Saves out PID files, for example:
master.pid
worker.0.pid
worker.1.pid
worker.2.pid
worker.3.pid
The pidfiles([path]) plugin saves pid (process-id) files to the given path or ./pids.
save to ./pids:
cluster(server)
.use(cluster.pidfiles())
.listen(3000);
save to /var/run/node:
cluster(server)
.use(cluster.logger('/var/run/node'))
.listen(3000);