Lately we have been seeing this behavior where Icinga throws flood of alerts now and then. We have one single instance running for now.
Checking error logs around the time when alerts were thrown, it seems there are error messages similar to "exited with error code 128". At the same time we received check_load critical on that icinga server.
Load : Additional Info: CRITICAL - load average: 18.85, 12.01, 5.95
Version and Platform details:
icinga2 - The Icinga 2 network monitoring daemon (version: r2.6.0-1)
Platform version: 14.04.5 LTS, Trusty Tahr
Kernel version: 3.13.0-53-generic
Compiler: GNU 4.8.4
Build host: lgw01-16