Daisuke Maki > ZMQ-LibZMQ2 > ZMQ::LibZMQ2

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Module Version: 1.09   Source  

NAME ^

ZMQ::LibZMQ2 - A libzmq 2.x wrapper for Perl

SYNOPSIS ^

    use ZMQ::LibZMQ;

    my $ctxt = zmq_init($threads);
    my $rv   = zmq_term($ctxt);

    my $msg  = zmq_msg_init();
    my $msg  = zmq_msg_init_size( $size );
    my $msg  = zmq_msg_init_data( $data );
    my $rv   = zmq_msg_close( $msg );
    my $rv   = zmq_msg_move( $dest, $src );
    my $rv   = zmq_msg_copy( $dest, $src );
    my $data = zmq_msg_data( $msg );
    my $size = zmq_msg_size( $msg);

    my $sock = zmq_socket( $ctxt, $type );
    my $rv   = zmq_close( $sock );
    my $rv   = zmq_setsockopt( $socket, $option, $value );
    my $val  = zmq_getsockopt( $socket, $option );
    my $rv   = zmq_bind( $sock, $addr );
    my $rv   = zmq_send( $sock, $msg, $flags );
    my $msg  = zmq_recv( $sock, $flags );

INSTALLATION ^

If you have libzmq registered with pkg-config:

    perl Makefile.PL
    make 
    make test
    make install

If you don't have pkg-config, and libzmq is installed under /usr/local/libzmq:

    ZMQ_HOME=/usr/local/libzmq \
        perl Makefile.PL
    make
    make test
    make install

If you want to customize include directories and such:

    ZMQ_INCLUDES=/path/to/libzmq/include \
    ZMQ_LIBS=/path/to/libzmq/lib \
    ZMQ_H=/path/to/libzmq/include/zmq.h \
        perl Makefile.PL
    make
    make test
    make install

If you want to compile with debugging on:

    perl Makefile.PL -g

DESCRIPTION ^

The ZMQ::LibZMQ2 module is a wrapper of the 0MQ message passing library for Perl.

Before you start using this module, please make sure you have read and understood the zguide.

    http://zguide.zeromq.org/page:all

For specifics on each function, please refer to their documentation for the definitive explanation of each.

    http://api.zeromq.org/2-2:_start

This module is merely a thin wrapper around the C API: You need to understand how the C API works in order to properly use this module.

Note that this is a wrapper for libzmq 2.x. For 3.x, you need to check ZMQ::LibZMQ3

BASIC USAGE ^

Please make sure you already have ZMQ::Constants module. If you installed ZMQ::L ibZMQ3 from CPAN via cpan/cpanm, it should have already been installed for you. All socket types and other flags are declared in this module.

To start using ZMQ::LibZMQ2, you need to create a context object, then as many ZMQ::LibZMQ2::Socket obects as you need:

    my $ctxt = zmq_init;
    my $socket = zmq_socket( $ctxt, ... options );

You need to call zmq_bind() or zmq_connect() on the socket, depending on your usage. For example on a typical server-client model you would write on the server side:

    zmq_bind( $socket, "tcp://127.0.0.1:9999" );

and on the client side:

    zmq_connect( $socket, "tcp://127.0.0.1:9999" );

The underlying zeromq library offers TCP, multicast, in-process, and ipc connection patterns. Read the zeromq manual for more details on other ways to setup the socket.

When sending data, you can either pass a ZMQ::LibZMQ2::Message object or a Perl string.

    # the following two send() calls are equivalent
    my $msg = zmq_msg_init_data( "a simple message" );
    zmq_send( $socket, $msg );
    
    zmq_send( $socket, "a simple message" ); 

In most cases using ZMQ::LibZMQ2::Message is redundunt, so you will most likely use the string version.

To receive, simply call zmq_recv() on the socket

    my $msg = zmq_recv( $socket );

The received message is an instance of ZMQ::LibZMQ2::Message object, and you can access the content held in the message via the data() method:

    my $data = zmq_msg_data( $msg );

ASYNCHRONOUS I/O WITH ZEROMQ ^

By default 0MQ comes with its own zmq_poll() mechanism that can handle non-blocking sockets. You can use this by calling zmq_poll with a list of hashrefs:

    zmq_poll([
        {
            fd => fileno(STDOUT),
            events => ZMQ_POLLOUT,
            callback => \&callback,
        },
        {
            socket => $zmq_socket,
            events => ZMQ_POLLIN,
            callback => \&callback
        },
    ], $timeout );

Unfortunately this custom polling scheme doesn't play too well with AnyEvent.

