After reading the article there, I don't think that locking is going to help me in the long run. The idea is to speed things up, but it appears that this may introduce a lag while the output is being written, and the next process is waiting to write. That being said, I could be wrong. It may just cache the data being sent, and not written to the log without holding up the script generating the data. I will have to play with that later.

Here is what I did. Instead of writing the output from ssh to the log directly, I wrote it to a temp log, one for each thread using the captured server names for part of the file name. Then at the end of the script, I dump them all back into the main log. Still a lot of cleanup to do, but I think I am on the right track now. Thank you for pointing this out. I have no doubt you have saved me hours of confusion, and frustration!

Here is something that I missed earlier, the output being sent to the log in the fork is actually only a success or fail of the SSH call. I decided to just redirect STDOUT to the log so that I can capture the output of the command itself. 

#!/usr/bin/perl
use strict;
use warnings;
use Net::SSH qw(ssh);


my %serverPid;
my ($testkey, $testvalue);
die("Could not open file list: $!") unless
    open(FHServerList, "<", "./servers");
die("Could not open log file: $!") unless
    open(FHlog, ">>", "./log");
    
    
while(<FHServerList>) {
    my $serverName = $_;
    chomp($serverName);
    my $pid = fork();
    if($pid == '0'){
        #Child process
        #open(FHTempLog, ">", "/tmp/$serverName.tmp");
        open(STDOUT, '>', "/tmp/$serverName.tmp") or die ("Cannot crea
+te temp log file for $serverName: $!");
        open(STDERR, ">&STDOUT");
        ssh($serverName, "for x in 1 2 3 4 5 6; do echo -n \$x; hostna
+me; done");
        exit(0)
    }
    else {
        $serverPid{$serverName} = $pid;
    }
}

while(($testkey, $testvalue) = each %serverPid) {
    waitpid($testvalue, 0);
        print ("Done with $testkey\n");
    }

seek(FHServerList, 0, 0);
while(<FHServerList>) {
    chomp($_);
    my $tmpFileName = ("/tmp/$_" . ".tmp");
    open(FHtempFile, "<", $tmpFileName) or die "Could not open tempfil
+e: $!";
    while(<FHtempFile>) {
        print FHlog $_;
    }
    close(FHtempFile);
}

close(FHServerList);
exit()

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In reply to Re^3: Do I need threads? by TechFly
in thread Do I need threads? by TechFly

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