/ 
Memcached-libmemcached-0.1309
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/ Memcached::libmemcached

NAME

Memcached::libmemcached - Thin fast full interface to the libmemcached client API

VERSION

Version 0.1309

SYNOPSIS

use Memcached::libmemcached;

$memc = memcached_create();
memcached_server_add($memc, "localhost");

memcached_set($memc, $key, $value);

$value = memcached_get($memc, $key);

DESCRIPTION

Memcached::libmemcached is a very thin, highly efficient, wrapper around the libmemcached library.

It gives full access to the rich functionality offered by libmemcached. libmemcached is fast, light on memory usage, thread safe, and provide full access to server side methods.

- Synchronous and Asynchronous support.
- TCP and Unix Socket protocols.
- A half dozen or so different hash algorithms.
- Implementations of the new cas, replace, and append operators.
- Man pages written up on entire API.
- Implements both modulo and consistent hashing solutions.

(At the moment Memcached::libmemcached is very new and not all the functions in libmemcached have perl interfaces yet. We're focussing on the core infrastructure and the most common functions. It's usually trivial to add functions - just a few lines in libmemcached.xs, a few lines of documentation, and a few lines of testing. Volunteers welcome!)

The libmemcached library documentation (which is bundled with this module) serves as the primary reference for the functionality.

This documentation provides summary of the functions, along with any issues specific to this perl interface, and references to the documentation for the corresponding functions in the underlying library.

For more information on libmemcached, see http://tangent.org/552/libmemcached.html

CONVENTIONS

Terminology

The term "memcache" is used to refer to the memcached_st structure at the heart of the libmemcached library. We'll use $memc to represent this structure in perl code.

Function Arguments

There are no length arguments. Wherever the libmemcached documentation shows a length argument (input or output) the corresponding argument doesn't exist in the Perl API, because it's not needed.

For pointer arguments, undef is mapped to null on input and null is mapped to undef on output.

Return Status

Most of the methods return an integer status value. This is shown as memcached_return in the libmemcached documentation.

In the perl interface this value is a dualvar, like $!, that has both integer and string components set to different values. In a numeric context the value is the integer status code. In a string content the value is the corresponding error string.

All the functions documented below return a memcached_return unless otherwise indicated.

EXPORTS

All the public functions in libmemcached are available for import.

All the public constants and enums in libmemcached are available for import.

Exporter tags are defined for each enum. This allows you to import groups of constants easily. For example, to import all the contants for memcached_behavior_set() and memcached_behavior_get(), you can use:

use Memcached::libmemcached qw(:memcached_behavior).

FUNCTIONS

Functions For Managing Memcaches

memcached_create

my $memc = memcached_create();

Creates and returns a 'memcache' that represents the state of communication with a set of memcached servers. See Memcached::libmemcached::memcached_create.

memcached_clone

my $memc = memcached_clone(undef, undef);

XXX Not currently recommended for use. See Memcached::libmemcached::memcached_create.

memcached_free

memcached_free($memc); # void

Frees the memory associated with $memc. Your application will leak memory unless you call this. After calling it $memc must not be used. See Memcached::libmemcached::memcached_create.

memcached_server_push

memcached_server_push($memc, $server_list_object);

Adds a list of servers to the libmemcached object. See Memcached::libmemcached::memcached_servers.

memcached_server_count

$server_count= memcached_server_count($memc);

Returns a count of the number of servers associated with $memc. See Memcached::libmemcached::memcached_servers.

memcached_server_list

$server_list= memcached_server_list($memc);

Returns the server list structure associated with $memc. XXX Not currently recommended for use. See Memcached::libmemcached::memcached_servers.

memcached_server_add

memcached_server_add($memc, $hostname, $port);

Adds details of a single memcached server (accessed via TCP/IP) to $memc. See Memcached::libmemcached::memcached_servers.

memcached_server_add_unix_socket

memcached_server_add_unix_socket($memc, $socket_path);

Adds details of a single memcached server (accessed via a UNIX domain socket) to $memc. See Memcached::libmemcached::memcached_servers.

memcached_behavior_set

memcached_behavior_set($memc, $option_key, $option_value);

Changes the value of a particular option. See Memcached::libmemcached::memcached_behavior.

memcached_behavior_get

memcached_behavior_get($memc, $option_key);

Get the value of a particular option. See Memcached::libmemcached::memcached_behavior.

memcached_verbosity

memcached_verbosity($memc, $verbosity)

Modifies the "verbosity" of the associated memcached servers. See Memcached::libmemcached::memcached_verbosity.

memcached_flush

memcached_flush($memc, $expiration);

Wipe clean the contents of associated memcached servers. See Memcached::libmemcached::memcached_flush.

memcached_quit

memcached_quit($memc);

Disconnect from all currently connected servers and reset state. Not normally called explicitly. See Memcached::libmemcached::memcached_quit.

memcached_errstr

$errstr = memcached_errstr($memc);

Returns the error message and code from the most recent call to any libmemcached function that returns a memcached_return, which most do.

The return value is a dualvar, like $!, which means it has separate numeric and string values. The numeric value is the memcached_return integer value, and the string value is the corresponding error message what memcached_strerror() would return.

