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sendmesg (blocking) of class BasicSocket crashes the thread of the thread pool #2363

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headius opened this issue Dec 29, 2014 · 0 comments
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@headius headius commented Dec 29, 2014

From http://jira.codehaus.org/browse/JRUBY-7169

Original report

The error occurs with the method "sendmesg" (blocking) of class BasicSocket on Ruby jruby, but does not occur on RMI Ruby 1.9.3-p392 (rvm). RMI Ruby 2.0.0-p0 (rvm) works partially.

The error does not occur with the method "send" (non-blocking) of class BasicSocket on above Jrubby versions (rvm), Ruby 1.9.3-p392 (rvm) and Ruby 2.0.0-p0 (rvm).

The bug can be reproduced with the code attached.

How to reproduce the error:

run:

ruby halfsync_halfasync.rb

on second terminal (unix):

telnet localhost 10001

on Windows use telnet client e.g. putty and make sure to configure putty as passive ("Connection->Telnet->Telnet negotiation mode: Passive")

What the code does:

  • It implements the halfsync_halfasync design-pattern (see references in the code).
  • An EchoAcceptor is registered with the reactor to accept connection setup.
  • A thread pool is started waiting for tasks to be retrieved from a shared queue
  • Upon connection-setup of the telnet the EchoAcceptor is called and registers an EchoServerHandler with the Reactor to handle data received via the connection from the telnet client.
  • Upon reception of data via the telent connection, the EchoServerHandler assembles data until a newline (\n or \r\n) is received. When that is received, the whole line is put into the shared queue.
  • The first thread from the thread pool waiting grabs the received data and the socket from the shared queue and in line 50/51 adds the thread-ID, the number of messages handled by that thread and sends it as a reply to the sender using the received socket.
  • What to expect as output:
    Upon entering e.g. text "!1234" and pressing return
  • On Ruby 1.9.3-p392 on Linux:
    See the as response the thread ID, the number of messages within the thread and the text.
  • On jruby 1.7.3. & 1.7.4:
    No response to telnet is sent, but the sending thread crashes.
    Everything works fine, if instead of blocking sendmesg (line 50/51) the non-blocking send (line 52/53) is used. However correct implementation of the halfsync-halfasync pattern, requires reasonably the usage of blocking "sendmesg" in thread pool.
  • I have to apologize that the program to reproduce the error is slightly large and complicated, but I believe that there is value, when ruby is able to run well known design patterns correctly.

A similar bugs have been filed for Ruby MRI and Rubinius here:
http://bugs.ruby-lang.org/issues/8442
rubinius/rubinius#2362

Here's the script: https://gist.github.com/headius/0d14997b4758bf0cb128

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