Commit f39ee7d
doc: add snippet for AsyncResource and EE integration
PR-URL: #33751
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Vladimir de Turckheim <vlad2t@hotmail.com>1 parent f8baecc commit f39ee7d
1 file changed
Lines changed: 28 additions & 1 deletion
| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
@@ -512,7 +512,7 @@ createHook({ | |||
| 512 | 512 | } | |
| 513 | 513 | }).enable(); | |
| 514 | 514 | ||
| 515 | - const server = createServer(function(req, res) { | ||
| 515 | + const server = createServer((req, res) => { | ||
| 516 | 516 | executionAsyncResource()[sym] = { state: req.url }; | |
| 517 | 517 | setTimeout(function() { | |
| 518 | 518 | res.end(JSON.stringify(executionAsyncResource()[sym])); | |
@@ -867,6 +867,31 @@ for (let i = 0; i < 10; i++) { | |||
| 867 | 867 | } | |
| 868 | 868 | ``` | |
| 869 | 869 | ||
| 870 | + ### Integrating `AsyncResource` with `EventEmitter` | ||
| 871 | + | ||
| 872 | + Event listeners triggered by an [`EventEmitter`][] may be run in a different | ||
| 873 | + execution context than the one that was active when `eventEmitter.on()` was | ||
| 874 | + called. | ||
| 875 | + | ||
| 876 | + The following example shows how to use the `AsyncResource` class to properly | ||
| 877 | + associate an event listener with the correct execution context. The same | ||
| 878 | + approach can be applied to a [`Stream`][] or a similar event-driven class. | ||
| 879 | + | ||
| 880 | + ```js | ||
| 881 | + const { createServer } = require('http'); | ||
| 882 | + const { AsyncResource, executionAsyncId } = require('async_hooks'); | ||
| 883 | + | ||
| 884 | + const server = createServer((req, res) => { | ||
| 885 | + const asyncResource = new AsyncResource('request'); | ||
| 886 | + // The listener will always run in the execution context of `asyncResource`. | ||
| 887 | + req.on('close', asyncResource.runInAsyncScope.bind(asyncResource, () => { | ||
| 888 | + // Prints: true | ||
| 889 | + console.log(asyncResource.asyncId() === executionAsyncId()); | ||
| 890 | + })); | ||
| 891 | + res.end(); | ||
| 892 | + }).listen(3000); | ||
| 893 | + ``` | ||
| 894 | + | ||
| 870 | 895 | ## Class: `AsyncLocalStorage` | |
| 871 | 896 | <!-- YAML | |
| 872 | 897 | added: v12.17.0 | |
@@ -1105,8 +1130,10 @@ to associate the asynchronous operation with the correct execution context. | |||
| 1105 | 1130 | [`destroy` callback]: #async_hooks_destroy_asyncid | |
| 1106 | 1131 | [`init` callback]: #async_hooks_init_asyncid_type_triggerasyncid_resource | |
| 1107 | 1132 | [`promiseResolve` callback]: #async_hooks_promiseresolve_asyncid | |
| 1133 | + [`EventEmitter`]: events.html#events_class_eventemitter | ||
| 1108 | 1134 | [Hook Callbacks]: #async_hooks_hook_callbacks | |
| 1109 | 1135 | [PromiseHooks]: https://docs.google.com/document/d/1rda3yKGHimKIhg5YeoAmCOtyURgsbTH_qaYR79FELlk/edit | |
| 1136 | + [`Stream`]: stream.html#stream_stream | ||
| 1110 | 1137 | [`Worker`]: worker_threads.html#worker_threads_class_worker | |
| 1111 | 1138 | [promise execution tracking]: #async_hooks_promise_execution_tracking | |
| 1112 | 1139 | [`util.promisify()`]: util.html#util_util_promisify_original | |
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