502 Error / Unicorn Timeout on Rewind page for highly active users

[Don]

Hello

We are experiencing an issue with the Discourse Rewind plugin. For some of our most active users, the Rewind page fails to load and returns a 502 error.

• The issue seems to be a timeout during the data aggregation process.
• It consistently happens for users with high activity levels, while working fine for average users.
• The logs indicate that the Unicorn worker receives a USR2 signal because it exceeds the timeout limit while executing a database query.

Error in console:

Warning in logs:

Message

Unicorn worker received USR2 signal indicating it is about to timeout, dumping backtrace for main thread
config/unicorn.conf.rb:204:in `backtrace'
config/unicorn.conf.rb:204:in `block (2 levels) in reload'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/rack-mini-profiler-4.0.1/lib/patches/db/pg/alias_method.rb:112:in `exec'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/rack-mini-profiler-4.0.1/lib/patches/db/pg/alias_method.rb:112:in `async_exec'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activerecord-8.0.4/lib/active_record/connection_adapters/postgresql/database_statements.rb:167:in `perform_query'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activerecord-8.0.4/lib/active_record/connection_adapters/abstract/database_statements.rb:556:in `block (2 levels) in raw_execute'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activerecord-8.0.4/lib/active_record/connection_adapters/abstract_adapter.rb:1017:in `block in with_raw_connection'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activesupport-8.0.4/lib/active_support/concurrency/null_lock.rb:9:in `synchronize'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activerecord-8.0.4/lib/active_record/connection_adapters/abstract_adapter.rb:986:in `with_raw_connection'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activerecord-8.0.4/lib/active_record/connection_adapters/abstract/database_statements.rb:555:in `block in raw_execute'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activesupport-8.0.4/lib/active_support/notifications/instrumenter.rb:58:in `instrument'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activerecord-8.0.4/lib/active_record/connection_adapters/abstract_adapter.rb:1137:in `log'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activerecord-8.0.4/lib/active_record/connection_adapters/abstract/database_statements.rb:554:in `raw_execute'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activerecord-8.0.4/lib/active_record/connection_adapters/abstract/database_statements.rb:591:in `...

Backtrace

/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activesupport-8.0.4/lib/active_support/broadcast_logger.rb:218:in `block in dispatch'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activesupport-8.0.4/lib/active_support/broadcast_logger.rb:217:in `map'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activesupport-8.0.4/lib/active_support/broadcast_logger.rb:217:in `dispatch'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/activesupport-8.0.4/lib/active_support/broadcast_logger.rb:129:in `warn'
/var/www/discourse/lib/signal_trap_logger.rb:40:in `public_send'
/var/www/discourse/lib/signal_trap_logger.rb:40:in `block (2 levels) in ensure_logging_thread_running'
<internal:kernel>:187:in `loop'
/var/www/discourse/lib/signal_trap_logger.rb:37:in `block in ensure_logging_thread_running'

Thanks

[sam (Sam Saffron)]

Thanks @Don what scale are we talking here, can you give us a clue on how active this user is? (posts a year / likes a year)

[Don]

Sure, here are some stats (last year) for two of the affected users:

User 1

• Posts created: 11,709
• Reactions given: 41,569
• Reactions received: 74,603

User 2

• Posts created: 5,959
• Reactions given: 37,974
• Reactions received: 38,875

Both users trigger the 502 error, suggesting the timeout threshold is hit even with the moderately lower (but still high) activity of User 2.

[sam (Sam Saffron)]

Thanks heaps Don, someone will have a look over the next couple of weeks.

[martin (Martin Brennan)]

I think this fix should help:

https://github.com/discourse/discourse/pull/36940/