NAME

ZMQ::FFI - version agnostic Perl bindings for zeromq using ffi

VERSION

version 1.18

SYNOPSIS

    #### send/recv ####
    use 5.012;
    use ZMQ::FFI qw(ZMQ_REQ ZMQ_REP);
    my $endpoint = "ipc://zmq-ffi-$$";
    my $ctx      = ZMQ::FFI->new();
    my $s1 = $ctx->socket(ZMQ_REQ);
    $s1->connect($endpoint);
    my $s2 = $ctx->socket(ZMQ_REP);
    $s2->bind($endpoint);
    $s1->send('ohhai');
    say $s2->recv();
    # ohhai
    #### pub/sub ####
    use 5.012;
    use ZMQ::FFI qw(ZMQ_PUB ZMQ_SUB);
    use Time::HiRes q(usleep);
    my $endpoint = "ipc://zmq-ffi-$$";
    my $ctx      = ZMQ::FFI->new();
    my $s = $ctx->socket(ZMQ_SUB);
    my $p = $ctx->socket(ZMQ_PUB);
    $s->connect($endpoint);
    $p->bind($endpoint);
    # all topics
    {
        $s->subscribe('');
        until ($s->has_pollin) {
            # compensate for slow subscriber
            usleep 100_000;
            $p->send('ohhai');
        }
        say $s->recv();
        # ohhai
        $s->unsubscribe('');
    }
    # specific topics
    {
        $s->subscribe('topic1');
        $s->subscribe('topic2');
        until ($s->has_pollin) {
            usleep 100_000;
            $p->send('topic1 ohhai');
            $p->send('topic2 ohhai');
        }
        while ($s->has_pollin) {
            say join ' ', $s->recv();
            # topic1 ohhai
            # topic2 ohhai
        }
    }
    #### multipart ####
    use 5.012;
    use ZMQ::FFI qw(ZMQ_DEALER ZMQ_ROUTER);
    my $endpoint = "ipc://zmq-ffi-$$";
    my $ctx      = ZMQ::FFI->new();
    my $d = $ctx->socket(ZMQ_DEALER);
    $d->set_identity('dealer');
    my $r = $ctx->socket(ZMQ_ROUTER);
    $d->connect($endpoint);
    $r->bind($endpoint);
    $d->send_multipart([qw(ABC DEF GHI)]);
    say join ' ', $r->recv_multipart;
    # dealer ABC DEF GHI
    #### nonblocking ####
    use 5.012;
    use ZMQ::FFI qw(ZMQ_PUSH ZMQ_PULL);
    use AnyEvent;
    use EV;
    my $endpoint = "ipc://zmq-ffi-$$";
    my $ctx      = ZMQ::FFI->new();
    my @messages = qw(foo bar baz);
    my $pull = $ctx->socket(ZMQ_PULL);
    $pull->bind($endpoint);
    my $fd = $pull->get_fd();
    my $recv = 0;
    my $w = AE::io $fd, 0, sub {
        while ( $pull->has_pollin ) {
            say $pull->recv();
            # foo, bar, baz
            $recv++;
            if ($recv == 3) {
                EV::break();
            }
        }
    };
    my $push = $ctx->socket(ZMQ_PUSH);
    $push->connect($endpoint);
    my $sent = 0;
    my $t;
    $t = AE::timer 0, .1, sub {
        $push->send($messages[$sent]);
        $sent++;
        if ($sent == 3) {
            undef $t;
        }
    };
    EV::run();
    #### specifying versions ####
    use ZMQ::FFI;
    # 2.x context
    my $ctx = ZMQ::FFI->new( soname => 'libzmq.so.1' );
    my ($major, $minor, $patch) = $ctx->version;
    # 3.x context
    my $ctx = ZMQ::FFI->new( soname => 'libzmq.so.3' );
    my ($major, $minor, $patch) = $ctx->version;

DESCRIPTION

ZMQ::FFI exposes a high level, transparent, OO interface to zeromq independent of the underlying libzmq version. Where semantics differ, it will dispatch to the appropriate backend for you. As it uses ffi, there is no dependency on XS or compilation.

As of 1.00 ZMQ::FFI is implemented using FFI::Platypus. This version has substantial performance improvements and you are encouraged to use 1.00 or newer.

CONTEXT API

    my $ctx = ZMQ::FFI->new(%options);

    my ($major, $minor, $patch) = $ctx->version();

    my $threads = $ctx->get(ZMQ_IO_THREADS)

    $ctx->set(ZMQ_MAX_SOCKETS, 42)

    my $socket = $ctx->socket(ZMQ_REQ)

    $ctx->proxy($frontend, $backend);
    $ctx->proxy($frontend, $backend, $capture);

    $ctx->device($type, $frontend, $backend);

SOCKET API

The following API is available on socket objects created by "$ctx->socket".

For core attributes and functions, common across all versions of zeromq, convenience methods are provided. Otherwise, generic get/set methods are provided that will work independent of version.

