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async_hooks: rename currentId and triggerId
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currentId is renamed to executionAsyncId
triggerId is renamed to triggerAsyncId
AsyncResource.triggerId is renamed to AsyncResource.triggerAsyncId
AsyncHooksGetCurrentId is renamed to AsyncHooksGetExecutionAsyncId
AsyncHooksGetTriggerId is renamed to AsyncHooksGetTriggerAsyncId

PR-URL: #13490
Reviewed-By: Refael Ackermann <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Trevor Norris <[email protected]>
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@AndreasMadsen @addaleax
AndreasMadsen authored and addaleax committed Jun 17, 2017
1 parent 4298f9e commit 87f6c21
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105 changes: 53 additions & 52 deletions doc/api/async_hooks.md
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Original file line number Diff line number Diff line change
Expand Up @@ -29,11 +29,11 @@ Following is a simple overview of the public API.
const async_hooks = require('async_hooks');

// Return the ID of the current execution context.
const cid = async_hooks.currentId();
const eid = async_hooks.executionAsyncId();

// Return the ID of the handle responsible for triggering the callback of the
// current execution scope to call.
const tid = async_hooks.triggerId();
const tid = async_hooks.triggerAsyncId();

// Create a new AsyncHook instance. All of these callbacks are optional.
const asyncHook = async_hooks.createHook({ init, before, after, destroy });
Expand All @@ -53,7 +53,7 @@ asyncHook.disable();
// init is called during object construction. The resource may not have
// completed construction when this callback runs, therefore all fields of the
// resource referenced by "asyncId" may not have been populated.
function init(asyncId, type, triggerId, resource) { }
function init(asyncId, type, triggerAsyncId, resource) { }

// before is called just before the resource's callback is called. It can be
// called 0-N times for handles (e.g. TCPWrap), and will be called exactly 1
Expand Down Expand Up @@ -163,11 +163,11 @@ Key events in the lifetime of asynchronous events have been categorized into
four areas: instantiation, before/after the callback is called, and when the
instance is destructed.

##### `init(asyncId, type, triggerId, resource)`
##### `init(asyncId, type, triggerAsyncId, resource)`

* `asyncId` {number} a unique ID for the async resource
* `type` {string} the type of the async resource
* `triggerId` {number} the unique ID of the async resource in whose
* `triggerAsyncId` {number} the unique ID of the async resource in whose
execution context this async resource was created
* `resource` {Object} reference to the resource representing the async operation,
needs to be released during _destroy_
Expand Down Expand Up @@ -214,20 +214,20 @@ when listening to the hooks.

###### `triggerId`

`triggerId` is the `asyncId` of the resource that caused (or "triggered") the
`triggerAsyncId` is the `asyncId` of the resource that caused (or "triggered") the
new resource to initialize and that caused `init` to call. This is different
from `async_hooks.currentId()` that only shows *when* a resource was created,
while `triggerId` shows *why* a resource was created.
from `async_hooks.executionAsyncId()` that only shows *when* a resource was
created, while `triggerAsyncId` shows *why* a resource was created.


The following is a simple demonstration of `triggerId`:
The following is a simple demonstration of `triggerAsyncId`:

```js
async_hooks.createHook({
init(asyncId, type, triggerId) {
const cId = async_hooks.currentId();
init(asyncId, type, triggerAsyncId) {
const eid = async_hooks.executionAsyncId();
fs.writeSync(
1, `${type}(${asyncId}): trigger: ${triggerId} scope: ${cId}\n`);
1, `${type}(${asyncId}): trigger: ${triggerAsyncId} execution: ${eid}\n`);
}
}).enable();

Expand All @@ -237,18 +237,18 @@ require('net').createServer((conn) => {}).listen(8080);
Output when hitting the server with `nc localhost 8080`:

