Automattic/node-canvas

make module context-aware

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#1,394 建立於 2019年3月23日

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 (49 留言) (89 反應) (0 負責人)JavaScript (9,524 star) (1,140 fork)batch import
Help wanted

描述

Issue or Feature

I've been experimenting with worker threads in node.js recently and noticed that the canvas module does not appear to be context-aware. In other words, the module will load/instantiate once, but as soon as another thread attempts to require canvas for it's own use, the following error is thrown:

Error: Module did not self-register.
    at Object.Module._extensions..node (internal/modules/cjs/loader.js:840:18)
    at Module.load (internal/modules/cjs/loader.js:666:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:606:12)
    at Function.Module._load (internal/modules/cjs/loader.js:598:3)
    at Module.require (internal/modules/cjs/loader.js:705:19)
    at require (internal/modules/cjs/helpers.js:14:16)
    at Object.<anonymous> (~/node_modules/canvas/lib/bindings.js:3:18)
    at Module._compile (internal/modules/cjs/loader.js:799:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:810:10)
    at Module.load (internal/modules/cjs/loader.js:666:32)

Steps to Reproduce

In main thread...

const {Worker} = require('worker_threads');
var worker1 = new Worker('./child-thread.js'); 
var worker2 = new Worker('./child-thread.js');
// etc.

In child-thread.js...

var Canvas = require('canvas');
var canvas = Canvas.createCanvas(200, 200);
var ctx = canvas.getContext('2d');
// etc.

References

Node.js documentation: https://nodejs.org/api/addons.html#addons_context_aware_addons Similar issue: https://github.com/schroffl/node-lzo/pull/11

Environment

  • node-canvas version 2.4.1
  • Mac OS 10.14.3
  • node version 11.12.1

貢獻者指南

技術棧
nodejsccpp
領域
backend
議題類型
bug
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
4
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
over 1 week
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
active
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
Node.js native addon developmentC++ fundamentalsUnderstanding of worker threads
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
20
研究方向
The issue arises because the native Canvas addon is not context aware, meaning it fails when required in multiple Node.js worker threads. The error 'Module did not self register' indicates that the addon's initialization is not per context. The Node.js documentation on context aware addons (https://nodejs.org/api/addons.html#addons context aware addons) provides guidance on using N API or the NODE MODULE INIT macro. A similar fix in another repo (https://github.com/schroffl/node lzo/pull/11) can serve as reference. The solution likely involves restructuring the native module's initialization to be per v8::Context, possibly by using node::AddEnvironmentCleanupHook or per context data.
make module context-aware · Automattic/node-canvas#1394 | Good First Issue