TeqFW: Plugin Initialization and Shutdown

Publication date: 2021-08-17

Some TeqFW plugins need to perform work when an application starts or stops—for example, opening database connections at startup and closing them at shutdown.

A plugin can declare in its TeqFW descriptor (./teqfw.json) an ES6 module with a factory for its initializer and another one for its finalizer:

{
  "core": {
    "plugin": {
      "onInit": "Vnd_Prj_Back_Plugin_Init",
      "onStop": "Vnd_Prj_Back_Plugin_Stop"
    }
  }
}

An ES6 module normally has this shape:

export default function Factory(spec) {
  // EXTRACT DEPS
  // ...
  // COMPOSE RESULT
  async function action() {
    // ...
  }
  return action;
}

Plugin hierarchy

All application plugins form a hierarchy according to their dependencies. TeqFW derives these dependencies from the /dependencies node in package.json:

{
  "name": "@teqfw/web",
  "dependencies": {
    "@teqfw/core": "*"
  }
}

Base-level plugins such as core are initialized and stopped first; higher-level plugins such as web follow.

Initialization

Plugin initialization happens while a TeqFW application starts, in TeqFw_Core_Back_App.init, after local configuration is loaded, plugins are scanned, and the DI container is initialized:

this.init = async function ({path, version}) {
  initBootConfig(config, path, version);
  // ...
  config.loadLocal(path);
  const registry = await pluginScan.exec(path);
  initDiContainer(registry);
  await initPlugins(registry);
};

The application calls plugin initializers one after another, from lower levels such as core up to higher levels such as app.

Shutdown

Plugin shutdown is performed by the public TeqFw_Core_Back_App.stop method, which can be called directly. When the process receives a signal, TeqFW calls it automatically:

this.run = async function () {
  const me = this;
  async function onStop() {
    await me.stop();
    process.exit();
  }
  process.on('SIGINT', onStop);
  process.on('SIGTERM', onStop);
  process.on('SIGQUIT', onStop);
};
this.stop = async function () { /* ... */ };

Finalizers run in the same bottom-up order, from core to app.

Additional source-code excerpts

this.init = async function ({path, version}) {
initBootConfig(config, path, version);
// …
config.loadLocal(path);
const registry = await pluginScan.exec(path);
initDiContainer(registry);
await initPlugins(registry);
// …
}

this.run = async function () {
const me = this; async function onStop() {
await me.stop();
process.exit();
} process.on(‘SIGINT’, onStop);
process.on(‘SIGTERM’, onStop);
process.on(‘SIGQUIT’, onStop);
// …
};this.stop = async function () {/* … */} Функции останова плагинов запускаются также по очереди, снизу-вверх — от базовых уровне (core) к верхним (app).