twitter/finagle

ExceptionSourceFilter does not properly attribute CancelledRequestExceptions

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#760 opened on Mar 13, 2019

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 (1 comment) (0 reactions) (0 assignees)Scala (8,864 stars) (1,435 forks)batch import
help wanted

Description

ExceptionSourceFilter does not properly attribute CancelledRequestExceptions

Expected behavior

The source should be attributed to the client (or at least not to the downstream service)

Actual behavior

When a future is cancelled by a client, the source is still attributed to the downstream service. This leads to confusion when the error message is along the lines of:

com.twitter.finagle.CancelledRequestException: request cancelled. Remote Info: Upstream Address: Not Available, Upstream id: Not Available, Downstream Address: my.downstream.host/X.X.X.X:443, Downstream label: my.downstream.host:443, Trace Id: efdec7e41b7c30fa.d535d24f770f3fa8<:efdec7e41b7c30fa

even though the downstream was not involved in the request at all.

Steps to reproduce the behavior

Cancel a future and observe the attribution from ExceptionSourceFilter.

Contributor guide

Tech stack
scala
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Scala basicsFamiliarity with Finagle
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
Investigate the ExceptionSourceFilter implementation in the Finagle codebase to understand how it attributes exceptions to sources. Specifically, examine how CancelledRequestExceptions are handled during client cancellation. Look at the flow where a future is cancelled by a client and trace the exception attribution logic. Check the existing comment on the issue for additional context. Consider modifying the filter to correctly attribute the source to the client or set it to 'Not Available' when cancellation occurs.