feat: queue time capture for Rack by dingsdax · Pull Request #2838 · getsentry/sentry-ruby

dingsdax · 2026-01-15T10:20:31Z

Captures how long requests wait for a e.g. Puma thread from X-Request-Start headers and attaches it to transactions as http.server.request.time_in_queue. Sentry only measures after Puma picks up the request. Under load, requests might wait long in the queue but only take a fraction to process. Similar to what judoscale and scout do.

works with all major reverse proxies:

Nginx: X-Request-Start: t=1234567890.123 (seconds)
Heroku: X-Request-Start: t=1234567890123456 (microseconds)
HAProxy 1.9+: X-Request-Start: t=1234567890123456 (microseconds)
HAProxy < 1.9: X-Request-Start: t=1234567890 (seconds)
Generic: Raw timestamps in seconds/milliseconds/microseconds

subtracts puma.request_body_wait for accuracy (excludes slow client uploads from queue time).

Usage

works 🤞 if your reverse proxy sets the header:

# Nginx
proxy_set_header X-Request-Start "t=${msec}";

opt-out

config.capture_queue_time = false

resolves: Add Puma request queue time as a transaction attribute #2813
resolves: RUBY-130

default to true

linear · 2026-01-15T10:20:35Z

RUBY-130 Add Puma request queue time as a transaction attribute

github-actions · 2026-01-15T10:20:57Z

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

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sentry-ruby/lib/sentry/rack/capture_exceptions.rb

sl0thentr0py · 2026-01-15T13:03:58Z

sentry-ruby/lib/sentry/span.rb

      MESSAGING_MESSAGE_RETRY_COUNT = "messaging.message.retry.count"
+
+      # Time in ms the request spent in the server queue before processing began.
+      HTTP_QUEUE_TIME_MS = "http.queue_time_ms"


@AbhiPrasad @lcian is there an attribute convention for time spent in queue waiting for the http request to be picked up in an HTTP server?

The closest I could find is http.client.request.time_in_queue but that's for clients.

Hmmm I cannot find anything like that. Maybe we introduce our own http.server.request.time_in_queue counterpart?

sounds good; shall I add to sentry-conventions too?

sl0thentr0py

some small stuff, and mainly want to wait for feedback on the attribute convention name

sentry-ruby/lib/sentry/rack/capture_exceptions.rb

sentry-ruby/test-app/sentry_queue_test.rb

sentry-ruby/spec/sentry/rack/capture_exceptions_spec.rb

Co-authored-by: Neel Shah <neel.shah@sentry.io>

sentry-ruby/lib/sentry/rack/capture_exceptions.rb

solnic

✅ but I left a bunch of minor 💅🏻 suggestions 🙃

sentry-ruby/lib/sentry/rack/capture_exceptions.rb

Co-authored-by: Peter Solnica <peter@solnica.online>

Non-numeric t= values like "t=invalid" or "t=" were silently converted to 0.0 by Ruby's String#to_f, resulting in a Unix epoch timestamp and a queue time of ~56 years instead of nil. Apply the same numeric regex guard already used for raw timestamps to the t= branch before calling to_f. Co-Authored-By: Claude <noreply@anthropic.com>

Co-authored-by: Peter Solnica <peter@solnica.online>

sentry-ruby/lib/sentry/rack/capture_exceptions.rb

parse_request_start_header returned nil for headers that arrived with leading/trailing whitespace or as comma-separated values (multiple header occurrences collapsed by a proxy). Strip whitespace from the token and split on commas, taking the first (earliest) timestamp. Co-Authored-By: Claude <noreply@anthropic.com>

When env["puma.request_body_wait"] is a String (e.g. serialized by middleware), the `> 0` comparison raised ArgumentError, which was silently swallowed by the broad rescue, causing queue time to be dropped even with a valid X-Request-Start header. Call to_f on String values before the comparison. Numeric strings ("40") convert correctly; non-numeric strings ("N/A") become 0.0 and are treated as absent, so total_time_ms is returned unchanged. Co-Authored-By: Claude <noreply@anthropic.com>

…-ruby into puma-queue-time

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cursor · 2026-02-24T15:51:08Z

sentry-ruby/lib/sentry/rack/capture_exceptions.rb

+          queue_time_ms >= 0 ? queue_time_ms : 0.0 # more sanity check
+        else
+          total_time_ms
+        end


Queue time spoofable via client header

Medium Severity

extract_queue_time trusts env["HTTP_X_REQUEST_START"] without verifying it was set/overwritten by a trusted proxy and without any upper-bound sanity check, so a client-supplied X-Request-Start can inject arbitrarily large http.server.request.time_in_queue values and skew transaction data.

