Spring Boot (Webflux): many unrelated http breadcrumbs are recorded with events

[sergey-volkov-lm]

Platform:

• Spring Boot (Webflux server & WebClient) -> 2.5.5

IDE:

• IntelliJ -> 2021.2

Build system:

• Maven -> 3.6.3-jdk-11

Platform installed with:

• Maven Central

The version of the SDK:
5.2.4

---

I have the following issue:

Many (tens or even ~hundred) unrelated http breadcrumbs recorded with events. These breadcrumbs are:

• Incoming server http requests (to actuator endpoints, for example)
• Outgoing http client requests to external services, but they are old and/or unrelated to original incoming server request

Steps to reproduce:

• Use spring-boot webflux server application
• Use sentry-spring-boot-starter
• Use actual sentry server (probably won't work with NoOpHub)
• Start app locally
• Put some load on application
  • I used 50 threads in jmeter accessing actuator health, info and prometheus endpoints without delays
  • prometheus worked better
• Make some meaningful requests which should cause some kind of error which should be sent to sentry
• Observe events on sentry server or via debugging SentryClient (less effective)

Actual result:
Screenshot from actual server-running instance

Expected result:
Only a couple of related http breadcrumbs are present

Personal thoughts
Both SentryWebFilter & SentrySpanClientWebRequestFilter use HubAdapter, which uses static Sentry.getCurrentHub() method, which returns ThreadLocal instance of Hub.

It seems like this mechanism may not work correctly with reactive application, which serves requests on a small number of threads, and they are switched frequently.

As far as I know, there is a way of storing arbitrary request-related data in webflux:

• org.springframework.web.server.ServerWebExchange.getAttributes()
• org.springframework.web.reactive.function.client.ClientRequest.attributes()

[marandaneto]

cc @maciejwalkowiak

[hu-chia]

Based on ThreadLocal, this issue seems unsolvable.

[adinauer]

We have just released 6.15.0 of the Java SDK. If you're on Spring Boot 3.0.3+ you can give ThreadLocalAccessor a try.

Here's a copy of the changelog so you know what's required:
Implement ThreadLocalAccessor for propagating Sentry hub with reactor / WebFlux (#2570)

• Requires io.micrometer:context-propagation:1.0.2+ as well as Spring Boot 3.0.3+
• Enable the feature by setting sentry.reactive.thread-local-accessor-enabled=true
• This is still considered experimental. Once we have enough feedback we may turn this on by default.
• Checkout the sample here: https://github.com/getsentry/sentry-java/tree/main/sentry-samples/sentry-samples-spring-boot-webflux-jakarta
• A new hub is now cloned from the main hub for every request

We've also fixed a bug for the WebFlux integration (#2580) in this release for older versions of Spring Boot and when not using context-propagation. In case you give it a try it would be great if you could give us feedback 🙏 .

[adinauer]

Closing this now as it should be resolved (see comment above), feel free to reopen if you run into the problem again.

[adinauer]

This is still an issue for our Spring Boot 2 integration.

We could take another stab at it by trying to use reactor.core.CoreSubscriber and Hooks.onEachOperator as described here. Needs testing whether this is has a lot of impact on performance.

Putting this in the backlog but can't say when we'll get to it.