Marten.ScaleTesting: daemonload over pooled sharded databases — O(databases) connection gate (#4882, epic jasperfx#486 WS6)#4890
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--databases N pools the tenants across N scaletest_dl_shard_* databases via MultiTenantedWithShardedDatabases (explicit round-robin placement, one daemon per shard). ShardConnectionSampler groups pg_stat_activity by datname so the --max-connections gate is enforced PER DATABASE, plus per-tenant catch-up verification on every shard and a database-affine placement check (per-tenant sequence in exactly the home shard). Local-scale result (25 tenants x 2 shards x 2 projections, 60s): shard peaks 16/11, all 25 tenants caught up, zero placement violations. Single-database path (--databases 1, the default) unchanged. Addresses #4882 Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01XNfeNz73Q3EdiTgSeDbo96
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Closes #4882 (epic #486 WS6). Stacked on #4887 (
feat/4684-batch-instrumentation) — review/merge that first; this PR's own diff is the top two commits.What's here
Extends
daemonload(#4875) from single-database to sharded multi-tenancy with database pooling:--databases Ncreatesscaletest_dl_shard_0..N-1on the same server (--wipedrops themWITH (FORCE)first), builds the store withMultiTenantedWithShardedDatabases(registry in the master DB'sscaletest_daemonloadschema,UseExplicitAssignment), assigns tenants round-robin with explicit placement, and runs one projection daemon per shard (sharded tenancy has oneMartenDatabaseper shard; the default-tenant daemon overload is invalid there)pg_stat_activitysampling — newShardConnectionSamplerpolls once per interval on the maintenance DB and groups the store's Application-Name-attributed backends bydatname(ShardedTenancyOptions.ApplicationNamestamps every pooled connection string). Master/registry DB reported separately--max-connectionsenforced per shard database (the O(databases) gate)mt_events_sequence_{tenant}must exist in exactly its assigned shard; foreign-shard or missing-at-home sequences fail the run as cross-shard bleed--databases 1(default) is the untouched original single-DB WS2 scenario (regression-verified).Measured (local reduced scale — sibling agents share this Postgres; full scale is a CLI-knob rerun)
daemonload --databases 2 --tenants 25 --projections 2 --duration-seconds 60 --wipe --max-connections 16scaletest_dl_shard_0peak / meanscaletest_dl_shard_1peak / meanPer-shard peaks sit at the single-DB governor plateau (12–14 baseline from the #494 measurement record; 16 here with 4 appender writers steering into 2 DBs), i.e. connections scale O(databases), not O(agents) — 50 agents produced a summed peak of 27, not 50+.
Full-scale rerun for the epic record:
--databases 4 --tenants 100 --projections 2 --duration-seconds 120 --max-connections 16.🤖 Generated with Claude Code
https://claude.ai/code/session_01XNfeNz73Q3EdiTgSeDbo96