HTTP Monitor cURL Basic POST
Problem this snippet solves:
External HTTP monitor script that sends a POST request to the pool member to which it is applied, marking it up if the expected response is received. URI, POST data, and response string are user-configurable. cURL by default uses HTTP/1.1 and, since no hostname is specified in the cURL command, inserts the IP address in the Host header.
NOTE: Use external monitors only when a built-in monitor won't do the trick. This monitor is intended as an example of using cURL (which offers a large number of other useful options) to perform a POST. More basic HTTP monitors are much more efficiently configured using the built-in HTTP monitor template instead.
UPDATE: The script below had a logic error in it where by it was using the NODE and PORT variables to create a PID file before the variables were defined. This meant that if your monitor took long enough to run the PID running monitor was killed before it finished and a new process ran in its place. This gave the appearence of the monitor not functioning correctly. I have corrected this below.
How to use this snippet:
- Create a new file containing the code below in /usr/bin/monitors on the LTM filesystem. Permissions on the file must be 700 or better, giving root rwx access to the file.
-
Create a monitor profile of type "External" with the following values:
- External Program: . . the name of the script file created in step 1
-
Variables:
- Name.......Value
- URI . . . . .the URI to which the POST will be sent (URI only, no hostname)
- DATA . . . . the POST data to be sent to the server
- RECV . . . . the expected response
-
Adjust the interval and timeout as appropriate for your application
Jan 3 00:00:00 local/bigip err logger: EAV exceeded runtime needed to kill 10.0.0.10:80
If the interval and timeout is smaller then the execution time of the script, the monitor marks the element down and logs a message in /var/log/ltm. This is a false negative. To fix this, please increase the interval and timeout accordingly.
Code :
#!/bin/sh # # (c) Copyright 1996-2007 F5 Networks, Inc. # # This software is confidential and may contain trade secrets that are the # property of F5 Networks, Inc. No part of the software may be disclosed # to other parties without the express written consent of F5 Networks, Inc. # It is against the law to copy the software. No part of the software may # be reproduced, transmitted, or distributed in any form or by any means, # electronic or mechanical, including photocopying, recording, or information # storage and retrieval systems, for any purpose without the express written # permission of F5 Networks, Inc. Our services are only available for legal # users of the program, for instance in the event that we extend our services # by offering the updating of files via the Internet. # # @(#) $Id: http_monitor_cURL+POST,v 1.0 2007/06/28 16:36:11 deb Exp $ # (based on sample_monitor,v 1.3 2005/02/04 18:47:17 saxon) # # # these arguments supplied automatically for all external monitors: # $1 = IP (nnn.nnn.nnn.nnn notation) # $2 = port (decimal, host byte order) # # additional command line arguments ($3 and higher) may be specified in the monitor template # This example does not expect any additional command line arguments # # Name/Value pairs may also be specified in the monitor template # This example expects the following Name/Value pairs: # URI = the URI to which the POST will be sent # DATA = the POST data to send to the server # RECV = the expected response (not case sensitive) # # remove IPv6/IPv4 compatibility prefix (LTM passes addresses in IPv6 format) NODE=`echo ${1} | sed 's/::ffff://'` PORT=${2} PIDFILE="/var/run/`basename ${0}`.${NODE}_${PORT}.pid" # kill of the last instance of this monitor if hung and log current pid if [ -f $PIDFILE ] then echo "EAV exceeded runtime needed to kill ${IP}:${PORT}" | logger -p local0.error kill -9 `cat $PIDFILE` > /dev/null 2>&1 fi echo "$$" > $PIDFILE # send request & check for expected response curl -fNs http://${NODE}:${PORT}${URI} -d "${DATA}" | grep -i "${RECV}" 2>&1 > /dev/null # mark node UP if expected response was received if [ $? -eq 0 ] then # Remove the PID file rm -f $PIDFILE echo "UP" else # Remove the PID file rm -f $PIDFILE fi exit