ZeroMQ(3pm)

User Contributed Perl Documentation

ZeroMQ(3pm)

NAME¶

ZeroMQ - A ZeroMQ2 wrapper for Perl (DEPRECATED)

SYNOPSIS ( HIGH-LEVEL API )¶

    # echo server
    use ZeroMQ qw/:all/;
    my $cxt = ZeroMQ::Context->new;
    my $sock = $cxt->socket(ZMQ_REP);
    $sock->bind($addr);
  
    my $msg;
    foreach (1..$roundtrip_count) {
        $msg = $sock->recv();
        $sock->send($msg);
    }
    # json (if JSON.pm is available)
    $sock->send_as( json => { foo => "bar" } );
    my $thing = $sock->recv_as( "json" );
    # custom serialization
    ZeroMQ::register_read_type(myformat => sub { ... });
    ZeroMQ::register_write_type(myformat => sub { .. });
    $sock->send_as( myformat => $data ); # serialize using above callback
    my $thing = $sock->recv_as( "myformat" );

SYNOPSIS ( LOW-LEVEL API )¶

    use ZeroMQ::Raw;
    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¶

Please note that this module has been DEPRECATED in favor of ZMQ::LibZMQ2, ZMQ::LibZMQ3, and ZMQ. see https://github.com/lestrrat/p5-ZMQ and other CPAN pages.

The "ZeroMQ" module is a wrapper of the 0MQ message passing library for Perl. It's a thin wrapper around the C API. Please read <http://zeromq.org> for more details on ZeroMQ.

CLASS WALKTHROUGH¶

ZeroMQ::Raw: Use ZeroMQ::Raw to get access to the C API such as "zmq_init", "zmq_socket", et al. Functions provided in this low level API should follow the C API exactly.

ZeroMQ::Constants: ZeroMQ::Constants contains all of the constants that are known to be extractable from zmq.h. Do note that sometimes the list changes due to additions/deprecations in the underlying zeromq2 library. We try to do our best to make things available (at least to warn you that some symbols are deprecated), but it may not always be possible.

ZeroMQ::Context

ZeroMQ::Socket

ZeroMQ::Message: ZeroMQ::Context, ZeroMQ::Socket, ZeroMQ::Message contain the high-level, more perl-ish interface to the zeromq functionalities.

ZeroMQ: Loading "ZeroMQ" will make the ZeroMQ::Context, ZeroMQ::Socket, and ZeroMQ::Message classes available as well.

BASIC USAGE¶

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

    my $ctxt = ZeroMQ::Context->new;
    my $socket = $ctxt->socket( ... options );

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

    $socket->bind( "tcp://127.0.0.1:9999" );

and on the client side:

    $socket->connect( "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 ZeroMQ::Message object or a Perl string.

    # the following two send() calls are equivalent
    my $msg = ZeroMQ::Message->new( "a simple message" );
    $socket->send( $msg );
    $socket->send( "a simple message" );

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

To receive, simply call "recv()" on the socket

    my $msg = $socket->recv;

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

    my $data = $msg->data;

SERIALIZATION¶

ZeroMQ.pm comes with a simple serialization/deserialization mechanism.

To serialize, use "register_write_type()" to register a name and an associated callback to serialize the data. For example, for JSON we do the following (this is already done for you in ZeroMQ.pm if you have JSON.pm installed):

    use JSON ();
    ZeroMQ::register_write_type('json' => \&JSON::encode_json);
    ZeroMQ::register_read_type('json' => \&JSON::decode_json);

Then you can use "send_as()" and "recv_as()" to specify the serialization type as the first argument:

    my $ctxt = ZeroMQ::Context->new();
    my $sock = $ctxt->socket( ZMQ_REQ );
    $sock->send_as( json => $complex_perl_data_structure );

The otherside will receive a JSON encoded data. The receivind side can be written as:

    my $ctxt = ZeroMQ::Context->new();
    my $sock = $ctxt->socket( ZMQ_REP );
    my $complex_perl_data_structure = $sock->recv_as( 'json' );

If you have JSON.pm (must be 2.00 or above), then the JSON serializer / deserializer is automatically enabled. If you want to tweak the serializer option, do something like this:

    my $coder = JSON->new->utf8->pretty; # pretty print
    ZeroMQ::register_write_type( json => sub { $coder->encode($_[0]) } );
    ZeroMQ::register_read_type( json => sub { $coder->decode($_[0]) } );

Note that this will have a GLOBAL effect. If you want to change only your application, use a name that's different from 'json'.

ASYNCHRONOUS I/O WITH ZEROMQ¶

By default ZeroMQ 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 ZeroMQ 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¶

ZeroMQ works on both multi-process and multi-threaded use cases, but you need to be careful bout sharing ZeroMQ 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.

FUNCTIONS¶

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 $version_string = ZeroMQ::version();
    my ($major, $minor, $patch) = ZeroMQ::version();

device($type, $sock1, $sock2)¶

register_read_type($name, \&callback)¶

Register a read callback for a given $name. This is used in "recv_as()". The callback receives the data received from the socket.

register_write_type($name, \&callback)¶

Register a write callback for a given $name. This is used in "send_as()" The callback receives the Perl structure given to "send_as()"

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 ZeroMQ.pm 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 2.1.4. Semantics of this module rely heavily on the underlying zeromq version. Make sure you know which version of zeromq you're working with.

AUTHOR¶

Daisuke Maki "<daisuke@endeworks.jp>"

Steffen Mueller, "<smueller@cpan.org>"

COPYRIGHT AND LICENSE¶

The ZeroMQ module is

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.

2012-10-16

perl v5.20.0

Source file:	ZeroMQ.3pm.en.gz (from libzeromq-perl 0.23-1+b2)
Source last updated:	2014-08-15T22:18:17Z
Converted to HTML:	2018-08-09T23:05:02Z