fix

[HoseokWon99]

pm2 cluster -> fork로 모드 변경

[gemini-code-assist]

Summary of Changes

Hello @HoseokWon99, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

I've updated the PM2 configuration for the comeet application. The primary goal of this change is to switch the process management mode from cluster to fork, ensuring the application runs as a single instance rather than multiple clustered instances.

Highlights

• PM2 Configuration Update: Modified ecosystem.config.js to change the application's PM2 execution mode.
• Instance Count Reduction: Reduced the number of application instances from 3 to 1.
• Execution Mode Change: Removed the explicit exec_mode: "cluster" setting, which, combined with instances: 1, effectively switches the PM2 process management to fork mode.

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[gemini-code-assist]

Code Review

This pull request changes the PM2 configuration to run the application in fork mode with a single instance, instead of cluster mode with three instances. While this might fix issues related to multi-process execution (like duplicated scheduled tasks), it severely impacts the application's scalability and availability by not leveraging multiple CPU cores and removing redundancy. My review includes a detailed comment explaining these risks and suggests alternative approaches, such as using a dedicated worker instance for scheduled tasks, to handle such issues in a clustered environment without sacrificing performance.

[gemini-code-assist]

Switching from cluster mode with 3 instances to fork mode with a single instance will significantly impact the application's performance and scalability, as it will no longer be able to utilize multiple CPU cores for handling requests. This also reduces availability as there is no longer any redundancy.

If this change is intended to resolve issues with scheduled tasks (@nestjs/schedule) running on multiple instances, which is a common problem with cluster mode, please consider alternative solutions that don't sacrifice scalability:

• Use a distributed lock: Implement a locking mechanism (e.g., using Redis or a database) to ensure that a scheduled task is executed by only one instance at a time.
• Designate a worker instance: You could have a separate PM2 app definition for a single worker instance that is responsible for running scheduled tasks, while the main app continues to run in cluster mode for handling API requests. For example:

  // ecosystem.config.js
  module.exports = {
    apps: [
      {
        name: "comeet-api",
        script: "dist/main.js",
        instances: -1, // Use all available CPUs
        exec_mode: "cluster",
        env: {
          IS_WORKER: "false"
        }
      },
      {
        name: "comeet-worker",
        script: "dist/main.js",
        instances: 1,
        exec_mode: "fork", // Explicitly fork mode for worker
        env: {
          IS_WORKER: "true"
        }
      }
    ]
  };

  In your application code, you would then conditionally register the ScheduleModule based on the IS_WORKER environment variable.

If this change is made for other reasons, it's highly recommended to add a comment to the configuration file explaining the rationale for running in single-instance fork mode to aid future maintenance.