Notification if server unreachable? Post: 302173149

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Top Forums UNIX for Dummies Questions & Answers Notification if server unreachable? Post 302173149 by Smiling Dragon on Wednesday 5th of March 2008 07:03:21 PM

03-05-2008

Registered User

It sort of depends what you want to use to alert, how many alerts you will tollerate in the event of a problem, and how vital it is that you get the alert.

Having each server watch the other 4 will mean that it's very likely you will hear about it if one of them fails, but you will get 4 messages about one machine. If you have a network interruption, you might get 20 messages as each server tells you the other 4 are dead. This can get quite bad if you plan to scale this up.

Having just one server watch the other 4 means that if that one server fails, you won't know. Further more, if it fails then another goes, you won't hear about that either. On the up-side, if one server fails, you only get one message. If the network fails, you only get 4 messages.

You can pick something halfway between (eg have two server watch everything else, or have two servers watch each other and 1 or 2 other servers) to find the balance you need.

A quick framework of what you'd probably want to run:

Code:

#!/bin/sh
while true
do
  for host in $HOSTLIST
  do
    if ping $host
    then
      echo "`date` $host ok" >> log
    else
      echo "`date` $host NOT OK" >> log
      echo "Hi, `hostname` here to tell you that its all gone Pete Tong on $host" | mail_prog_of_your_choice
      echo "`hostname` says: $host has left the building" | your_favourite_pager_or_sms_gateway
      /cool/noises/play_alarming_sounds aaawuuuuga.au
    fi
  done
  sleep $INTERVAL
done

Smiling Dragon

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LEARN ABOUT SUSE

watch

WATCH(1)							Linux User's Manual							  WATCH(1)

NAME

       watch - execute a program periodically, showing output fullscreen

SYNOPSIS

       watch [-dhvt] [-n <seconds>] [--differences[=cumulative]] [--help] [--interval=<seconds>] [--no-title] [--version] <command>

DESCRIPTION

       watch runs command repeatedly, displaying its output (the first screenfull).  This allows you to watch the program output change over time.
       By default, the program is run every 2 seconds; use -n or --interval to specify a different interval.

       The -d or --differences flag will highlight the differences  between  successive  updates.   The  --cumulative  option  makes  highlighting
       "sticky",  presenting  a running display of all positions that have ever changed.  The -t or --no-title option turns off the header showing
       the interval, command, and current time at the top of the display, as well as the following blank line.

       watch will run until interrupted.

NOTE

       Note that command is given to "sh -c" which means that you may need to use extra quoting to get the desired effect.

       Note that POSIX option processing is used (i.e., option processing stops at the first non-option argument).  This means	that  flags  after
       command don't get interpreted by watch itself.

EXAMPLES

       To watch for mail, you might do

	      watch -n 60 from

       To watch the contents of a directory change, you could use

	      watch -d ls -l

       If you're only interested in files owned by user joe, you might use

	      watch -d 'ls -l | fgrep joe'

       To see the effects of quoting, try these out

	      watch echo $$

	      watch echo '$$'

	      watch echo "'"'$$'"'"

       You can watch for your administrator to install the latest kernel with

	      watch uname -r

       (Just kidding.)

BUGS

       Upon  terminal  resize, the screen will not be correctly repainted until the next scheduled update.  All --differences highlighting is lost
       on that update as well.

       Non-printing characters are stripped from program output.  Use "cat -v" as part of the command pipeline if you want to see them.

AUTHORS

       The original watch was written by Tony Rems <rembo@unisoft.com> in 1991, with mods and corrections by Francois Pinard.  It was reworked and
       new features added by Mike Coleman <mkc@acm.org> in 1999.

								    1999 Apr 3								  WATCH(1)

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