sidecar-echo-responder

Simple shell script to add "pong" feature to services not having it, such as SMTP

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Requirements:

• netcat (nc)
• socket statistics (ss)

Both should be already be installed on the majority of Linux distributions.

How it works

• it spans a nc process, in listening and keep-alive mode, on a configurable port (defaults 6666)
• it loops forever and checks for a live socket on the given port/protocol
• you (your Load Balancer) can ping it to check the monitored service health
• since the main loop is executed with set -e -o pipefail bash options it will exit if the socket is not found
• your LB will receive no more pongs :)

Execution

nohup sidecar-echo-responder.sh > /dev/null &

Enjoy