检查蚊子健康的脚本

Question

I'm trying to create a health check script for mosquitto (to be used by docker).

if [ -z "$USERNAME" ]; then
 mosquitto_sub -t '$SYS/#' -C 1 | grep -v Error || exit 1
else 
 mosquitto_sub -t '$SYS/#' -C 1 -u $USERNAME -P $PASSWRD | grep -v Error || exit 1
fi

The issue I'm having is that if an incorrect password is given mosquitto_sub just keeps outputting Connection Refused: not authorised. over and over, and the timeout stuff in docker appears flakey, so it just never ends.

It doesn't look like mosquitto gives any way to fail better. I think I might need to execute it as a background process that I can kill, but my bash isn't really that great, so does anyone have any better ideas?

[EDIT - updated as per BMitch's suggestion]

I have modified the script to look like this:

#!/bin/sh

if [ -z "$USERNAME" ]; then
        (sleep 10; kill $$) & exec mosquitto_sub -t '$SYS/#' -C 1 | grep -v Error || exit 1 "$@"
else
        (sleep 10; kill $$) & exec mosquitto_sub -t '$SYS/#' -u $USERNAME -P $PASSWORD -C 1 | grep -v Error || exit 1  "$@"
fi

but running it just gives the following output:

Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.
Terminated
root@e30e9cadd8fc:/# Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.
Connection Refused: not authorised.

Answer 1

There's a bash FAQ on how to timeout your running script. Try replacing mosquitto_sub with a mosquitto_sub_timeout.sh that contains the following:

#!/bin/bash
(sleep 10; kill $$) & exec mosquitto_sub "$@"

Then your healthcheck script will look like:

if [ -z "$USERNAME" ]; then
 mosquitto_sub_timeout.sh -t '$SYS/#' -C 1 | grep -v Error || exit 1
else 
 mosquitto_sub_timeout.sh -t '$SYS/#' -C 1 -u $USERNAME -P $PASSWRD | grep -v Error || exit 1
fi

---

And one last update, as mentioned in the bash FAQ, the timeout command may be the best solution of them all as long as it's installed in your container:

if [ -z "$USERNAME" ]; then
 timeout --foreground 10 mosquitto_sub -t '$SYS/#' -C 1 | grep -v Error || exit 1
else 
 timeout --foreground 10 mosquitto_sub -t '$SYS/#' -C 1 -u $USERNAME -P $PASSWRD | grep -v Error || exit 1
fi

Answer 2

(changed idea of BMitch )

I had to change the timeout argument from --foreground to -t and escape the $ by putting one more $ sign before it.

In my docker-compose it look next( keep in mind that username and password are removed, you still can add them - just escape the $ sign again ): version: '3' services: mosquitto: image: 'eclipse-mosquitto:1.6.7' container_name: mosquitto hostname: mosquitto volumes: - ./mosquitto/data:/mosquitto/data - ./mosquitto/log:/mosquitto/log - ./mosquitto/config:/mosquitto/config networks: - cluster restart: on-failure healthcheck: test: ["CMD-SHELL", "timeout -t 5 mosquitto_sub -t '$$SYS/#' -C 1 | grep -v Error || exit 1"] interval: 10s timeout: 10s retries: 6