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author | Andrey Pechkurov <apechkurov@gmail.com> | 2020-03-14 09:06:06 +0300 |
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committer | Beth Griggs <Bethany.Griggs@uk.ibm.com> | 2020-04-14 13:03:56 +0300 |
commit | 63f0dd1ab9a47d1682f48e2f68cfbc583d00aa3e (patch) | |
tree | af61ff7b110b93ce9f9bc1ab8f5b63a73addb27f /doc/api | |
parent | a683e87cd089a005aa9d899198c04f0095b84c7d (diff) |
async_hooks: merge run and exit methods
PR-URL: https://github.com/nodejs/node/pull/31950
Reviewed-By: Vladimir de Turckheim <vlad2t@hotmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Diffstat (limited to 'doc/api')
-rw-r--r-- | doc/api/async_hooks.md | 146 |
1 files changed, 16 insertions, 130 deletions
diff --git a/doc/api/async_hooks.md b/doc/api/async_hooks.md index 86c086ae4b2..5e5c328229a 100644 --- a/doc/api/async_hooks.md +++ b/doc/api/async_hooks.md @@ -922,7 +922,7 @@ added: v13.10.0 --> Creates a new instance of `AsyncLocalStorage`. Store is only provided within a -`run` or a `runSyncAndReturn` method call. +`run` method call. ### `asyncLocalStorage.disable()` <!-- YAML @@ -931,8 +931,7 @@ added: v13.10.0 This method disables the instance of `AsyncLocalStorage`. All subsequent calls to `asyncLocalStorage.getStore()` will return `undefined` until -`asyncLocalStorage.run()` or `asyncLocalStorage.runSyncAndReturn()` -is called again. +`asyncLocalStorage.run()` is called again. When calling `asyncLocalStorage.disable()`, all current contexts linked to the instance will be exited. @@ -954,8 +953,7 @@ added: v13.10.0 This method returns the current store. If this method is called outside of an asynchronous context initialized by -calling `asyncLocalStorage.run` or `asyncLocalStorage.runSyncAndReturn`, it will -return `undefined`. +calling `asyncLocalStorage.run`, it will return `undefined`. ### `asyncLocalStorage.enterWith(store)` <!-- YAML @@ -1008,73 +1006,6 @@ added: v13.10.0 * `callback` {Function} * `...args` {any} -Calling `asyncLocalStorage.run(callback)` will create a new asynchronous -context. Within the callback function and the asynchronous operations from -the callback, `asyncLocalStorage.getStore()` will return the object or -the primitive value passed into the `store` argument (known as "the store"). -This store will be persistent through the following asynchronous calls. - -The callback will be ran asynchronously. Optionally, arguments can be passed -to the function. They will be passed to the callback function. - -If an error is thrown by the callback function, it will not be caught by -a `try/catch` block as the callback is ran in a new asynchronous resource. -Also, the stacktrace will be impacted by the asynchronous call. - -Example: - -```js -const store = { id: 1 }; -asyncLocalStorage.run(store, () => { - asyncLocalStorage.getStore(); // Returns the store object - someAsyncOperation(() => { - asyncLocalStorage.getStore(); // Returns the same object - }); -}); -asyncLocalStorage.getStore(); // Returns undefined -``` - -### `asyncLocalStorage.exit(callback[, ...args])` -<!-- YAML -added: v13.10.0 ---> - -* `callback` {Function} -* `...args` {any} - -Calling `asyncLocalStorage.exit(callback)` will create a new asynchronous -context. -Within the callback function and the asynchronous operations from the callback, -`asyncLocalStorage.getStore()` will return `undefined`. - -The callback will be ran asynchronously. Optionally, arguments can be passed -to the function. They will be passed to the callback function. - -If an error is thrown by the callback function, it will not be caught by -a `try/catch` block as the callback is ran in a new asynchronous resource. -Also, the stacktrace will be impacted by the asynchronous call. - -Example: - -```js -asyncLocalStorage.run('store value', () => { - asyncLocalStorage.getStore(); // Returns 'store value' - asyncLocalStorage.exit(() => { - asyncLocalStorage.getStore(); // Returns undefined - }); - asyncLocalStorage.getStore(); // Returns 'store value' -}); -``` - -### `asyncLocalStorage.runSyncAndReturn(store, callback[, ...args])` -<!