- Assertion testing
- Asynchronous context tracking
- Async hooks
- Buffer
- C++ addons
- C/C++ addons with Node-API
- C++ embedder API
- Child processes
- Cluster
- Command-line options
- Console
- Corepack
- Crypto
- Debugger
- Deprecated APIs
- Diagnostics Channel
- DNS
- Domain
- Errors
- Events
- File system
- Globals
- HTTP
- HTTP/2
- HTTPS
- Inspector
- Internationalization
- Modules: CommonJS modules
- Modules: ECMAScript modules
- Modules:
node:module
API - Modules: Packages
- Net
- OS
- Path
- Performance hooks
- Permissions
- Process
- Punycode
- Query strings
- Readline
- REPL
- Report
- Single executable applications
- Stream
- String decoder
- Test runner
- Timers
- TLS/SSL
- Trace events
- TTY
- UDP/datagram
- URL
- Utilities
- V8
- VM
- WASI
- Web Crypto API
- Web Streams API
- Worker threads
- Zlib
Node.js v21.0.0-nightly20230501b5fe45fb9a documentation
- Node.js v21.0.0-nightly20230501b5fe45fb9a
- ► Table of contents
-
►
Index
- Assertion testing
- Asynchronous context tracking
- Async hooks
- Buffer
- C++ addons
- C/C++ addons with Node-API
- C++ embedder API
- Child processes
- Cluster
- Command-line options
- Console
- Corepack
- Crypto
- Debugger
- Deprecated APIs
- Diagnostics Channel
- DNS
- Domain
- Errors
- Events
- File system
- Globals
- HTTP
- HTTP/2
- HTTPS
- Inspector
- Internationalization
- Modules: CommonJS modules
- Modules: ECMAScript modules
- Modules:
node:module
API - Modules: Packages
- Net
- OS
- Path
- Performance hooks
- Permissions
- Process
- Punycode
- Query strings
- Readline
- REPL
- Report
- Single executable applications
- Stream
- String decoder
- Test runner
- Timers
- TLS/SSL
- Trace events
- TTY
- UDP/datagram
- URL
- Utilities
- V8
- VM
- WASI
- Web Crypto API
- Web Streams API
- Worker threads
- Zlib
- ► Other versions
- ► Options
Table of contents
Diagnostics Channel#
Source Code: lib/diagnostics_channel.js
The node:diagnostics_channel
module provides an API to create named channels
to report arbitrary message data for diagnostics purposes.
It can be accessed using:
import diagnostics_channel from 'node:diagnostics_channel';
const diagnostics_channel = require('node:diagnostics_channel');
It is intended that a module writer wanting to report diagnostics messages will create one or many top-level channels to report messages through. Channels may also be acquired at runtime but it is not encouraged due to the additional overhead of doing so. Channels may be exported for convenience, but as long as the name is known it can be acquired anywhere.
If you intend for your module to produce diagnostics data for others to consume it is recommended that you include documentation of what named channels are used along with the shape of the message data. Channel names should generally include the module name to avoid collisions with data from other modules.
Public API#
Overview#
Following is a simple overview of the public API.
import diagnostics_channel from 'node:diagnostics_channel';
// Get a reusable channel object
const channel = diagnostics_channel.channel('my-channel');
function onMessage(message, name) {
// Received data
}
// Subscribe to the channel
diagnostics_channel.subscribe('my-channel', onMessage);
// Check if the channel has an active subscriber
if (channel.hasSubscribers) {
// Publish data to the channel
channel.publish({
some: 'data',
});
}
// Unsubscribe from the channel
diagnostics_channel.unsubscribe('my-channel', onMessage);
const diagnostics_channel = require('node:diagnostics_channel');
// Get a reusable channel object
const channel = diagnostics_channel.channel('my-channel');
function onMessage(message, name) {
// Received data
}
// Subscribe to the channel
diagnostics_channel.subscribe('my-channel', onMessage);
// Check if the channel has an active subscriber
if (channel.hasSubscribers) {
// Publish data to the channel
channel.publish({
some: 'data',
});
}
// Unsubscribe from the channel
diagnostics_channel.unsubscribe('my-channel', onMessage);
diagnostics_channel.hasSubscribers(name)
#
Check if there are active subscribers to the named channel. This is helpful if the message you want to send might be expensive to prepare.