As of zeromq2-2.1.0, you can use getsockopt to retrieve the underlying file descriptor, so use that to integrate ZMQ::LibZMQ2 and AnyEvent:

    my $socket = zmq_socket( $ctxt, ZMQ_REP );
    my $fh = zmq_getsockopt( $socket, ZMQ_FD );
    my $w; $w = AE::io $fh, 0, sub {
        while ( my $msg = zmq_recv( $socket, ZMQ_RCVMORE ) ) {
            # do something with $msg;
        }
        undef $w;
    };

NOTES ON MULTI-PROCESS and MULTI-THREADED USAGE ^

0MQ works on both multi-process and multi-threaded use cases, but you need to be careful bout sharing ZMQ::LibZMQ2 objects.

For multi-process environments, you should not be sharing the context object. Create separate contexts for each process, and therefore you shouldn't be sharing the socket objects either.

For multi-thread environemnts, you can share the same context object. However you cannot share sockets. Note that while the Perl Socket objects survive between threads, their underlying C structures do not, and you will get an error if you try to use them between sockets.

FUNCTIONS ^

ZMQ::LibZMQ2 attempts to stick to the libzmq interface as much as possible. Unless there is a structural problem (say, an underlying poitner that the Perl binding expects was missing), no function should throw an exception.

Return values should resemble that of libzmq, except for when new data is allocated and returned to the user - That includes things like zmq_init(), zmq_socket(), zmq_msg_data(), etc.

Where applicable, $! should be updated to match the value set by libzmq, so you should be able to do:

    my $cxt = zmq_init();
    if (! $cxt) {
        die "zmq_init() failed with $!";
    }

$errno = zmq_errno()

Returns the value of errno variable for the calling thread. You normally should not need to use this function. See the man page for zmq_errno() provided by libzmq.

$string = zmq_strerror( $errno )

Returns the string representation of $errno. Use this to stringify errors that libzmq provides.

$cxt = zmq_init( $threads )

Creates a new context object. $threads argument is optional. Context objects can be reused across threads.

Returns undef upon error, and sets $!.

$rv = zmq_term( $cxt )

Terminates the context. Be careful, as it might hang if you have pending socket operations.

Returns a non-zero status upon failure, and sets $!.

$socket = zmq_socket( $cxt, $socket_type )

Creates a new socket object. $socket_types are constants declared in ZMQ::Constants. Sockets cannot be reused across threads.

Returns undef upon error, and sets $!.

ZMQ::LibZMQ2::Socket objects aren't thread safe due to the underlying library. Therefore, they are currently not cloned when a new Perl ithread is spawned. The variables in the new thread that contained the socket in the parent thread will be a scalar reference to undef in the new thread. This makes the Perl wrapper thread safe (i.e. no segmentation faults).T

$rv = zmq_bind( $sock, $address )

Binds the socket to listen to specified $address.

Returns a non-zero status upon failure, and sets $!

$rv = zmq_connect( $sock, $address )

Connects the socket to specified $address.

Returns a non-zero status upon failure, and sets $!

$rv = zmq_close( $sock )

Closes the socket explicitly.

Returns a non-zero status upon failure, and sets $!.

$value = zmq_getsockopt( $socket, $option )

Gets the value of the specified option.

If the particular version of ZMQ::LibZMQ2 does not implement the named socket option, an exception will be thrown:

    /* barfs, because we don't know what type this new option is */
    zmq_getsockopt( $socket, ZMQ_NEW_SHINY_OPTION );

In this case you can either use ZMQ::Constants, or you can use one of the utility functions that ZMQ::LibZMQ2 provides.

Using ZMQ::Constants

ZMQ::LibZMQ2 internally refers to ZMQ::Constants to learn about the type of a socket option. You can easily add new constants to this map:

    use ZMQ::Constants;
    ZMQ::Constants::add_sockopt_type( "int" => ZMQ_NEW_SHINY_OPTION );
Using utilities in ZMQ::LibZMQ2

You need to know which socket options are integers, which are strings, etc, to manipulate the socket options. Choose the right one from the following helpers that ZMQ::LibZMQ2 provides (they are not part of the libzmq interface)

    /* say you know that the value is an int, int64, uint64, or char *
       by reading the zmq docs */
    $int    = zmq_getsockopt_int( $socket, ZMQ_NEW_SHINY_OPTION );
    $int64  = zmq_getsockopt_int64( $socket, ZMQ_NEW_SHINY_OPTION );
    $uint64 = zmq_getsockopt_uint64( $socket, ZMQ_NEW_SHINY_OPTION );
    $string = zmq_getsockopt_string( $socket, ZMQ_NEW_SHINY_OPTION );

Corresponding zmq_setsockopt_* functions should also exist.

$status = zmq_setsockopt( $socket, $option, $value )

Sets the value of the specified option. Returns the status.

See zmq_getsockopt() if you have problems with ZMQ::LibZMQ2 not knowing the type of the option.

$rv = zmq_send($sock, $message, $flags)

Sends $message via $sock. Argument $flags may be omitted.

If $message is a non-ref, creates a new ZMQ::LibZMQ2::Message object via zmq_msg_init_data(), and uses that to pass to the underlying C layer..

