[ruby-core:112912] [Ruby master Bug#19412] Socket starts queueing and not responding after a certain amount of requests
From:
"brodock (Gabriel Mazetto) via ruby-core" <ruby-core@...>
Date:
2023-03-16 11:15:58 UTC
List:
ruby-core #112912
Issue #19412 has been updated by brodock (Gabriel Mazetto).
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@jeremyevans0 I'm new to debugging C code. Your idea on filedescriptors seems to to be somewhat spot on.
I'm not sure if this is the right way to debug this or not, but I managed to capture "Filesystem activity" through MacOS instrumentor.
As you can see, there is a big gap between a chunk of request it processed which can illustrate what I was observing.
looking at the description of what is happening you can see that the code couldn't get "accept" to return with success after some number of executions.
What is interesting is that I can't see any `close` calls, only `accept` and `writev` which is weird. Could it be that somehow in MacOS we are not issuing `close` calls and it is just "timing out"?
----------------------------------------
Bug #19412: Socket starts queueing and not responding after a certain amount of requests
https://bugs.ruby-lang.org/issues/19412#change-102430
* Author: brodock (Gabriel Mazetto)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.2.1 (2023-02-08 revision 31819e82c8) [arm64-darwin22]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
Here is a an example code:
```ruby
require 'socket'
PORT = 8080
BACKLOG = 50
LISTEN = '127.0.0.1'
def handle_connection(connection, _addrinfo)
request = connection.gets
puts request
connection.write "HTTP/1.1 200\r\n"
connection.write "Content-Type: text/html\r\n"
connection.write "\r\n"
connection.write "Hello world! Current time is #{Time.now}"
ensure
connection.close
end
begin
socket = Socket.new(:INET, :STREAM)
socket.bind(Addrinfo.tcp(LISTEN, PORT))
socket.listen(BACKLOG)
puts "Requested queue size: #{BACKLOG} bigger then limit: #{Socket::SOMAXCONN}" if BACKLOG > Socket::SOMAXCONN
loop do
listening, = IO.select([socket])
io, = listening
connection, addrinfo = io.accept
handle_connection(connection, addrinfo)
end
ensure
socket.close
end
```
This tries to simulate a TCP server that responds as if it was an HTTP server.
The amount of requests it can sustain seems to depend on the OS. On a Linux machine running ubuntu 20.04 I get something around 7.6K to 7.8K until it stops responding.
```
$ uname -a
Linux ... 5.17.5-x86_64-linode154 #1 SMP PREEMPT Mon May 2 15:07:22 EDT 2022 x86_64 x86_64 x86_64 GNU/Linux
$ ab -n 20000 -c 50 http://127.0.0.1:8080/
This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking 127.0.0.1 (be patient)
Completed 2000 requests
Completed 4000 requests
Completed 6000 requests
apr_pollset_poll: The timeout specified has expired (70007)
Total of 7883 requests completed
```
on MacOS Ventura I get around 16K:
```
$ uname -a
Darwin ... 22.2.0 Darwin Kernel Version 22.2.0: Fri Nov 11 02:04:44 PST 2022; root:xnu-8792.61.2~4/RELEASE_ARM64_T8103 arm64
$ ab -n 20000 -c 50 http://127.0.0.1:8080/
This is ApacheBench, Version 2.3 <$Revision: 1901567 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking 127.0.0.1 (be patient)
Completed 2000 requests
Completed 4000 requests
Completed 6000 requests
Completed 8000 requests
Completed 10000 requests
Completed 12000 requests
Completed 14000 requests
Completed 16000 requests
apr_socket_recv: Operation timed out (60)
Total of 16375 requests completed
```
in both cases when that limit reaches, if I abort the program (CTRL-C) and try to run it again it takes a while until the port is released:
```
...
GET / HTTP/1.0
GET / HTTP/1.0
GET / HTTP/1.0
^Csocketserver.rb:29:in `select': Interrupt
from socketserver.rb:29:in `block in <main>'
from socketserver.rb:28:in `loop'
from socketserver.rb:28:in `<main>'
$ ruby socketserver.rb
socketserver.rb:23:in `bind': Address already in use - bind(2) for 127.0.0.1:8080 (Errno::EADDRINUSE)
from socketserver.rb:23:in `<main>'
```
After killing the process it seems no process is holding the port:
```
lsof -wni tcp:8080
```
Running the command above does not return anything (it does when the program is still running).
I think we may be failing to release something when interacting with the Socket on syscalls/kernel level and we endup filling up some queue/buffer that eventually gets freed.
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--
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