Requests throttling for Plack
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Plack::Middleware::Throttle::Lite - Requests throttling for Plack


version 0.05


# inside your app.psgi
my $app = builder {
    enable 'Throttle::Lite',
        limits => '100 req/hour', backend => 'Simple',
        routes => [ qr{^/(host|item)/search}, qr{^/users/add} ],
        blacklist => [ '', '', '', '' ];
    sub {
        [ 200, ['Content-Type' => 'text/plain'], [ 'OK' ] ];


This middleware allows to restrict access to PSGI application based on requests per unit of time (hour/day at the moment). Implemetation of the middleware inspired by Plack::Middleware::Throttle.


  • Blacklisting

    Requests from specified IPs (including ranges) or CIDRs are rejects immediately with response 403 Forbidden.

  • Whitelisting

    Requests from specified IPs (including ranges) or CIDRs allows to get an unlimited access to the application.

  • Flexible and simple throttling policy

    Access to an application might be configured by using one of the several time measuring units (minute, hour, day).

  • Routes configuration

    Flexible settings for routes matching based on regular expressions.

  • Various storage backends

    There is an API which allows to write and use any database or cache system to manipulate throttling data.

  • Very lightweight

    It will not install a-half-of-CPAN or heavy dependencies!



By this option is defined the throttling policy. At the moment, there are two variants in limiting of requests: per hour, per day and per minute. Value of maximum requests might be pointed as number and measuring units (hour, day, min). Some examples:

# restrict to 520 request in an hour
enable 'Throttle::Lite', limits => '520 req/hour';
# ..maybe 10000 requests in a day?
enable 'Throttle::Lite', limits => '10000 req/day';
# or 30 per minute:
enable 'Throttle::Lite', limits => '30 req/min';

Also valid more short constructions:

# should not exceed 315 request in an hour
enable 'Throttle::Lite', limits => '315 r/h';
# ..19999 requests in a day
enable 'Throttle::Lite', limits => '19999 r/d';
# ..55 requests per minute:
enable 'Throttle::Lite', limits => '55 r/m';

Or even

# works
enable 'Throttle::Lite', limits => '51 req per hour';
# ..this one also okay
enable 'Throttle::Lite', limits => '99 r per d';
# ..and this
enable 'Throttle::Lite', limits => '72 r per hour';
# space between number and units also allowed
enable 'Throttle::Lite', limits => '34r/hour';
# ..oops! and this one does not work, yet ;-) sorry..
enable 'Throttle::Lite', limits => '100rph';

If this option is omitted, there are some defaults will be assigned. For maximum requests default value will be 199 and measuring units - req/hour. So this option must be set to desired value to have get correct throttling policy.

When a client exceeds rate limit, middleware returns a 429 Too Many Requests response with an associated Rate Limit Exceeded message in the response body.


Storage backend and its configuration options. Accepted values either string or list reference contains backend name and options as hash reference. Backend name can be pointed in short module name or in fully qualified module name. If module name does not belongs to Plack::Middleware::Throttle::Lite::Backend namespace it can be pointed by adding + (plus) sign before name.

# means Plack::Middleware::Throttle::Lite::Backend::Simple
enable 'Throttle::Lite', backend => 'Simple';

# means Plack::Middleware::Throttle::Lite::Backend::OwnStore
enable 'Throttle::Lite', backend => 'OwnStore';

# means My::Own::Throttle::Backend
enable 'Throttle::Lite', backend => '+My::Own::Throttle::Backend';

If backend name passed as list reference, the first element will be handle as backend module and the second as options passed to constructor during initialization.

# treat as Plack::Middleware::Throttle::Lite::Backend::Anything
enable 'Throttle::Lite',
    backend => [
        'Anything' => { server => '', port => 23250 }
# My::Own::Any
enable 'Throttle::Lite',
    backend => [
        '+My::Own::Any' => { server => '', port => 23250 }

If no backend specified then will be used in-memory backend Plack::Middleware::Throttle::Lite::Backend::Simple shipped with this distribution.


