fix(observability): record key-service latency and error rate at the KMS unwrap seam - #3920
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📝 WalkthroughWalkthroughThe change adds OpenTelemetry metrics for KMS-wrapped JWE calls and unwrap outcomes. It updates ChangesKMS instrumentation
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I reviewed the latest commits and found no new bugs; the import-path nit from my previous review is now fixed (commit 911ffd4). Because this still touches the KMS-backed key-unwrap/crypto path, a human look remains worthwhile before merging.
- Confirmed the actual decrypt/AES-GCM logic is unchanged — the old
#unwrapContentEncryptionKeybody moved verbatim into the new#decryptContentEncryptionKey. - Checked the metrics calls sitting unguarded inside the surrounding try/catch blocks — OTel's Counter/Histogram API is specified not to throw, so they can't mask the real KMS result.
- Checked
ENCRYPTED_KEY_REJECTEDbeing counted as a key-service failure here versusDataKeyUnwrapperService's at-rest classification of the same failure — this is a known, PR-documented dashboard-query nuance, not a functional bug.
Extended reasoning...
Overview
This PR adds OpenTelemetry instrumentation (a duration histogram and a call/outcome counter) around the KMS-backed content-encryption-key unwrap path in apps/api. The new KmsWrappedJweInstrumentationService follows the codebase's existing *-instrumentation.service.ts pattern and is injected as a second constructor dependency into KmsWrappedJweService. The crypto behavior itself is unchanged: the prior #unwrapContentEncryptionKey body was moved verbatim into a new #decryptContentEncryptionKey, with the outer method becoming a thin wrapper that records the unwrap outcome. Three existing test/integration files that construct KmsWrappedJweService directly were updated to pass mock<KmsWrappedJweInstrumentationService>(), consistent with this repo's "use mock() instead of as unknown as" convention.
Security risks
No new security risk is introduced. Metric attributes are limited to status and, on failure, the failure enum value — no user id, key id, key version, or key material reaches a metric, consistent with the PR's own stated design. The underlying decrypt/authentication logic (createDecipheriv, AES-256-GCM, KMS asymmetricDecrypt) is untouched by this diff; only measurement calls were added around it.
Level of scrutiny
This is my third pass on this PR. My previous review left one cosmetic nit (an absolute-path import for a same-directory sibling file) and otherwise found no issues; that nit has since been fixed in a follow-up commit, and a new test was added pinning the meter name and measured duration. This run's bug hunt reported no new findings. Because the change sits directly in the KMS/crypto unwrap seam even though it only adds instrumentation, I'm treating it as warranting a human glance rather than an automated approval, per this system's guidance to avoid approving security-adjacent/crypto-path code.
Other factors
Test coverage is thorough: the updated spec exercises all five key-service failure modes, times both the raw KMS call and the outer unwrap boundary, and includes the exact "answered unusably but timed as successful" scenario the PR description calls out as the point of the placement. I also independently checked two things beyond the reported findings: (1) the metrics record/add calls run unguarded inside the same try/catch as the real logic, but OTel's Counter/Histogram API contract guarantees these calls don't throw, so they can't shadow the real result; (2) ENCRYPTED_KEY_REJECTED is counted as a KMS-service failure here while DataKeyUnwrapperService.KEY_SERVICE_FAILURES excludes it (treating it as an at-rest fault) — this discrepancy is explicitly called out and accepted by the PR author as a dashboard-query nuance, not a functional bug.
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In `@apps/api/node_modules`:
- Line 1: Remove the machine-local node_modules symbolic link from the change;
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📒 Files selected for processing (10)
apps/api/node_modulesapps/api/src/deployment/services/kms-wrapped-jwe/kms-wrapped-jwe-instrumentation.service.spec.tsapps/api/src/deployment/services/kms-wrapped-jwe/kms-wrapped-jwe-instrumentation.service.tsapps/api/src/deployment/services/kms-wrapped-jwe/kms-wrapped-jwe.service.integration.tsapps/api/src/deployment/services/kms-wrapped-jwe/kms-wrapped-jwe.service.spec.tsapps/api/src/deployment/services/kms-wrapped-jwe/kms-wrapped-jwe.service.tsapps/api/src/deployment/services/sdl-secrets-unsealer/sdl-secrets-unsealer.service.spec.tsapps/api/src/secret/services/data-key-rewrap/data-key-rewrap.service.integration.tsapps/api/src/secret/services/data-key-unwrapper/data-key-unwrapper.service.spec.tsapps/api/src/secret/services/secret-cipher/secret-cipher.service.integration.ts
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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.
