in reply to Re^2: Do I need threads?
in thread Do I need threads?
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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Re^4: Do I need threads?
by Marshall (Canon) on Dec 23, 2011 at 23:54 UTC |