-- YAML -added: v13.10.0 ---> - -* `store` {any} -* `callback` {Function} -* `...args` {any} - This methods runs a function synchronously within a context and return its return value. The store is not accessible outside of the callback function or the asynchronous operations created within the callback. @@ -1082,16 +1013,16 @@ the asynchronous operations created within the callback. Optionally, arguments can be passed to the function. They will be passed to the callback function. -If the callback function throws an error, it will be thrown by -`runSyncAndReturn` too. The stacktrace will not be impacted by this call and -the context will be exited. +If the callback function throws an error, it will be thrown by `run` too. +The stacktrace will not be impacted by this call and the context will +be exited. Example: ```js const store = { id: 2 }; try { - asyncLocalStorage.runSyncAndReturn(store, () => { + asyncLocalStorage.run(store, () => { asyncLocalStorage.getStore(); // Returns the store object throw new Error(); }); @@ -1101,7 +1032,7 @@ try { } ``` -### `asyncLocalStorage.exitSyncAndReturn(callback[, ...args])` +### `asyncLocalStorage.exit(callback[, ...args])` <!-- YAML added: v13.10.0 --> @@ -1116,17 +1047,17 @@ the asynchronous operations created within the callback. Optionally, arguments can be passed to the function. They will be passed to the callback function. -If the callback function throws an error, it will be thrown by -`exitSyncAndReturn` too. The stacktrace will not be impacted by this call and +If the callback function throws an error, it will be thrown by `exit` too. +The stacktrace will not be impacted by this call and the context will be re-entered. Example: ```js -// Within a call to run or runSyncAndReturn +// Within a call to run try { asyncLocalStorage.getStore(); // Returns the store object or value - asyncLocalStorage.exitSyncAndReturn(() => { + asyncLocalStorage.exit(() => { asyncLocalStorage.getStore(); // Returns undefined throw new Error(); }); @@ -1136,59 +1067,14 @@ try { } ``` -### Choosing between `run` and `runSyncAndReturn` - -#### When to choose `run` - -`run` is asynchronous. It is called with a callback function that -runs within a new asynchronous call. This is the most explicit behavior as -everything that is executed within the callback of `run` (including further -asynchronous operations) will have access to the store. - -If an instance of `AsyncLocalStorage` is used for error management (for -instance, with `process.setUncaughtExceptionCaptureCallback`), only -exceptions thrown in the scope of the callback function will be associated -with the context. - -This method is the safest as it provides strong scoping and consistent -behavior. - -It cannot be promisified using `util.promisify`. If needed, the `Promise` -constructor can be used: - -```js -const store = new Map(); // initialize the store -new Promise((resolve, reject) => { - asyncLocalStorage.run(store, () => { - someFunction((err, result) => { - if (err) { - return reject(err); - } - return resolve(result); - }); - }); -}); -``` - -#### When to choose `runSyncAndReturn` - -`runSyncAndReturn` is synchronous. The callback function will be executed -synchronously and its return value will be returned by `runSyncAndReturn`. -The store will only be accessible from within the callback -function and the asynchronous operations created within this scope. -If the callback throws an error, `runSyncAndReturn` will throw it and it will -not be associated with the context. - -This method provides good scoping while being synchronous. - -#### Usage with `async/await` +### Usage with `async/await` If, within an async function, only one `await` call is to run within a context, the following pattern should be used: ```js async function fn() { - await asyncLocalStorage.runSyncAndReturn(new Map(), () => { + await asyncLocalStorage.run(new Map(), () => { asyncLocalStorage.getStore().set('key', value); return foo(); // The return value of foo will be awaited }); @@ -1196,8 +1082,8 @@ async function fn() { ``` In this example, the store is only available in the callback function and the -functions called by `foo`. Outside of `runSyncAndReturn`, calling `getStore` -will return `undefined`. +functions called by `foo`. Outside of `run`, calling `getStore` will return +`undefined`. [`after` callback]: #async_hooks_after_asyncid [`before` callback]: #async_hooks_before_asyncid |