This API is optional but helpful when trying to publish messages from very performance-sensitive code.
import diagnostics_channel from 'node:diagnostics_channel';
if (diagnostics_channel.hasSubscribers('my-channel')) {
// There are subscribers, prepare and publish message
}
const diagnostics_channel = require('node:diagnostics_channel');
if (diagnostics_channel.hasSubscribers('my-channel')) {
// There are subscribers, prepare and publish message
}
diagnostics_channel.channel(name)
#
This is the primary entry-point for anyone wanting to publish to a named channel. It produces a channel object which is optimized to reduce overhead at publish time as much as possible.
import diagnostics_channel from 'node:diagnostics_channel';
const channel = diagnostics_channel.channel('my-channel');
const diagnostics_channel = require('node:diagnostics_channel');
const channel = diagnostics_channel.channel('my-channel');
diagnostics_channel.subscribe(name, onMessage)
#
name
<string> | <symbol> The channel nameonMessage
<Function> The handler to receive channel messages
Register a message handler to subscribe to this channel. This message handler
will be run synchronously whenever a message is published to the channel. Any
errors thrown in the message handler will trigger an 'uncaughtException'
.
import diagnostics_channel from 'node:diagnostics_channel';
diagnostics_channel.subscribe('my-channel', (message, name) => {
// Received data
});
const diagnostics_channel = require('node:diagnostics_channel');
diagnostics_channel.subscribe('my-channel', (message, name) => {
// Received data
});
diagnostics_channel.unsubscribe(name, onMessage)
#
name
<string> | <symbol> The channel nameonMessage
<Function> The previous subscribed handler to remove- Returns: <boolean>
true
if the handler was found,false
otherwise.
Remove a message handler previously registered to this channel with
diagnostics_channel.subscribe(name, onMessage)
.
import diagnostics_channel from 'node:diagnostics_channel';
function onMessage(message, name) {
// Received data
}
diagnostics_channel.subscribe('my-channel', onMessage);
diagnostics_channel.unsubscribe('my-channel', onMessage);
const diagnostics_channel = require('node:diagnostics_channel');
function onMessage(message, name) {
// Received data
}
diagnostics_channel.subscribe('my-channel', onMessage);
diagnostics_channel.unsubscribe('my-channel', onMessage);
diagnostics_channel.tracingChannel(nameOrChannels)
#
nameOrChannels
<string> | <TracingChannel> Channel name or object containing all the TracingChannel Channels- Returns: <TracingChannel> Collection of channels to trace with
Creates a TracingChannel
wrapper for the given
TracingChannel Channels. If a name is given, the corresponding tracing
channels will be created in the form of tracing:${name}:${eventType}
where
eventType
corresponds to the types of TracingChannel Channels.
import diagnostics_channel from 'node:diagnostics_channel';
const channelsByName = diagnostics_channel.tracingChannel('my-channel');
// or...
const channelsByCollection = diagnostics_channel.tracingChannel({
start: diagnostics_channel.channel('tracing:my-channel:start'),
end: diagnostics_channel.channel('tracing:my-channel:end'),
asyncStart: diagnostics_channel.channel('tracing:my-channel:asyncStart'),
asyncEnd: diagnostics_channel.channel('tracing:my-channel:asyncEnd'),
error: diagnostics_channel.channel('tracing:my-channel:error'),
});
const diagnostics_channel = require('node:diagnostics_channel');
const channelsByName = diagnostics_channel.tracingChannel('my-channel');
// or...
const channelsByCollection = diagnostics_channel.tracingChannel({
start: diagnostics_channel.channel('tracing:my-channel:start'),
end: diagnostics_channel.channel('tracing:my-channel:end'),
asyncStart: diagnostics_channel.channel('tracing:my-channel:asyncStart'),
asyncEnd: diagnostics_channel.channel('tracing:my-channel:asyncEnd'),
error: diagnostics_channel.channel('tracing:my-channel:error'),
});
Class: Channel
#
The class Channel
represents an individual named channel within the data
pipeline. It is used to track subscribers and to publish messages when there
are subscribers present. It exists as a separate object to avoid channel
lookups at publish time, enabling very fast publish speeds and allowing
for heavy use while incurring very minimal cost. Channels are created with
diagnostics_channel.channel(name)
, constructing a channel directly
with new Channel(name)
is not supported.
channel.hasSubscribers
#
- Returns: <boolean> If there are active subscribers
Check if there are active subscribers to this channel. This is helpful if the message you want to send might be expensive to prepare.
