Yaffle/EventSource

.close() does not abort current event source fetch connections

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#120 opened on Oct 23, 2018

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 (20 comments) (2 reactions) (0 assignees)JavaScript (1,873 stars) (320 forks)batch import
help wanted

Description

Fetch supports abort, if it is not provided or called it leaves long leaving TCP connections open. Abort package : https://www.npmjs.com/package/abortcontroller-polyfill

Example code/changes that could make this work:

  1. Create a controller as described in https://www.npmjs.com/package/abortcontroller-polyfill

  2. Add the abort signal to the call of transport

  transport.open(xhr, onStart, onProgress, onFinish, requestURL, withCredentials, requestHeaders, controller.signal);
  1. Store the controller in order to be able to access it in close
    es.controller = controller;
  1. Update close
  EventSourcePolyfill.prototype.close = function () {
    this.controller.abort();
    this._close();
  };
  1. Update the definition of transport when the browser supports fetch
  FetchTransport.prototype.open = function (xhr, onStartCallback, onProgressCallback, onFinishCallback, url, withCredentials, headers, signal) {
    // cache: "no-store"
    // https://bugs.chromium.org/p/chromium/issues/detail?id=453190
    var textDecoder = new TextDecoder();
    fetch(url, {
      headers: headers,
      credentials: withCredentials ? "include" : "same-origin",
      signal: signal
    })

Contributor guide

Tech stack
javascript
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
under 1 hour
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
JavaScriptFetch APIAbortController
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75
Research direction
Investigate the transport implementation in the EventSource polyfill, specifically FetchTransport.prototype.open. Add an AbortController signal to the fetch call and store the controller on the instance. Update the close method to call controller.abort() before close(). Ensure backward compatibility by using an AbortController polyfill if the browser does not support it natively. Reference the example code provided in the issue for exact implementation details.
.close() does not abort current event source fetch connections · Yaffle/EventSource#120 | Good First Issue