phacility/phabricator · critical · Exception

Failed to %s!

Error message

Failed to %s!

What it means

Thrown in the daemonization path when pcntl_fork() returns a negative value, i.e. the OS refused to create a child process. This is an environment-level failure (not config), reported by the parent CLI process before it exits; the '%s' in the template is filled with 'fork()'.

Source

Thrown at src/applications/aphlict/management/PhabricatorAphlictManagementWorkflow.php:456

/* -(  Commands  )----------------------------------------------------------- */


  final protected function executeStartCommand() {
    $console = PhutilConsole::getConsole();
    $this->willLaunch();

    $log = $this->getOverseerLogPath();
    if ($log !== null) {
      echo tsprintf(
        "%s\n",
        pht(
          'Writing logs to: %s',
          $log));
    }

    $pid = pcntl_fork();
    if ($pid < 0) {
      throw new Exception(
        pht(
          'Failed to %s!',
          'fork()'));
    } else if ($pid) {
      $console->writeErr("%s\n", pht('Aphlict Server started.'));
      exit(0);
    }

    // Redirect process errors to the error log. If we do not do this, any
    // error the `aphlict` process itself encounters vanishes into thin air.
    if ($log !== null) {
      ini_set('error_log', $log);
    }

    // When we fork, the child process will inherit its parent's set of open
    // file descriptors. If the parent process of bin/aphlict is waiting for
    // bin/aphlict's file descriptors to close, it will be stuck waiting on
    // the daemonized process. (This happens if e.g. bin/aphlict is started

View on GitHub (pinned to 5720a38cfe)

Solutions

1. Check limits: ulimit -u and systemd's TasksMax; raise them for the aphlict service user or unit
2. Free headroom by stopping leaked processes, or reboot to clear PID exhaustion
3. Run `bin/aphlict debug --client ... --admin ...` in the foreground (no fork) to confirm the failure is fork-specific, and consider a supervisor running it in foreground mode

Example fix

# before: pcntl_fork() fails under tight limits
$ ulimit -u
# raise limit (systemd): [Service] TasksMax=512
# after: bin/aphlict start forks successfully

// Pre-flight: can we fork at all?
$test = pcntl_fork();
if ($test < 0) {
  throw new Exception('pcntl_fork unavailable: check ulimit -u / TasksMax');
}
if ($test === 0) { exit(0); } // child exits immediately
pcntl_waitpid($test, $status);

try {
  launch_daemonized($argv);
} catch (Exception $ex) {
  if (preg_match('/fork/', $ex->getMessage())) {
    // fallback: run in foreground under a supervisor instead
    launch_foreground($argv);
  }
}

When it happens

Trigger: Hitting RLIMIT_NPROC (per-user process limit) or system-wide PID exhaustion; forking denied by a container/seccomp policy that blocks clone(). Debug mode (--debug/--foreground) skips the fork and avoids the call.

Common situations: Shared hosts or cgroup-limited containers with tight ulimit -u; systemd service without TasksMax headroom; security-hardened containers blocking fork.

Related errors

• Unable to start notifications server because it is already r
• The notification server should not be run as root.
• Specify a user to notify with "--user".
• No user with username "%s" exists.
• Specify a message to send with "--message".

AI-assisted analysis of phacility/phabricator@5720a38cfe (2026-08-21). Data as JSON: /api/errors/b3d05b892df4fc5c. Report an issue: GitHub.