This API is optional but helpful when trying to publish messages from very performance-sensitive code.
import diagnostics_channel from 'node:diagnostics_channel';
const channel = diagnostics_channel.channel('my-channel');
if (channel.hasSubscribers) {
// There are subscribers, prepare and publish message
}
const diagnostics_channel = require('node:diagnostics_channel');
const channel = diagnostics_channel.channel('my-channel');
if (channel.hasSubscribers) {
// There are subscribers, prepare and publish message
}
channel.publish(message)
#
message
<any> The message to send to the channel subscribers
Publish a message to any subscribers to the channel. This will trigger message handlers synchronously so they will execute within the same context.
import diagnostics_channel from 'node:diagnostics_channel';
const channel = diagnostics_channel.channel('my-channel');
channel.publish({
some: 'message',
});
const diagnostics_channel = require('node:diagnostics_channel');
const channel = diagnostics_channel.channel('my-channel');
channel.publish({
some: 'message',
});
channel.subscribe(onMessage)
#
diagnostics_channel.subscribe(name, onMessage)
onMessage
<Function> The handler to receive channel messages
Register a message handler to subscribe to this channel. This message handler
will be run synchronously whenever a message is published to the channel. Any
errors thrown in the message handler will trigger an 'uncaughtException'
.
import diagnostics_channel from 'node:diagnostics_channel';
const channel = diagnostics_channel.channel('my-channel');
channel.subscribe((message, name) => {
// Received data
});
const diagnostics_channel = require('node:diagnostics_channel');
const channel = diagnostics_channel.channel('my-channel');
channel.subscribe((message, name) => {
// Received data
});
channel.unsubscribe(onMessage)
#
diagnostics_channel.unsubscribe(name, onMessage)
onMessage
<Function> The previous subscribed handler to remove- Returns: <boolean>
true
if the handler was found,false
otherwise.
Remove a message handler previously registered to this channel with
channel.subscribe(onMessage)
.
import diagnostics_channel from 'node:diagnostics_channel';
const channel = diagnostics_channel.channel('my-channel');
function onMessage(message, name) {
// Received data
}
channel.subscribe(onMessage);
channel.unsubscribe(onMessage);
const diagnostics_channel = require('node:diagnostics_channel');
const channel = diagnostics_channel.channel('my-channel');
function onMessage(message, name) {
// Received data
}
channel.subscribe(onMessage);
channel.unsubscribe(onMessage);
channel.bindStore(store[, transform])
#
store
<AsyncLocalStorage> The store to which to bind the context datatransform
<Function> Transform context data before setting the store context
When channel.runStores(context, ...)
is called, the given context data
will be applied to any store bound to the channel. If the store has already been
bound the previous transform
function will be replaced with the new one.
The transform
function may be omitted to set the given context data as the
context directly.
import diagnostics_channel from 'node:diagnostics_channel';
import { AsyncLocalStorage } from 'node:async_hooks';
const store = new AsyncLocalStorage();
const channel = diagnostics_channel.channel('my-channel');
channel.bindStore(store, (data) => {
return { data };
});
const diagnostics_channel = require('node:diagnostics_channel');
const { AsyncLocalStorage } = require('node:async_hooks');
const store = new AsyncLocalStorage();
const channel = diagnostics_channel.channel('my-channel');
channel.bindStore(store, (data) => {
return { data };
});
channel.unbindStore(store)
#
store
<AsyncLocalStorage> The store to unbind from the channel.- Returns: <boolean>
true
if the store was found,false
otherwise.