Adds the `http.server.request.time_in_queue` semantic convention attribute to capture the time (in milliseconds) a request spent waiting in the server queue before processing began. This attribute is populated from the `X-Request-Start` header set by reverse proxies (Nginx, HAProxy, Heroku router, etc.) and first introduced in sentry-ruby: getsentry/sentry-ruby#2838 Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* feat(http): add http.server.request.time_in_queue attribute Adds the `http.server.request.time_in_queue` semantic convention attribute to capture the time (in milliseconds) a request spent waiting in the server queue before processing began. This attribute is populated from the `X-Request-Start` header set by reverse proxies (Nginx, HAProxy, Heroku router, etc.) and first introduced in sentry-ruby: getsentry/sentry-ruby#2838 Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> * feat(http): add generated attribute definitions for http.server.request.time_in_queue Generate TypeScript and Python attribute definitions including type exports, metadata entries, and TypedDict annotations. Co-Authored-By: Claude <noreply@anthropic.com> --------- Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

The Rails CaptureExceptions middleware subclass overrode start_transaction without calling super, so the http.server.request.time_in_queue attachment added in #2838 was silently skipped for all Rails apps. Extract queue time attachment into a private attach_queue_time method on the Rack base class so the Rails subclass can invoke it explicitly while keeping its own options hash (preserving the correct SPAN_ORIGIN constant "auto.http.rails" via lexical scoping). Fixes #2873 Co-Authored-By: Claude <noreply@anthropic.com>

The Rails CaptureExceptions middleware subclass overrode start_transaction without calling super, so the http.server.request.time_in_queue attachment added in #2838 was silently skipped for all Rails apps. Extract queue time attachment into a private attach_queue_time method on the Rack base class so the Rails subclass can invoke it explicitly while keeping its own options hash (preserving the correct SPAN_ORIGIN constant "auto.http.rails" via lexical scoping). Fixes #2873 Co-authored-by: Claude <noreply@anthropic.com>

## DESCRIBE YOUR PR docs for Ruby queue-time capture getsentry/sentry-ruby#2838 ## IS YOUR CHANGE URGENT? Help us prioritize incoming PRs by letting us know when the change needs to go live. - [ ] Urgent deadline (GA date, etc.):  - [ ] Other deadline:  - [x] None: Not urgent, can wait up to 1 week+ ## SLA - Teamwork makes the dream work, so please add a reviewer to your PRs. - Please give the docs team up to 1 week to review your PR unless you've added an urgent due date to it. Thanks in advance for your help! ## PRE-MERGE CHECKLIST *Make sure you've checked the following before merging your changes:* - [ ] Checked Vercel preview for correctness, including links - [ ] PR was reviewed and approved by any necessary SMEs (subject matter experts) - [ ] PR was reviewed and approved by a member of the [Sentry docs team](https://github.com/orgs/getsentry/teams/docs) ## LEGAL BOILERPLATE  Look, I get it. The entity doing business as "Sentry" was incorporated in the State of Delaware in 2015 as Functional Software, Inc. and is gonna need some rights from me in order to utilize my contributions in this here PR. So here's the deal: I retain all rights, title and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Sentry can use, modify, copy, and redistribute my contributions, under Sentry's choice of terms. ## EXTRA RESOURCES - [Sentry Docs contributor guide](https://docs.sentry.io/contributing/) --------- Co-authored-by: getsantry[bot] <66042841+getsantry[bot]@users.noreply.github.com> Co-authored-by: Alex Krawiec <alex.krawiec@sentry.io> Co-authored-by: Claude <noreply@anthropic.com>

dingsdax added 3 commits January 15, 2026 09:41

add configuration for capturing queue time

39a875b

default to true

Extract, normalize & add queue time to transaction

8b2e2b8

Test app for queue time in Sentry

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dingsdax marked this pull request as ready for review January 15, 2026 10:23

dingsdax added 4 commits January 15, 2026 11:26

Fix redos issue

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feat: queue time metric getsentry/sentry-docs#16030

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Update sentry-ruby/lib/sentry/rack/capture_exceptions.rb

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Co-authored-by: Neel Shah <neel.shah@sentry.io>

Delete sentry_queue_test.rb

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Update sentry-ruby/lib/sentry/rack/capture_exceptions.rb

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Update sentry-ruby/lib/sentry/rack/capture_exceptions.rb

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Update sentry-ruby/lib/sentry/rack/capture_exceptions.rb

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dingsdax and others added 5 commits February 24, 2026 14:35

Merge branch 'master' into puma-queue-time

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Merge branch 'puma-queue-time' of https://github.com/getsentry/sentry…

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feat(http): add http.server.request.time_in_queue attribute getsentry/sentry-conventions#267

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publish: getsentry/sentry-ruby@6.4.0 getsentry/publish#7262

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davekaro mentioned this pull request Feb 27, 2026

Request queue time not tracked in rails #2873

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dingsdax mentioned this pull request Mar 2, 2026

fix(rails): Track request queue time in Rails middleware #2877

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Queue time spoofable via client header

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