akka/akka-http

Bug: Server responses with 431 when uri length exceeds headers length limit

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#2,472 opened on Mar 15, 2019

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Description

I use Akka = "2.5.19" and AkkaHttp = "10.1.7". server config:

akka {
  http {
    parsing {
      max-uri-length = 96k
      max-header-value-length = 16k
    }
  }
}

I need to send relatively long query(more than 16k (list of ~ 300-500 uuids)). I was getting 414 status code when akka.http.parsing.max-uri-length was 8k. To fix that I've increased value up to 96k and it partially solved problem. Now server responses with (431,HttpEntity.Strict(text/plain; charset=UTF-8,HTTP header value exceeds the configured limit of 16384 characters)) which seems weird cause I send only only Auth header with short String value. To fix that I've increased akka.http.parsing.max-header-value-length up to 32k. This change has solved issue but it looks like an Akka bug.

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.
half day
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.
needs investigation
Prerequisites
basic Akka HTTP knowledgeHTTP protocol understanding
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate the Akka HTTP parsing configuration to understand why increasing max uri length to 96k triggers the max header value length limit for a URI that only contains query parameters. The issue may be in the parsing logic where the URI is treated as part of the header value. Look at the source code for URI and header length checks, particularly in the Akka HTTP parsing module. Check related GitHub issues or PRs for similar reports.
Bug: Server responses with 431 when uri length exceeds headers length limit · akka/akka-http#2472 | Good First Issue