URL pattern to match request to throttle. Accepted values are scalar (e.g. /api), regex (qr{^/(host|item)/search}) or a list reference with scalar/regex elements. Below some examples:

# passing routes as scalar..
enable 'Throttle::Lite',
    routes => '/api';

# regex
enable 'Throttle::Lite',
    routes => qr{^/api/(user|host)};

# ..shaken, not stirred
enable 'Throttle::Lite',
    routes => [

All requests will be passed through (won't be handled by this middleware) if no routes given.


Blacklist is aimed to restrict some bad guys to have get access to application which uses this middleware. IP addresses can be passed either as string or as list of strings in a different forms. It might be simple IP address (quad-dotted notation), IP block in CIDR notation or range of IP addresses (delimited by a hyphen).

# passing IP address as string..
enable 'Throttle::Lite',
    blacklist => '';

# CIDR block
enable 'Throttle::Lite',
    blacklist => '';

# a range of IPs
enable 'Throttle::Lite',
    blacklist => '';

# ..stirred, not shaken
enable 'Throttle::Lite',
    blacklist => [

More details in Net::CIDR::Lite.

When a client's IP address is in the blacklist, middleware by default returns a 403 Forbidden response with an associated IP Address Blacklisted message in the response body.

Warning! Blacklist has higher priority than "whitelist".


Whitelist is aimed to grant some good guys to have get access to application which uses this middleware. Whitelisted client's IP address will receive unlimited access to application. In generated header which is pointed to maximum requests for whitelisted guy will be unlimited instead of actually given maximum requests.

Rules of configuration IP addresses for whitelist the same as for the "blacklist".

Warning! Whitelist has lower priority than "blacklist". Be sure that IP does not exists in blacklist by adding IP to whitelist.


This one allows to change prefix in output headers. A value should be passed as string. It will be normalized before using. Any alpha-numeric characters and spaces are allowed. The parts of passed string will be capitalized and joined with a hyphen.

header_prefix => ' tom di*ck harry  ' # goes to X-Tom-Dick-Harry-Limit, X-Tom-Dick-Harry-Used, ..
header_prefix => 'lucky 13'           # ..X-Lucky-13-Limit, X-Lucky-13-Used, ..
header_prefix => ''                   # ..X-Throttle-Lite-Limit, X-Throttle-Lite-Used, ..
header_prefix => '$ @ # & * /| ; '    # also would be X-Throttle-Lite-Limit, X-Throttle-Lite-Used, ..
header_prefix => 'a-b-c'              # ..X-Abc-Limit, X-Abc-Used, ..
header_prefix => '2.71828182846'      # ..X-271828182846-Limit, X-271828182846-Used, ..

This option is not required. Default value is Throttle-Lite. Header prefix will be set to the default value in cases of specified value won't pass checks. This option does not affect the Retry-After response header.



See Plack::Middleware


See Plack::Middleware


Adds extra headers to each throttled response such as maximum requests (X-Throttle-Lite-Limit), measuring units (X-Throttle-Lite-Units), requests done (X-Throttle-Lite-Used). If maximum requests is equal to requests done X-Throttle-Lite-Expire and Retry-After headers will be injected.

Headers (except of Retry-After) might be customized by using configuration option "header_prefix".


Rejects incoming request with specific code and reason. It might be either request from blacklisted IP or throttled one.


Checks if requested PATH_INFO matches the routes list and should be throttled.


Checks if the requester's IP exists in the blacklist.


Checks if the requester's IP exists in the whitelist.


Checks if client is not exceeded maximum allowed requests.


Builds unique (as possible) indentificator of the client based on its IP address and name.


  • Moritz Lenz (moritz)


Please report any bugs or feature requests through the web interface at




RFC 2616

Hypertext Transfer Protocol - HTTP/1.1. Section 14.37: Retry-After

RFC 6585

Additional HTTP Status Codes. Section 4: 429 Too Many Requests


Anton Gerasimov


This software is copyright (c) 2013 by Anton Gerasimov.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.