HTTP Monitor cURL Basic GET

Problem this snippet solves:

External HTTP monitor script that requests a URI from the pool member to which it is applied, marking it up if the expected response is received. URI 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 example is intended to demonstrate the basic use of cURL (which offers a large number of other useful options) in an external monitor. However, if you don't need those extra options, a very simple HTTP monitor such as this is much more efficiently configured using the built-in HTTP monitor template instead.

How to use this snippet:

  1. 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. 2. 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 request from the server
      • RECV . . . . the expected response
  2. 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

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 :

# (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+GET,v 1.0 2007/06/28 16:10:15 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 (IPv6 notation. IPv4 addresses are passed in the form 
#                         ::ffff:w.x.y.z
#                         where "w.x.y.z" is the IPv4 address)
# $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/Vaule pairs:
#  URI  = the URI to request from the server
#  RECV = the expected response (not case sensitive)

# remove IPv6/IPv4 compatibility prefix (LTM passes addresses in IPv6 format)
IP=`echo ${1} | sed 's/::ffff://'`

PIDFILE="/var/run/`basename ${0}`.${IP}_${PORT}.pid"
# kill of the last instance of this monitor if hung and log current pid
if [ -f $PIDFILE ]
   echo "EAV exceeded runtime needed to kill ${IP}:${PORT}" | logger -p local0.error
   kill -9 `cat $PIDFILE` > /dev/null 2>&1
echo "$$" > $PIDFILE

# send request & check for expected response
curl -fNs http://${IP}:${PORT}${URI} | grep -i "${RECV}" 2>&1 > /dev/null

# mark node UP if expected response was received
if [ $? -eq 0 ]
    rm -f $PIDFILE
    echo "UP"
    rm -f $PIDFILE

Published Mar 12, 2015
Version 1.0

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  • Hello, we have tried this option and created an script to test out some monitor that we need.


    However, we do not see that file in the drop down list when we try to create the Monitor with type External.


    Thanks!! N.


  • N.


    Import the script to: System > File Management > External Monitor Program File List


  • The above steps might not exactly work, but are good enough to point you in the right directions.




    1. Copy the script
    2. Paste it on your textpad (notepad, etc)
    3. Import the script System > File Management > External Monitor Program File List
    4. Once the import is completed, a file is automatically generated under /config/filestore/files_d/Common_d/external_monitor_d.
    5. In this example the name if the created file is curl_monitor_ex_68725_1
    6. Run the following command
    7. sed -i 's/\r$//' /config/filestore/files_d/Common_d/external_monitor_d/\:Common\:curl_monitor_ex_68725_1
    8. Create the monitor and attach it to the pool


    STEP #7 in an important step. If STEP 7 is skipped then you can see the following errors in /var/log/monitors/<name> (if monitor logging is enabled)


    l_up=0 immed=0 next_ping=[1564634525.155247][2019-08-01 12:42:05] last_ping=[1564634520.236345][2019-08-01 12:42:00] deadline=[1564634523.946757][2019-08-01 12:42:03] on_service_list=True snd_cnt=12 rcv_cnt=0 ]

    [0][6419] 2019-08-01 12:42:00.237862: ID 79  :(spawn_external_pinger): EAV execve: No such file or directory

    [0][6419] 2019-08-01 12:42:00.238338: ID 79  :(_main_loop): Service ready for read, now=[1564634520.238304][2019-08-01 12:42:00] [ addr=::ffff: srcaddr=::%0:0 fd=13 pend=0 #conn=0 ]

    [0][6419] 2019-08-01 12:42:00.238374: ID 79  :(_recv_external_node_ping): reading [ addr=::ffff:x.x.x.x:80 ]

    [0][6419] 2019-08-01 12:42:00.238397: ID 79  :(recv_external_node_ping): EAV failed [ addr=::ffff:x.x.x.x:80 ]

    [0][6419] 2019-08-01 12:42:00.238421: ID 79  :(_kill_external_pinger): killing pid=2642 [ addr=::ffff:x.x.x.x:80 fd=13 ]

  • Hello,


    I did the exact same thing and ran the command sed -i 's/\r$//' /config/filestore/files_d/Common_d/external_monitor_d/\:Common\:curl_monitor_ex_68725_210231_1


    but I dont get anything after the command is run!

  • Hello when I import the script to: System > File Management > External Monitor Program File List, HA status changes to Sync Failed, and I am unable to synchronize HA. If I upload the script via SCP to folder /usr/bin/monitors then I am not able to use it in: Local Traffic > Monitors > New Monitor (External Monitor)