Moira is a simple (but not quite trivial) library for monitoring and, if necessary, restarting long-running threads. In principle, it is like an in-Lisp process supervisor.

To start the monitor, you call start-monitor:


Once the monitor is started, you can spawn new threads:

(moira:spawn "Background worker"

Which is syntactic sugar for

 (lambda () ...)
 :name "Background worker")

If the thread created by spawn-thread should crash, or otherwise exit abnormally, Moira will step in and restart the thread.

You can stop monitoring with stop-monitor


Although this will not affect the spawned threads.

On Linux only, Moira also tracks the thread ID (value of gettid) of the Lisp threads it launches. This can be useful for tracking the resource usage of individual threads.

Paul M. Rodriguez <>