nq(1) - A simple last-job-in-queue command executor

# Start the server

$ nq -s
...
INFO[20:36:29.4928] Starting server


# Push commands to the server

$ nq -- sh -c 'make build test'  # Returns immediately, does not block
$ nq -- sh -c 'make build test'

Why?

In most CI pipelines, build tasks/jobs are blocking and this causes queue management problems.

If the system triggering the CI commands does so at a rate greater than the rate the CI system can process jobs - two unwanted things arise (1) the queue length increases (2) new commands cannot be submitted as the previous commands block.

nq allows the non-blocking intake of multiple (identical) jobs and will begin processing the last job taken, disregarding all previous jobs.

As the nq client does not block, it cannot wait to check the exit status of the command(s) submitted to the queue. In a future version, the ability to query the health of the "builds" will be possible.

Use case - Triggering builds from file changes in the editor

e.g. in vim + tmux/tslime, you may wish to run tests on every file write

:au BufWritePost,FileWritePost * silent :Tmux make build test

While this works for quick test suites (desirable), make blocks until the tests have completed and so a subsequent make ... command cannot be accepted over an already running command.

With nq wrapping the command, flow is non-blocking and you can make as many edits and saves as you like - only the last issued command is triggered.

:au BufWritePost,FileWritePost * silent :Tmux nq -- make build test

Use case - Running builds from file changes detected by inotify, etc

nq can listen in on STDIN being a pipe and react only when the input matches a regular expression.

inotifywait -q -e close_write -m . | nq -p CREATE -- make build test

Using a custom client

Simply write an array of strings as a JSON string to the named pipe.

{ echo -e '["sh", "-c", "'echo foo'"]';  } > "$TMP/nq.fifo"

Building nq

$ make build