My ASM On Premise Monitoring Station (OPMS) is no longer running my monitors, and they fail with "checkpoint unavailable". When checking logs on the OPMS server (/var/log/smartpop folder on the OPMS), I noted the following in the smartpop-api.log:
Error 111 connecting to unix socket: /var/run/redis/redis.sock. Connection refused.
Debian OPMS server running OPMS 8.3 or 8.4.
This can be caused by corruption of a redis database used internally by the OPMS. Check the log -f /var/log/redis/redis-server.log, and see if it contains log entries reading to this:
 19 Apr 09:48:38.803 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
 19 Apr 09:48:38.904 # Bad file format reading the append only file: make a backup of your AOF file, then use ./redis-check-aof --fix <filename>
If the /var/log/redis/redis-server.log contain these entries, then a tool can be run to repair this database. Do the following:
-Stop the redis-server service if it is running by entering the following command on the OPMS:
# monit stop redis-server
-Run the following command to repair the database:
# redis-check-aof --fix /var/lib/redis/appendonly.aof
-restart the redis-server service:
# monit start redis-server