```
TCPWRAP(2): trigger: 1 scope: 1
TCPWRAP(4): trigger: 2 scope: 0
TCPWRAP(2): trigger: 1 execution: 1
TCPWRAP(4): trigger: 2 execution: 0
```

The first `TCPWRAP` is the server which receives the connections.

The second `TCPWRAP` is the new connection from the client. When a new
connection is made the `TCPWrap` instance is immediately constructed. This
happens outside of any JavaScript stack (side note: a `currentId()` of `0`
happens outside of any JavaScript stack (side note: a `executionAsyncId()` of `0`
means it's being executed from C++, with no JavaScript stack above it).
With only that information it would be impossible to link resources together in
terms of what caused them to be created, so `triggerId` is given the task of
terms of what caused them to be created, so `triggerAsyncId` is given the task of
propagating what resource is responsible for the new resource's existence.

###### `resource`
Expand Down Expand Up @@ -280,12 +280,13 @@ elaborate to make calling context easier to see.
```js
let indent = 0;
async_hooks.createHook({
init(asyncId, type, triggerId) {
const cId = async_hooks.currentId();
init(asyncId, type, triggerAsyncId) {
const eid = async_hooks.executionAsyncId();
const indentStr = ' '.repeat(indent);
fs.writeSync(
1,
`${indentStr}${type}(${asyncId}): trigger: ${triggerId} scope: ${cId}\n`);
`${indentStr}${type}(${asyncId}):` +
` trigger: ${triggerAsyncId} execution: ${eid}\n`);
},
before(asyncId) {
const indentStr = ' '.repeat(indent);
Expand All @@ -306,28 +307,28 @@ async_hooks.createHook({
require('net').createServer(() => {}).listen(8080, () => {
// Let's wait 10ms before logging the server started.
setTimeout(() => {
console.log('>>>', async_hooks.currentId());
console.log('>>>', async_hooks.executionAsyncId());
}, 10);
});
```

Output from only starting the server:

```
TCPWRAP(2): trigger: 1 scope: 1
TickObject(3): trigger: 2 scope: 1
TCPWRAP(2): trigger: 1 execution: 1
TickObject(3): trigger: 2 execution: 1
before: 3
Timeout(4): trigger: 3 scope: 3
TIMERWRAP(5): trigger: 3 scope: 3
Timeout(4): trigger: 3 execution: 3
TIMERWRAP(5): trigger: 3 execution: 3
after: 3
destroy: 3
before: 5
before: 4
TTYWRAP(6): trigger: 4 scope: 4
SIGNALWRAP(7): trigger: 4 scope: 4
TTYWRAP(8): trigger: 4 scope: 4
TTYWRAP(6): trigger: 4 execution: 4
SIGNALWRAP(7): trigger: 4 execution: 4
TTYWRAP(8): trigger: 4 execution: 4
>>> 4
TickObject(9): trigger: 4 scope: 4
TickObject(9): trigger: 4 execution: 4
after: 4
after: 5
before: 9
Expand All @@ -337,11 +338,11 @@ destroy: 9
destroy: 5
```

*Note*: As illustrated in the example, `currentId()` and `scope` each specify
the value of the current execution context; which is delineated by calls to
`before` and `after`.
*Note*: As illustrated in the example, `executionAsyncId()` and `execution`
each specify the value of the current execution context; which is delineated by
calls to `before` and `after`.

Only using `scope` to graph resource allocation results in the following:
Only using `execution` to graph resource allocation results in the following:

```
TTYWRAP(6) -> Timeout(4) -> TIMERWRAP(5) -> TickObject(3) -> root(1)
Expand All @@ -353,7 +354,7 @@ hostname is actually synchronous, but to maintain a completely asynchronous API
the user's callback is placed in a `process.nextTick()`.

The graph only shows *when* a resource was created, not *why*, so to track
the *why* use `triggerId`.
the *why* use `triggerAsyncId`.


##### `before(asyncId)`
Expand Down Expand Up @@ -396,39 +397,39 @@ the `resource` object passed to `init` it's possible that `destroy` is
never called, causing a memory leak in the application. Of course if
the resource doesn't depend on GC then this isn't an issue.

#### `async_hooks.currentId()`
#### `async_hooks.executionAsyncId()`

* Returns {number} the `asyncId` of the current execution context. Useful to track
when something calls.

For example:

```js
console.log(async_hooks.currentId()); // 1 - bootstrap
console.log(async_hooks.executionAsyncId()); // 1 - bootstrap
fs.open(path, 'r', (err, fd) => {
console.log(async_hooks.currentId()); // 6 - open()
console.log(async_hooks.executionAsyncId()); // 6 - open()
});
```

