IsoLatte

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.

Simple Process Isolation

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.

Complex Example

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! }

Options

• 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)

Supported Platforms

IsoLatte requires Process.fork, Process.waitpid2, and IO.pipe, and also requires Timeout.timeout and Process.kill to function properly. That means that Jruby is unsupported (no fork), and that Windows is certainly unsupported (no anything).

Currently tested in travis and supported: MRI 2.2, 2.1, 2.0, 1.9, 1.8.7, and REE 1.8.7

The tests (and the Gemfile) requires that a C extension be compiles for the segfault gem - that gem is not required for functioning, but it's an important test to run - if you know of a good way to compatibly test that on other platforms, I'm interested in a pull request.

Roadmap

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.