In #387 I wrote: > _But_ sadly, we also tried running 1.7.8 in production and had similar problems. Only a downgrade to 1.6.3 helped our application to run stable again. So there might be a similar or closely related issue that is not covered by the repro above. Sorry that I do not have more data on that one. And indeed, running with the fix for #387 still led to workers getting stuck and using 100% CPU. While I was able to reproduce #387 locally (and eventually found a very minimal repro), I have no idea how to reproduce this one. Since #387 was related to connect timeouts, it happened when requesting from servers that displayed flaky behavior. This other problem seems to happen with random servers (including ones that we host ourselves, so we know they work correctly). One thing that is odd apart from the servers being requested from seeming to be random is that the lock up seems to happen almost simultaneously across threads and processes. I used a gem to get a stacktrace from a running process and I believe the relevant part is this: ``` /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/cache/base.rb:93:in 'Hash#delete' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/cache/base.rb:93:in 'HTTPX::Resolver::Cache::Base#_se t' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/cache/memory.rb:23:in 'block in HTTPX::Resolver::Cach e::Memory#set' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/cache/memory.rb:38:in 'block in HTTPX::Resolver::Cach e::Memory#synchronize' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/cache/memory.rb:38:in 'Thread::Mutex#synchronize' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/cache/memory.rb:38:in 'HTTPX::Resolver::Cache::Memory #synchronize' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/cache/memory.rb:22:in 'HTTPX::Resolver::Cache::Memory #set' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/native.rb:431:in 'HTTPX::Resolver::Native#parse_addre sses' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/native.rb:318:in 'HTTPX::Resolver::Native#parse' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/native.rb:285:in 'block in HTTPX::Resolver::Native#dr ead' <internal:kernel>:168:in 'Kernel#loop' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/native.rb:244:in 'HTTPX::Resolver::Native#dread' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/native.rb:159:in 'block in HTTPX::Resolver::Native#co nsume' <internal:kernel>:168:in 'Kernel#loop' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/native.rb:158:in 'HTTPX::Resolver::Native#consume' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/resolver/native.rb:86:in 'HTTPX::Resolver::Native#call' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/selector.rb:61:in 'block (2 levels) in HTTPX::Selector#next_ti ck' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/selector.rb:288:in 'HTTPX::Selector#select_one' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/selector.rb:209:in 'HTTPX::Selector#select' /usr/local/bundle/ruby/3.4.0/bundler/gems/httpx-f940d8dddce7/lib/httpx/selector.rb:58:in 'block in HTTPX::Selector#next_tick' ``` I think the resolver cache code was added in 1.7, so that would fit. Sorry I do not have any other clues.