It is important to note that the ID returned fom `currentId()` is related to
execution timing, not causality (which is covered by `triggerId()`). For
It is important to note that the ID returned fom `executionAsyncId()` is related
to execution timing, not causality (which is covered by `triggerAsyncId()`). For
example:

```js
const server = net.createServer(function onConnection(conn) {
// Returns the ID of the server, not of the new connection, because the
// onConnection callback runs in the execution scope of the server's
// MakeCallback().
async_hooks.currentId();
async_hooks.executionAsyncId();

}).listen(port, function onListening() {
// Returns the ID of a TickObject (i.e. process.nextTick()) because all
// callbacks passed to .listen() are wrapped in a nextTick().
async_hooks.currentId();
async_hooks.executionAsyncId();
});
```

#### `async_hooks.triggerId()`
#### `async_hooks.triggerAsyncId()`

* Returns {number} the ID of the resource responsible for calling the callback
that is currently being executed.
Expand All @@ -438,15 +439,15 @@ For example:
```js
const server = net.createServer((conn) => {
// The resource that caused (or triggered) this callback to be called
// was that of the new connection. Thus the return value of triggerId()
// was that of the new connection. Thus the return value of triggerAsyncId()
// is the asyncId of "conn".
async_hooks.triggerId();
async_hooks.triggerAsyncId();

}).listen(port, () => {
// Even though all callbacks passed to .listen() are wrapped in a nextTick()
// the callback itself exists because the call to the server's .listen()
// was made. So the return value would be the ID of the server.
async_hooks.triggerId();
async_hooks.triggerAsyncId();
});
```

Expand Down Expand Up @@ -475,9 +476,9 @@ The following is an overview of the `AsyncResource` API.
const { AsyncResource } = require('async_hooks');

// AsyncResource() is meant to be extended. Instantiating a
// new AsyncResource() also triggers init. If triggerId is omitted then
// async_hook.currentId() is used.
const asyncResource = new AsyncResource(type, triggerId);
// new AsyncResource() also triggers init. If triggerAsyncId is omitted then
// async_hook.executionAsyncId() is used.
const asyncResource = new AsyncResource(type, triggerAsyncId);

// Call AsyncHooks before callbacks.
asyncResource.emitBefore();
Expand All @@ -492,14 +493,14 @@ asyncResource.emitDestroy();
asyncResource.asyncId();

// Return the trigger ID for the AsyncResource instance.
asyncResource.triggerId();
asyncResource.triggerAsyncId();
```

#### `AsyncResource(type[, triggerId])`
#### `AsyncResource(type[, triggerAsyncId])`

* arguments
* `type` {string} the type of ascyc event
* `triggerId` {number} the ID of the execution context that created this async
* `triggerAsyncId` {number} the ID of the execution context that created this async
event

Example usage:
Expand Down Expand Up @@ -558,9 +559,9 @@ never be called.

* Returns {number} the unique `asyncId` assigned to the resource.

#### `asyncResource.triggerId()`
#### `asyncResource.triggerAsyncId()`

* Returns {number} the same `triggerId` that is passed to the `AsyncResource`
* Returns {number} the same `triggerAsyncId` that is passed to the `AsyncResource`
constructor.

[`Hook Callbacks`]: #hook-callbacks
30 changes: 30 additions & 0 deletions doc/api/deprecations.md
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Original file line number Diff line number Diff line change
Expand Up @@ -600,6 +600,36 @@ The DebugContext will be removed in V8 soon and will not be available in Node

*Note*: DebugContext was an experimental API.

<a id="DEP0070"></a>
### DEP0070: async_hooks.currentId()

Type: Runtime

`async_hooks.currentId()` was renamed to `async_hooks.executionAsyncId()` for
clarity.

*Note*: change was made while `async_hooks` was an experimental API.

<a id="DEP0071"></a>
### DEP0071: async_hooks.triggerId()

Type: Runtime

`async_hooks.triggerId()` was renamed to `async_hooks.triggerAsyncId()` for
clarity.

*Note*: change was made while `async_hooks` was an experimental API.

<a id="DEP0072"></a>
### DEP0072: async_hooks.AsyncResource.triggerId()

Type: Runtime

`async_hooks.AsyncResource.triggerId()` was renamed to
`async_hooks.AsyncResource.triggerAsyncId()` for clarity.

*Note*: change was made while `async_hooks` was an experimental API.

[`Buffer.allocUnsafeSlow(size)`]: buffer.html#buffer_class_method_buffer_allocunsafeslow_size
[`Buffer.from(array)`]: buffer.html#buffer_class_method_buffer_from_array
[`Buffer.from(buffer)`]: buffer.html#buffer_class_method_buffer_from_buffer
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