As attributes are constantly being added/removed from zeromq, it is unlikely the 'static' accessors will grow much beyond the current set.

    my ($major, $minor, $patch) = $socket->version();

    $socket->connect($endpoint);

    $socket->disconnect($endpoint);

    $socket->bind($endpoint);

    $socket->unbind($endpoint);

    my $linger = $socket->get_linger();
    $socket->set_linger($millis);

    my $ident = $socket->get_identity();
    $socket->set_identity($ident);

    my $fd = $socket->get_fd();

    my $option_value = $socket->get($option_name, $option_type);
    my $linger = $socket->get(ZMQ_LINGER, 'int');

    $socket->set($option_name, $option_type, $option_value);
    $socket->set(ZMQ_IDENTITY, 'binary', 'foo');

    $socket->subscribe($topic);

    $socket->unsubscribe($topic);

    $socket->send($msg);
    $socket->send($msg, $flags);

    $socket->send($parts_aref);
    $socket->send($parts_aref, $flags);

    my $msg = $socket->recv();
    my $msg = $socket->recv($flags);

    my @parts = $socket->recv_multipart();
    my @parts = $socket->recv_multipart($flags);

    while ( $socket->has_pollin ) { ... }

    $socket->die_on_error(0);
    $socket->die_on_error(1);

CLEANUP

With respect to cleanup "ZMQ::FFI" follows either the zeromq guide <http://zguide.zeromq.org/page:all#Making-a-Clean-Exit> recommendations or the behavior of other zmq bindings. That is:

• it uses 0 linger by default (this is the default used by czmq <https://github.com/zeromq/czmq> and jzmq <https://github.com/zeromq/jzmq>)
• during object destruction it will call close/destroy for you
• it arranges the reference hierarchy such that sockets will be properly
  cleaned up before their associated contexts
• it detects fork/thread situations and ensures sockets/contexts are only
  cleaned up in their originating process/thread
• it guards against double closes/destroys

Given the above you're probably better off letting "ZMQ::FFI" handle cleanup for you. But if for some reason you want to do explicit cleanup yourself you can. All the below will accomplish the same thing:

    # implicit cleanup
    {
        my $context = ZMQ::FFI->new();
        my $socket  = $ctx->socket($type);
        ...
        # close/destroy called in destructors at end of scope
    }
    # explicit cleanup
    $socket->close();
    $context->destroy();
    # ditto
    undef $socket;
    undef $context;

Regarding "linger", you can always set this to a value you prefer if you don't like the default. Once set the new value will be used when the socket is subsequently closed (either implicitly or explicitly):

    $socket->set_linger(-1); # infinite linger
                             # $context->destroy will block forever
                             # (or until all pending messages have been sent)

ERROR HANDLING

By default, ZMQ::FFI checks the return codes of underlying zmq functions for you, and in the case of an error it will die with the human readable system error message.

    $ctx->socket(-1);
    # dies with 'zmq_socket: Invalid argument'

Usually this is what you want, but not always. Some zmq operations can return errors that are not fatal and should be handled. For example using "ZMQ_DONTWAIT" with send/recv can return "EAGAIN" and simply means try again, not die.

For situations such as this you can turn off exceptional error handling by setting "die_on_error" to 0. It is then for you to check and manage any zmq errors by checking "last_errno":

    use Errno qw(EAGAIN);
    my $ctx = ZMQ::FFI->new();
    my $s   = $ctx->socket(ZMQ_DEALER);
    $s->bind('tcp://*:7200');
    $s->die_on_error(0); # turn off exceptional error handling
    while (1) {
        my $msg = $s->recv(ZMQ_DONTWAIT);
        if ($s->last_errno == EAGAIN) {
            sleep 1;
        }
        elsif ($s->last_errno) {
            die $s->last_strerror;
        }
        else {
            warn "recvd: $msg";
            last;
        }
    }
    $s->die_on_error(1); # turn back on exceptional error handling

FFI VS XS PERFORMANCE

ZMQ::FFI uses FFI::Platypus on the backend. In addition to a friendly, usable interface, FFI::Platypus's killer feature is "attach". "attach" makes it possible to bind ffi functions in memory as first class Perl xsubs. This results in dramatic performance gains and gives you the flexibility of ffi with performance approaching that of XS.

Testing indicates FFI::Platypus xsubs are around 30% slower than "real" XS xsubs. That may sound like a lot, but to put it in perspective that means, for zeromq, the XS bindings can send 10 million messages 1-2 seconds faster than the ffi ones.

If you really care about 1-2 seconds over 10 million messages you should be writing your solution in C anyways. An equivalent C implementation will be several hundred percent faster or more.

Keep in mind also that the small speed bump you get using XS can easily be wiped out by crappy and poorly optimized Perl code.

Now that Perl finally has a great ffi interface, it is hard to make the case to continue using XS. The slight speed bump just isn't worth giving up the convenience, flexibility, and portability of ffi.

You can find the detailed performance results that informed this section at: <https://gist.github.com/calid/17df5bcfb81c83786d6f>

BUGS

"ZMQ::FFI" is free as in beer in addition to being free as in speech. While I've done my best to ensure it's tasty, high quality beer, it probably isn't perfect. If you encounter problems, or otherwise see room for improvement, please open an issue (or even better a pull request!) on github <https://github.com/zeromq/perlzmq>

SEE ALSO

• ZMQ::FFI::Constants
• ZMQ::FFI::Util
• FFI::Platypus
• FFI::Raw
• ZMQ::LibZMQ3

CREDITS

Thank you to the following for patches, bug reports, feedback, or suggestions:

Dave Lambley, Graham Ollis, Klaus Ita, Marc Mims, Parth Gandhi, Pawel Pabian, Robert Hunter, Sergey KHripchenko, Slaven Rezic, Whitney Jackson, pipcet

AUTHOR

Dylan Cali <calid1984@gmail.com>

COPYRIGHT AND LICENSE

This software is copyright (c) 2022 by Dylan Cali.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.