Process Agent

midway encapsulates @midwayjs/process-agent to solve data inconsistencies between processes in some multi-process scenarios in node scenarios, or it is impossible to specify the master process to execute a method.

Examples:

• If pm2, cluster, and multi-process deployment methods are used, and memory cache is used, then the cache is in its own process.
• prometheus, when acquiring /metrics, it is necessary to collect data from all processes, not from one process.
• Health check, if there are 4 processes, if one process is abnormal, the health check should fail.

Related information:

Description
Can be used for standard projects	✅
Can be used for Serverless	❌
Can be used for integration	✅
Contains independent main framework	❌
Contains independent logs	❌

Installation method

Usage:

$ npm install @midwayjs/process-agent@3 --save

Or reinstall the following dependencies in package.json.

{
  "dependencies": {
    "@midwayjs/process-agent": "^3.0.0",
    // ...
  },
  "devDependencies": {
    // ...
  }
}

Introducing components

Usage of configuration.ts:

import * as processAgent from '@midwayjs/process-agent';

@Configuration({
  imports: [
    // ...
    processAgent
  ],
})
export class MainConfiguration {
}

Usage

Business code UserService:

import { Provide, Inject } from '@midwayjs/core';
import { TestService } from './test';

@Provide()
export class UserService {

  @Inject()
  testService: TestService;

  async getUser() {
    let result = await this.testService.setData(1);
    return result;
  }
}

Then when calling the testService, it is hoped that it will only be executed in the main process:

import { Provide, Scope, ScopeEnum } from '@midwayjs/core';
import { RunInPrimary } from '@midwayjs/process-agent';

@Provide()
@Scope(ScopeEnum.Singleton)
export class TestService {

  data: any = 0;

  @RunInPrimary()
  async setData( B) {
    this.data = B;
    return this.data;
  }

  @RunInPrimary()
  async getData() {
    return this.data;
  }
}

Note that the data returned by the execution is limited to serializable data, such as ordinary JSON, and does not support data that cannot be serialized such as including methods.

Effect description

Assume that it is started in a multi-process manner such as pm2 or egg-script. Assume that this is a request.

First:

• 1. Set setData
• 2. Then get the getData

If this decorator is not RunInPrimary, the request may fall on process 2 or process 3, and the updated data may not be obtained.

So RunInPrimary can ensure that the execution of this function falls to the main process.

Function Solicitation

If you have other related functions that can be placed in this package, please mention them in the comment area or issue. We will discuss and implement them with you.