MVFC.Messaging.GCP 3.0.2

MVFC.Messaging.GCP

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A .NET messaging provider for Google Cloud Pub/Sub, built on top of MVFC.Messaging.Core. Provides PubSubPublisher<T> and PubSubConsumer<T> for publishing and consuming JSON-serialized messages using the official Google Cloud client library with built-in emulator support.

Package

Package	Downloads
MVFC.Messaging.GCP

Installation

dotnet add package MVFC.Messaging.GCP

This package depends on MVFC.Messaging.Core (installed automatically) and Google.Cloud.PubSub.V1.

Configuration

Authentication

Google Cloud client libraries use Application Default Credentials (ADC). Common setups:

Emulator Detection

Both PubSubPublisher<T> and PubSubConsumer<T> are configured with EmulatorDetection.EmulatorOrProduction. This means:

• If PUBSUB_EMULATOR_HOST is set → connects to the emulator.
• Otherwise → connects to production Google Cloud Pub/Sub.

No code changes needed between local and production environments.

Constructor Parameters

• Publisher: projectId (your GCP project) and topicId (the Pub/Sub topic name).
• Consumer: projectId and subscriptionId (the Pub/Sub subscription name).

appsettings.json Example

{
  "GCP": {
    "ProjectId": "my-gcp-project",
    "TopicId": "orders",
    "SubscriptionId": "orders-subscription"
  }
}

var projectId = builder.Configuration["GCP:ProjectId"]!;
var topicId = builder.Configuration["GCP:TopicId"]!;
var subscriptionId = builder.Configuration["GCP:SubscriptionId"]!;

Usage

Publishing a Single Message

using MVFC.Messaging.GCP.PubSub;

var projectId = "my-gcp-project";
var topicId = "orders";

await using var publisher = new PubSubPublisher<OrderCreated>(projectId, topicId);

var order = new OrderCreated(1, "Keyboard", 149.90m);
await publisher.PublishAsync(order);

The message is serialized to JSON and published as the Pub/Sub message data.

Publishing a Batch

Batch publishing sends all messages concurrently using Task.WhenAll:

var orders = new[]
{
    new OrderCreated(1, "Keyboard", 149.90m),
    new OrderCreated(2, "Mouse", 59.90m),
    new OrderCreated(3, "Monitor", 899.00m)
};

await publisher.PublishBatchAsync(orders);

Consuming Messages

The consumer wraps Google Cloud's SubscriberClient, which handles pull-based message delivery with automatic flow control. Each message receives an Ack (success) or Nack (failure) reply:

using MVFC.Messaging.GCP.PubSub;

var projectId = "my-gcp-project";
var subscriptionId = "orders-subscription";

await using var consumer = new PubSubConsumer<OrderCreated>(projectId, subscriptionId);

await consumer.StartAsync(async (message, ct) =>
{
    Console.WriteLine($"Processing order #{message.OrderId}: {message.Product}");
    // Your business logic here
}, cancellationToken);

// ... later, when shutting down:
await consumer.StopAsync();

Consumer behavior:

• Uses Google Cloud's SubscriberClient.StartAsync for managed message delivery.
• Successful handler execution results in an Ack — the message is removed from the subscription.
• If the handler throws an exception, a Nack is sent — the message will be redelivered.
• A 1-second initialization delay ensures the subscriber is fully ready before returning.
• StopAsync gracefully stops the subscriber and waits for all pending handlers to complete.

Complete Publish + Consume Example

using MVFC.Messaging.GCP.PubSub;

// Using emulator: set PUBSUB_EMULATOR_HOST=localhost:8085
var projectId = "my-gcp-project";
var topicId = "orders";
var subscriptionId = "orders-subscription";

await using var publisher = new PubSubPublisher<OrderCreated>(projectId, topicId);
await using var consumer = new PubSubConsumer<OrderCreated>(projectId, subscriptionId);

// Start consuming
var received = new TaskCompletionSource<OrderCreated>();
await consumer.StartAsync(async (msg, ct) =>
{
    Console.WriteLine($"Received: Order #{msg.OrderId} — {msg.Product}");
    received.SetResult(msg);
}, CancellationToken.None);

// Publish
await publisher.PublishAsync(new OrderCreated(42, "Keyboard", 149.90m));

// Wait for the message to be consumed
var result = await received.Task.WaitAsync(TimeSpan.FromSeconds(30));

// Cleanup
await consumer.StopAsync();

API Reference

PubSubPublisher<T>

PubSubConsumer<T>

Requirements

• .NET 9.0+
• Google.Cloud.PubSub.V1 (installed automatically)
• Google Cloud credentials (ADC) or Pub/Sub emulator

License

Apache-2.0