a simple PSGI/Plack server that uses threads
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Latest commit b8e2054 Jan 3, 2017 @dex4er Document new SSL options
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thrall - a simple PSGI/Plack HTTP server which uses threads


$ thrall --workers=20 --max-reqs-per-child=100 app.psgi

$ thrall --port=80 --ipv6=1 app.psgi

$ thrall --port=443 --ssl=1 --ssl-key-file=file.key --ssl-cert-file=file.crt app.psgi

$ thrall --socket=/tmp/thrall.sock 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.

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().


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


Number of worker threads. (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 synchronize its processes and it requires a small delay in main process so it doesn't consume all CPU. (default: 0.1)


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)


Specifies the path to SSL CA certificate file which will be a part of server's certificate chain. (default: none)


Specifies the path to SSL CA certificate file for client verification. (default: none)


Specifies the verification mode for the client certificate. See "SSL_verify_mode" in IO::Socket::SSL for details. (default: 0)


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)


Changes the user id or user name that the server process should switch to after binding to the port. The pid file, error log or unix socket also are created before changing privileges. This options is usually used if main process is started with root privileges beacause binding to the low-numbered (<1024) port. (default: none)


Changes the group ids or group names that the server should switch to after binding to the port. The ids or names can be separated with comma or space character. (default: none)


Changes file mode creation mask. The "umask" in perlfunc is an octal number representing disabled permissions bits for newly created files. It is usually 022 when group shouldn't have permission to write or 002 when group should have permission to write. (default: none)


Makes the process run in the background. It doesn't work (yet) in native Windows (MSWin32). (default: 0)


Specify the pid file path. Use it with -D|--daemonize option. (default: none)


Specify the pathname of a file where the error log should be written. This enables you to still have access to the errors when using --daemonize. (default: none)

-q, --quiet

Suppress the message about starting a server.


Starlight, 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 https://rt.perl.org/rt3/Public/Bug/Display.html?id=119003 and https://github.com/dex4er/Thrall/issues/5 for more information about this issue.


If you find the bug or want to implement new features, please report it at https://github.com/dex4er/Starlight/issues

The code repository is available at http://github.com/dex4er/Starlight


Piotr Roszatycki dexter@cpan.org

Based on Starlet by:

Kazuho Oku



Some code based on Plack:

Tatsuhiko Miyagawa

Some code based on Net::Server::Daemonize:

Jeremy Howard <j+daemonize@howard.fm>

Paul Seamons paul@seamons.com


Copyright (c) 2013-2017 Piotr Roszatycki dexter@cpan.org.

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

See http://dev.perl.org/licenses/artistic.html