Google Cloud Pub/Sub

Google Cloud Pub/Sub is a fully managed messaging service for sending and receiving messages between independent applications. The gRPC API is exposed through the google.pubsub.v1.Publisher service (topics and publishing) and the google.pubsub.v1.Subscriber service (subscriptions and message delivery), reached at pubsub.googleapis.com:443 over TLS.

Requests and responses are built with typed classes such as TsgcGRPCPubSubListTopicsRequest / TsgcGRPCPubSubListTopicsResponse, TsgcGRPCPubSubTopic, TsgcGRPCPubSubPublishRequest / TsgcGRPCPubSubPublishResponse, TsgcGRPCPubSubSubscription, TsgcGRPCPubSubPullRequest / TsgcGRPCPubSubPullResponse and TsgcGRPCPubSubAcknowledgeRequest, so you do not need to encode Protocol Buffers by hand.

The example below authenticates with a service-account JWT, wires a TsgcGRPCClient over a TsgcHTTP2Client to the Pub/Sub host, sets the authorization Bearer metadata and calls ListTopics for a project:

    oHTTP2 := TsgcHTTP2Client.Create(nil);
    oHTTP2.Host := 'pubsub.googleapis.com';
    oHTTP2.Port := 443;
    oHTTP2.TLS := True;

    oGRPC := TsgcGRPCClient.Create(nil);
    oGRPC.Client := oHTTP2;

    // service-account JWT authentication
    oGRPC.GoogleCloudOptions.JWT.KeyFile := 'service-account.json';
    oGRPC.GoogleCloudOptions.JWT.API_Endpoint := 'https://pubsub.googleapis.com/';
    oGRPC.DefaultMetadata.AddValue('authorization', 'Bearer ' + oGRPC.GoogleCloudOptions.JWT.Token);

    // build the typed request and call the method
    oRequest := TsgcGRPCPubSubListTopicsRequest.Create;
    try
      oRequest.Project := 'projects/my-project-id';
      oResponse := oGRPC.Call('google.pubsub.v1.Publisher', 'ListTopics', oRequest.ToBytes);
      ShowMessage(oResponse.DataString);
    finally
      oRequest.Free;
    end;