test: add Worker initialization failure test case

Cover the scenario fixed through
#31621
Unfortunately there is no easy way to test this, in a
cross-platform manner. So the approach is:
 - open a child process with ulimit restriction on file descriptors
 - in the child process, start few workers - more than the fd limit
 - make sure some workers fail, with the expected error type.
 - skip the test in windows, as there is no ulimit there.

Refs: #31621

PR-URL: #31929
Reviewed-By: Denys Otrishko <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>

test/parallel/test-worker-init-failure.js

@@ -0,0 +1,67 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const child_process = require('child_process');
+
+// Test that workers fail with meaningful error message
+// when their initialization fails.
+
+if (common.isWindows) {
+  common.skip('ulimit does not work on Windows.');
+}
+
+// A reasonably low fd count. An empty node process
+// creates around 30 fds for its internal purposes,
+// so making it too low will crash the process early,
+// making it too high will cause too much resource use.
+const OPENFILES = 128;
+
+// Double the open files - so that some workers fail for sure.
+const WORKERCOUNT = 256;
+
+if (process.argv[2] === 'child') {
+  const { Worker } = require('worker_threads');
+  for (let i = 0; i < WORKERCOUNT; ++i) {
+    const worker = new Worker(
+      'require(\'worker_threads\').parentPort.postMessage(2 + 2)',
+      { eval: true });
+    worker.on('message', (result) => {
+      assert.strictEqual(result, 4);
+    });
+
+    // We want to test that if there is an error in a constrained running
+    // environment, it will be one of `EMFILE` or `ERR_WORKER_INIT_FAILED`.
+    // `common.mustCall*` cannot be used here as in some environments
+    // (i.e. single cpu) `ulimit` may not lead to such an error.
+
+    worker.on('error', (e) => {
+      assert.match(e.message, /EMFILE/);
+      assert.ok(e.code === 'ERR_WORKER_INIT_FAILED' || e.code === 'EMFILE');
+    });
+  }
+
+} else {
+  // Limit the number of open files, to force workers to fail.
+  let testCmd = `ulimit -n ${OPENFILES} && `;
+  testCmd += `${process.execPath} ${__filename} child`;
+  const cp = child_process.exec(testCmd);
+
+  // Turn on the child streams for debugging purposes.
+  let stdout = '';
+  cp.stdout.setEncoding('utf8');
+  cp.stdout.on('data', (chunk) => {
+    stdout += chunk;
+  });
+  let stderr = '';
+  cp.stderr.setEncoding('utf8');
+  cp.stderr.on('data', (chunk) => {
+    stderr += chunk;
+  });
+
+  cp.on('exit', common.mustCall((code, signal) => {
+    console.log(`child stdout: ${stdout}\n`);
+    console.log(`child stderr: ${stderr}\n`);
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
+  }));
+}