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NginxHttpMemcModule

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Edit section: Name Name

memc-nginx-module - An extended version of the standard memcached module that supports set, add, delete, and many more memcached commands.

This module is not distributed with the Nginx source. See the installation instructions.

Edit section: Version Version

This document describes memc-nginx-module v0.09 released on June 29, 2010.

Edit section: Synopsis Synopsis 

    # GET /foo?key=dog
    #
    # POST /foo?key=cat
    # Cat's value...
    #
    # PUT /foo?key=bird
    # Bird's value...
    #
    # DELETE /foo?key=Tiger
    location /foo {
        set $memc_key $arg_key;
 
        # $memc_cmd defaults to get for GET,
        #   add for POST, set for PUT, and
        #   delete for the DELETE request method.
 
        memc_pass 127.0.0.1:11211;
    }

    # GET /bar?cmd=get&key=cat
    #
    # POST /bar?cmd=set&key=dog
    # My value for the "dog" key...
    #
    # DELETE /bar?cmd=delete&key=dog
    # GET /bar?cmd=delete&key=dog
    location /bar {
        set $memc_cmd $arg_cmd;
        set $memc_key $arg_key;
        set $memc_flags $arg_flags; # defaults to 0
        set $memc_exptime $arg_exptime; # defaults to 0
 
        memc_pass 127.0.0.1:11211;
    }

    # GET /bar?cmd=get&key=cat
    # GET /bar?cmd=set&key=dog&val=animal&flags=1234&exptime=2
    # GET /bar?cmd=delete&key=dog
    # GET /bar?cmd=flush_all
    location /bar {
        set $memc_cmd $arg_cmd;
        set $memc_key $arg_key;
        set $memc_value $arg_val;
        set $memc_flags $arg_flags; # defaults to 0
        set $memc_exptime $arg_exptime; # defaults to 0
 
        memc_cmds_allowed get set add delete flush_all;
 
        memc_pass 127.0.0.1:11211;
    }

  http {
    ...
    upstream backend {
       server 127.0.0.1:11984;
       server 127.0.0.1:11985;
    }
    server {
        location /stats {
            set $memc_cmd stats;
            memc_pass backend;
        }
        ...
    }
  }
  ...

    # read the memcached flags into the Last-Modified header
    # to respond 304 to conditional GET
    location /memc {
        set $memc_key $arg_key;
 
        memc_pass 127.0.0.1:11984;
 
        memc_flags_to_last_modified on;
    }

Edit section: Description Description

This module extends the standard memcached module to support almost the whole memcached TCP protocol.

It allows you to define a custom REST interface to your memcached servers or access memcached in a very efficient way from within the nginx server by means of subrequests or independent fake requests.

This module is not supposed to be merged into the Nginx core because I've used Ragel to generate the memcached response parsers (in C) for joy :)

Edit section: Keep-alive connections to memcached servers Keep-alive connections to memcached servers

You need Maxim Dounin's ngx_upstream_keepalive module together with this module for keep-alive TCP connections to your backend memcached servers.

Here's a sample configuration: 

  http {
    upstream backend {
      server 127.0.0.1:11211;
 
      # a pool with at most 1024 connections
      # and do not distinguish the servers:
      keepalive 1024 single;
    }
 
    server {
        ...
        location /memc {
            set $memc_cmd get;
            set $memc_key $arg_key;
            memc_pass backend;
        }
    }
  }

Edit section: How it works How it works

It implements the memcached TCP protocol all by itself, based upon the upstream mechansim. Everything involving I/O is non-blocking.

The module itself does not keep TCP connections to the upstream memcached servers across requests, just like other upstream modules. For a working solution, see section Keep-alive connections to memcached servers.

Edit section: Memcached commands supported Memcached commands supported

The memcached storage commands set, add, replace, prepend, and append uses the $memc_key as the key, $memc_exptime as the expiration time (or delay) (defaults to 0), $memc_flags as the flags (defaults to 0), to build the corresponding memcached queries.

