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- Encrypt scrape auth headers when an encryption key is configured - Test-scrape new URLs and keep OTLP engine ids unique
- Add the unknown_engine drop reason for unmatched LMCache resources - Leave the Valkey/Redis OTLP path unchanged
- Add kv_cache.hit_rate_low and kv_cache.eviction_risk Pro webhook events - Store per-connection alert settings behind GET/PUT /kv-cache/settings
- Skip hit rate windows whose engine is missing or disabled - Keep evaluating the remaining windows when one dispatch fails - Never reject from the hit rate evaluation timer
- Add betterdb_kv_cache_hit_rate, _chunks and _bytes gauges - Map the gauges to OTel semconv instruments - Export footprint and hit rates from the KV cache alerts service - Clear series on connection removal
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Check name Status Explanation Title check The title clearly identifies the primary change: LMCache hit-rate tracking for linked vLLM/SGLang engines. It is concise and specific. Description check The description is detailed, on-topic, and covers the summary, implementation changes, risk, and testing. It omits the template's explicit Changes and Checklist headings, but the main required informa… Linked Issues check Check skipped because no linked issues were found for this pull request. Out of Scope Changes check Check skipped because no linked issues were found for this pull request.
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- Resolve DNS only for hostnames, so private IP scrape URLs work in production - Strip IPv6 brackets and block ::1 even when private networks are allowed - Forget delta-tracker state for engines of a removed connection
- Unwrap ::ffff: mapped addresses (dotted and hex) before classifying - Cover the full fe80::/10 link-local and fc00::/7 unique-local ranges - Reject a second engine with the same name on a connection, so hit rate series keyed by engine name never collide
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Actionable comments posted: 6
- 🪄 Fix CodeRabbit comments on this PR
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Inline comments:
Review comments at @apps/api/src/common/utils/outbound-url-guard.ts:
- Around line 12-21: Update the blocked-address classification used by
isBlockedIp to include the IPv4 shared address space 100.64.0.0/10, so addresses
such as 100.100.100.200 are rejected when private networks are disallowed. Add a
test covering this metadata address.
- Around line 88-93: Update the outbound URL guard so the connection made by
fetchMetricsText uses a DNS address that was validated against blocked IP
ranges, covering both A and AAAA records and preventing a second, unchecked DNS
lookup. Keep redirects disabled and anchor the change to the outbound request
flow around dns.resolve and fetchMetricsText.
- Line 86: Update the hostname validation guarded by isProduction so
non-localhost hostnames undergo DNS destination-address validation in every
environment. Preserve the explicit localhost exception and reject hostnames
resolving to prohibited addresses, including link-local destinations.
Review comments at @proprietary/kv-cache/kv-cache-otlp-sink.service.ts:
- Around line 61-84: In the sum data-point loop, skip points with the OTLP
NO_RECORDED_VALUE flag before calling pointValue or recording drops. Apply this
check in the same manner as collectMetric so flagged stale values never reach
samples.observe or affect cumulative baselines.
Review comments at @proprietary/kv-cache/kv-cache-scrape.service.ts:
- Around line 56-73: In scrape, after fetchMetricsText completes and before
parsing or calling samples.observe, retrieve the current engine from
this.registry using engine.id and discard the response if it is missing,
disabled, or its scrapeUrl differs from the captured engine’s scrapeUrl.
Review comments at @proprietary/kv-cache/metrics-fetch.ts:
- Line 13: Cancel the response body before throwing for an oversized
Content-Length in the response-size check, and before the HTTP-error and
redirect rejections in the same response-handling flow. Preserve the existing
rejection behavior after cancellation.
