package Memcached::libmemcached; use warnings; use strict; =head1 NAME Memcached::libmemcached - Thin fast full interface to the libmemcached client API =head1 VERSION Version 0.4202 (with libmemcached-0.42 embedded) =cut our $VERSION = '0.4202'; use Carp; use base qw(Exporter); use Memcached::libmemcached::API; our @EXPORT_OK = ( libmemcached_functions(), libmemcached_constants(), ); our %EXPORT_TAGS = libmemcached_tags(); require XSLoader; XSLoader::load('Memcached::libmemcached', $VERSION); =head1 SYNOPSIS use Memcached::libmemcached; $memc = memcached_create(); memcached_server_add($memc, "localhost"); memcached_set($memc, $key, $value); $value = memcached_get($memc, $key); =head1 DESCRIPTION Memcached::libmemcached is a very thin, highly efficient, wrapper around the libmemcached library. It's implemented almost entirely in C. 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 L =head1 CONVENTIONS =head2 Terminology The term "memcache" is used to refer to the C structure at the heart of the libmemcached library. We'll use $memc to represent this structure in perl code. (The libmemcached library documentation uses C.) =head2 Traditional and Object-Oriented There are two ways to use the functionality offered by this module: B<*> You can import the functions you want to use and call them explicitly. B<*> Or, you can use $memc as an object and call most of the functions as methods. You can do that for any function that takes a $memc (ptr) as its first argument, which is almost all of them. Since the primary focus of this module is to be a thin wrapper around libmemcached, the bulk of this documentation describes the traditional functional interface. The object-oriented interface is mainly targeted at modules wishing to subclass Memcached::libmemcached, such as Cache::Memcached::libmemcached. For more information see L. =head2 Function Names and Arguments The function names in the libmemcached library have exactly the same names in Memcached::libmemcached. The function arguments are also the same as the libmemcached library and documentation, with two exceptions: B<*> There are no I 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. B<*> Some arguments are optional. Many libmemcached function arguments are I: the argument is the address of the value that the function will modify. For these the perl function will modify the argument directly if it can. For example, in this call: $value = memcached_get($memc, $key, $flags, $rc); The $flags and $rc arguments are output values that are modified by the memcached_get() function. See the L section for the fine detail of how each argument type is handled. =head2 Return Status Most of the functions return an integer status value. This is shown as C in the libmemcached documentation. In the perl interface this value is I returned directly. Instead a simple boolean is returned: true for 'success', defined but false for some 'unsuccessful' conditions like 'not found', and undef for all other cases (i.e., errors). All the functions documented below return this simple boolean value unless otherwise indicated. The actual C integer value, and corresponding error message, for the last libmemcached function call can be accessed via the L method. =head2 Unimplemented Functions Functions relating to managing lists of servers (memcached_server_push, and memcached_server_list) have not been implemenetd because they're not needed and likely to be deprecated by libmemcached. Functions relating to iterating through results (memcached_result_*) have not been implemented yet. They're not a priority because similar functionality is available via the callbacks. See L. Functions relating to stats should be implemented soonish. Patches welcome! =cut =head1 EXPORTS All the public functions in libmemcached are available for import. All the public constants and enums in libmemcached are also available for import. Exporter tags are defined for each enum. This allows you to import groups of constants easily. For example, to enable consistent hashing you could use: use Memcached::libmemcached qw(:memcached_behavior :memcached_server_distribution); memcached_behavior_set($memc, MEMCACHED_BEHAVIOR_DISTRIBUTION(), MEMCACHED_DISTRIBUTION_CONSISTENT()); The L module allows patterns in the import list, so to import all the functions, for example, you can use: use Memcached::libmemcached qw(/^memcached/); Refer to L for a full list of the available constants and the tags they are grouped by. =head1 FUNCTIONS =head2 Functions For Managing Memcaches =head3 memcached_create my $memc = memcached_create(); Creates and returns a 'memcache' that represents the state of communication with a set of memcached servers. See L. =head3 memcached_clone my $memc = memcached_clone(undef, undef); XXX Not currently recommended for use. See L. =head3 memcached_free memcached_free($memc); Frees the memory associated with $memc. After calling it $memc can't be used. See L. =head3 memcached_server_count $server_count= memcached_server_count($memc); Returns a count of the number of servers associated with $memc. See L. =head3 memcached_server_add memcached_server_add($memc, $hostname, $port); Adds details of a single memcached server (accessed via TCP/IP) to $memc. See L. =head3 memcached_server_add_unix_socket memcached_server_add_unix_socket($memc, $socket_path); Adds details of a single