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doc: Warn against uncaughtException dependency.

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State in the documentation that `uncaughtException` is not a reliable
way to restart a crashed application, and clarify that an application
may crash in ways that do not trigger this event.

Use a documented synchronous function in example code.

Fixes: https://github.com/nodejs/node/issues/6223

Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
PR-URL: https://github.com/nodejs/node/pull/6378
This commit is contained in:
Lance Ball 2016-04-25 15:48:50 -04:00
parent c09dfe3a0b
commit 2fe277a05c
1 changed files with 17 additions and 12 deletions
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19
doc/api/process.md
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@ -149,10 +149,11 @@ most convenient for scripts).
added: v0.1.18
-->
The `'uncaughtException'` event is emitted when an exception bubbles all the
way back to the event loop. By default, Node.js handles such exceptions by
printing the stack trace to `stderr` and exiting. Adding a handler for the
`'uncaughtException'` event overrides this default behavior.
The `'uncaughtException'` event is emitted when an uncaught JavaScript
exception bubbles all the way back to the event loop. By default, Node.js
handles such exceptions by printing the stack trace to `stderr` and exiting.
Adding a handler for the `'uncaughtException'` event overrides this default
behavior.
The listener function is called with the `Error` object passed as the only
argument.
@ -161,7 +162,7 @@ For example:
```js
process.on('uncaughtException', (err) => {
console.log(`Caught exception: ${err}`);
fs.writeSync(1, `Caught exception: ${err}`);
});
setTimeout(() => {
@ -192,8 +193,12 @@ times nothing happens - but the 10th time, the system becomes corrupted.
The correct use of `'uncaughtException'` is to perform synchronous cleanup
of allocated resources (e.g. file descriptors, handles, etc) before shutting
down the process. It is not safe to resume normal operation after
`'uncaughtException'`.
down the process. **It is not safe to resume normal operation after
`'uncaughtException'`.**
To restart a crashed application in a more reliable way, whether `uncaughtException`
is emitted or not, an external monitor should be employed in a separate process
to detect application failures and recover or restart as needed.
### Event: 'unhandledRejection'
<!-- YAML