Confirmed: restarting the agents when zero-length files are present in /var/lib/juju/metricspool/ reproduces the log error shown, and the agents do not recover. Workaround is removing those zero-length files and restarting juju agents.
Confirmed: restarting the agents when zero-length files are present in /var/lib/ juju/metricspoo l/ reproduces the log error shown, and the agents do not recover. Workaround is removing those zero-length files and restarting juju agents.