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TakTuk.3pm

NAME

TakTuk - Perl module that provides an interface to taktuk(1) communication facilities

SYNOPSIS

   use TakTuk;
   
   my $rank = TakTuk::get('rank');
   my $count = TakTuk::get('count');
   
   print "I'm process $rank among $count\n";
   
   if ($rank > 1) {
       my ($to, $from, $message) = TakTuk::recv();
       if (not defined($message)) {
           print "Trying to recv: ",
                 TakTuk::error_msg($TakTuk::error), "\n";
       } else {
           print "$to received $message from $from\n";
       }
   }
   
   sleep 1;
   my $next = $rank+1;
   $next = 1 if ($next > $count);
   if (not TakTuk::send(to=>$next, body=>"[Salut numero $rank]")) {
       print "Trying to send to $next: ",
             TakTuk::error_msg($TakTuk::error), "\n";
   }
   
   if ($rank == 1) {
       my ($to, $from, $message) = TakTuk::recv(timeout=>5);
       if (not defined($message)) {
           print "Trying to recv :",
                 TakTuk::error_msg($TakTuk::error), "\n";
       } else {
           print "$to received $message from $from\n";
       }
   }
 
 

DESCRIPTION

The TakTuk communication layer Perl interface provides a way for programs executed using the taktuk(1) command to exchange data. It is based on a simple send/receive model using multicast-like sends and optionally timeouted receives. This is only designed to be a control facility, in particular this is not a high performance communication library.

WARNING: the TakTuk communication interface is not process-safe : it is probably a very bad idea to use point-to-point communication in more than one process related to a single TakTuk instance (these processes might be several local commands or forked processes).

The Perl communication interface for TakTuk is made of functions that can be called by scripts executed using the "taktuk_perl" command of the TakTuk engine (prefered way, less installation requirements on remote machines) or using the TakTuk Perl module provided with the TakTuk distribution. These functions are:

TakTuk::get($)

gets some information from TakTuk. Currently available informations are 'rank', 'count', 'father', 'child_min' and 'child_max". This is a better way to get these informations than environment variables as its takes into account renumbering that might occur after process spawn.

TakTuk::send(%)

sends a scalar to a single peer or a set specification (see taktuk(1) for informations about set specifications). The two mandatory fields in the arguments are "to" (with a set specification) and "body". Returns an undefined value upon error.

TakTuk::recv(%)

blocks until the reception of a message. Returns a list of three elements: the logical number of the destination of the message, the logical number of its source and the message itself. Accepts an optional "timeout" argument with a numeric value. Returns an empty list upon error.

When an error occur, both of these functions set the variable $TakTuk::error to the numeric code of the error that occured. A textual description of the error is provided by the function TakTuk::error_msg($) that takes the error code as an argument.

Error codes are the following :

TakTuk::ESWRIT

a call to "TakTuk::syswrite" failed. This is due to a "syswrite" error different than "EAGAIN". The code should be accessible using $!.

TakTuk::EFCLSD

the communication channel to the TakTuk engine has been closed. This typically occur when shutting down the logical network (using Ctrl-C on root node for instance).

TakTuk::ESREAD ("TakTuk::recv" only)

a call to "sysread" failed (the code should be accessible using $!).

TakTuk::EARGTO ("TakTuk::send" only)

"to" field missing in the arguments.

TakTuk::EARGBD ("TakTuk::send" only)

"body" field missing in the arguments.

TakTuk::ETMOUT ("TakTuk::recv" only)

The call to "TakTuk::recv" timeouted. This only occur when giving a "timeout" field as "TakTuk::recv" argument.

SEE ALSO

tatkuk(1), taktukcomm(3), TakTuk::Pilot(3)

AUTHOR

The original concept of TakTuk has been proposed by Cyrille Martin in his PhD thesis. People involved in this work include Jacques Briat, Olivier Richard, Thierry Gautier and Guillaume Huard.

The author of the version 3 (perl version) and current maintainer of the package is Guillaume Huard.

COPYRIGHT

The "TakTuk" communication interface library is provided under the terms of the GNU General Public License version 2 or later.