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📒 Files selected for processing (53)
apps/api/src/common/interfaces/storage-port.interface.tsapps/api/src/common/utils/__tests__/outbound-url-guard.spec.tsapps/api/src/common/utils/outbound-url-guard.tsapps/api/src/connections/connection-registry.service.tsapps/api/src/external-metrics/__tests__/otel-metrics-ingest.controller.spec.tsapps/api/src/external-metrics/__tests__/otel-metrics-ingest.service.spec.tsapps/api/src/external-metrics/kv-cache-otlp-sink.tsapps/api/src/external-metrics/otel-metrics-ingest.service.tsapps/api/src/external-metrics/otlp-metric-map.tsapps/api/src/external-metrics/otlp-metrics-types.tsapps/api/src/otel-telemetry/__tests__/semconv-map.spec.tsapps/api/src/otel-telemetry/semconv-map.tsapps/api/src/prometheus/__tests__/prometheus.kv-cache.spec.tsapps/api/src/prometheus/prometheus.service.tsapps/api/src/storage/adapters/__tests__/kv-cache-storage.spec.tsapps/api/src/storage/adapters/memory.adapter.tsapps/api/src/storage/adapters/postgres.adapter.tsapps/api/src/storage/adapters/sqlite.adapter.tsapps/api/src/webhooks/webhooks.service.tsapps/web/src/components/webhooks/WebhookForm.tsxpackages/shared/src/webhooks/types.tsproprietary/kv-cache/__tests__/counter-deltas.spec.tsproprietary/kv-cache/__tests__/fixtures/lmcache-metrics.txtproprietary/kv-cache/__tests__/kv-cache-alert-rules.spec.tsproprietary/kv-cache/__tests__/kv-cache-alerts.service.spec.tsproprietary/kv-cache/__tests__/kv-cache-engine-registry.spec.tsproprietary/kv-cache/__tests__/kv-cache-engines.service.spec.tsproprietary/kv-cache/__tests__/kv-cache-footprint.service.spec.tsproprietary/kv-cache/__tests__/kv-cache-otlp-sink.service.spec.tsproprietary/kv-cache/__tests__/kv-cache-samples.service.spec.tsproprietary/kv-cache/__tests__/kv-cache-scrape.service.spec.tsproprietary/kv-cache/__tests__/kv-cache-status.service.spec.tsproprietary/kv-cache/__tests__/kv-cache.controller.spec.tsproprietary/kv-cache/__tests__/metrics-fetch.spec.tsproprietary/kv-cache/__tests__/prometheus-text.spec.tsproprietary/kv-cache/counter-deltas.tsproprietary/kv-cache/dto/kv-cache-engine.dto.tsproprietary/kv-cache/dto/kv-cache-settings.dto.tsproprietary/kv-cache/kv-cache-alert-rules.tsproprietary/kv-cache/kv-cache-alerts.service.tsproprietary/kv-cache/kv-cache-engine-registry.tsproprietary/kv-cache/kv-cache-engines.service.tsproprietary/kv-cache/kv-cache-footprint.service.tsproprietary/kv-cache/kv-cache-otlp-sink.service.tsproprietary/kv-cache/kv-cache-samples.service.tsproprietary/kv-cache/kv-cache-scrape.service.tsproprietary/kv-cache/kv-cache-status.service.tsproprietary/kv-cache/kv-cache.controller.tsproprietary/kv-cache/kv-cache.module.tsproprietary/kv-cache/metrics-fetch.tsproprietary/kv-cache/prometheus-text.tsproprietary/webhook-pro/__tests__/kv-cache-events.spec.tsproprietary/webhook-pro/webhook-events-pro.service.ts
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- Block 100.64.0.0/10 shared address space with the other private ranges - Check DNS answers for non-localhost hostnames in every environment - Resolve with lookup(all) so AAAA answers are validated too - Skip OTLP points flagged as having no recorded value in the KV sink - Drop a scrape result if its engine was removed, disabled or repointed - Cancel the response body before rejecting a scrape response
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The network and parsing paths are defensively written and I like the test coverage, but the core delta tracker has a double-counting bug and there is an SSRF gap, so I'd like changes before merge.