Returns a non-zero status upon failure, and sets $!.

$message = zmq_recv($sock, $flags)

Receives a new message from $sock. Argument $flags may be omitted.

Returns undef upon failure, and sets $!.

$msg = zmq_msg_init()

Creates a new message object.

Returns undef upon failure, and sets $!.

$msg = zmq_msg_init_data($string)

Creates a new message object, and sets the message payload to the string in $string.

Returns undef upon failure, and sets $!.

$msg = zmq_msg_init_size($size)

Creates a new message object, allocating $size bytes. This call isn't so useful from within Perl

Returns undef upon failure, and sets $!.

$string = zmq_msg_data( $msg )

Returns the payload contained in $msg

$size = zmq_msg_size( $msg )

Returns the size of payload contained in $msg

zmq_msg_copy( $dst, $src )

Copies contents of $src to $dst.

Returns a non-zero status upon failure, and sets $!.

zmq_msg_move( $dst, $src )

Moves contents of $src to $dst

Returns a non-zero status upon failure, and sets $!.

$rv = zmq_msg_close( $msg )

Closes, cleans up the message.

Returns a non-zero status upon failure, and sets $!.

$rv = zmq_poll( \@pollitems, $timeout )

@pollitems are list of hash references containing the following elements:

fd or socket

One of either fd or socket key must exist. fd should contain a UNIX file descriptor. socket should contain a ZMQ::LibZMQ2::Socket socket object.

events

A bit mask containing ZMQ_POLLOUT, ZMQ_POLLIN, ZMQ_POLLERR or combination there of.

callback

A subroutine reference, which will be called without arguments when the socket or descriptor is available.

In scalar context, returns the return value of zmq_poll() in the C layer, and sets $!.

    my $rv = zmq_poll( .... ); # do scalar(zmq_poll(...)) if you're nuerotic
    if ( $rv == -1 ) {
        warn "zmq_poll failed: $!";
    }

In list context, return a list containing as many booleans as there are elements in @pollitems. These booleans indicate whether the socket in question has fired the callback.

    my @pollitems = (...);
    my @fired     = zmq_poll( @pollitems ... );
    for my $i ( 0 .. $#pollitems ) {
        my $fired = $fired[$i];
        if ( $fired ) {
            my $item = $pollitems[$i];
            ...
        }
    }

zmq_version()

Returns the version of the underlying zeromq library that is being linked. In scalar context, returns a dotted version string. In list context, returns a 3-element list of the version numbers:

    my $version_string = ZMQ::LibZMQ2::zmq_version();
    my ($major, $minor, $patch) = ZMQ::LibZMQ2::zmq_version();

$rv = zmq_device($type, $sock1, $sock2)

Creates a new "device". See zmq_device for details. zmq_device() will only return if/when the current context is closed. Therefore, the return value is always -1, and $! is always ETERM

FUNCTIONS PROVIDED BY ZMQ::LIBZMQ2 ^

These functions are provided by ZMQ::LibZMQ2 to make some operations easier in the Perl binding. They are not part of the official libzmq interface.

$value = zmq_getsockopt_int( $sock, $option )

$value = zmq_getsockopt_int64( $sock, $option )

$value = zmq_getsockopt_string( $sock, $option )

$value = zmq_getsockopt_uint64( $sock, $option )

$rv = zmq_setsockopt_int( $sock, $option, $value );

$rv = zmq_setsockopt_int64( $sock, $option, $value );

$rv = zmq_setsockopt_string( $sock, $option, $value );

$rv = zmq_setsockopt_uint64( $sock, $option, $value );

DEBUGGING XS ^

If you see segmentation faults, and such, you need to figure out where the error is occuring in order for the maintainers to figure out what happened. Here's a very very brief explanation of steps involved.

First, make sure to compile ZMQ::LibZMQ2 with debugging on by specifying -g:

    perl Makefile.PL -g
    make

Then fire gdb:

    gdb perl
    (gdb) R -Mblib /path/to/your/script.pl

When you see the crash, get a backtrace:

    (gdb) bt

CAVEATS ^

This is an early release. Proceed with caution, please report (or better yet: fix) bugs you encounter.

This module has been tested againt zeromq 2.1.11. Semantics of this module rely heavily on the underlying zeromq version. Make sure you know which version of zeromq you're working with.

SEE ALSO ^

http://zeromq.org

http://github.com/lestrrat/p5-ZMQ

ZMQ::Constants

ZMQ::LibZMQ3

AUTHOR ^

Daisuke Maki <daisuke@endeworks.jp>

Steffen Mueller, <smueller@cpan.org>

COPYRIGHT AND LICENSE ^

The ZMQ::LibZMQ2 module is

Copyright (C) 2010 by Daisuke Maki

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.0 or, at your option, any later version of Perl 5 you may have available.

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