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Piotr Roszatycki > Thrall-0.0202 > Thrall



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Module Version: 0.0202   Source   Latest Release: Thrall-0.0305


Thrall - a simple PSGI/Plack HTTP server which uses threads


  $ plackup -s Thrall --port=80 [options] your-app.psgi

  $ plackup -s Thrall --port=443 --ssl=1 --ssl-key-file=file.key --ssl-cert-file=file.crt [options] your-app.psgi

  $ plackup -s Thrall --port=80 --ipv6 [options] your-app.psgi

  $ plackup -s Thrall --socket=/tmp/thrall.sock [options] your-app.psgi


Thrall is a standalone HTTP/1.1 server with keep-alive support. It uses threads instead pre-forking, so it works correctly on Windows. It is pure-Perl implementation which doesn't require any XS package.


In addition to the options supported by plackup, Thrall accepts following options(s).


number of worker processes (default: 10)


seconds until timeout (default: 300)


timeout for persistent connections (default: 2)


max. number of requests allowed per single persistent connection. If set to one, persistent connections are disabled (default: 1)


max. number of requests to be handled before a worker process exits (default: 1000)


if set, randomizes the number of requests handled by a single worker process between the value and that supplied by --max-reqs-per-chlid (default: none)


if set, worker processes will not be spawned more than once than every given seconds. Also, when SIGHUP is being received, no more than one worker processes will be collected every given seconds. This feature is useful for doing a "slow-restart". (default: none)


the Thrall does not use signals or semaphores and it requires a small delay in main thread so it doesn't consume all CPU. (default: 0.1)


sets a new default per-thread stack size. (default: none)


enables SSL support. The IO::Socket::SSL module is required. (default: 0)


specifies the path to SSL key file. (default: none)


specifies the path to SSL certificate file. (default: none)


enables IPv6 support. The IO::Socket::IP module is required. (default: 0)


enables UNIX socket support. The IO::Socket::UNIX module is required. The socket file have to be not yet created. The first character @ or \0 in the socket file name means that abstract socket address will be created. (default: none)


Thrall was started as a fork of Starlet server. It has almost the same code as Starlet and it was adapted to use threads instead fork().


Starlet, Starman


See "BUGS AND LIMITATIONS" in threads and "Thread-Safety of System Libraries" in perlthrtut to read about limitations for PSGI applications started with Thrall and check if you encountered a known problem.

Especially, PSGI applications should avoid: changing current working directory, catching signals, starting new processes. Environment variables might (Linux, Unix) or might not (Windows) be shared between threads.

Thrall is very slow on first request for each thread. It is because spawning new thread is slow in Perl itself. Thrall is very fast on another requests and generally is faster than any implementation which uses fork.


There is a problem with Perl threads implementation which occurs on Windows. Some requests can fail with message:

  failed to set socket to nonblocking mode:An operation was attempted on
  something that is not a socket.


  Bad file descriptor at (eval 24) line 4.

Cygwin version seems to be correct.

This problem was introduced in Perl 5.16 and fixed in Perl 5.19.5.

See and for more information about this issue.


If you find the bug or want to implement new features, please report it at

The code repository is available at


Piotr Roszatycki <>

Based on Starlet by:

Kazuho Oku



Some code based on Plack:

Tatsuhiko Miyagawa


Copyright (c) 2013-2014 Piotr Roszatycki <>.

This is free software; you can redistribute it and/or modify it under the same terms as perl itself.


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