for few server it might take hour, ... idea is to collect data after every 10 minutes or 30 minutes,

So, you going to collect data that takes an hour to query, every 10 or 30 minutes.

depends on interval time or we can decide the best way.

What is "the interval time"? Like, a value you choose to program? In which case, how is that different from "or we can decide the best way."?

Reading between the lines, what I think you are saying is; "as often as possible"? If so, that is good, because it is very easy to program "as often as possible".

But if it is imperative that server X be serviced every 10 minutes; and server Y every 30 minutes; and server Z every 19.27071 minutes; things get much, much more complicated.

idea is to collect data after every 10 minutes or 30 minutes, from each server

"the idea"? This sounds like a "suck thumb and wave finger in air" metric. And that is no basis upon which to make design decisions.

So far, there is so much contradiction in your 'spec', it is pretty much impossible to make any real assessment of whether a single, multi-threaded program is a suitable way of tackling the problem. You'll need to be a lot clearer in specifiying the actual requirements, rather than speculative "it would be nice ifs".

Another question: why are you considering threads rather than processes?

thanks again and sorry for being not very clear in my reply.

we want to collect infromation from each server in every 30 minutes. for time being we will not consider servers which takes >=1 hour
We will have one group which will contain 30 data servers, if we process each server sequentially, might not be good idea. If we use thread then we can process parallely, execution will be faster and will be easy to manage.
Why not considring process ?
since forking many process( may be 100s) in one time and monitoring them will be complex. Also will consume lots of memory. But if you think forking is better option than threads, we can consider that option as well.

Given your very vague specifications, I would very strongly consider using completely separate programs. Both, fork and threads will consume many resources and make debugging your program very hard.

As you need to perform very different tasks (connect via ssh, connect via DBI, ...), putting all the code for these different tasks into one program makes little sense.

Have one central program that starts the specific programs as separate children. Consider maybe Parallel::Jobs or simple open "$child |" to run your child processes in parallel.

But before thinking about how to do things in parallel, I really, really urge you to first get things working in a serial fashion.

Here's a very basic skeleton that will serve as a basis for you to tweak to do the job. It uses a prioritising subclass of Thread::Queue to 'schedule' the repeat jobs:

#! perl -slw
use strict;
use threads;
use Thread::Queue;
use LWP::Simple;

{
    package T::Q::O;
    use Data::Dump qw[ pp ];
    require Thread::Queue;
    use threads;
    use threads::shared;
    our @ISA = 'Thread::Queue';

    sub enqueue {
        local $^W;
        my $Q = shift;
        lock @$Q;
        for( @_ ) {
            push @$Q, $_;
            my $n = $#$Q;
            @{ $Q }[ $n, $n-1 ] = @{ $Q }[ $n-1, $n ], --$n
                while $n-1 and $Q->[ $n ] < $Q->[ $n - 1 ];
        }
        cond_signal( @$Q );
    }

    sub dump {
        my $Q = shift;
        lock @$Q;
        pp $Q;
        cond_signal( @$Q );
    }
}

sub dbiFetch {
   my @args = @_;
   return getstore $args[ 0 ], 'nul';
}

sub sshFetch {
   my @args = @_;
   return getstore $args[ 0 ], 'nul';
}

sub tcpFetch {
   my @args = @_;
   return getstore $args[ 0 ], 'nul';
}

sub worker {
    no strict 'refs';
    my $Q = shift;

    while( my $work = $Q->dequeue ) {
        my( $time, $interval, $sub, @args ) = split $;, $work;
        sleep 1 while time() < $time;
#        printf "now: %.f time:$time int:$interval sub:$sub [@args]", 
+time();
        my $result = $sub->( @args );
#        print $result;
        $Q->enqueue( join $;, $time + $interval, $interval, $sub, @arg
+s );
    }
}

our $W //= 10;

my $Q = new T::Q::O;

my @workers = map async( \&worker, $Q ), 1 .. $W;

while( <> ) {
    chomp;
    $Q->enqueue( join $;,
        time(), (map $_*60, 1,2,3 )[ rand 3 ],
        ( qw[dbiFetch sshFetch tcpFetch ] )[ rand 3 ],
        $_
    );
}

1 while sleep 1;
[download]

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In the absence of evidence, opinion is indistinguishable from prejudice.

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