Google Cloud Functions 發送訊息到 Google Cloud Pub/Sub

因為公司部份產品建置在 SaaS 基礎上，但這些 SaaS 都有自己維護的時間跟計劃，所以為了避免 SaaS 維護造成產品服務異常，所以想要將 SaaS 的相關通知先打進 Google Cloud Pub/Sub，後續再介接進團隊的 IM 系統

在這個目標下，就想透過 Google Cloud Functions 來處理這個需求，不需額外建立 server 也不用 container，今天就先紀錄一下如何透過 Cloud Functions 將訊息送到 Cloud Pub/Sub

基本環境說明

macOS Ventura 13.2
.NET SDK 7.0.203
JetBrains Rider 2023.1
- Google.Cloud.Functions.Templates
NuGet packages
- Google.Cloud.Functions.Hosting 1.1.0
- Google.Cloud.PubSub.V1 3.5.0

使用方式

安裝 Google Cloud Functions project template

dotnet new install Google.Cloud.Functions.Templates::2.0.0

透過 Google Cloud Functions project template 建立專案
安裝 NuGet packages：Google.Cloud.PubSub.V1 3.5.0

新增 PublishMessages.cs (用來發送訊息至 Google Cloud Pub/Sub)

using Google.Cloud.PubSub.V1;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
    
namespace PublishPubSub;
    
public class PublishMessages
{
    public async Task<int> PublishMessagesAsync(string projectId, string topicId,IEnumerable<string> messageTexts)
    {
        TopicName topicName = TopicName.FromProjectTopic(projectId, topicId);
        PublisherClient publisher = await PublisherClient.CreateAsync(topicName);
    
        int publishedMessageCount = 0;
        var publishTasks = messageTexts.Select(async text =>
        {
            try
            {
                string message = await publisher.PublishAsync(text);
                Console.WriteLine($"Published message {message}");
                Interlocked.Increment(ref publishedMessageCount);
            }
            catch (Exception exception)
            {
                Console.WriteLine($"An error ocurred when publishing message {text}: {exception.Message}");
            }
        });
        await Task.WhenAll(publishTasks);
        return publishedMessageCount;
    }
}

修改 Function.cs

using System.IO;
using System.Text.Json;
using Google.Cloud.Functions.Framework;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using System.Threading.Tasks;
    
namespace PublishPubSub;
    
public class Function : IHttpFunction
{
    private readonly ILogger _logger;
    private const string projectId = "";
    private const string topicId = "";
    
    public Function(ILogger<Function> logger) => _logger = logger;
    
    public async Task HandleAsync(HttpContext context)
    {
        HttpRequest request = context.Request;
    
        // Check URL parameters for "message" field
        string message = request.Query["message"];
    
        // If there's a body, parse it as JSON and check for "message" field.
        using TextReader reader = new StreamReader(request.Body);
        string text = await reader.ReadToEndAsync();
    
        try
        {
            if (text.Length > 0)
            {
                JsonElement json = JsonSerializer.Deserialize<JsonElement>(text);
                if (json.TryGetProperty("message", out JsonElement messageElement) && messageElement.ValueKind == JsonValueKind.String)
                {
                    message = messageElement.GetString();
                }
            }
    
            if (!string.IsNullOrWhiteSpace(message))
            {
                var pubsubClient = new PublishMessages();
                await pubsubClient.PublishMessagesAsync(projectId, topicId, new[] { message });
            }
        }
        catch (JsonException parseException)
        {
            _logger.LogError(parseException, "Error parsing JSON request");
        }
    
    
        await context.Response.WriteAsync(message ?? "Empty message");
    }
}

GCP 設定
- 建立 Google Cloud Pub/Sub topic
  預設會建立 subscription，最終的 message 是在 subscription 可以 pull 到的
- 建立 Google Cloud Function
  - Configuration
    除了 name 與 Region 可依需求調整，其他部份皆可使用預設值
  - Code
    將前面幾個步驟的結果貼上，或是可以打包成 zip 上傳
  建立完成後，有個 TESTING tab 可以直接執行，並看到相關的 response 與 log
實際效果