lowlevel_error_handler called with EOFError even when there is no actual error

[iain]

Describe the bug

This started happening in Puma 5. Even with a very simple success case, I am seeing EOFError being passed to the lowlevel_error_handler. It seems to be coming from inside puma itself. The output is ignored, because the actual request works fine.

Puma config:

The only thing is I specify is

# frozen_string_literal: true

lowlevel_error_handler do |ex, env, status|
  p ex
  puts(*ex.backtrace)
  p env
  p status
  [ status, {}, ["Internal Server Error #9"] ]
end

To Reproduce

Using a simple hello world app, it seems to be running fine from the client's perspective:

$ curl http://localhost:9292 -v
*   Trying ::1...
* TCP_NODELAY set
* Connection failed
* connect to ::1 port 9292 failed: Connection refused
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 9292 (#0)
> GET / HTTP/1.1
> Host: localhost:9292
> User-Agent: curl/7.64.1
> Accept: */*
>
< HTTP/1.1 200 OK
< Content-Type: text/plain
< Content-Length: 11
<
* Connection #0 to host localhost left intact
Hello World* Closing connection 0

However, in the server output I see the following:

Puma starting in single mode...
* Version 5.0.2 (ruby 2.7.1-p83), codename: Spoony Bard
* Min threads: 0, max threads: 5
* Environment: development
* Listening on http://0.0.0.0:9292
Use Ctrl-C to stop
#<EOFError: EOFError>
/Users/iain/.asdf/installs/ruby/2.7.1/lib/ruby/gems/2.7.0/gems/puma-5.0.2/lib/puma/client.rb:170:in `try_to_finish'
/Users/iain/.asdf/installs/ruby/2.7.1/lib/ruby/gems/2.7.0/gems/puma-5.0.2/lib/puma/reactor.rb:224:in `block in run_internal'
/Users/iain/.asdf/installs/ruby/2.7.1/lib/ruby/gems/2.7.0/gems/puma-5.0.2/lib/puma/reactor.rb:157:in `each'
/Users/iain/.asdf/installs/ruby/2.7.1/lib/ruby/gems/2.7.0/gems/puma-5.0.2/lib/puma/reactor.rb:157:in `run_internal'
/Users/iain/.asdf/installs/ruby/2.7.1/lib/ruby/gems/2.7.0/gems/puma-5.0.2/lib/puma/reactor.rb:307:in `block in run_in_thread'
{"rack.version"=>[1, 6], "rack.errors"=>#<IO:<STDERR>>, "rack.multithread"=>true, "rack.multiprocess"=>false, "rack.run_once"=>false, "SCRIPT_NAME"=>"", "QUERY_STRING"=>"", "SERVER_PROTOCOL"=>"HTTP/1.1", "SERVER_SOFTWARE"=>"puma 5.0.2 Spoony Bard", "GATEWAY_INTERFACE"=>"CGI/1.2", "puma.request_body_wait"=>0}\
500

In the env, QUERY_STRING and SCRIPT_NAME are never filled in, even if they are provided in the curl request.

Desktop (please complete the following information):

• OS: macOS Catalina, ruby 2.7.1p83 (2020-03-31 revision a0c7c23c9c) [x86_64-darwin19]
• Puma Version: 5.0.2
• rack: 2.2.3

[nateberkopec]

Thanks for reporting. This is a duplicated of #2390.