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mod_ratelimit works by splitting data in "chunks" to send to the client, sleeping a predefined amount of time between them (200ms). So for example, a rate-limit 40 value would correspond to a chunk size of 8192 bytes, flushed to the client every 200ms. The idea works fine when httpd directly serves the content, since the filter will be called once with a single bucket brigade. In the context of a proxied content though the filter is likely to be called multiple times, with a bucket brigade size that corresponds to the maximum allowed buffer size. If this value is lower or higher than the chunk size, the filter will not properly rate limit the data going to the client. This patch solves the problem with two fix: 1) do_sleep is now stored in the ctx context struct, so if the filter is invoked multiple times it will still sleep when needed. For example, say that the chunk_size is 8192 and the bucket brigate len is 10240: the filter will flush 8192 bytes on the first invocation, sleep 200ms, flush the remaining bytes and then finish. The next invocation will do the same, clearly not leading to the correct "sleeping pattern". 2) The example above highlights also another issue: mod_ratelimit should flush only chunk_size bytes at the time (I am now excluding the burst calculation from the picture), and buffer between invocations unless the brigade contains EOS. The change has been tested with various scenarios and it looks working as expected, but of course more feedback/testing is welcome. The original patch was written by me and then Yann refactored the code to be more precise and efficient, basically transforming an axe in a wonderful Japanese katana sword, so credits to him for this work. PR: 62362 git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1833875 13f79535-47bb-0310-9956-ffa450edef68
The directory structure for this level is as follows: aaa/ This directory contains modules dealing with authorization and authentication. arch/ cache/ This directory houses modules that implement file and data caching capability. database/ The apache DBD framework manages connections to SQL backends efficiently. cluster/ Modules for working with multiple servers. dav/ This directory houses modules that implement WebDAV functionality. echo/ examples/ This directory contains some sample code that should help you on your way to develop your own Apache modules. experimental/ In this directory we've placed some modules which we think provide some pretty interesting functionality, but which are still in the early stages of development and could evolve radically in the future. This code isn't supported officially. filters/ This directory houses modules that perform general inline data filtering. generators/ This directory houses modules that perform data generation functions. http/ This directory houses modules that basic HTTP protocol implementation. http2/ This directory houses modules that provide HTTP/2 protocol implementation. loggers/ This directory houses modules that handle logging functions. mappers/ This directory houses modules that handle URL mapping and rewriting. metadata/ This directory houses modules that deal with Header metadata. proxy/ This houses the code for the proxy module for Apache. ssl/ This directory houses code for OpenSSL functionality. test/ This directory houses modules which test various components of Apache. You should not compile these into a production server.