Crash after upgrading to 2.8.0 from 2.7.0

[Hritik Soni]

Encountering the following crash post upgrade from 2.7.0 to 2.8.0 and had to revert the upgrade:

2021-03-08 10:31:35.812 [error] <0.13212.0>@cowboy_req:reply:812 CRASH REPORT Process <0.13212.0> with 0 neighbours crashed with reason: no match of right hand value 2 in cowboy_req:reply/4 line 812 2021-03-08 10:31:35.813 [error] <0.13212.0>@cowboy_req:reply:812 Cowboy stream 1 with ranch listener butler_base_http and connection process <0.13211.0> had its request process exit with reason: no match of right hand value 2 in cowboy_req:reply/4 line 812

2021-03-08 10:31:35 =CRASH REPORT====
  crasher:
    initial call: cowboy_stream_h:request_process/3
    pid: <0.13212.0>
    registered_name: []
    exception error: {{badmatch,2},[{cowboy_req,reply,4,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/_build/default/lib/cowboy/src/cowboy_req.erl"},{line,812}]},{butler_pps_api_handler,api_seat_login,4,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/apps/pf/src/interfaces/in/butler_pps_api_handler.erl"},{line,508}]},{cowboy_rest,call,3,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/_build/default/lib/cowboy/src/cowboy_rest.erl"},{line,1575}]},{cowboy_rest,process_content_type,3,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/_build/default/lib/cowboy/src/cowboy_rest.erl"},{line,1096}]},{cowboy_rest,upgrade,4,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/_build/default/lib/cowboy/src/cowboy_rest.erl"},{line,284}]},{cowboy_stream_h,execute,3,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/_build/default/lib/cowboy/src/cowboy_stream_h.erl"},{line,300}]},{cowboy_stream_h,request_process,3,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/_build/default/lib/cowboy/src/cowboy_stream_h.erl"},{line,291}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,226}]}]}
    ancestors: [<0.13211.0>,<0.3629.0>,<0.3628.0>,ranch_sup,<0.2229.0>]
    message_queue_len: 0
    messages: []
    links: [<0.13211.0>]
    dictionary: []
    trap_exit: false
    status: running
    heap_size: 6772
    stack_size: 28
    reductions: 34973
  neighbours:
2021-03-08 10:31:35 =ERROR REPORT====
Ranch listener butler_base_http, connection process <0.13211.0>, stream 1 had its request process <0.13212.0> exit with reason {badmatch,2} and stacktrace [{cowboy_req,reply,4,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/_build/default/lib/cowboy/src/cowboy_req.erl"},{line,812}]},{butler_pps_api_handler,api_seat_login,4,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/apps/pf/src/interfaces/in/butler_pps_api_handler.erl"},{line,508}]},{cowboy_rest,call,3,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/_build/default/lib/cowboy/src/cowboy_rest.erl"},{line,1575}]},{cowboy_rest,process_content_type,3,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/_build/default/lib/cowboy/src/cowboy_rest.erl"},{line,1096}]},{cowboy_rest,upgrade,4,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/_build/default/lib/cowboy/src/cowboy_rest.erl"},{line,284}]},{cowboy_stream_h,execute,3,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/_build/default/lib/cowboy/src/cowboy_stream_h.erl"},{line,300}]},{cowboy_stream_h,request_process,3,[{file,"/var/lib/jenkins/workspace/ButlerPipeline_ButlerServer-1.5-Build-commit-id/_build/default/lib/cowboy/src/cowboy_stream_h.erl"},{line,291}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,226}]}]

[Hritik Soni]

This commit is probably responsible: 39b2816

[Loïc Hoguin]

Yes that's the commit. But I'm not sure what you want me to fix, your code is incorrect, the only problem in Cowboy is the unhelpful error message.

[Hritik Soni]

This maybe present at a lot of places in our tech stack so fixing everywhere may not be viable and this will prevent us from upgrading cowboy. I wish if there was a much nicer backwards compatible way to do this

[Loïc Hoguin]

You can make your own cowboy_req:reply function if you really want this behavior. But sending bodies with these status codes is not correct so it may break again later on.

[Loïc Hoguin]

The error message has been improved and will be in 2.11. Closing, thanks!