Multiple Monitor Timers

Strictly speaking, the external monitor could change the timeout value on itself by executing tmsh -- or an iCall periodic script could run the monitor page check and modify the timeout value -- but I strongly recommend against doing that, or ever having an external monitor change configuration, for that matter. The reason is, if the BIG-IP is part of an HA cluster, it will make the member out-of-sync (and if autosync is turned on, it may push the config when somebody is making changes on another unit, wiping out whatever changes were made).

An external monitor could solve this in a number of ways, but here is logic for one way to do it:

1. Run the test that was being performed by the monitor (e.g., if the monitor if http, use curl to retrieve the page and parse the result);
2. If the test in 1 succeeds, return an "up" value (that is, print something to stdout), remove the file cited in 5 (if it exists), then exit;
3. If the test in 1 fails, run the test against the monitoring page;
4. If the test in 3 fails or if the results do not indicate that maintenance is happening, remove the file cited in 5 (if it exists), then exit without writing anything to stdout (this will trigger a "down" status);
5. If the test in 3 succeeds and indicates that maintenance is happening, check to see if there is file named /var/tmp/mymonitor.$ip:$port.tmp ($ip and $port are always the first two command-line argument provided to the monitor);
6. If the file does not exist, grab the current unix epoch time in seconds and write it to the file, return an "up" value, then exit;
7. If the file does exist, read the value, grab the current unix epoch time in seconds and compare them;
8. If the delta in 5 is less than your second threshold (30 seconds), return an "up" value and exit;
9. If the delta in 5 is greater than or equal to your second threshold, exit without writing anything to stdout (which triggers a "down" status).

Here it is in psuedo-code(ish) ($1 and $2 are the command-line arguments supplied to the script):

 all external monitors are automatically passed the target IP and port
 as the first two positional parameters.  If the IP is IPv4, it will
 start with ::ffff:, followed by the IPv4 address as dotted-quad
 (e.g., ::ffff:10.10.10.1).

ip=`echo $1 | sed 's/::ffff://'`
port=$2
file="/var/tmp/$0.$ip:$port.tmp"
monitor_page="https://my.monitor.example.com/status"

first_test=`curl -Lis http://$ip/ | grep -E '^HTTP/1.1 200'

if [ "$first_test" != "" ]; then
    rm -f "$file"
    echo "UP"
    exit 0
fi

 assuming that I'm looking for the string "In Maintenance Mode"
second_test=`curl -Ls $monitor_page | grep 'In Maintenance Mode'`

if [ "$second_test" == "" ]; then
    rm -f "$file"
    exit 1
fi

if [ -f "$file" ]; then
    last_time=`cat "$file"`
    curr_time=`date +%s`
else
    date +%s > "$file"
    echo "UP"
    exit 0
fi

if [ $(( $curr_time - $last_time )) -lt 30 ]; then
    echo "UP"
    exit 0
else
    exit 1
fi