akka/akka-http

Http2: Optimize HPACK header encoding for high entropy headers

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#2,892 创建于 2020年1月16日

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1 - triagedhackathonhelp wantedt:coret:http2t:performance

描述

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.

贡献者指南

技术栈
scala
领域
backendperformance
议题类型
performance
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
3
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
half day
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
stale
清晰度议题是否清楚说明期望改动、验收标准和下一步。
clear
前置要求
HTTP/2 basicsHPACK encodingScala
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
30
研究方向
Investigate the HPACK implementation used (twitter hpack) and how encodeHeader is called in akka http. Identify high entropy headers like Date or Content Length that should be encoded with the sensitive flag. Review the existing code and comments, particularly the reference to @surendarchandra's observation. Modify the relevant call to pass the sensitive flag for those headers to prevent eviction of useful entries from the dynamic table.