agent: Fixed a bug where syslog error messages marked as notice.

[jrasell]

The mapping between Nomad log level identifiers and syslog priorities did not handle the error level string correctly.

The change includes a new function which can be used for lookups in all places the conversion is needed. This function makes the translation easier to test.

Testing & Reproduction steps

Running on a Linux workstation (Ubuntu 24.04) I added the following lines to the /etc/rsyslog.conf before restarting rsyslog via sudo service rsyslog restart.

$template verbose, "%syslogseverity-text%, %syslogfacility%, %timegenerated%, %HOSTNAME%, %syslogtag%, %msg%\n"
*.* /var/log/all-messages.log;verbose

I then ran Nomad via sudo -i nomad agent -config=/home/jrasell/config.hcl using the following configuration to ensure errors are generated in the log:

enable_syslog = true
data_dir      = "/var/lib/nomad"

server {
  enabled          = true
  bootstrap_expect = 3
}

Error log lines are successfully and correctly entered via the err priority:

err, 16, Jan  9 10:29:42, workstation-0, nomad[26105]:,  worker: failed to dequeue evaluation: worker_id=c933e716-c5dc-c73a-571f-0bccb052a727 error="No cluster leader"
err, 16, Jan  9 10:29:42, workstation-0, nomad[26105]:,  worker: failed to dequeue evaluation: worker_id=5d982fbd-1d5f-c0eb-b091-f14d8afdd178 error="No cluster leader"
err, 16, Jan  9 10:29:42, workstation-0, nomad[26105]:,  worker: failed to dequeue evaluation: worker_id=a5c2f0dd-88d6-347f-4527-ef2b1d653987 error="No cluster leader"
err, 16, Jan  9 10:29:42, workstation-0, nomad[26105]:,  worker: failed to dequeue evaluation: worker_id=60463b64-adc9-d344-ad95-21b4dbd4214b error="No cluster leader"

Links

Jira: https://hashicorp.atlassian.net/browse/NET-11972

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