envoyproxy/envoy

add memory filesystem for making tests faster, more hermetic, and more robust

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#11,121 opened on May 8, 2020

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Description

Currently real files are used for file i/o during tests. An alternative I've used in the past is to have an in-memory representation of a file-system: https://github.com/apache/incubator-pagespeed-mod/blob/master/pagespeed/kernel/base/mem_file_system.h

This has these advantages:

  • completely hermetic, with a clean slate between tests
  • very fast (no I/O), speeding up the running of massive numbers of tests
  • you can inject notifiers etc, so you can for example get a callback or condvar wakeup or similar when a file is written

Envoy already has a filesystem abstraction (yay!) and a way to squirrel that into code that needs to read/write files (Api::Api) just no in-memory impl for it.

I think this would be a good intern project. The example I gave above would not exactly meet Envoy's needs but it could be a reference point.

Contributor guide

Research direction
Study the existing filesystem abstraction in Envoy (Api::Api) and the reference implementation from Apache Pagespeed. Design an in memory filesystem that implements the same interface, ensuring hermeticity and speed for tests.
Tech stack
cpp
Domain
backend
Issue type
Feature
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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Envoy filesystem abstraction
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60