Google-cloud-dotnet: Using pubsub emulator with SubscriberClient

[Eldar-Ahmadov]

Good day,

I was using "Google.Cloud.PubSub.V1 Api Version="1.0.0-beta20" which allowed me to switch between pubsub emulator and the “real” cloud pubsub as per code below:

                var emulatorHostAndPort = Environment.GetEnvironmentVariable("PUBSUB_EMULATOR_HOST");

        var subscriberApiClient = string.IsNullOrEmpty(emulatorHostAndPort)
            ? SubscriberServiceApiClient.Create(CreateChannelWithCredentials(credentialPath))
            : SubscriberServiceApiClient.Create(new Channel(emulatorHostAndPort, ChannelCredentials.Insecure));

        var subscriber = SubscriberClient.Create(subscription.SubscriptionName, new[] { subscriberApiClient });

In the code above I’m able to pass subscriberApiClient with the preconfigured Channel pointing to pubsub emulator host/port to SubscriberClient.Create method, and then use SubscriberClient which allows for simpler api specifically StartAsync method which I use quite a lot throughout the codebase.

After upgrading to "Google.Cloud.PubSub.V1" Version="1.0.0" (not beta) I cannot find any corresponding way of being able to pass a preconfigured Channel which would allow me to make a switch similar to how I was doing it using older api; the SubscriberClient.Create method has been replaced with SubscriberClient.CreateAsync which takes SubscriberClient.ClientCreationSettings and SubscriberClient.Settings but I wasn’t able to identify which of those can be used to use pubsub emulator (using a Channel or otherwise).

Is there anything I may have missed? I’d greatly appreciate your response.

[chrisdunelm]

You are correct that the SubscriberClient.Create(...) method has been removed.
The way to achieve this in v1.0.0 is to configure the ChannelCredentials and ServiceEndpoint in the ClientCreationSettings; then pass this to SubscriberClient.CreateAsync(...).
You will need to refactor your code slightly, but this will allow you to achieve the same outcome.

[Eldar-Ahmadov]

Thanks for your prompt response.

Are there any plans to use an "PUBSUB_EMULATOR_HOST" environment variable to take care of it automatically, i.e. how it's done in Python api, where you only need to set the environment variable?

[chrisdunelm]

we may support an environment variable in a later version, but this isn't certain and won't be soon.

[chrisdunelm]

Closing. Please leave a further comment if you think it needs re-opening.

[ivan-penchev]

Hi @chrisdunelm ,

I am refactoring our code for the non-beta version, and am stuck on the same problem.

Basic setup: We alternate between dockerized pubsub emulator in development and the real pubsub in production.

Basic problem: Unsure how to setup "ServiceEndpoint" for this case.

Same code:

`
public abstract class Publisher : IDisposable
{

    private readonly PubSubOption _options;
    private readonly Emulator _emulator;
    private readonly Task<PublisherClient> _client;

    protected Publisher(PubSubOption options, IApplicationLifetime applicationLifetime )
    {
        _options = options;

        if (_options.UseEmulator)
        {
            _emulator = Emulator.Create(new UriBuilder
            {
                Host = _options.EmulatorHost,
                Port = _options.EmulatorPort
            }.Uri);

            _client = Task.FromResult(_emulator.CreatePublisherClient(TopicName));
        }
        else
        {
            _client = PublisherClient.CreateAsync(TopicName, _options.PublisherClientCreationSettings,
                _options.PublisherClientSettings);
        }

        applicationLifetime.ApplicationStopping.Register(() =>
        {
         //do cleanup
        });
    }

}`

And the Emulator class
`
public class Emulator
{
public Uri Uri { get; }
private readonly PublisherServiceApiClient _pubApiClient;

    public Emulator(Uri uri)
    {
        _startInfo = new ProcessStartInfo
        {
            FileName = "gcloud",
            Arguments = $"beta emulators pubsub start --host-port={uri.Host}:{uri.Port}",
            UseShellExecute = true
        };
        Uri = uri;
        _pubApiClient = CreatePublisherServiceApiClient();
    }

    public static Emulator Create(Uri uri)
    {
        return new Emulator(uri);
    }
    public PublisherServiceApiClient CreatePublisherServiceApiClient()
    {
        var channel = new Channel(Uri.Host, Uri.Port, ChannelCredentials.Insecure);
        return PublisherServiceApiClient.Create(channel);
    }
   public PublisherClient CreatePublisherClient(TopicName topic, PublisherClient.Settings settings = null)
    {
        return PublisherClient.Create(topic, new []{_pubApiClient}, settings);
    }

`

[chrisdunelm]

The ServiceEndpoint is the hostname and port of the service. So for the emulator I would expect the code to be something like: new Google.Api.Gax.Grpc.ServiceEndpoint(uri.Host, uri.Port);