As a special case, if the memcached_return is MEMCACHED_ERRNO, indicating a system call error, then the string returned by strerror() is appended.

Functions for Setting Values in memcached

See Memcached::libmemcached::memcached_set.

memcached_set

memcached_set($memc, $key, $value);
memcached_set($memc, $key, $value, $expiration, $flags);

Set $value as the value of $key. $expiration and $flags are both optional and default to 0.

memcached_append

memcached_append($memc, $key, $value);
memcached_append($memc, $key, $value, $expiration, $flags);

Append $value to the value of $key. $key must already exist. $expiration and $flags are both optional and default to 0.

memcached_prepend

memcached_prepend($memc, $key, $value)
memcached_prepend($memc, $key, $value, $expiration, $flags)

Prepend $value to the value of $key. $key must already exist. $expiration and $flags are both optional and default to 0.

memcached_replace

memcached_replace($memc, $key, $value)
memcached_replace($memc, $key, $value, $expiration, $flags)

Replace with $value the existing value of the value stored with $key. $key must already exist. $expiration and $flags are both optional and default to 0.

memcached_cas

memcached_cas($memc, $key, $value, $expiration, $flags, $cas)

Overwrites data in the server stored as $key as long as $cas is still the same in the server. Cas is still buggy in memached. Turning on support for it in libmemcached is optional. Please see memcached_behavior_set() for information on how to do this.

XXX and the memcached_result_cas() function isn't implemented yet so you can't get the $cas to use.

Functions for Fetching Values from memcached

See Memcached::libmemcached::memcached_get.

memcached_get

$value = memcached_get($memc, $key);
$value = memcached_get($memc, $key, $flags, $rc);

Get and return the value of $key. Returns undef on error.

Also updates $flags to the value of the flags stored with $value, and updates $rc with the return code.

memcached_mget

memcached_mget($memc, \@keys);
memcached_mget($memc, \%keys);

Triggers the asynchronous fetching of multiple keys at once. For multiple key operations it is always faster to use this function. You must then use memcached_fetch() or memcached_fetch_result() to retrieve any keys found. No error is given on keys that are not found.

Instead of this function, you'd normally use "memcached_mget_into_hashref".

memcached_mget_into_hashref

memcached_mget_into_hashref($memc, $keys_ref, \%dest_hash);

Combines memcached_mget() and a memcached_fetch() loop into a single highly efficient call.

Fetched values are stored in \%dest_hash, updating existing values or adding new ones as appropriate.

memcached_fetch

$value = memcached_fetch($memc, $key);
$value = memcached_fetch($memc, $key, $flag, $rc);

Fetch the next $key and $value pair returned in response to a memcached_mget() call. Returns undef if there are no more values.

If $flag is given then it will be updated to whatever flags were stored with the value. If $rc is given then it will be updated to the return code.

Functions for Incrementing and Decrementing Values from memcached

memcached_increment

$return = memcached_increment( $key, $offset, $new_value_out );

Increments the value associated with $key by $offset and returns the new value in $new_value_out. See also Memcached::libmemcached::memcached_auto.

memcached_decrement

memcached_decrement( $key, $offset, $new_value_out );

Decrements the value associated with $key by $offset and returns the new value in $new_value_out. See also Memcached::libmemcached::memcached_auto.

Functions for Managing Results from memcached

XXX http://hg.tangent.org/libmemcached/file/4001ba159d62/docs/memcached_result_st.pod

Functions for Deleting Values from memcached

See Memcached::libmemcached::memcached_delete.

memcached_delete

memcached_delete($memc, $key);
memcached_delete($memc, $key, $expiration);

Delete $key. If $expiration is greater than zero then the key is deleted by memcached after that many seconds.

Functions for Accessing Statistics from memcached

See Memcached::libmemcached::memcached_stats.

Miscellaneous Functions

memcached_strerror

$string = memcached_strerror($memc, $return_code)

memcached_strerror() takes a memcached_return value and returns a string describing the error. The string should be treated as read-only (it may be so in future versions). See also Memcached::libmemcached::memcached_strerror.

This function is rarely needed in the Perl interface because the return code is a dualvar that already contains the error string.

Unsupported Functions

memcached_cas

(stats)

(disconnect/quit)

memcached_flush

memcached_replace

AUTHOR

Tim Bunce, <Tim.Bunce@pobox.com> with help from Patrick Galbraith.

PORTABILITY

See Slaven Rezic's excellent CPAN Testers Matrix at http://bbbike.radzeit.de/~slaven/cpantestersmatrix.cgi?dist=Memcached-libmemcached

Along with Dave Cantrell's excellent CPAN Dependency tracker at http://cpandeps.cantrell.org.uk/?module=Memcached%3A%3Alibmemcached&perl=any+version&os=any+OS

BUGS

Please report any bugs or feature requests to bug-memcached-libmemcached@rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Memcached-libmemcached. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

ACKNOWLEDGEMENTS

COPYRIGHT & LICENSE

Copyright 2008 Tim Bunce, All Rights Reserved.

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