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PostgreSQL: /usr/share/temboard-agent/auto_configure.sh: line 54: used_a[*]: unbound variable

If you try to deploy a new temBoard Agent (Version temboard-agent-7.4-1.el7.noarch) on RHEL/CentOS 7, you might end up with the following error:

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$ sudo /usr/share/temboard-agent/auto_configure.sh https://host.example.ch:8888
Using hostname host.example.ch.
Configuring for PostgreSQL user postgres.
Configuring for cluster on port 55031.
Configuring for cluster at /app/lib/postgres/pgdata/12/P01A.
Configuring temboard-agent in /etc/temboard-agent/12/pg55031/temboard-agent.conf .
Saving auto-configuration in /etc/temboard-agent/12/pg55031/temboard-agent.conf.d/auto.conf
Failure. See /var/log/temboard-agent-auto-configure.log for details.

In the log you will find the following error which point to an unbound variable.

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+++ ss -ln4t '( sport >= 2345 and sport <= 3000 )'
+++ grep -Po ':\K\d+'
/usr/share/temboard-agent/auto_configure.sh: line 54: used_a[*]: unbound variable
+ port=
+ catchall
+ '[' 1 -gt 0 ']'

A workaround, which worked for me, is to replace the upper port of 3000 with 300000.

Simply change the file /usr/share/temboard-agent/auto_configure.sh and replace sport <= 3000 with sport <= 300000.

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From
mapfile -t used_a < <(ss -ln4t '( sport >= 2345 and sport <= 3000 )' | grep -Po ':\K\d+')
 
To
mapfile -t used_a < <(ss -ln4t '( sport >= 2345 and sport <= 300000 )' | grep -Po ':\K\d+')
 
find_next_free_port() {
        local port
        local used_a
        local used
        mapfile -t used_a < <(ss -ln4t '( sport >= 2345 and sport <= 300000 )' | grep -Po ':\K\d+')
        # To mock ss output, use seq:
        # mapfile -t used_a < <(seq 2345 3000)
        used="${used_a[*]}"
        for port in {2345..3000} ; do
                if [[ " $used " =~ \ $port\  ]] ; then continue ; fi
                echo $port;
                return
        done
        log "No free TCP port found between 2345 and 3000. Force with env TEMBOARD_PORT."
        return 1
}

Another workaround that you can use, is to replace the line

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used="${used_a[*]}"

with

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used="${used_a[*]:-}"

Now the deployment of the new temBoard agent worked. 🙂

Conclusion

In case you need to deploy a 7.4 temBoard agent quickly, you might want to use these workarounds. The other possibility is to wait for temBoard agent 7.5 until the following bug is fixed. https://github.com/dalibo/temboard-agent/issues/507

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