Background

While investigating a CI timeout for BACKPORT-29789 (PR #62867, backporting SERVER-134080 to v9.0-staging), jstests/sharding/query/change_streams/change_stream_metrics_update_lookup.js was found to intermittently stall for many minutes under the sharding_csrs_continuous_config_stepdown suite, eventually hitting the Evergreen task timeout and the hang analyzer. The cause is not yet identified.

Evidence

• Burn-in run (arm64, with the backport patch): stalled ~11 minutes inside a single it() test case's getMore retry loop before hitting the task timeout. Task
• Required run, arm64 enterprise (with the backport patch): passed cleanly in 17 minutes. Task
• Required run, linux-64-debug (with the backport patch): failed in a different, pre-existing test's beforeEach hook, when all three config-server members briefly went Connection refused simultaneously. Task
• Base commit (v9.0-staging mainline, no patch applied): also hit the hang analyzer on this same task, stalling in yet another unrelated test in the same file. Task

change_stream_metrics_update_lookup.js has been excluded from sharding_csrs_continuous_config_stepdown.yml as an interim measure (see PR #62867), consistent with the existing exclusion of change_stream_lookup_post_image_chunk_migration.js for what appears to be the same class of issue.