If $memc_value is not defined at all, then the request body will be used as the value of the $memc_value except for the incr and decr commands. Note that if $memc_value is defined as an empty string (""), that empty string will still be used as the value as is.

The following memcached commands have been implemented and tested (with their parameters marked by corresponding nginx variables defined by this module):

Edit section: get $memc_key get $memc_key

Retrieves the value using a key. 

  location /foo {
      set $memc_cmd 'get';
      set $memc_key 'my_key';
 
      memc_pass 127.0.0.1:11211;
 
      add_header X-Memc-Flags $memc_flags;
  }

Returns 200 OK with the value put into the response body if the key is found, or 404 Not Found otherwise. The flags number will be set into the $memc_flags variable so it's often desired to put that info into the response headers by means of the standard add_header directive.

It returns 502 for ERROR, CLIENT_ERROR, or SERVER_ERROR.

Edit section: set $memc_key $memc_flags $memc_exptime $memc_value set $memc_key $memc_flags $memc_exptime $memc_value

To use the request body as the memcached value, just avoid setting the $memc_value variable: 

  # POST /foo
  # my value...
  location /foo {
      set $memc_cmd 'set';
      set $memc_key 'my_key';
      set $memc_flags 12345;
      set $memc_exptime 24;
 
      memc_pass 127.0.0.1:11211;
  }

Or let the $memc_value hold the value: 

  location /foo {
      set $memc_cmd 'set';
      set $memc_key 'my_key';
      set $memc_flags 12345;
      set $memc_exptime 24;
      set $memc_value 'my_value';
 
      memc_pass 127.0.0.1:11211;
  }

Returns 201 Created if the upstream memcached server replies STORED, 200 for NOT_STORED, 404 for NOT_FOUND, 502 for ERROR, CLIENT_ERROR, or SERVER_ERROR.

The original memcached responses are returned as the response body except for 404 NOT FOUND.

Edit section: add $memc_key $memc_flags $memc_exptime $memc_value add $memc_key $memc_flags $memc_exptime $memc_value

Similar to the set command.

Edit section: replace $memc_key $memc_flags $memc_exptime $memc_value replace $memc_key $memc_flags $memc_exptime $memc_value

Similar to the set command.

Edit section: append $memc_key $memc_flags $memc_exptime $memc_value append $memc_key $memc_flags $memc_exptime $memc_value

Similar to the set command.

Note that at least memcached version 1.2.2 does not support the "append" and "prepend" commands. At least 1.2.4 and later versions seem to supports these two commands.

Edit section: prepend $memc_key $memc_flags $memc_exptime $memc_value prepend $memc_key $memc_flags $memc_exptime $memc_value

Similar to the append command.

Edit section: delete $memc_key delete $memc_key

Deletes the memcached entry using a key. 

  location /foo
      set $memc_cmd delete;
      set $memc_key my_key;
 
      memc_pass 127.0.0.1:11211;
  }

Returns 200 OK if deleted successfully, 404 Not Found for NOT_FOUND, or 502 for ERROR, CLIENT_ERROR, or SERVER_ERROR.

The original memcached responses are returned as the response body except for 404 NOT FOUND.

Edit section: delete $memc_key $memc_exptime delete $memc_key $memc_exptime

Similar to the delete $memc_key command except it accepts an optional expiration time specified by the $memc_exptime variable.

This command is no longer available in the latest memcached version 1.4.4.

Edit section: incr $memc_key $memc_value incr $memc_key $memc_value

Increments the existing value of $memc_key by the amount specified by $memc_value: 

  location /foo {
      set $memc_key my_key;
      set $memc_value 2;
      memc_pass 127.0.0.1:11211;
  }

In the preceding example, every time we access /foo will cause the value of my_key increments by 2.

Returns 200 OK with the new value associated with that key as the response body if successful, or 404 Not Found if the key is not found.

It returns 502 for ERROR, CLIENT_ERROR, or SERVER_ERROR.