counter-deltas.ts:95-110: the restart detector fires on any change of startMs in either direction and then returns the full counter value as the delta. There is no tracking of the newest startMs seen, so an older or duplicate start-time is accepted as a "restart." Concrete repro on one series: (1) value=1000,start=S1 baseline; (2) restart value=50,start=S2 gives delta 50; (3) a delayed/retried pre-restart export value=1000,start=S1 arrives, is not dropped (1000<50 is false) and is treated as a restart, emitting a spurious +1000; (4) next real value=70,start=S2 emits +70. One reordered datapoint inflates the minute by ~1050 tokens. Worse, if worker identity lives in an OTLP resource attribute rather than a datapoint attribute, all workers collapse to one series key and every datapoint flips startMs and returns its full counter, every cycle. Because hitRate() (kv-cache-samples.service.ts:14) is not clamped to [0,1], the inflated, independently-flapping hit/requested deltas can push the rate above 100% or collapse it, feeding the hit_rate_low/eviction_risk webhooks and the re-exported gauges false values.
Requests: track the newest startMs per series and treat only a strictly-newer start-time as a restart (ignore older/duplicate ones); include resource attributes in the series key so workers do not collapse; and clamp hitRate() to [0,1].
Separately, the SSRF guard: outbound-url-guard.ts ALWAYS_BLOCKED covers IPv4 169.254.x and fe80 but not IPv6 ULA fc00::/7, and fd00::/8 only lives in the private-network list, which the scrape path skips by default (allowPrivateNetworks defaults true). So AWS IMDSv6 (fd00:ec2::254) and internal ULA services are reachable via a scrape URL by default; please add ULA to the always-blocked set.
One process question: gh pr checks shows no build/test matrix running on this base branch (only CLA passes, CodeRabbit/Bugbot skipped), so none of the ~25 new specs execute in CI. Given how much correctness rests on them, can we get the matrix running on this branch, or merge the stack base to master first?
- Track the newest startMs per series; only a strictly newer start is a restart, older starts are stale and ignored - Include OTLP resource attributes in the series key so workers identified only by resource attributes stay separate - Clamp hitRate() to [0, 1] - Always block IPv6 unique local addresses (fc00::/7), covering AWS IMDSv6 at fd00:ec2::254
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@KIvanow addressed in f6338b0:
On CI: |
- Keep scrape results that land while an engine update is saving - Wait for in-flight writes on connection removal and never write removed engines again - Recover hit-rate alerts for windows that stop being checked
# Conflicts: # proprietary/kv-cache/__tests__/kv-cache-footprint.service.spec.ts
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Thanks for this, the engine scraping and OTLP ingest add a lot. I'm requesting changes for a few correctness and security issues I'd like fixed before merge.
Blocking
1. Deleting a connection can resurrect its engines (proprietary/kv-cache/kv-cache-footprint.service.ts:97)
On removal, storage rows are deleted before the removal listeners run, so the engine registry and sample tracker still hold the connection's engines in the meantime. An OTLP push that calls registry.recordResult during that window writes saveKvCacheEngine after the DELETE (the id isn't in removed yet), and a 15s sample flush can do the same for samples. After a restart, KvCacheEngineRegistry.onModuleInit loads the orphan engine and KvCacheScrapeService.tick keeps scraping it for a connection that no longer exists. Run the removal listeners (or mark the engines removed) before the storage delete.
2. Concurrent DELETE + PATCH re-inserts a deleted engine (proprietary/kv-cache/kv-cache-engine-registry.ts:66)
remove() never adds the id to removed. If a PATCH's owned() check passes while the delete is pending, its registry.save queues behind remove, sees removed.has(id) === false, and re-inserts the row and the in-memory entry. The engine comes back and is scraped again, with its samples already wiped. Add the id to removed in remove().
3. Webhook URL validation regressed outside production (apps/api/src/common/utils/outbound-url-guard.ts:89)
Webhook URLs now get a DNS lookup and private-IP blocking in every environment; the old validateUrl only did that when NODE_ENV=production. In dev and docker-compose, http://receiver:8080/hook (172.18.x.x) is now rejected, and webhooks.service.spec.ts / api-webhooks.e2e-spec.ts now make real DNS lookups for https://example.com, so they fail in CI without network access. This changes behaviour outside the KV cache feature, so please keep the previous gating for webhooks.
