cp5024 was restarted using the sre.cdn.roll-reboot cookbook at 00:05. 5 minutes later (TrafficServerRestarted) firing: ATS backend server restarted on cp5024:9122 is triggered.
A quick check of the journal log for the service shows that SIGUSR2 was received triggering an ATS restart:
-- Boot 02ca5ecebcc440548f81b0e82714eb6d -- Aug 22 00:05:04 cp5024 systemd[1]: Started Apache Traffic Server is a fast, scalable and extensible caching proxy server.. Aug 22 00:05:04 cp5024 trafficserver[1854]: [E. Mgmt] log ==> [TrafficManager] using root directory '/usr' Aug 22 00:05:04 cp5024 trafficserver[1854]: [Aug 22 00:05:04.648] traffic_manager NOTE: updated diags config Aug 22 00:05:04 cp5024 trafficserver[1854]: [Aug 22 00:05:04.649] traffic_manager NOTE: [LocalManager::listenForProxy] Listening on port: 3128 (ipv4) Aug 22 00:05:04 cp5024 trafficserver[1854]: [Aug 22 00:05:04.649] traffic_manager NOTE: [LocalManager::listenForProxy] Listening on port: 3128 (ipv6) Aug 22 00:05:04 cp5024 trafficserver[1854]: [Aug 22 00:05:04.650] traffic_manager NOTE: [TrafficManager] Setup complete Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.651] traffic_manager NOTE: [ProxyStateSet] Traffic Server Args: ' -M' Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.651] traffic_manager NOTE: [LocalManager::listenForProxy] Listening on port: 3128 (ipv4) Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.651] traffic_manager NOTE: [LocalManager::listenForProxy] Listening on port: 3128 (ipv6) Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.651] traffic_manager NOTE: [LocalManager::startProxy] Launching ts process Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.757] traffic_manager NOTE: [LocalManager::pollMgmtProcessServer] New process connecting fd '11' Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.757] traffic_manager NOTE: [Alarms::signalAlarm] Server Process born Aug 22 00:05:05 cp5024 trafficserver[1854]: [TrafficManager] ==> received SIGUSR2, rotating the logs. Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.828] traffic_manager NOTE: [TrafficManager] ==> received SIGUSR2, rotating the logs. Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.828] traffic_manager NOTE: Reseated manager.log Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.830] traffic_manager NOTE: [LocalManager::pollMgmtProcessServer] Server Process terminated due to Sig 12: User defined signal 2 Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.830] traffic_manager NOTE: [Alarms::signalAlarm] Server Process was reset Aug 22 00:05:05 cp5024 trafficserver[1854]: [TrafficManager] ==> received SIGUSR2, rotating the logs. Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.839] traffic_manager NOTE: [TrafficManager] ==> received SIGUSR2, rotating the logs. Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.839] traffic_manager NOTE: Reseated manager.log Aug 22 00:05:05 cp5024 trafficserver[1854]: [TrafficManager] ==> received SIGUSR2, rotating the logs. Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.849] traffic_manager NOTE: [TrafficManager] ==> received SIGUSR2, rotating the logs. Aug 22 00:05:05 cp5024 trafficserver[1854]: [Aug 22 00:05:05.850] traffic_manager NOTE: Reseated manager.log Aug 22 00:05:06 cp5024 trafficserver[1854]: [Aug 22 00:05:06.832] traffic_manager NOTE: Relaunching proxy after 1 sec.. Aug 22 00:05:07 cp5024 trafficserver[1854]: [Aug 22 00:05:07.832] traffic_manager NOTE: [ProxyStateSet] Traffic Server Args: ' -M' Aug 22 00:05:07 cp5024 trafficserver[1854]: [Aug 22 00:05:07.833] traffic_manager NOTE: [LocalManager::listenForProxy] Listening on port: 3128 (ipv4) Aug 22 00:05:07 cp5024 trafficserver[1854]: [Aug 22 00:05:07.833] traffic_manager NOTE: [LocalManager::listenForProxy] Listening on port: 3128 (ipv6) Aug 22 00:05:07 cp5024 trafficserver[1854]: [Aug 22 00:05:07.833] traffic_manager NOTE: [LocalManager::startProxy] Launching ts process Aug 22 00:05:07 cp5024 trafficserver[1854]: [Aug 22 00:05:07.907] traffic_manager NOTE: [LocalManager::pollMgmtProcessServer] New process connecting fd '4' Aug 22 00:05:07 cp5024 trafficserver[1854]: [Aug 22 00:05:07.907] traffic_manager NOTE: [Alarms::signalAlarm] Server Process born Aug 22 00:05:09 cp5024 traffic_server[2199]: NOTE: --- traffic_server Starting --- Aug 22 00:05:09 cp5024 traffic_server[2199]: NOTE: traffic_server Version: Apache Traffic Server - traffic_server - 9.1.4 - (build # 121919 on Dec 19 2022 at 19:14:36)
SIGUSR2 is used as part of the log rotation process for ATS: https://gerrit.wikimedia.org/r/c/operations/puppet/+/829034 and as already documented on the commit message of that change, SIGUSR2 should signal a log rotation to traffic_manager and not trigger a traffic_server restart: https://docs.trafficserver.apache.org/en/9.1.x/appendices/command-line/traffic_manager.en.html?highlight=traffic_manager#signals:
SIGUSR2 This signal causes the traffic_manager and traffic_server processes to close and reopen their file descriptors for all of their log files. This allows the use of external tools to handle log rotation and retention. For instance, logrotate(8) can be configured to rotate the various Apache Traffic Server™ logs and, via the logrotate postrotate script, send a -SIGUSR2 to the traffic_manager process. After the signal is received, Apache Traffic Server™ will stop logging to the now-rolled files and will reopen log files with the originally configured log names.