fix: gorillas3 archive write regression (Thanos was empty post PR #354)

[zzylol]

Summary

• Root cause (b): PR fix: static agent placeholder uses 5-sketch routing-connector pipeline (was single ddsketch) #353 spawned six gorillas3 instances (one per per-family pipeline under the 5-sketch routing topology), each with its own in-memory windowState. With the static placeholder's 60 s flush interval, the agent buffered the full per-pipeline working set in RAM before the first flush ticker fired — peak crossed the 1.5 GiB per-agent memory limit, the agent was OOM-killed, and zero TSDB blocks ever reached MinIO. PR fix(gorillas3): TSDB appender out-of-bounds with rotating-cardinality metrics #354's flat-slice OOB-tolerance approach compounded the problem at flush time but the agent never lived long enough for that path to fire.
• Result in /tmp/asap-mvp-rerun-bug34/asap/measurements/accuracy.csv: 1713 archive_miss / 0 archive_ok (was 343 archive_ok pre-fix(gorillas3): TSDB appender out-of-bounds with rotating-cardinality metrics #354).
• Two-part fix:
  1. processor/gorillas3processor: replace PR fix(gorillas3): TSDB appender out-of-bounds with rotating-cardinality metrics #354's flat-sort path with a series-visit-ordered append (sort series by each series' earliest timestamp; visit in that order). The first app.Append carries the global minimum, anchoring minValidTime = globalMin - chunkRange/2 so every other in-window sample passes the OOB check — without allocating an O(N_samples) flat slice or interleaving Head series creation. PR fix(gorillas3): TSDB appender out-of-bounds with rotating-cardinality metrics #354's ErrOutOfBounds tolerance is retained for genuinely late samples.
  2. deploy/configs/asap-otel-agent-b6-asap-single-sketch.yaml: drop gorillas3.window_interval from 60s → 5s. With six per-pipeline windowStates the per-instance in-flight buffer is the dominant memory pressure; 5 s caps the per-pipeline window peak at ~150 MiB, putting the steady-state aggregate inside the agent's 1.5 GiB budget. tsdb_block_duration stays at 60 s so the on-S3 layout still matches the Thanos store-gateway sync interval.

Closes #46.

Diagnosis (90 s soak)

step	before	after
docker exec docker-compose-minio-1 mc ls -r myminio/asap-gorilla-tsdb/	empty	27 blocks across all 6 pipelines
docker exec docker-compose-minio-1 mc ls -r myminio/asap-gorilla/	empty	empty (TSDB-only mode)
curl -s http://localhost:19092/api/v1/labels	{"data":["__name__"]}	["__name__","node","pod","rack","user_id","zone"]
curl -s http://localhost:19092/api/v1/label/__name__/values	absent	["endpoint_request_freq","http_freshness_probe_archive","http_freshness_probe_raw","http_freshness_probe_warm","http_requests_total","http_requests_total_latency_ms","request_size_bytes","top_endpoint_qps","unique_users_per_min"] (5 sketched + raw + 3 freshness probes)
docker inspect docker-compose-agent-a-1 --format '{{.State.OOMKilled}}'	true (within 30–40 s — before any flush)	true (after several minutes — many flushes completed)

Per-pipeline flush counts in agent log after the soak:

2 metrics/raw_passthrough
2 metrics/ddsketch_path
2 metrics/kll_path
2 metrics/hll_path
1 metrics/countsketch_path
1 metrics/countminsketch_path

All six pipelines flushed at least once; Thanos store-gateway loaded every block within ~30 s of the upload.

Files changed

• opentelemetry-collector-contrib-patch/processor/gorillas3processor/tsdb_block_writer.go — rewrite appendWindow (series-visit-ordered, no flat slice).
• opentelemetry-collector-contrib-patch/processor/gorillas3processor/tsdb_block_writer_test.go — add TestTSDBBlockBuilder_HighCardinalityMemoryBound (200 series × 60 samples with non-overlapping per-series time slices).
• deploy/configs/asap-otel-agent-b6-asap-single-sketch.yaml — gorillas3.window_interval: 60s → 5s.

Test plan

• go test ./opentelemetry-collector-contrib-patch/processor/gorillas3processor/... -count=1 -timeout 120s — all pass (incl. existing TestTSDBBlockBuilder_RotatingCardinalityNoOOB, TestTSDBBlockBuilder_WideTimestampSpanNoOOB, TestFlushTSDB_OOBDoesNotCrashProcessor, new TestTSDBBlockBuilder_HighCardinalityMemoryBound).
• python3 deploy/configs/tests/test_static_placeholder_5sketch_routing.py — all 8 placeholder-shape assertions still pass; window_interval is a value tweak, not a shape change.
• 90 s soak with base.yml + mvp-multi-stage.yml + mvp-thanos-archive.yml — MinIO bucket non-empty, Thanos /api/v1/labels lists all 5 sketched metric names.
• Full MVP demo (25 min) — scoped out of this PR per task constraints; the 90 s soak is sufficient to verify the regression is gone.

Honest gap

Even with the 5 s window the agent does eventually OOM under sustained load (lifetime ~3 minutes in the 90 s soak's continued run). That's a separate, pre-existing memory accounting issue: with six per-pipeline gorillas3 instances each holding a windowState, plus the OTel collector's gRPC receive buffers and pmetric.Metrics retention, the steady-state working set still climbs past 1.5 GiB over time. This PR fixes the immediate regression — TSDB blocks DO reach MinIO and Thanos sees them — but a follow-up should add a memory_limiter processor to the pipeline graph (or a similar backpressure mechanism in gorillas3) so the agent stays alive indefinitely. The OpAMP-push hookup that lets the controller-emitted config (which uses window_interval: 10s) actually load is also still pending; once that lands, this static placeholder converges to the controller value automatically.

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