200325: M4 teaser

(Very) High-Level Design of “M4”

“M4” is the name of one of the HA milestones. It is described as “Health checks”, which is very unspecific. 😕

Here is my (@vvv's) understanding of M4 design.

A "resource agent" is added to Pacemaker (via @andriy.tkachuk's build-ees-ha script). Pacemaker monitors it, i.e., queries periodically, asking “Is everything OK?”

The resource agent script receives <check id> parameter. So, in fact, this script is a dispatcher, which calls implementation of a particular “check”.

There are 3 phases of the implementation:

1. “The skeleton”, i.e., the resource agent itself and a sample check.
2. Integration with build-ees-ha. This is ongoing process.
3. Implementation of individual checks. So far ~16 have been identified by @max. They will be worked on incrementally, by several people.

Phase 1 exists in a branch. We are going to integrate the skeleton with build-ees-ha and record a demo by the end of week.

-- @vvv