Error and Crash on 404 Elixir.Phoenix.Router.NoRouteError

[tpitale]

Environment

• Elixir version (elixir -v): 1.8.1
• Erlang/OTP version (erl): 21
• Sentry version (mix deps): 7.0.3
• Operating system: Mac OS 10.14.2 and Docker elixir-slim-1.8.1

Description

After upgrading to Phoenix 1.4.x and plug_cowboy 2.0, We've seen some vague errors in our logs that appear to happen on 404:

[info] time=21:32:15.579 request_id=2m0e7it2clh3g54eq40001eh method=GET path=/ time_elapsed=21ms status=404  Sent
21:32:15.580 [error] CRASH REPORT Process <0.713.0> with 0 neighbours exited with reason: {{#{'__exception__' => true,'__struct__' => 'Elixir.Phoenix.Router.NoRouteError',conn => #{'__struct__' => 'Elixir.Plug.Conn',adapter => {'Elixir.Plug.Cowboy.Conn',#{bindings => #{},body_length => 0,cert => undefined,has_body => false,headers => #{<<"accept">> => <<"*/*">>,<<"host">> => <<"">>,<<"x-amzn-trace-id">> => <<"">>,<<"x-forwarded-for">> => <<"178.73.215.171">>,<<"x-forwarde...">> => ...,...},...}},...},...},...},...} in 'Elixir.Phoenix.Endpoint.Cowboy2Handler':init/2 line 43 in 'Elixir.Phoenix.Endpoint.Cowboy2Handler':init/2 line 43
21:32:15.591 [error] Cowboy stream 1 with ranch listener 'Elixir.MyApp.Endpoint.HTTP' and connection process <0.712.0> had its request process exit with reason: {{#{'__exception__' => true,'__struct__' => 'Elixir.Phoenix.Router.NoRouteError',conn => #{'__struct__' => 'Elixir.Plug.Conn',adapter => {'Elixir.Plug.Cowboy.Conn',#{bindings => #{},body_length => 0,cert => undefined,has_body => false,headers => #{<<"accept">> => <<"*/*">>,<<"host">> => <<"">>,<<"x-amzn-trace-id">> => <<"">>,<<"x-forwarded-for">> => <<"178.73.215.171">>,<<"x-forwarde...">> => ...,...},...}},...},...},...},...} in 'Elixir.Phoenix.Endpoint.Cowboy2Handler':init/2 line 43

When searching out these errors we've found that other products similar to sentry (appsignal, honeybadger) have experienced similar issues. I'm wondering if you've seen this before and if maybe a similar change needs to happen in Sentry.

Related:

• Phoenix.Router.NoRouteError being reported on 404 after upgrade to Phoenix 1.4 and Cowboy 2 appsignal/appsignal-elixir#417
• Erlang error: {{%Phoenix.Router.NoRouteError ... for not-found requests honeybadger-io/honeybadger-elixir#193

Expected Behavior

404 should not error and crash

Actual Behavior

404 appears to crash

[mitchellhenke]

Thanks for opening this issue!

I will take a look to see what I can do about this.

[mitchellhenke]

I am unfortunately unable to reproduce this. I've pushed a repository to show how I'm attempting to reproduce, and if anything in your setup looks different, let me know:

Repository: https://github.com/mitchellhenke/no_route_testing
Sentry installation commit: mitchellhenke/no_route_testing@53a2b1d

hitting any route other than / generates a 404, but I don't receive any events in Sentry, or logs like you are seeing.

Do you have any different Logger configuration or :error_logger things going on?

[tpitale]

We don't have this line use Sentry.Phoenix.Endpoint adding and deploying. Might have missed that when upgrading at some point in the past.

This could also all be a red herring. We have no real confirmation that sentry is the issue. Closing until I can reproduce reliably.

[mitchellhenke]

@tpitale My hunch is that Sentry.Phoenix.Endpoint wouldn't affect this issue, but rather that something different is going on with :logger config. Something Phoenix related is also possible, but I'm less sure.

If you'd like to discuss while you're working through it, I'm in IRC and Elixir Slack (same username) 🙂