4. Loopback is always blocked for scrapes in production (outbound-url-guard.ts:70)
The Docker images set NODE_ENV=production, and in production loopback is blocked even when KV_CACHE_SCRAPE_BLOCK_PRIVATE is unset. A vLLM sidecar or host-network setup at http://localhost:8000/metrics fails with "Test scrape failed: blocked address", with no workaround. Loopback should follow the same allow-private setting.
5. DNS rebinding bypasses the metadata block (proprietary/kv-cache/metrics-fetch.ts:44)
assertSafeOutboundUrl resolves the hostname, then fetch() resolves it again, so the address actually connected to is never checked. A short-TTL record can pass the guard with a public IP and then point at 169.254.169.254. Since the scraper re-checks and re-fetches every tick, a later scrape can hit cloud metadata with the engine's Authorization header. Pin the validated address (custom lookup / undici dispatcher) for the request.
6. null passes validation and is written to storage (proprietary/kv-cache/dto/kv-cache-engine.dto.ts:16)
@IsOptional also accepts null, and the services only check !== undefined. PATCH {"scrapeUrl": null} probes the old URL, saves null, and tick() then silently skips the engine. {"name": null}, {"enabled": null} or PUT settings {"hitRateThreshold": null} hit NOT NULL columns and return a 500. Use @ValidateIf((_, v) => v !== undefined) or reject null explicitly; the same applies to UpdateKvCacheSettingsDto.
Non-blocking
- Eviction-risk alert flaps (
kv-cache-alert-rules.ts:41): "evicting" needsevictedKeysDelta > 0on every snapshot, and it's dispatched as 0/1 withisAbove=true. Bursty eviction (50, 0, 30, 0) clears and re-fires the alert on each burst. Consider requiring a few clean snapshots before recovering. - Hit-rate alert recovers on low traffic (
kv-cache-alerts.service.ts:156): when a firing window falls belowKV_CACHE_HIT_RATE_MIN_TOKENS, a synthetichitRate=1is dispatched, which clears the alert though nothing improved. It re-fires when traffic returns. Skipping evaluation (keeping current state) would avoid that. - IPv6 ULA is never allowed (
outbound-url-guard.ts:24):fc00::/7is inALWAYS_BLOCKED, so the allow-private setting unblocks IPv4 private ranges but not IPv6 ones. Scrapes break on IPv6 / dual-stack clusters withfd00::/8pod IPs. - DNS failures during a scrape are reported as "blocked address" because the guard's error is caught and replaced. Surfacing the real reason would help debugging.
- Two concurrent creates with the same
otlpEngineIdcan both pass the uniqueness check, since it happens before anawait. - The counter series key only uses
worker_id/role(plus resource for OTLP), so series that differ byserved_model_nameor other labels can collide. pointsOfinkv-cache-otlp-sink.service.tsduplicatesmetricPointCountfromotel-metrics-ingest.service.ts; please reuse it.
Housekeeping
Please remove the Co-Authored-By: Claude ... trailers from the commits before merge (44679d3, 1c90392, 5b14733, f6338b0, 819b2a8), so they don't end up in master history.
