EPIPE

Error: write EPIPE
    at process.target._send (internal/child_process.js:832:20)
    at process.target.send (internal/child_process.js:703:19)
    at IPCTransport.send (/home/ubuntu/.nvm/versions/node/v14.15.1/lib/node_modules/pm2/node_modules/@pm2/io/build/main/transports/IPCTransport.js:84:21)
    at IPCTransport.setOptions (/home/ubuntu/.nvm/versions/node/v14.15.1/lib/node_modules/pm2/node_modules/@pm2/io/build/main/transports/IPCTransport.js:74:21)
    at Function.configureModule (/home/ubuntu/.nvm/versions/node/v14.15.1/lib/node_modules/pm2/node_modules/@pm2/io/build/main/configuration.js:13:62)
    at NotifyFeature.init (/home/ubuntu/.nvm/versions/node/v14.15.1/lib/node_modules/pm2/node_modules/@pm2/io/build/main/features/notify.js:34:33)
    at FeatureManager.init (/home/ubuntu/.nvm/versions/node/v14.15.1/lib/node_modules/pm2/node_modules/@pm2/io/build/main/featureManager.js:76:21)
    at PMX.init (/home/ubuntu/.nvm/versions/node/v14.15.1/lib/node_modules/pm2/node_modules/@pm2/io/build/main/pmx.js:86:29)
    at Object.<anonymous> (/home/ubuntu/.nvm/versions/node/v14.15.1/lib/node_modules/pm2/node_modules/@pm2/io/build/main/index.js:5:65)
    at Module._compile (internal/modules/cjs/loader.js:1063:30)
Emitted 'error' event on Worker instance at:
    at process.<anonymous> (internal/cluster/worker.js:29:12)
    at process.emit (events.js:315:20)
    at internal/child_process.js:836:39
    at processTicksAndRejections (internal/process/task_queues.js:75:11) {
  errno: -32,
  code: 'EPIPE',
  syscall: 'write'
}
events.js:292
      throw er; // Unhandled 'error' event
      ^

Error: write EPIPE
    at process.target._send (internal/child_process.js:832:20)
    at process.target.send (internal/child_process.js:703:19)
    at sendHelper (internal/cluster/utils.js:26:15)
    at send (internal/cluster/child.js:193:10)
    at EventEmitter.cluster._setupWorker (internal/cluster/child.js:46:3)
    at initializeClusterIPC (internal/bootstrap/pre_execution.js:343:13)
    at prepareMainThreadExecution (internal/bootstrap/pre_execution.js:66:3)
    at internal/main/run_main_module.js:7:1
Emitted 'error' event on Worker instance at:
    at process.<anonymous> (internal/cluster/worker.js:29:12)
    at process.emit (events.js:315:20)
    at internal/child_process.js:836:39
    at processTicksAndRejections (internal/process/task_queues.js:75:11) {
  errno: -32,
  code: 'EPIPE',
  syscall: 'write'
}

Start by reproducing the EPIPE failure with the shown Node.js cluster and PM2 IPCTransport stack trace, then trace the failure from process.target.send and IPCTransport.send. Identify the conditions that close or invalidate the IPC channel and add a regression test; done means the worker no longer emits an unhandled EPIPE error in that scenario.