Remove a message handler previously registered to this channel with
channel.bindStore(store)
.
import diagnostics_channel from 'node:diagnostics_channel';
import { AsyncLocalStorage } from 'node:async_hooks';
const store = new AsyncLocalStorage();
const channel = diagnostics_channel.channel('my-channel');
channel.bindStore(store);
channel.unbindStore(store);
const diagnostics_channel = require('node:diagnostics_channel');
const { AsyncLocalStorage } = require('node:async_hooks');
const store = new AsyncLocalStorage();
const channel = diagnostics_channel.channel('my-channel');
channel.bindStore(store);
channel.unbindStore(store);
channel.runStores(context, fn[, thisArg[, ...args]])
#
context
<any> Message to send to subscribers and bind to storesfn
<Function> Handler to run within the entered storage contextthisArg
<any> The receiver to be used for the function call....args
<any> Optional arguments to pass to the function.
Applies the given data to any AsyncLocalStorage instances bound to the channel for the duration of the given function, then publishes to the channel within the scope of that data is applied to the stores.
If a transform function was given to channel.bindStore(store)
it will be
applied to transform the message data before it becomes the context value for
the store. The prior storage context is accessible from within the transform
function in cases where context linking is required.
The context applied to the store should be accessible in any async code which continues from execution which began during the given function, however there are some situations in which context loss may occur.
import diagnostics_channel from 'node:diagnostics_channel';
import { AsyncLocalStorage } from 'node:async_hooks';
const store = new AsyncLocalStorage();
const channel = diagnostics_channel.channel('my-channel');
channel.bindStore(store, (message) => {
const parent = store.getStore();
return new Span(message, parent);
});
channel.runStores({ some: 'message' }, () => {
store.getStore(); // Span({ some: 'message' })
});
const diagnostics_channel = require('node:diagnostics_channel');
const { AsyncLocalStorage } = require('node:async_hooks');
const store = new AsyncLocalStorage();
const channel = diagnostics_channel.channel('my-channel');
channel.bindStore(store, (message) => {
const parent = store.getStore();
return new Span(message, parent);
});
channel.runStores({ some: 'message' }, () => {
store.getStore(); // Span({ some: 'message' })
});
Class: TracingChannel
#
The class TracingChannel
is a collection of TracingChannel Channels which
together express a single traceable action. It is used to formalize and
simplify the process of producing events for tracing application flow.
diagnostics_channel.tracingChannel()
is used to construct a
TracingChannel
. As with Channel
it is recommended to create and reuse a
single TracingChannel
at the top-level of the file rather than creating them
dynamically.
tracingChannel.subscribe(subscribers)
#
subscribers
<Object> Set of TracingChannel Channels subscribersstart
<Function> Thestart
event subscriberend
<Function> Theend
event subscriberasyncStart
<Function> TheasyncStart
event subscriberasyncEnd
<Function> TheasyncEnd
event subscribererror
<Function> Theerror
event subscriber
Helper to subscribe a collection of functions to the corresponding channels.
This is the same as calling channel.subscribe(onMessage)
on each channel
individually.
import diagnostics_channel from 'node:diagnostics_channel';
const channels = diagnostics_channel.tracingChannel('my-channel');
channels.subscribe({
start(message) {
// Handle start message
},
end(message) {
// Handle end message
},
asyncStart(message) {
// Handle asyncStart message
},
asyncEnd(message) {
// Handle asyncEnd message
},
error(message) {
// Handle error message
},
});
const diagnostics_channel = require('node:diagnostics_channel');
const channels = diagnostics_channel.tracingChannel('my-channel');
channels.subscribe({
start(message) {
// Handle start message
},
end(message) {
// Handle end message
},
asyncStart(message) {
// Handle asyncStart message
},
asyncEnd(message) {
// Handle asyncEnd message
},
error(message) {
// Handle error message
},
});
tracingChannel.unsubscribe(subscribers)
#
subscribers
<Object> Set of TracingChannel Channels subscribersstart
<Function> Thestart
event subscriberend
<Function> Theend
event subscriberasyncStart
<Function> TheasyncStart
event subscriberasyncEnd
<Function> TheasyncEnd
event subscribererror
<Function> Theerror
event subscriber
- Returns: <boolean>
true
if all handlers were successfully unsubscribed, andfalse
otherwise.
Helper to unsubscribe a collection of functions from the corresponding channels.
