Serge tor restart means no bridges marked Running for 30"

frosttall (irc handle) noticed that bridge was marked down on metrics.tpo earlier. Serge had restart (not HUP/reload) around the same time as reported issue:

Mar 23 20:44:20.000 [notice] Clean shutdown finished. Exiting. Mar 23 20:44:23.000 [notice] Tor 0.4.6.10 opening log file.

The ultimate conclusion was that Serge takes 30" before voting again on running bridges.

arma pointed this code snippet out:

feature/dirauth/dirauth_options.inc:CONF_VAR(TestingAuthDirTimeToLearnReachability, INTERVAL, 0, "30 minutes")

Apparently, this has been going on for a while, most recently 20220207-002949 20220208-195458 20220205-204058 20220205-175303 20220206-044751 are also times when there was no consensus/"all bridges down" as per Serge reporting. It was reported by trinity that there were examples in 2020,2021. Again, very strange that none of us noticed that there were no reported running bridges.

The issue came up recently, and I thought someone on the bridgedb end handled. There were no formal 'outages' on Serge since the IPv6 routing issues a month ago, and didn't connect the outages with tor restarting.

A workaround arma mentioned was ignoring Serge's reporting if no bridges are marked Running.