CODEWITHSUNDEEP
bashperlubuntussh
The Georgia
The Georgia

Reputation: 1075

Run a remote bash command through ssh

I have the following script that I plan to use to execute a bash command on a remote server. Every time this script runs it should check whether the remote MySQL (PXC) server is undergoing SST.

#!/usr/bin/perl

use strict;
use warnings;

my $time = localtime();

my $file = '/db-common-list/names.txt';
open my $info, $file or die "Could not open $file: $!";

while ( my $hostname = <$info> )  {

    my $wsrep_check = `ssh $hostname ps -ef |grep mysql | grep wsrep_sst_xtrabackup-v2`;

    if ( index($wsrep_check, 'State transfer in progress, setting sleep higher mysqld') != -1 ) {
        print "$time: Server $hostname";
        last if $. == 2;
    }
}

close $info;

Inside /db-common-list/names.txt is a list of databases that the script should loop through line by line. So it looks something like this:

db-test-1
db-test-2
db-test-3
db-test-4
...

But when I run the script, the command line just hangs and never displays anything, at which point I have to manually force the script to stop executing. So after several minutes with nothing but the script just hanging in the terminal, I use Ctrl-D to stop the script and I get this:

thegeorgia@cron-db$ ./test.cron
Connection to db-test-1 closed.
Connection to db-test-2 closed.
thegeorgia@cron-db$ ./test.cron

I can ssh and ping these remote as demonstrated below servers so thats not the issue for sure:

thegeorgis@cron-db$ ping db-test-1
PING db-test-1 (10.1.4.205) 56(84) bytes of data.
64 bytes from db-test-1 (10.1.4.205): icmp_seq=1 ttl=64 time=0.263 ms
64 bytes from db-test-1 (10.1.4.205): icmp_seq=2 ttl=64 time=0.222 ms

All servers involved are running Ubuntu.

NOTE: As suggested by Borodin, i added the chomp as follows:

    while( my $hostname = <$info>)  {
    my $server = chomp( $hostname );
    my $wsrep_check = `ssh $server ls`;
         if ( index($wsrep_check, 'State transfer in progress, setting sleep higher mysqld') != -1 ){
            print "$time: Server $server";
       }
last if $. == 2;
}

And when i run the perl script, i now get the following error:

ssh: connect to host 1 port 22: Invalid argument
ssh: connect to host 1 port 22: Invalid argument

SOLUTION:

#!/usr/bin/perl -w

use strict;
use warnings;

my $time = localtime();
my $file = '/db-common-list/names.txt';
open my $info, $file or die "Could not open $file: $!";

while( my $hostname = <$info>)  {
    chomp( $hostname );
    my $wsrep_check = `ssh $hostname ps -ef |grep mysql | grep wsrep_sst_xtrabackup-v2`;
         if ( $wsrep_check ne "" ){
            print "$time: Server $hostname\n";
       }
}
close $info;

Upvotes: 1

Views: 524

Answers (1)

Borodin
Borodin

Reputation: 126732

You need to

chomp $hostname;

before your ssh command to remove the trailing newline from the read

I also suspect that your last if $. == 2 should be outside the if block

Perl has built-in support for regular expressions, so there is rarely any need for a call to index

if ( index($wsrep_check, 'State transfer in progress, setting sleep higher mysqld') != -1 ) { ... }

would usually be written

if ( $wsrep_check =~ /State transfer in progress, setting sleep higher mysqld/ ) { ... }

but what you have written is fine

Upvotes: 3

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