Retention policy to TFS Code Search Server (Elastic Search) - elasticsearch

Question

We have TFS 2017.3 with separate Code Search server.
We have huge TFS DB (about 1.6TB), in the code search server we have 700GB dis space.
After few weeks the disk space running out and the code search not work in the tfs.
After we increase the disk space the search back to work.
How can we make retention policy to delete old code search data (index)? we don't want to increased more the disk space.

Answer 1

Search indexing (Code and Work Item) works in 2 phases:
Bulk Indexing (BI) where the entire code and work item artifacts in all projects/repositories under a Collection are indexed. This is a
time consuming operation and depends on the size of the artifacts
under the collection.
Continuous Indexing (CI) which handles all incremental updates to the artifacts (add/updated/delete) and indexes them. This is
notification based model where the indexer listens to TFS events
and operates based on those event notifications. CI handles almost
all update operations including CRUD operations at
Project/Repository/Collection layer (such as Repository renames,
Project add/deletes, etc.). The operation time for these CI would
depend again on the size of the incremental update. BI always
precedes CI i.e. a CI will never execute on a project/repository
until BI is completed for the same.
How to Clean-up Index Data and Re-index please follow below steps:
Pause Indexing for all collections. Run the following script on TFS
Configuration DB
https://github.com/Microsoft/Code-Search/blob/master/PauseIndexing.ps1
Login to the machine where the Elasticsearch (ES) is running
Stop the ES service
Delete the entire Search Index folder (something like,
C:\TfsData\Search\IndexStore, or wherever you had configured it to
be)
Restart the TFS Job Agent service(s) on the AT machines
Delete the following tables from each of the collection DBs
DELETE FROM [Search].[tbl_IndexingUnit]
DELETE FROM [Search].[tbl_IndexingUnitChangeEvent]
DELETE FROM [Search].[tbl_IndexingUnitChangeEventArchive]
DELETE FROM [Search].[tbl_JobYield]
DELETE FROM [Search].[tbl_TreeStore]
DELETE FROM [Search].[tbl_DisabledFiles]
DELETE FROM [Search].[tbl_ResourceLockTable]
Restart the ES service
Run this script on TFS Configuration DB:
https://github.com/Microsoft/Code-Search/blob/master/ResumeIndexing.ps1
Run this script (pick from the correct TFS release folder) on each of
the collections:
https://github.com/Microsoft/Code-Search/blob/master/TFS_2017Update2/MissingIndexFolderTriggerCollectionIndexing.ps1
Try the last script on a smaller collection first (which has less
number of repositories) so that you can verify that indexing happened
correctly and the results are query-able.
More details please refer this blog in MSDN: Resetting Search Index in Team Foundation Server

Answer 2

I was able to reduce the disk size after deleting the ES folders, reinstalling the code search extension, and sometimes had to run the MissingIndexFolderTriggerCollectionIndexing.ps1.
But - I came to the conclusion that it was not worth doing, the disk size was growing rapidly and reaching the original size, so I did not save anything.
Although Microsoft recommends giving disk space of 35% of the DB, it is not enough for us and we increase the size when the disk is full to the end (currently about 45% of the DB size).
The conclusion - don't touch the ES, if the disk fills up then increase the disk size.