karma-runner/karma

Performance issue with serving files in Karma 1.4

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#2538 opened on Jan 16, 2017

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help wantedneeds: investigation

Description

Expected behaviour

I have an Ext JS project with over 500 files. With karma 1.3, it was serving all these files in around 3-5s.

karma13

Actual behaviour

With Karma 1.4 and the exact same files, it was taking over 80 seconds to serve these files, which results in a timeout before the tests can even run.

karma14

Environment Details

  • Karma version (output of karma --version): 1.4

Steps to reproduce the behaviour

  1. Simply run npm test with Karma 1.3 and 1.4

Contributor guide

Tech stack
javascriptnodejs
Domain
testingperformance
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.
1-2 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.
mostly clear
Prerequisites
Familiarity with Node.js streamsUnderstanding of Karma's middleware architecture
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Investigate the file serving middleware in Karma, particularly the changes between versions 1.3 and 1.4. Look at files like `lib/middleware/file.js` and `lib/middleware/source files.js`. Profile the serving process to identify bottlenecks. Check if any new dependencies or changes in file handling (e.g., streams, compression) caused the delay. Comments in the issue may hint at a known regression.