feat(replacer): Tune REPLACE resources via a sentry-option

[sentry-junior]

Errors-replacer FINAL inserts can take more ClickHouse threads, block size, and memory per environment without another Snuba deploy.

A replacer sentry-option overlays those three knobs at query time. Defaults stay 1 thread / 512-row blocks / 10GiB. Missing fields fall back to REPLACER_MAX_THREADS, REPLACER_MAX_BLOCK_SIZE, and REPLACER_MAX_MEMORY_USAGE. The rest of the REPLACE client profile is unchanged.

replacer:
  max_threads: 32
  max_block_size: 65536
  max_memory_usage: 68719476736  # 64GiB

[phacops]

Looks like the requested change: REPLACE-only settings, no SQL, 32 / 65536 / 64GB.

Two things before this ships:

Prod already overrides memory. ops/k8s/services/snuba/templates/prod_settings.py.j2 sets REPLACER_MAX_MEMORY_USAGE = 50GB for every SaaS/ST environment. After this merges, SaaS stays at 50GB unless ops is updated. Threads and block size will apply in prod (those are not overridden). If the 80-core / 320GB errors boxes are the target, this PR only gets you 32 threads and 64k blocks there — still 50GB RAM.

These are now the defaults for everyone. Self-hosted / docker / CI inherit 32 threads and a 64GB max_memory_usage. That does not reserve 64GB, it only raises the per-query kill. On a laptop-sized ClickHouse it just means a runaway FINAL can OOM the host instead of aborting at 10GB. Fine if we accept that, but it is a behavior change outside SaaS.

Comment next to the constants cites “~80 CPUs / 320GB” as if that is the default deployment. It is not. I would drop the hardware numbers from the default-settings comment (keep them in the PR body) so self-hosted readers do not think this is sized for their box.

Otherwise the wiring is correct: max_threads is actually sent on the REPLACE client, tests pin the literals, and the errors user profile really is max_threads=1 unless the query overrides it.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

Non-positive values not rejected

Medium Severity

_replace_resource_settings forwards whatever get_mapped_option returns, including zero or negative values. The PR contract and the prior implementation treated non-positive fields as “use the settings default,” but that guard was removed. A 0 for max_threads or max_memory_usage can mean auto/unlimited in ClickHouse rather than the historical REPLACE profile.

 

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