Server hangs all requests after a while
It could be a symptom of RAM starvation due to the query cache getting too big. We saw this in one of our apps running on Heroku. The default query cache is set to 1000. Lowering the limit eased the RAM usage for us with no noticeable performance degradation:
database.yml:
default: &default adapter: postgresql pool: <%= ENV["DB_POOL"] || ENV['MAX_THREADS'] || 5 %> timeout: 5000 port: 5432 host: localhost statement_limit: <%= ENV["DB_STATEMENT_LIMIT"] || 200 %>However searching for "activerecord querycache slow" returns other causes, such as perhaps outdated versions of Ruby or Puma or rack-timeout: https://stackoverflow.com/a/44158724/126636
Or maybe a too large value for read_timeout: https://stackoverflow.com/a/30526430/126636