Forum Discussion
alertd to trigger script after seeing specific syslog n times
i need to trigger an script after detecting a specific syslog. However, for dampening purposes i would like to see the same syslog 3 times before taking any actions, what is the best way to achive this?
Recommendation to use alertd : https://support.f5.com/csp/article/K14397
Recommendation to trigger a script: https://devcentral.f5.com/s/question/0D51T00006i7YqX/f5-to-run-shell-script-on-remote-host-in-certain-event
- Simon_Blakely
Employee
So you need to start with something like
A utility script that can carry out a time-based filter on log files with various timestamp formats
#!/usr/bin/perl -ws # This script parse logfiles for a specific period of time sub usage { printf "Usage: %s -s=<start time> [-e=<end time>] <logfile>\n"; die $_[0] if $_[0]; exit 0; } use Date::Parse; usage "No start time submited" unless $s; my $startim=str2time($s) or die; my $endtim=str2time($e) if $e; $endtim=time() unless $e; usage "Logfile not submited" unless $ARGV[0]; open my $in, "<" . $ARGV[0] or usage "Can't open '$ARGV[0]' for reading"; $_=<$in>; exit unless $_; # empty file # Determining regular expression, depending on log format my $logre=qr{^(\S{3}\s+\d{1,2}\s+(\d{2}:){2}\d+)}; $logre=qr{^[^\[]*\[(\d+/\S+/(\d+:){3}\d+\s\+\d+)\]} unless /$logre/; while (<$in>) { /$logre/ && do { my $ltim=str2time($1); print if $endtim >= $ltim && $ltim >= $startim; }; };
user_alert.conf
this is the custom user alert that looks for logged events
alert syslog_status_trigger_action "your critical message" { exec command="/shared/trigger_action.sh"; exec command="/bin/logger -p local0.info 'action_triggered'" }
Then in your bash script trigger_action.sh:
#!/bin/bash TRIGGER_LEVEL=3 if [ ! -e /tmp/trigger_action_count ]; then # filter ltm1 and ltm into a single file so we don't miss events around log-rotation grep 'trigger_action' /var/log/ltm.1 > /tmp/trigger_action_count grep 'trigger_action' /var/log/ltm >> /tmp/trigger_action_count # set your time period below - I have chosen 10 minutes COUNT=$(/shared/timelapseinlog.pl -s=`/bin/date -d'now-10 minutes' +%H:%M` /tmp/trigger_action_count | wc -l) rm -f /tmp/trigger_action_count if [ -p $NP ] && [ "$COUNT" -gt "$TRIGGER_LEVEL" ]; then # do something here fi fi
Note that there are some things that will not run in the alertd SELinux context (tcpdump, for example).
You may need to run a script on startup that waits on a named pipe, and then the above trigger script signals using the named pipe.
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