akka/akka-http

Http2: Optimize HPACK header encoding for high entropy headers

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#2,892 opened on Jan 16, 2020

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1 - triagedhackathonhelp wantedt:coret:http2t:performance

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Description

As @surendarchandra noticed, our HPACK header tries to encode as many header values as possible into dynamic table entries. The effect can be that high entropy headers like Date or Content-Length evict more useful headers from the dynamic table.

The HPACK implementation from twitter that we use, allows to pass the sensitive flag to encodeHeader which prevents that the values are put into the dynamic table. We should consider to encode high entropy header using the sensitive flag for better use of the dynamic header table.

Contributor guide

Research direction
Identify high entropy headers (e.g., Date, Content Length) in the HPACK encoding path and modify encodeHeader calls to pass the sensitive flag to prevent them from being stored in the dynamic table.
Tech stack
scala
Domain
backendperformance
Issue type
Performance
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.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
ScalaHTTPHPACK
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60