bash - 检查蚊子健康的脚本

Question

我正在尝试为mosquitto创建一个运行状况检查脚本(供docker使用)。

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

我遇到的问题是，如果给了不正确的密码，mosquitto_sub只会不断输出Connection Refused: not authorised.，而docker中的超时内容似乎是flakey，所以它永远不会结束。

看起来mosquitto并没有提供更好的失败方法。我认为我可能需要将其作为可以杀死的后台进程执行，但是我的bash并不是那么好，所以有人有更好的主意吗？

[编辑-根据BMitch的建议进行了更新]

我已将脚本修改为如下所示:

#!/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

但是运行它只会得到以下输出:

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

关于如何使正在运行的脚本超时，有一个bash FAQ。尝试将mosquitto_sub替换为包含以下内容的mosquitto_sub_timeout.sh:

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

然后，您的运行状况检查脚本将如下所示:

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

正如bash FAQ中提到的那样，最后一次更新，只要安装在您的容器中，timeout命令可能是所有它们的最佳解决方案:

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