| Author: | Aaron Stone |
|---|---|
| Date: | 2012-01-25 |
| Version: | 0.1 |
| Manual section: | 3 |
import memcached;
Varnish vmod using libmemcached to access memcached servers
Implements the basic memcached operations of get, set, incr, decr.
- Prototype
servers(STRING servers)
- Return value
- NONE
- Description
Set the list of memcached servers available for requests handled by this VCL. The syntax is a whitespace or comma separated list of one or more "hostname[:port]" items.
If you have libmemcached > 0.49 you can use the new syntax, specified in http://docs.libmemcached.org/libmemcached_configuration.html#description , which uses "--SERVER=ip:port" to specify a server. Warning: There is no error checking for this string, if it's wrong you won't get an error but memcached won't work as well. Check first if the connection string is valid.
- Example
memcached.servers("localhost,anotherhost:12345");memcached.servers("--SERVER=localhost --SERVER=anotherhost:12345");// with consistent hashing enabled memcached.servers("--SERVER=localhost --SERVER=anotherhost:12345 --DISTRIBUTION=consistent");// with consistent hashing enabled and namespace memcached.servers({"--SERVER=web1.gloople:11211 --SERVER=web2.gloople:11211 --DISTRIBUTION=consistent --NAMESPACE="memc.sess.key.""});
- Prototype
behavior_set(STRING memcached_behavior_flag, STRING memcached_behavior_value)
- Return value
- NONE
- Description
- Change the value for particular options of the memcached client. This is not an exhaustive implementation and not all flags/values are available. See memcached_behavior(3) for more detail on behaviors. Only that shown in the example below is available.
- Example
memcached.behavior_set("MEMCACHED_BEHAVIOR_DISTRIBUTION", "MEMCACHED_DISTRIBUTION_CONSISTENT");
- Prototype
STRING get(STRING key)
- Return value
- STRING V
- Description
- Retrieve key from memcached, returns string value.
- Example
memcached.servers("localhost"); set resp.http.hello = memcached.get("your_memcached_key");
- Prototype
set(STRING key, STRING value, INT expiration, INT flags)
- Return value
- NONE
- Description
- Set key to value, with an expiration time and flags.
- Example
memcached.servers("localhost"); memcached.set("your_memcached_key", "Hello, World", 100, 0); set resp.http.hello = memcached.get("your_memcached_key");
- Prototype
INT incr(STRING key, INT offset)
- Return value
- INT
- Description
- Increment key by offset, unless key is not set. Return value is 0 if not set.
- Example
memcached.servers("localhost"); memcached.set("your_counter", "1", 100, 0); memcached.incr("your_counter", 10); set resp.http.count = memcached.incr("your_counter", 1); // Header value is Count: 12
- Prototype
INT decr(STRING key, INT offset)
- Return value
- INT
- Description
- Decrement key by offset, unless key is not set. Return value is 0 if not set.
- Example
memcached.servers("localhost"); memcached.set("your_counter", "10", 100, 0); memcached.decr("your_counter", 8); set resp.http.count = memcached.decr("your_counter", 1); // Header value is Count: 1
If you received this packge without a pre-generated configure script, you must have the GNU Autotools installed, and can then run the 'autogen.sh' script. If you received this package with a configure script, skip to the second command-line under Usage to configure.
Usage:
# Generate configure script ./autogen.sh # Execute configure script ./configure VARNISHSRC=DIR [VMODDIR=DIR] [PKG_CONFIG=PATH] [LIBMEMCACHED_CFLAGS=COMPILE] [LIBMEMCACHED_LIBS=LINK]
VARNISHSRC is the directory of the Varnish source tree for which to compile your vmod. Both the VARNISHSRC and VARNISHSRC/include will be added to the include search paths for your module.
Optionally you can also set the vmod install directory by adding VMODDIR=DIR (defaults to the pkg-config discovered directory from your Varnish installation).
The configure script uses pkg-config to find the libmemcached library. You may specify the pkg-config binary by setting the PKG_CONFIG option. If you do not wish to use pkg-config, you may set LIBMEMCACHED_CFLAGS and LIBMEMCACHED_LIBS as necessary to compile and link with libmemcached.
Make targets:
- make - builds the vmod
- make install - installs your vmod in VMODDIR
- make check - runs the unit tests in
src/tests/*.vtc
The first revision of this document sketches out a rough plan for approaching a general purpose memcached client module for Varnish. More features are sure to be added as we go along.
This manual page is based on the template man page from libvmod-example.
- Copyright (c) 2012 Aaron Stone
- See COPYING for copyright holders and descriptions.
- See LICENSE for full copyright terms.