memcached server (accessed via a UNIX domain socket) to $memc. See L. =head3 memcached_behavior_set memcached_behavior_set($memc, $option_key, $option_value); Changes the value of a particular option. See L. =head3 memcached_behavior_get memcached_behavior_get($memc, $option_key); Get the value of a particular option. See L. =cut =head2 Functions for Setting Values See L. =head3 memcached_set memcached_set($memc, $key, $value); memcached_set($memc, $key, $value, $expiration, $flags); Set $value as the value of $key. $expiration and $flags are both optional and default to 0. =head3 memcached_add memcached_add($memc, $key, $value); memcached_add($memc, $key, $value, $expiration, $flags); Like L except that an error is returned if $key I already stored in the server. =head3 memcached_replace memcached_replace($memc, $key, $value); memcached_replace($memc, $key, $value, $expiration, $flags); Like L except that an error is returned if $key I already error is returned. =head3 memcached_prepend memcached_prepend($memc, $key, $value); memcached_prepend($memc, $key, $value, $expiration, $flags); Prepend $value to the value of $key. $key must already exist. $expiration and $flags are both optional and default to 0. =head3 memcached_append memcached_append($memc, $key, $value); memcached_append($memc, $key, $value, $expiration, $flags); Append $value to the value of $key. $key must already exist. $expiration and $flags are both optional and default to 0. =head3 memcached_cas memcached_cas($memc, $key, $value, $expiration, $flags, $cas) Overwrites data in the server stored as $key as long as $cas still has the same value 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. =cut =head2 Functions for Fetching Values See L. The memcached_fetch_result() and =head3 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 $rc with the return code. =head3 memcached_mget memcached_mget($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 I 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 the L method. =head3 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. This is similar to L except its fetching the results from the previous call to L and $key is an output parameter instead of an input. Usually you'd just use the L method instead. =cut =head2 Functions for Incrementing and Decrementing Values =head3 memcached_increment memcached_increment( $key, $offset, $new_value_out ); Increments the integer value associated with $key by $offset and returns the new value in $new_value_out. See also L. =head3 memcached_decrement memcached_decrement( $key, $offset, $new_value_out ); Decrements the integer value associated with $key by $offset and returns the new value in $new_value_out. See also L. =cut =head2 Functions for Deleting Values from memcached See L. =head3 memcached_delete memcached_delete($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. =cut =head2 Functions for Accessing Statistics from memcached Not yet implemented. See L. =cut =head2 Miscellaneous Functions =head2 memcached_lib_version $version = memcached_lib_version() Returns a simple version string, like "0.15", representing the libmemcached version (version of the client library, not server). =head2 memcached_version $version = memcached_version($memc) ($version1, $version2, $version3) = memcached_version($memc) Returns the version of all memcached servers to respond to the version request. In scalar context returns a simple version string, like "1.2.3". In list context returns the individual version component numbers. Returns an empty list if there was an error. Note that the return value differs from that of the underlying libmemcached library memcached_version() function. =head2 memcached_verbosity memcached_verbosity($memc, $verbosity) Modifies the "verbosity" of the memcached servers associated with $memc. See L. =head3 memcached_flush memcached_flush($memc, $expiration); Wipe clean the contents of associated memcached servers. See L. =head2 memcached_quit memcached_quit($memc) Disconnect from all currently connected servers and reset libmemcached state associated with $memc. Not normally called explicitly. See L. =head3 memcached_strerror $string = memcached_strerror($memc, $return_code) memcached_strerror() takes a C 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 L. This function is rarely needed in the Perl interface because the return code is a I that already contains the error string. =cut =head2 Unsupported Functions =head3 (stats) =cut =head2 Grouping Keys On Servers Normally libmemcached hashes the $key value to select which memcached server to communicate with. If you have several keys relating to a single object then it's very likely that the corresponding values will be stored in different memcached servers. It would be more efficient, in general, when setting and getting multiple related values, if it was possible to specify a different value to be hashed to select which memcached server to communicate with. With libmemcached, you can. Most of the functions for setting and getting values have C<*_by_key> variants for exactly this reason. These all have an extra $master_key parameter immediately after the $memc parameter. For example: memcached_mget($memc, \%keys, \%dest); memcached_mget_by_key($memc, $maskey_key, \%keys, \%dest); The C<*_by_key> variants all work in exactly the same way as the corresponding