This commit refactors the `IndexLifecycleRunner` to split out and
consolidate the number of methods that change state from within ILM. It
adds a new class `IndexLifecycleTransition` that contains a number of
static methods used to modify ILM's state. These methods all return new
cluster states rather than making changes themselves (they can be
thought of as helpers for modifying ILM state).
Rather than having multiple ways to move an index to a particular step
(like `moveClusterStateToStep`, `moveClusterStateToNextStep`,
`moveClusterStateToPreviouslyFailedStep`, etc (there are others)) this
now consolidates those into three with (hopefully) useful names:
- `moveClusterStateToStep`
- `moveClusterStateToErrorStep`
- `moveClusterStateToPreviouslyFailedStep`
In the move, I was also able to consolidate duplicate or redundant
arguments to these functions. Prior to this commit there were many calls
that provided duplicate information (both `IndexMetaData` and
`LifecycleExecutionState` for example) where the duplicate argument
could be derived from a previous argument with no problems.
With this split, `IndexLifecycleRunner` now contains the methods used to
actually run steps as well as the methods that kick off cluster state
updates for state transitions. `IndexLifecycleTransition` contains only
the helpers for constructing new states from given scenarios.
This also adds Javadocs to all methods in both `IndexLifecycleRunner`
and `IndexLifecycleTransition` (this accounts for almost all of the
increase in code lines for this commit). It also makes all methods be as
restrictive in visibility, to limit the scope of where they are used.
This refactoring is part of work towards capturing actions and
transitions that ILM makes, by consolidating and simplifying the places
we make state changes, it will make adding operation auditing easier.
8205cdd423