Edit section: decr $memc_key $memc_value decr $memc_key $memc_value

Similar to incr $memc_key $memc_value.

Edit section: flush_all flush_all

Mark all the keys on the memcached server as expired: 

  location /foo {
      set $memc_cmd flush_all;
      memc_pass 127.0.0.1:11211;
  }

Edit section: flush_all $memc_exptime flush_all $memc_exptime

Just like flush_all but also accepts an expiration time specified by the $memc_exptime variable.

Edit section: stats stats

Causes the memcached server to output general-purpose statistics and settings 

  location /foo {
      set $memc_cmd stats;
      memc_pass 127.0.0.1:11211;
  }

Returns 200 OK if the request succeeds, or 502 for ERROR, CLIENT_ERROR, or SERVER_ERROR.

The raw stats command output from the upstream memcached server will be put into the response body.

Edit section: version version

Queries the memcached server's version number: 

  location /foo {
      set $memc_cmd version;
      memc_pass 127.0.0.1:11211;
  }

Returns 200 OK if the request succeeds, or 502 for ERROR, CLIENT_ERROR, or SERVER_ERROR.

The raw version command output from the upstream memcached server will be put into the response body.

Edit section: Directives Directives

All the standard memcached module directives in nginx 0.8.28 are directly inherited, with the memcached_ prefixes replaced by memc_. For example, the memcached_pass directive is spelled memc_pass. Consult the NginxHttpMemcachedModule documentation for more details.

Here we only document the most important two directives (the latter is a new directive introduced by this module).

Edit section: memc_pass memc_pass

syntax: memc_pass <memcached server IP address>:<memcached server port>

syntax (2): memc_pass <memcached server hostname>:<memcached server port>

syntax (3): memc_pass <upstream_backend_name>

default: none

context: http, server, location, if

Specify the memcached server backend.

Edit section: memc_cmds_allowed memc_cmds_allowed

syntax: memc_cmds_allowed <cmd>...

default: none

context: http, server, location, if

Lists memcached commands that are allowed to access. By default, all the memcached commands supported by this module are accessible. An example is 

   location /foo {
       set $memc_cmd $arg_cmd;
       set $memc_key $arg_key;
       set $memc_value $arg_val;
 
       memc_pass 127.0.0.1:11211;
 
       memc_cmds_allowed get;
   }

Edit section: memc_flags_to_last_modified memc_flags_to_last_modified

syntax: memc_flags_to_last_modified on|off

default: off

context: http, server, location, if

Read the memcached flags as epoch seconds and set it as the value of the Last-Modified header. For conditional GET, it will signal nginx to return 304 Not Modified response to save bandwidth.

Edit section: Installation Installation

Grab the nginx source code from nginx.net, for example, the version 0.8.29 (see nginx compatibility), and then build the source with this module: 

    $ wget 'http://sysoev.ru/nginx/nginx-0.8.29.tar.gz'
    $ tar -xzvf nginx-0.8.29.tar.gz
    $ cd nginx-0.8.29/
 
    # Here we assume you would install you nginx under /opt/nginx/.
    $ ./configure --prefix=/opt/nginx \
        --add-module=/path/to/memc-nginx-module
 
    $ make -j2
    $ make install

Download the latest version of the release tarball of this module from memc-nginx-module file list.

Edit section: For Developers For Developers

The memached response parsers were generated by Ragel. If you want to regenerate the parser's C file, i.e., src/ngx_http_memc_response.c, use the following command from the root of the memc module's source tree: 

    $ ragel -G2 src/ngx_http_memc_response.rl

Edit section: Compatibility Compatibility

The following versions of Nginx should work with this module:

  • 0.8.x (last tested version is 0.8.38)
  • 0.7.x >= 0.7.46 (last tested version is 0.7.65)

It's worth mentioning that some 0.7.x versions older than 0.7.46 might also work, but I can't easily test them because the test suite makes extensive use of the echo module's echo_location directive, which requires at least nginx 0.7.46 :)

Earlier versions of Nginx like 0.6.x and 0.5.x will not work.

