SSLClientCoordinator: SSL config is reloaded multiple times

[cmcfarlen]

If multiple ssl related config files are changed and then traffic_ctl config reload is executed, the ssl config will reload multiple times.

Reproduction:

1. Run traffic_server with a sni.yaml and ssl_multicert.config file configured
2. touch sni.yaml
3. traffic_ctl config reload
4. Observerve the log output:

[Aug 20 13:59:35.145] [ET_TASK 0] NOTE: /opt/ats/etc/trafficserver/sni.yaml loading ...
[Aug 20 13:59:35.147] [ET_TASK 0] NOTE: /opt/ats/etc/trafficserver/sni.yaml finished loading
[Aug 20 13:59:35.147] [ET_TASK 0] NOTE: ssl_multicert.config loading ...
[Aug 20 13:59:35.158] [ET_TASK 0] NOTE: /opt/ats/etc/trafficserver/ssl_multicert.config finished loading

5. touch sni.yaml and ssl_multicert.config files
6. traffic_ctl config reload
7. Observer the log output:

[Aug 20 13:59:53.154] [ET_TASK 0] NOTE: /opt/ats/etc/trafficserver/sni.yaml loading ...
[Aug 20 13:59:53.156] [ET_TASK 0] NOTE: /opt/ats/etc/trafficserver/sni.yaml finished loading
[Aug 20 13:59:53.156] [ET_TASK 0] NOTE: ssl_multicert.config loading ...
[Aug 20 13:59:53.166] [ET_TASK 0] NOTE: /opt/ats/etc/trafficserver/ssl_multicert.config finished loading
[Aug 20 13:59:53.166] [ET_TASK 0] NOTE: /opt/ats/etc/trafficserver/sni.yaml loading ...
[Aug 20 13:59:53.167] [ET_TASK 0] NOTE: /opt/ats/etc/trafficserver/sni.yaml finished loading
[Aug 20 13:59:53.168] [ET_TASK 0] NOTE: ssl_multicert.config loading ...
[Aug 20 13:59:53.174] [ET_TASK 0] NOTE: /opt/ats/etc/trafficserver/ssl_multicert.config finished loading

This happens because the callbacks setup in SSLClientCoordinator are independently attached and so the reconfigure function will be called for every updated config item specified.

This happens on the master branch, but also for 9.2.x

[JosiahWI]

Is this closed by #11723 @cmcfarlen @maskit?

[maskit]

No, we found the QUIC reload issue while we work on this one. With #11723 fixed, we'd see 4 "ssl_multicert.config loading ..." lines in total if QUIC is available.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. Marking it stale to flag it for further consideration by the community.

[bryancall]

This was fixed by PR #12892 (the configuration reload token model). The root cause was exactly as described here: SSLClientCoordinator::startup() used a ConfigUpdateHandler and called attach() once per record, so the reconfigure callback fired independently for each changed SSL config file, producing duplicate reloads. That PR replaced the per-record attach mechanism with a single coordinated registration (ConfigRegistry::register_record_config under the key ssl_client_coordinator), so the reconfigure handler now runs once per reload regardless of how many SSL files changed. The follow-up PR #13075 added a Test.AddConfigReload() autest extension covering reload behavior. For reference, PR #11723 was a separate QUIC reload bug found while investigating this one and is not the fix here. The fix is on the master branch and is scheduled for the 11.0.0 release. Closing as resolved.