plain function, except that libmemcached hashes $master_key instead of $key to which memcached server to communicate with. If $master_key is undef then the functions behave the same as their non-by-key variants, i.e., $key is used for hashing. By-key variants of L: =head3 memcached_get_by_key =head3 memcached_mget_by_key By-key variants of L: =head3 memcached_set_by_key =head3 memcached_replace_by_key =head3 memcached_add_by_key =head3 memcached_append_by_key =head3 memcached_cas_by_key =head3 memcached_prepend_by_key =head3 memcached_delete_by_key =head1 OBJECT-ORIENTED INTERFACE =head2 Methods =head3 new $memc = $class->new; # same as memcached_create() =head3 errstr $errstr = $memc->errstr; Returns the error message and code from the most recent call to any libmemcached function that returns a C, which most do. The return value is a I, 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. This method is also currently callable as memcached_errstr() for compatibility with an earlier version, but that deprecated alias will start warning and then cease to exist in future versions. =head3 mget_into_hashref $memc->mget_into_hashref( \@keys, \%dest_hash); # keys from array $memc->mget_into_hashref( \%keys, \%dest_hash); # keys from 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. This method is also currently callable as memcached_mget_into_hashref() for compatibility with an earlier version, but that deprecated alias will start warning and then cease to exist in future versions. =head3 get_multi $hash_ref = $memc->get_multi( @keys ); Effectively the same as: $memc->mget_into_hashref( \@keys, $hash_ref = { } ) So it's very similar to L but less efficient for large numbers of keys (because the keys have to be pushed onto the argument stack) and less flexible (because you can't add/update elements into an existing hash). This method is provided to optimize subclasses that want to provide a Cache::Memcached compatible API with maximum efficiency. Note, however, that C does I support the L feature where a key can be a reference to an array [ $master_key, $key ]. Use L directly if you need that feature. =head3 get $value = $memc->get( $key ); Effectively the same as: $value = memcached_get( $memc, $key ); The C method also supports the L feature where $key can be a reference to an array [ $master_key, $key ]. In which case the call is effectively the same as: $value = memcached_get_by_key( $memc, $key->[0], $key->[1] ) =head3 set_callback_coderefs $memc->set_callback_coderefs(\&set_callback, \&get_callback); This interface is I and I. (It's also currently used by Cache::Memcached::libmemcached, so don't use it if you're using that module.) Specify functions which will be executed when values are set and/or get using $memc. When the callbacks are executed $_ is the value and the arguments are the key and flags value. Both $_ and the flags may be modified. Currently the functions must return an empty list. This method is also currently callable as memcached_set_callback_coderefs() for compatibility with an earlier version, but that deprecated alias will start warning and then cease to exist in future versions. =head3 walk_stats $memc->walk_stats( $stats_args, \&my_stats_callback ); This interface is I and I. Calls the memcached_stat() function to issue a "STAT $stats_args" command to the connected memcached servers. The $stats_args argument is usually an empty string. The callback function is called for each return value from each server. The callback will be passed 4 parameters: sub my_stats_callback { my ($key, $value, $hostport, $stats_args) = @_; # Do what you like with the above! return; } Currently the callback I return an empty list. =head1 EXTRA INFORMATION =head2 Tracing Execution The C environment variable can be used to control tracing. The value is read when L is called. If set >= 1 then any non-success memcached_return value will be logged via warn(). If set >= 2 or more then some data types will list conversions of input and output values for function calls. More flexible mechanisms will be added later. =head2 Type Mapping For pointer arguments, undef is mapped to null on input and null is mapped to undef on output. XXX expand with details from typemap file =head2 Deprecated Functions The following functions are available but deprecated in this release. In the next release they'll generate warnings. In a future release they'll be removed. =head3 memcached_errstr Use L instead. =head3 memcached_mget_into_hashref Use L instead. =head3 memcached_set_callback_coderefs Use L instead. =head1 AUTHOR EMERITUS Tim Bunce, C<< >> with help from Patrick Galbraith and Daisuke Maki. L =head1 CURRENT MAINTAINER Daisuke Maki C<< >> =head1 ACKNOWLEDGEMENTS Larry Wall for Perl, Brad Fitzpatrick for memcached, Brian Aker for libmemcached, and Patrick Galbraith and Daisuke Maki for helping with the implementation. =head1 PORTABILITY See Slaven Rezic's excellent CPAN Testers Matrix at L Along with Dave Cantrell's excellent CPAN Dependency tracker at L =head1 BUGS Please report any bugs or feature requests to C, or through the web interface at L. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes. =head1 CONTRIBUTING The source is hosted at github: L Patches and volunteers always welcome. =head1 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. =cut 1; # End of Memcached::libmemcached