api

Overview ¶

Package api is the root of the packages used to access Google Cloud Services. See https://godoc.org/google.golang.org/api for a full list of sub-packages.

Within api there exist numerous clients which connect to Google APIs, and various utility packages.

Client Options ¶

All clients in sub-packages are configurable via client options. These options are described here: https://godoc.org/google.golang.org/api/option.

Authentication and Authorization ¶

All the clients in sub-packages support authentication via Google Application Default Credentials (see https://cloud.google.com/docs/authentication/production), or by providing a JSON key file for a Service Account. See the authentication examples in https://godoc.org/google.golang.org/api/transport for more details.

Versioning and Stability ¶

Due to the auto-generated nature of this collection of libraries, complete APIs or specific versions can appear or go away without notice. As a result, you should always locally vendor any API(s) that your code relies upon.

Google APIs follow semver as specified by https://cloud.google.com/apis/design/versioning. The code generator and the code it produces - the libraries in the google.golang.org/api/... subpackages - are beta.

Note that versioning and stability is strictly not communicated through Go modules. Go modules are used only for dependency management.

Integers ¶

Many parameters are specified using ints. However, underlying APIs might operate on a finer granularity, expecting int64, int32, uint64, or uint32, all of whom have different maximum values. Subsequently, specifying an int parameter in one of these clients may result in an error from the API because the value is too large.

To see the exact type of int that the API expects, you can inspect the API's discovery doc. A global catalogue pointing to the discovery doc of APIs can be found at https://www.googleapis.com/discovery/v1/apis.

ForceSendFields ¶

This field can be found on all Request/Response structs in the generated clients. All of these types have the JSON `omitempty` field tag present on their fields. This means if a type is set to its default value it will not be marshalled. Sometimes you may actually want to send a default value, for instance sending an int of `0`. In this case you can override the `omitempty` feature by adding the field name to the `ForceSendFields` slice. See docs on any struct for more details.

Inspecting errors ¶

An error returned by a client's Do method may be cast to a *googleapi.Error or unwrapped to an *apierror.APIError.

The https://pkg.go.dev/google.golang.org/api/googleapi#Error type is useful for getting the HTTP status code:

if _, err := svc.FooCall().Do(); err != nil {
	if gErr, ok := err.(*googleapi.Error); ok {
		fmt.Println("Status code: %v", gErr.Code)
	}
}

The https://pkg.go.dev/github.com/googleapis/gax-go/v2/apierror#APIError type is useful for inspecting structured details of the underlying API response, such as the reason for the error and the error domain, which is typically the registered service name of the tool or product that generated the error:

if _, err := svc.FooCall().Do(); err != nil {
	var aErr *apierror.APIError
	if ok := errors.As(err, &aErr); ok {
		fmt.Println("Reason: %s", aErr.Reason())
		fmt.Println("Domain: %s", aErr.Domain())
	}
}

Polling Operations ¶

If an API call returns an Operation, that means it could take some time to complete the work initiated by the API call. Applications that are interested in the end result of the operation they initiated should wait until the Operation.Done field indicates it is finished. To do this, use the service's Operation client, and a loop, like so:

  import (
		gax "github.com/googleapis/gax-go/v2"
  )

  // existing application code...

  // API call that returns an Operation.
	 op, err := myApiClient.CalculateFoo().Do()
	 if err != nil {
		// handle err
	 }

	 operationsService = myapi.NewOperationsService(myApiClient)
  pollingBackoff := gax.Backoff{
	    Initial:    time.Second,
	    Max:        time.Minute, // Max time between polling attempts.
	    Multiplier: 2,
  }
	 for {
		if op.Done {
			break
		}
		// not done, sleep with backoff, then poll again
		if err := gax.Sleep(ctx, pollingBackoff.Pause()); err != nil {
			// handle error
		}
		op, err := operationsService.Get(op.Name).Do()
		if err != nil {
			// handle error
		}
	 }

	 if op.Error != nil {
		// handle operation err
	 }

	 // Do something with the response
	 fmt.Println(op.Response)