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

Hi Gurus,

Yes - I know, what I am trying to do may have been discussed a lot but I couldn't find what I am trying to do.

Here's what I need. I have a list of servers, which I have stored in an array. These servers aren't all that reliable, so I need to make sure I can connect to them before using them in my code. Obviously, I cannot stick to one working server and keep using it, as it's not good load balancing. What I want is something like this:

my connectionStatus = "down";
@listOfServers=("abc","def","lmn","stu","xyz");
while (connectionStatus eq "down")
{
    my $randomServer = $listOfServers[rand @listOfServers];
    #Try to connect to $randomServer
    if ($connect == 1)
    {
        connectionStatus = "up";
    }
    else
    {
        connectionStatus = "down";
    }
## Need to Delete the server in $randomServer from @listOfServers and 
+pick one randomly and try again ##
}

[download]

I read about using hashes and grep, but is there something simpler? I dont think I can use splice here as I dont know the index of the random element I just picked...

Any Suggestions?

Replies are listed 'Best First'.
Re: Pick random element from array and delete it
by daxim (Curate) on Jul 17, 2012 at 08:13 UTC
    I dont think I can use splice here as I dont know the index of the random element I just picked
    my $index = rand @listOfServers;

    [download]
    Problem solved.
[reply]
[d/l]
Re: Pick random element from array and delete it
by frozenwithjoy (Priest) on Jul 17, 2012 at 08:17 UTC
    You say you "Need to Delete the server in $randomServer from @listOfServers and pick one randomly and try again." Are you sure? what if you empty your array of servers? Is this ok with what you have in mind?

    edit: in case, you don't mind just going through your array once if all the servers are down, take a look at the two examples here:

    #!/usr/bin/env perl
use strict;
use warnings;
use List::Util 'shuffle';
use feature 'say';

my $connectionStatus = "down";
my @listOfServers = ( "abc", "def", "lmn", "stu", "xyz" );

while (@listOfServers) {

    ##THIS:
    @listOfServers = shuffle @listOfServers;
    my $randomServer = shift @listOfServers;

    ##OR THIS, BUT NOT BOTH:
    my $randomServer = splice @listOfServers, rand @listOfServers, 1;

    my $connect = 0;
    say $randomServer;    # replace this with your connection test
    if ( $connect == 1 ) {
        $connectionStatus = "up";
        last;
    }
}

    [download]
[reply]
[d/l]
Re: Pick random element from array and delete it
by Ratazong (Monsignor) on Jul 17, 2012 at 08:16 UTC

    I dont think I can use splice here as I dont know the index of the random element I just picked...

    If you are comfortable with a splice-solution, you may change the way you select your random element: just select a random index (instead of the element itself.)

    HTH, Rata
[reply]
Re: Pick random element from array and delete it
by Khen1950fx (Canon) on Jul 17, 2012 at 09:25 UTC
    You were on the right track. Try this: 
    #!/usr/bin/perl -l

use strict;
use warnings;

my $connectionStatus = "down";

my @listOfServers = qw(abc def lmn stu xyz);
foreach my $server ( @listOfServers ) {
    if ($connectionStatus eq 1) {
        print "Connection status is: 'up'";
        last;
    }
    elsif ($connectionStatus ne 1) {
        $server = $listOfServers[rand @listOfServers];
        print "Connection status is: 'down'";
        next unless $connectionStatus eq 1;
    }
    else {
        print "This is not going to work ...";
    }
}

    [download]
[reply]
[d/l]
Re: Pick random element from array and delete it
by cheekuperl (Monk) on Jul 17, 2012 at 08:15 UTC
    Do you wish to remove the inactive server in $randomServer from @listOfServers in its entirety so that it does not appear again?
[reply]

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