This is the same as calling channel.unsubscribe(onMessage)
on each channel
individually.
import diagnostics_channel from 'node:diagnostics_channel';
const channels = diagnostics_channel.tracingChannel('my-channel');
channels.unsubscribe({
start(message) {
// Handle start message
},
end(message) {
// Handle end message
},
asyncStart(message) {
// Handle asyncStart message
},
asyncEnd(message) {
// Handle asyncEnd message
},
error(message) {
// Handle error message
},
});
const diagnostics_channel = require('node:diagnostics_channel');
const channels = diagnostics_channel.tracingChannel('my-channel');
channels.unsubscribe({
start(message) {
// Handle start message
},
end(message) {
// Handle end message
},
asyncStart(message) {
// Handle asyncStart message
},
asyncEnd(message) {
// Handle asyncEnd message
},
error(message) {
// Handle error message
},
});
tracingChannel.traceSync(fn[, context[, thisArg[, ...args]]])
#
fn
<Function> Function to wrap a trace aroundcontext
<Object> Shared object to correlate events throughthisArg
<any> The receiver to be used for the function call...args
<any> Optional arguments to pass to the function- Returns: <any> The return value of the given function
Trace a synchronous function call. This will always produce a start
event
and end
event around the execution and may produce an error
event
if the given function throws an error. This will run the given function using
channel.runStores(context, ...)
on the start
channel which ensures all
events should have any bound stores set to match this trace context.
import diagnostics_channel from 'node:diagnostics_channel';
const channels = diagnostics_channel.tracingChannel('my-channel');
channels.traceSync(() => {
// Do something
}, {
some: 'thing',
});
const diagnostics_channel = require('node:diagnostics_channel');
const channels = diagnostics_channel.tracingChannel('my-channel');
channels.traceSync(() => {
// Do something
}, {
some: 'thing',
});
tracingChannel.tracePromise(fn[, context[, thisArg[, ...args]]])
#
fn
<Function> Promise-returning function to wrap a trace aroundcontext
<Object> Shared object to correlate trace events throughthisArg
<any> The receiver to be used for the function call...args
<any> Optional arguments to pass to the function- Returns: <Promise> Chained from promise returned by the given function
Trace a promise-returning function call. This will always produce a
start
event and end
event around the synchronous portion of the
function execution, and will produce an asyncStart
event and
asyncEnd
event when a promise continuation is reached. It may also
produce an error
event if the given function throws an error or the
returned promise rejects. This will run the given function using
channel.runStores(context, ...)
on the start
channel which ensures all
events should have any bound stores set to match this trace context.
import diagnostics_channel from 'node:diagnostics_channel';
const channels = diagnostics_channel.tracingChannel('my-channel');
channels.tracePromise(async () => {
// Do something
}, {
some: 'thing',
});
const diagnostics_channel = require('node:diagnostics_channel');
const channels = diagnostics_channel.tracingChannel('my-channel');
channels.tracePromise(async () => {
// Do something
}, {
some: 'thing',
});
tracingChannel.traceCallback(fn[, position[, context[, thisArg[, ...args]]]])
#
fn
<Function> callback using function to wrap a trace aroundposition
<number> Zero-indexed argument position of expected callbackcontext
<Object> Shared object to correlate trace events throughthisArg
<any> The receiver to be used for the function call...args
<any> Optional arguments to pass to the function- Returns: <any> The return value of the given function
Trace a callback-receiving function call. This will always produce a
start
event and end
event around the synchronous portion of the
function execution, and will produce a asyncStart
event and
asyncEnd
event around the callback execution. It may also produce an
error
event if the given function throws an error or the returned
promise rejects. This will run the given function using
channel.runStores(context, ...)
on the start
channel which ensures all
events should have any bound stores set to match this trace context.
