[Backport 5.3.9104] search: support draining Zoekt instances #62043
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This PR implements support for draining a zoekt replica via including its hostname in the comma-separated environment variable INDEXED_SEARCH_DRAIN_SERVERS on sourcegraph-frontend. The way this functionality is implemented is via adjusting the endpoint map we use when making assignment of repos. We still report the hostname as part of the list of endpoints. However, the endpoint is left out of the consistent hash which maps the repositories to endpoints. Our interactions with zoekt are already designed to do smooth rebalancing when the set of endpoints changes. We have logic to only remove repos from a replica once its new endpoint has it, and we support deduplication of search results across endpoints. Co-authored-by: Stefan Hengl <stefan@sourcegraph.com> (cherry picked from commit 3313683)
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This is an alternative implementation to #61833
This PR implements support for draining a zoekt replica via including its hostname in the comma-separated environment variable
INDEXED_SEARCH_DRAIN_SERVERSon sourcegraph-frontend.The way this functionality is implemented is via adjusting the endpoint map we use when making assignment of repos. We still report the hostname as part of the list of endpoints. However, the endpoint is left out of the consistent hash which maps the repositories to endpoints.
Our interactions with zoekt are already designed to do smooth rebalancing when the set of endpoints changes. We have logic to only remove repos from a replica once its new endpoint has it, and we support deduplication of search results across endpoints.
Test Plan: Stefan manually tested it.
Co-authored-by: @stefanhengl
Backport 3313683 from #62005