ReloadServerPlugin.js

ReloadServerPlugin.js

const cluster = require('cluster');
const path = require('path');

const defaultOptions = {
  script: 'server.js',
  execArgv: [],
};

class ReloadServerPlugin {
  constructor({ script, execArgv = [] } = defaultOptions) {
    this.done = null;
    this.workers = [];
    this.hotReloadSucceeded = false;
    this.initialCompilationDone = false;

    cluster.setupPrimary({
      exec: path.resolve(process.cwd(), script),
      execArgv,
    });

    cluster.on('online', (worker) => {
      this.workers.push(worker);

      if (this.done) {
        this.done();
      }
    });
  }

  startServer() {
    const envs = {
      NODE_OPTIONS: '--enable-source-maps --no-experimental-fetch --trace-warnings --trace-deprecation',
    };

    cluster.fork(envs);
  }

  apply(compiler) {
    compiler.hooks.afterEmit.tap(
      {
        name: 'reload-server',
      },
      (compilation, callback) => {
        this.done = callback;

        // this does not work
        if (compilation.errors.length === 0) {
          this.hotReloadSucceeded = true;
        } else {
          this.hotReloadSucceeded = false;
        }

        const shouldReload = !this.initialCompilationDone || !this.hotReloadSucceeded;

        if (!this.initialCompilationDone) {
          this.initialCompilationDone = true;
        }

        if (!shouldReload) {
          return;
        }

        this.workers.forEach((worker) => {
          try {
            process.kill(worker.process.pid, 'SIGTERM');
          } catch (e) {
            // eslint-disable-next-line
            console.warn(`Unable to kill process #${worker.process.pid}`);
          }
        });

        this.workers = [];

        this.startServer();
      },
    );

    compiler.hooks.done.tap('reload-server', (stats) => {
      if (this.hotReloadSucceeded) {
        // eslint-disable-next-line
        console.log('Hot reload succeeded, server not restarted.');
      } else {
        // eslint-disable-next-line
        console.log('Hot reload failed, server restarted.');
      }
    });
  }
}

module.exports = ReloadServerPlugin;