- Run connection removal listeners before deleting stored KV data and wait for pending engine writes and sample flushes - Mark an engine removed as soon as remove() is called so a queued save cannot re-insert it - Snapshot the status version when save() is called so scrape results recorded while the save is queued are kept - Reject null for optional engine and settings DTO fields
- Resolve webhook hostnames only in production again, as before the shared outbound URL guard - Let loopback and IPv6 unique local addresses follow the scrape allow-private setting; keep link-local and fd00:ec2::254 blocked - Connect KV scrapes through a lookup that validates every resolved address, so the connected IP is the checked one - Surface guard and DNS failure reasons instead of "blocked address"
- Include extra labels such as served_model_name in counter series keys - Reserve OTLP engine ids while a create is in flight - Reuse metricPointCount in the KV cache OTLP sink - Hold the evicting alert until three clean snapshots in a row - Keep hit-rate alert state while a window has too little traffic
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@KIvanow everything is pushed to Blocking
Non-blocking
Housekeeping
The Cursor threads on #529 are addressed in the same commits. |
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- Track the drained-up-to minute in CounterDeltaTracker - Observations stamped for an already flushed minute go to the open one
# Conflicts: # proprietary/kv-cache/__tests__/kv-cache-footprint.service.spec.ts # proprietary/kv-cache/kv-cache-footprint.service.ts
- Disabling eviction alerts resets the evicting hold and sends both reasons as inactive - An undetected snapshot clears the evicting hold at once instead of waiting three clean snapshots across the undetected back-off
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Cursor Bugbot has reviewed your changes using default effort and found 2 potential issues.
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Reviewed by Cursor Bugbot for commit 54275b7. Configure here.
| this.checkedWindows.delete(connectionId); | ||
| this.evictingCleanStreaks.delete(connectionId); | ||
| this.prometheus?.clearKvCache(connectionId); | ||
| }); |
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Removal skips eviction alert reset
Low Severity
Connection removal drops checkedWindows and evictingCleanStreaks without the healthy dispatch used everywhere else to clear webhook hysteresis. Eviction alert keys are scoped by connectionId, so a reused id can stay latched and never fire again until the process restarts.
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Reviewed by Cursor Bugbot for commit 54275b7. Configure here.
- Throw NotFound from registry save when the engine was removed - Fail PATCH that overlaps an in-flight delete instead of returning success
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Part 2 of 3 of KV Cache Monitoring for vLLM / SGLang (LMCache). Stacked on
kv-cache/footprint.Valkey cannot see cache lookups, so hit rate comes from the inference engine's LMCache counters.
Summary
KV_CACHE_SCRAPE_BLOCK_PRIVATE).betterdb.lmcache.engineresource attribute).lmcache:num_requested_tokens/num_hit_tokens/ lookup counters, with counter-reset and OTLP start-time handling.KV_CACHE_SCRAPE_INTERVAL_MS; OTLP ingestion routes LMCache metrics to linked engines (unknown_enginedrop reason otherwise).kv_cache.hit_rate_lowandkv_cache.eviction_riskwith hysteresis, token floor and per-connection settings; disabled engines never alert.betterdb_kv_cache_*hit rate and footprint metrics to Prometheus and OTel.Testing
Unit specs for guard, parser, delta tracker, engines service, scraper, OTLP routing, alerts, exporters and storage adapters.
Note
Medium Risk
Touches SSRF validation for webhooks and new metrics scraping/OTLP ingestion paths; misconfiguration could block legitimate URLs or accept metrics to the wrong engine, but behavior is heavily tested.
Overview
Adds LMCache hit-rate and engine telemetry for KV cache monitoring: users can register per-connection scrape or OTLP engines, ingest
lmcache:*counters into minute buckets, query sample history, and get Pro webhooks for low hit rate and eviction risk (with settings, hysteresis, and disabled-engine handling).Ingestion path: periodic Prometheus scrapes (guarded fetch + text parser + counter delta tracker) and OTLP routing when resources carry
betterdb.lmcache.engineor all metrics arelmcache:—otherwise points drop asunknown_engine. Engine registry coordinates storage, encrypted scrape auth viagetEncryptionService(), and sample cleanup on delete.Security / shared infra: new
outbound-url-guardcentralizes SSRF checks (DNS, private/link-local rules, optional private networks for scrapers,guardedLookup); webhooks drop inline validation and callassertSafeOutboundUrlwith production-only DNS.Observability:
PrometheusServiceexportsbetterdb_kv_cache_*footprint and hit-rate series with per-connection cleanup; OTel semconv maps the same names. Storage gainsdeleteKvCacheEngineSamples(engineId).Reviewed by Cursor Bugbot for commit 928e2c5. Bugbot is set up for automated code reviews on this repo. Configure here.
Summary by CodeRabbit