Package cloud is the root of the packages used to access Google CloudServices. Seehttps://godoc.org/cloud.google.com/go for a full listof sub-packages.

Client Options

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

Authentication and Authorization

All the clients in sub-packages support authentication via Google Application DefaultCredentials (seehttps://cloud.google.com/docs/authentication/production), orby providing a JSON key file for a Service Account. See examples below.

Google Application Default Credentials (ADC) is the recommended way to authorizeand authenticate clients. For information on how to create and obtainApplication Default Credentials, seehttps://cloud.google.com/docs/authentication/production. Here is an exampleof a client using ADC to authenticate:

client,err:=secretmanager.NewClient(context.Background())iferr!=nil{// TODO: handle error.}_=client// Use the client.

You can use a file with credentials to authenticate and authorize, such as a JSONkey file associated with a Google service account. Service Account keys can becreated and downloaded fromhttps://console.cloud.google.com/iam-admin/serviceaccounts. This example usesthe Secret Manger client, but the same steps apply to the other client librariesunderneath this package. Example:

client,err:=secretmanager.NewClient(context.Background(),option.WithCredentialsFile("/path/to/service-account-key.json"))iferr!=nil{// TODO: handle error.}_=client// Use the client.

In some cases (for instance, you don't want to store secrets on disk), you cancreate credentials from in-memory JSON and use the WithCredentials option.The google package in this example is at golang.org/x/oauth2/google.This example uses the Secret Manager client, but the same steps apply tothe other client libraries underneath this package. Note that scopes can befound athttps://developers.google.com/identity/protocols/oauth2/scopes, andare also provided in all auto-generated libraries: for example,cloud.google.com/go/secretmanager/apiv1 provides DefaultAuthScopes. Example:

ctx:=context.Background()creds,err:=google.CredentialsFromJSON(ctx,[]byte("JSON creds"),secretmanager.DefaultAuthScopes()...)iferr!=nil{// TODO: handle error.}client,err:=secretmanager.NewClient(ctx,option.WithCredentials(creds))iferr!=nil{// TODO: handle error.}_=client// Use the client.

Timeouts and Cancellation

By default, non-streaming methods, like Create or Get, will have a default deadline applied to thecontext provided at call time, unless a context deadline is already set. Streamingmethods have no default deadline and will run indefinitely. To set timeouts orarrange for cancellation, use contexts. Transienterrors will be retried when correctness allows.

Here is an example of how to set a timeout for an RPC, use context.WithTimeout:

ctx:=context.Background()// Do not set a timeout on the context passed to NewClient: dialing happens// asynchronously, and the context is used to refresh credentials in the// background.client,err:=secretmanager.NewClient(ctx)iferr!=nil{// TODO: handle error.}// Time out if it takes more than 10 seconds to create a dataset.tctx,cancel:=context.WithTimeout(ctx,10*time.Second)defercancel()// Always call cancel.req:=&secretmanagerpb.DeleteSecretRequest{Name:"projects/project-id/secrets/name"}iferr:=client.DeleteSecret(tctx,req);err!=nil{// TODO: handle error.}

Here is an example of how to arrange for an RPC to be canceled, use context.WithCancel:

ctx:=context.Background()// Do not cancel the context passed to NewClient: dialing happens asynchronously,// and the context is used to refresh credentials in the background.client,err:=secretmanager.NewClient(ctx)iferr!=nil{// TODO: handle error.}cctx,cancel:=context.WithCancel(ctx)defercancel()// Always call cancel.// TODO: Make the cancel function available to whatever might want to cancel the// call--perhaps a GUI button.req:=&secretmanagerpb.DeleteSecretRequest{Name:"projects/proj/secrets/name"}iferr:=client.DeleteSecret(cctx,req);err!=nil{// TODO: handle error.}

To opt out of default deadlines, set the temporary environment variableGOOGLE_API_GO_EXPERIMENTAL_DISABLE_DEFAULT_DEADLINE to "true" prior to clientcreation. This affects all Google Cloud Go client libraries. This opt-outmechanism will be removed in a future release. File an issue athttps://github.com/googleapis/google-cloud-go if the default deadlinescannot work for you.

Do not attempt to control the initial connection (dialing) of a service by setting atimeout on the context passed to NewClient. Dialing is non-blocking, so timeoutswould be ineffective and would only interfere with credential refreshing, which usesthe same context.

Connection Pooling

Connection pooling differs in clients based on their transport. Cloudclients either rely on HTTP or gRPC transports to communicatewith Google Cloud.

Cloud clients that use HTTP (bigquery, compute, storage, and translate) rely on theunderlying HTTP transport to cache connections for later re-use. These are cached tothe default http.MaxIdleConns and http.MaxIdleConnsPerHost settings inhttp.DefaultTransport.

For gRPC clients (all others in this repo), connection pooling is configurable. Usersof cloud client libraries may specify option.WithGRPCConnectionPool(n) as a clientoption to NewClient calls. This configures the underlying gRPC connections to bepooled and addressed in a round robin fashion.

Using the Libraries with Docker

Minimal docker images like Alpine lack CA certificates. This causes RPCs to appear tohang, because gRPC retries indefinitely. Seehttps://github.com/googleapis/google-cloud-go/issues/928for more information.

Debugging

To see gRPC logs, set the environment variable GRPC_GO_LOG_SEVERITY_LEVEL. Seehttps://godoc.org/google.golang.org/grpc/grpclog for more information.

For HTTP logging, set the GODEBUG environment variable to "http2debug=1" or "http2debug=2".

Inspecting errors

Most of the errors returned by the generated clients can be converted into agrpc.Status. Converting your errors to this type can be a useful to getmore information about what went wrong while debugging.

iferr!={ifs,ok:=status.FromError(err);ok{log.Println(s.Message())for_,d:=ranges.Proto().Details{log.Println(d)}}}

Client Stability

Clients in this repository are considered alpha or beta unless otherwisemarked as stable in the README.md. Semver is not used to communicate stabilityof clients.

Alpha and beta clients may change or go away without notice.

Clients marked stable will maintain compatibility with future versions for aslong as we can reasonably sustain. Incompatible changes might be made in somesituations, including:

- Security bugs may prompt backwards-incompatible changes.

- Situations in which components are no longer feasible to maintain withoutmaking breaking changes, including removal.

- Parts of the client surface may be outright unstable and subject to change.These parts of the surface will be labeled with the note, "It is EXPERIMENTALand subject to change or removal without notice."