If you deploy multiple YK-VAL instances, it is important to monitor them to make sure the data they have is synchronized. While there are many mechanisms to achieve this, we provide a simple yet flexible approach. The ykval-checksum-clients tool reads out the important fields from the database and computes a SHA-1 hash of it, and truncates the hash to 10 hex characters and prints them to stdout.
The "important fields" are currently considered to be the id, active, and secret columns of the clients table.
The typical way to use this is either manually or to run it in a cron job and output the hash to a file that can be downloaded by a remote monitor system such as Nagios.
user@val:~$ sudo sh -c 'cat > /etc/cron.hourly/run-ykval-checksum-clients'
#!/bin/sh
FILE=/var/www/checksum-clients.txt
(date --utc +%s; ykval-checksum-clients) > $FILE.tmp
mv $FILE.tmp $FILE
user@val:~$ sudo chmod +x /etc/cron.hourly/run-ykval-checksum-clients
If you notice mismatches, you may want to run ykval-checksum-clients with the -v parameter on the different hosts and then use diff -ur or similar tool to compare the outputs. This should make it possible to identify the missmatching entries easily.