concurrent use. Any call to it after the first is ignored.
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