If you find that any particular version of Nginx above 0.7.46 does not work with this module, please consider reporting a bug.

Edit section: Report Bugs Report Bugs

Although a lot of effort has been put into testing and code tuning, there must be some serious bugs lurking somewhere in this module. So whenever you are bitten by any quirks, please don't hesitate to

  1. send a bug report or even patches to <agentzh@gmail.com>,
  2. or create a ticket on the issue tracking interface provided by GitHub.

Edit section: Source Repository Source Repository

Available on github at agentzh/memc-nginx-module.

Edit section: ChangeLog ChangeLog

Edit section: v0.09 v0.09

  • now we copy out r->request_body->bufs for our memcached request to avoid modifying the original request body. Thanks Matthieu Tourne.

Edit section: v0.08 v0.08

  • now the memc commands other than get work with subrequests in memory. Thanks Yao Xinming for reporting it. Using storage memcached commands in ngx_eval module's eval blocks no longer hang the server.

Edit section: v0.07 v0.07

  • applied the patch from nginx 0.8.35 that fixed a bug that ngx_eval may issue the incorrect error message "memcached sent invalid trailer".

Edit section: v0.06 v0.06

Edit section: v0.05 v0.05

  • removed the memc_bind directive since it won't compile with nginx 0.8.31.

Edit section: v0.04 v0.04

  • to ensure Maxim's ngx_http_upstream_keepalive module caches our connections even if u->headers_in->status is 201 (Created).
  • updated docs to make it clear that this module can work with "upstream" multi-server backends. thanks Bernd Dorn for reporting it.

Edit section: v0.03 v0.03

  • fixed a connection leak caused by an extra r->main->count++ operation: we should NOT do r->main->count++ after calling the ngx_http_read_client_request_body function in our content handler.

Edit section: v0.02 v0.02

  • applied the (minor) optimization trick suggested by Marcus Clyne: creating our variables and save their indexes at post-config phase when the memc_pass directive is actually used in the config file.

Edit section: v0.01 v0.01

  • initial release.

Edit section: Test Suite Test Suite

This module comes with a Perl-driven test suite. The test cases are declarative too. Thanks to the Test::Base module in the Perl world.

To run it on your side: 

    $ cd test
    $ PATH=/path/to/your/nginx-with-memc-module:$PATH prove -r t

You need to terminate any Nginx processes before running the test suite if you have changed the Nginx server binary.

Either LWP::UserAgent or IO::Socket is used by the test scaffold.

Because a single nginx server (by default, localhost:1984) is used across all the test scripts (.t files), it's meaningless to run the test suite in parallel by specifying -jN when invoking the prove utility.

You should also keep a memcached server listening on the 11984 port at localhost before running the test suite.

Some parts of the test suite requires modules rewrite and echo to be enabled as well when building Nginx.

Edit section: TODO TODO

  • add support for the memcached commands cas, gets and stats $memc_value.
  • add support for the noreply option.

Edit section: Getting involved Getting involved

You'll be very welcomed to submit patches to the author or just ask for a commit bit to the source repository on GitHub.

Edit section: Author Author

agentzh (章亦春) <agentzh@gmail.com>

This wiki page is also maintained by the author himself, and everybody is encouraged to improve this page as well.

Edit section: Copyright & License Copyright & License

The code base is borrowed directly from the standard memcached module in the Nginx 0.8.28 core. This part of code is copyrighted by Igor Sysoev.

Copyright (c) 2009, Taobao Inc., Alibaba Group ( http://www.taobao.com ).

Copyright (c) 2009, agentzh <agentzh@gmail.com>.

This module is licensed under the terms of the BSD license.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
  • Neither the name of the Taobao Inc. nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Edit section: See Also See Also

Retrieved from "http://wiki.nginx.org/NginxHttpMemcModule"