Announcements
There are no changes in this release that change how Curator will appear to behave to the user. However...
This release ends the practice of collecting all stats and metadata at IndexList initiation. This should make execution much faster for users with enormous clusters with hundreds to thousands of indices. In the past, this was handled at IndexList instantiation by making a cluster state API call. This is rather heavy, and can be so much data as to slow down Curator for minutes on clusters with hundreds to thousands of shards. This is all changed in this release.
For example, the pattern filter requires no index metadata, as it only works against the index name. If you use a pattern filter first, the actionable list of indices is reduced. Then if you need to filter based on age using the creation_date, the age filter will call get_index_settings to pull the necessary data for that filter to complete. Some filters will not work against closed indices. Those filters will automatically call get_index_state to get the open/close status of the indices in the actionable list. The disk space filter will require the index state as it won't work on closed indices, and will call get_index_stats to pull the size_in_bytes stats.
Additionally, the cat API is used to get index state (open/close), now, as it is the only API call besides the cluster state which can inform on this matter. Not calling for a huge dump of the entire cluster state should drastically reduce memory requirements, though that may vary for some users still after all of the index data is polled, depending on what filters are used.
There is a potential caveat to all this rejoicing, however. Searchable snapshot behavior with ILM policies usually keeps indices out of Curator's vision. You need to manually tell Curator to allow it to work on ILM enabled indices. But for some users who need to restore a snapshot to remove PII or other data from an index, it can't be in ILM anymore. This has caused some headaches. For example, if you are tracking an index in the hot tier named 'index1' and it is in process of being migrated to the cold tier as a searchable snapshot, it may suddenly disappear from the system as 'index1' and suddenly re-appear as 'restored-index1'. The original index may now be an alias that points to the newly mounted cold-tier index. Before this version, Curator would choke if it encountered this scenario. In fact, one user saw it repeatedly. See the last comment of issue 1682 in the GitHub repository for more information.
To combat this, many repeated checks for index integrity have become necessary. This also involves verifying that indices in the IndexList are not actually aliases. Elasticsearch provides exists tests for these, but they cannot be performed in bulk. They are, however, very lightweight. But network turnaround times could make large clusters slower. For this reason, it is highly recommended that regex filters be used first, early, and often, before using any other filters. This will reduce the number of indices Curator has to check and/or verify during execution, which will speed things up drastically.
Other Changes
Most of the unit tests needed updating due to these changes (adding a few more Mock responses), so I took the time to refactor them to use a builder method instead of repeating the same few lines of code in each test. This represents the vast majority of code deletions (2,085 lines!). All of the tests are passing, both integration and unit tests.