Beyond the inline finding, I also checked whether a metrics-recording call itself could throw and get miscategorized by the surrounding try/catch in #asymmetricDecrypt/#unwrapContentEncryptionKey — recordCallSucceeded/recordCallFailed/recordUnwrapSucceeded/recordUnwrapFailed all return void with no thrown-exception path in the instrumentation service, so this is not an issue.
Extended reasoning...
A confirmed finding from this run (DataKeyRewrapService as an unmentioned third caller of the shared, untagged KMS metrics) is being posted as an inline comment, so the top-level body should not restate it. I independently verified the finding is accurate: DataKeyRewrapService injects KmsWrappedJweService directly (apps/api/src/secret/services/data-key-rewrap/data-key-rewrap.service.ts:56) and its #rewrap flow loops over data keys during key rotation, which would indeed feed the same untagged kms_key_service_call_duration_ms/kms_key_service_calls_total instruments described in the PR as covering only two callers. Separately, I checked a candidate exception-isolation concern around the try/catch blocks in #asymmetricDecrypt and #unwrapContentEncryptionKey (kms-wrapped-jwe.service.ts lines 160-224) — the instrumentation service's record* methods are synchronous void-returning calls with no throwing paths in kms-wrapped-jwe-instrumentation.service.ts, so a metrics call cannot itself trip the surrounding catch and misclassify a KMS outcome. This is new information not previously posted (prior runs on this PR reported no issues), so a brief ruled-out note is warranted per the review protocol, without repeating the inline finding's content.
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #3920 +/- ##
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- Coverage 82.52% 81.99% -0.54%
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Files 1292 1193 -99
Lines 35792 33192 -2600
Branches 8624 8100 -524
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- Hits 29539 27215 -2324
+ Misses 5527 5271 -256
+ Partials 726 706 -20
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Why
During an incident nothing in the console can say whether a slow deploy is the key service or the database. Every deploy spends one Cloud KMS
asymmetricDecryptcall to unwrap the user's data key, and that call is currently unmeasured in both latency and failure rate.Part of CON-878 — slice 1 of 3. The next two carry the wrapping key version on
USER_DATA_KEY_UNWRAPPEDand record unwraps per request.What
A new
KmsWrappedJweInstrumentationServiceowns two OTel instruments, following the existing*-instrumentation.service.tspattern.KmsWrappedJweServicetakes it as a second constructor dependency.kms_key_service_call_duration_msms)status=success|failurekms_key_service_calls_totalstatus, plusfailureon failureNo identifier is a metric attribute — no user id, no data key id, no key version — so the time series stay bounded. No secret, key material, wrapped JWE or ciphertext reaches a metric or a log.
The placement is the point
Latency is timed around the
asymmetricDecryptcall; the counter sits one level out, at the#unwrapContentEncryptionKeyboundary. Three of the five key-service failures (KEY_SERVICE_REQUEST_CORRUPTED,KEY_SERVICE_PLAINTEXT_MISSING,KEY_SERVICE_RESPONSE_CORRUPTED) are raised after the call returns successfully, so a counter placed literally at the call would report a total KMS response-corruption outage as a perfectly healthy key service and point the on-call at the database.The two instruments therefore disagree on purpose, and a test pins it:
The same scenario is counted as a failed unwrap — a table over all five failures asserts
recordUnwrapFailedwas called with each. ConverselyAUTHENTICATION_FAILEDand the parse-time failures stay out of the counter entirely: those are corruption at rest, and admitting them would blur the same separation from the other side. A parse-only failure records nothing at all.Changes
kms-wrapped-jwe-instrumentation.service.ts+ spec.#unwrapContentEncryptionKey's existing body moved unchanged into#decryptContentEncryptionKey, giving the counting boundary somewhere to sit. Unwrapping itself is unchanged.KmsWrappedJweServicedirectly take a plainmock<KmsWrappedJweInstrumentationService>()— everyrecord*method returnsvoid, so nothing needs behavioural stubbing.Notes for the dashboard slice
ENCRYPTED_KEY_REJECTEDfeedsstatus="failure"here, butDataKeyUnwrapperServiceclassifies it as an at-rest fault. A row wrapped under a retired key version would spike the key-service error rate while KMS is healthy — thefailureattribute disambiguates, so the error-rate query should exclude it or break out by label.KmsWrappedJweServicehas two callers: the deploy path (DataKeyUnwrapperService) and the client transport-seal path (SdlSecretsUnsealerService). Both are measured under one untagged pair of instruments, so a burst of inbound sealed payloads shifts a p99 that reads as affecting deploys. Adding an operation attribute later is additive — the instruments live in one file.Scope
No schema, migration, HTTP contract, auth or billing change. Nothing user-facing; visible to operators via OTel only.
Size: 292 changes.
apps/apitests, lint andtsc --noEmitall green.Summary by CodeRabbit
New Features
Bug Fixes
Tests