Sometimes you need to run background jobs that you can't make important guarantees about - they may run out of memory and get killed, or produce segmentation faults, or exit! directly - and you need to be able to clean up after such problems.

IsoLatte is a gem that allows a block of code to be executed in a subprocess. Exceptions get passed back to the parent process through a pipe, and various exit conditions are handled via configurable callbacks.

IsoLatte.fork do
  do_something_crazy!
end

do_something_crazy! is now being invoked in a forked subprocess - if it crashes the interpreter, or gets killed by the OS, instead of taking down the original process, it will invoke the appropriate callback in the parent.

IsoLatte.fork(
  stderr:   "/tmp/suberr.txt",
  finish:   ->(success, rc) { warn "Finished. Success? #{success}" },
  success:  ->() { warn "Was successful" },
  kill:     ->() { warn "Received a SIGKILL" },
  fault:    ->() { warn "Received a SIGABRT, probably a segmentation fault" },
  exit:     ->(rc) { warn "subprocess exited explicitly with #{rc}" }
) { do_something_crazy! }

• stderr - A path to write the subprocess' stderr stream into. Defaults to '/dev/null', supplying nil lets the subprocess continue writing to the parent's stderr stream.
• success - a callable to execute if the subprocess completes successfully.
• fault - a callable to execute if the subprocess receives a SIGABRT (segfault).
• kill - a callable to execute if the subprocess receives a SIGKILL (from kill -9 or oom-killer)
• exit - a callable to execute if the subprocess explicitly exits with nonzero status. Receives the exit status value as its argument.
• finish - a callable to execute when the subprocess terminates in any way. It receives a boolean 'success' value and an exit status as its arguments.
• timeout - a number of seconds to wait - if the process has not terminated by then, the parent will kill it by issuing a SIGKILL signal (triggering the kill callback)

1. Add a convenient mechanism for sending a single marshaled object back to the parent afterward.
2. Allow the stderr to accept a callback to call for each line instead.
3. Improve compatibility with various gems that modify Exception, like better_errors.