vxp has asked for the wisdom of the Perl Monks concerning the following question:

ive a @server_list and i connect to each $server in it using net::ssh::perl like so: 
  foreach $server (@server_list) {
    $ssh = Net::SSH::Perl->new($server);
   ...
  }

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however it connects to them one after another, and i want/need to connect to them simoultaneously. anyone have any suggestions?

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Re: simoultaneous connections using Net::SSH::Perl
by Aristotle (Chancellor) on Sep 15, 2002 at 16:41 UTC
    It should work to do it this way: 
    my @connection;
foreach (@server_list) {
    my $ssh = Net::SSH::Perl->new($_) or next;
    push @connection, $ssh;
}

foreach my $ssh (@connection) {
    # ...
}

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    Alternatively, if this isn't simultaneous enough, you might want to look at fork or modules like Parallel::ForkManager.

    Makeshifts last the longest.

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Re: simoultaneous connections using Net::SSH::Perl
by jj808 (Hermit) on Sep 15, 2002 at 18:52 UTC
    Here's some example code with the fork()'s in place: 
    #! /usr/bin/perl -w

use strict;

$SIG{CHLD} = \&REAPER;
my @server_list = qw/one two three four/;
my $children = 0;

foreach my $server (@server_list) {
  print "$$ Forking for server: $server\n";
  if (my $pid = fork) {
    # Parent process
    # Nothing to do except go to the next server in the list
    $children++;
    sleep 2;
    next;
  } else {
    # Child process
    # Note that you *must* use 'exit;' when processing is
    # finished or the child will continue going through the
    # loop
    print "$$ Processing for server: $server\n";
    sleep 3;
    exit;
  }
}

# Wait for children to finish
while ($children > 0) {
  sleep;
}

sub REAPER {
  my $pid = wait;
  print "Process $pid has done it's stuff!\n";
  $children--;
}

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    When a forked process dies, the parent process will get a SIGCHLD signal (I am assuming you are using UNIX). Unless the parent does something with this signal, the child process will becoma a 'zombie', and eventually the process table will fill up (not good). If you don't need to keep track of the children as they finish, do $SIG{CHLD} = 'IGNORE'. I've put some delays in the example code so you can see this happening.

    You should also be aware that as with any system call, a fork() can fail. Read page 715 of 'Programming Perl, 3rd edition' for more info.

    JJ

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Re: simoultaneous connections using Net::SSH::Perl
by mem (Acolyte) on Sep 15, 2002 at 17:02 UTC 
      foreach $server (@server_list) {
    $ssh = Net::SSH::Perl->new($server);
   ...
  }

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    What are the ...? You are not spawning processes with each new call, you are just opening network connections. If you really want to spawn a process, you are missing a fork in there.

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Re: simoultaneous connections using Net::SSH::Perl
by jj808 (Hermit) on Sep 15, 2002 at 19:08 UTC
    *** I know I've posted this twice, because the question was duplicated and I didn't know which one would get reaped. If this is against etiquette, please /msg me.

    Here's some example code with the fork()'s in place: 

    #! /usr/bin/perl -w

use strict;

$SIG{CHLD} = \&REAPER;
my @server_list = qw/one two three four/;
my $children = 0;

foreach my $server (@server_list) {
  print "$$ Forking for server: $server\n";
  if (my $pid = fork) {
    # Parent process
    # Nothing to do except go to the next server in the list
    $children++;
    sleep 2;
    next;
  } else {
    # Child process
    # Note that you *must* use 'exit;' when processing is
    # finished or the child will continue going through the
    # loop
    print "$$ Processing for server: $server\n";
    sleep 3;
    exit;
  }
}


# Wait for children to finish
while ($children > 0) {
  sleep;
}

sub REAPER {
  my $pid = wait;
  print "Process $pid has done it's stuff!\n";
  $children--;
}

    [download]
    When a forked process dies, the parent process will get a SIGCHLD signal (I am assuming you are using UNIX). Unless the parent does something with this signal, the child process will becoma a 'zobmie', and eventually the process table will fill up (not good). If you don't need to keep track of the children as they finish, do $SIG{CHLD} = 'IGNORE'. I've put some delays in the example code so you can see this happening.

    You should also be aware that as with any system call, a fork() can fail. Read page 715 of 'Programming Perl, 3rd edition' for more info.

    JJ

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