The position
will be -1 by default to indicate the final argument should
be used as the callback.
import diagnostics_channel from 'node:diagnostics_channel';
const channels = diagnostics_channel.tracingChannel('my-channel');
channels.traceCallback((arg1, callback) => {
// Do something
callback(null, 'result');
}, 1, {
some: 'thing',
}, thisArg, arg1, callback);
const diagnostics_channel = require('node:diagnostics_channel');
const channels = diagnostics_channel.tracingChannel('my-channel');
channels.traceCallback((arg1, callback) => {
// Do something
callback(null, 'result');
}, {
some: 'thing',
}, thisArg, arg1, callback);
The callback will also be run with channel.runStores(context, ...)
which
enables context loss recovery in some cases.
import diagnostics_channel from 'node:diagnostics_channel';
import { AsyncLocalStorage } from 'node:async_hooks';
const channels = diagnostics_channel.tracingChannel('my-channel');
const myStore = new AsyncLocalStorage();
// The start channel sets the initial store data to something
// and stores that store data value on the trace context object
channels.start.bindStore(myStore, (data) => {
const span = new Span(data);
data.span = span;
return span;
});
// Then asyncStart can restore from that data it stored previously
channels.asyncStart.bindStore(myStore, (data) => {
return data.span;
});
const diagnostics_channel = require('node:diagnostics_channel');
const { AsyncLocalStorage } = require('node:async_hooks');
const channels = diagnostics_channel.tracingChannel('my-channel');
const myStore = new AsyncLocalStorage();
// The start channel sets the initial store data to something
// and stores that store data value on the trace context object
channels.start.bindStore(myStore, (data) => {
const span = new Span(data);
data.span = span;
return span;
});
// Then asyncStart can restore from that data it stored previously
channels.asyncStart.bindStore(myStore, (data) => {
return data.span;
});
TracingChannel Channels#
A TracingChannel is a collection of several diagnostics_channels representing
specific points in the execution lifecycle of a single traceable action. The
behavior is split into five diagnostics_channels consisting of start
,
end
, asyncStart
, asyncEnd
, and error
. A single traceable action will
share the same event object between all events, this can be helpful for
managing correlation through a weakmap.
These event objects will be extended with result
or error
values when
the task "completes". In the case of a synchronous task the result
will be
the return value and the error
will be anything thrown from the function.
With callback-based async functions the result
will be the second argument
of the callback while the error
will either be a thrown error visible in the
end
event or the first callback argument in either of the asyncStart
or
asyncEnd
events.
Tracing channels should follow a naming pattern of:
tracing:module.class.method:start
ortracing:module.function:start
tracing:module.class.method:end
ortracing:module.function:end
tracing:module.class.method:asyncStart
ortracing:module.function:asyncStart
tracing:module.class.method:asyncEnd
ortracing:module.function:asyncEnd
tracing:module.class.method:error
ortracing:module.function:error
start(event)
#
- Name:
tracing:${name}:start
The start
event represents the point at which a function is called. At this
point the event data may contain function arguments or anything else available
at the very start of the execution of the function.
end(event)
#
- Name:
tracing:${name}:end
The end
event represents the point at which a function call returns a value.
In the case of an async function this is when the promise returned not when the
function itself makes a return statement internally. At this point, if the
traced function was synchronous the result
field will be set to the return
value of the function. Alternatively, the error
field may be present to
represent any thrown errors.
It is recommended to listen specifically to the error
event to track errors
as it may be possible for a traceable action to produce multiple errors. For
example, an async task which fails may be started internally before the sync
part of the task then throws an error.
asyncStart(event)
#
- Name:
tracing:${name}:asyncStart
The asyncStart
event represents the callback or continuation of a traceable
function being reached. At this point things like callback arguments may be
available, or anything else expressing the "result" of the action.
For callbacks-based functions, the first argument of the callback will be
assigned to the error
field, if not undefined
or null
, and the second
argument will be assigned to the result
field.
For promises, the argument to the resolve
path will be assigned to result
or the argument to the reject
path will be assign to error
.
It is recommended to listen specifically to the error
event to track errors
as it may be possible for a traceable action to produce multiple errors. For
example, an async task which fails may be started internally before the sync
part of the task then throws an error.
asyncEnd(event)
#
- Name:
tracing:${name}:asyncEnd
The asyncEnd
event represents the callback of an asynchronous function
returning. It's not likely event data will change after the asyncStart
event,
however it may be useful to see the point where the callback completes.
error(event)
#
- Name:
tracing:${name}:error
The error
event represents any error produced by the traceable function
either synchronously or asynchronously. If an error is thrown in the
synchronous portion of the traced function the error will be assigned to the
error
field of the event and the error
event will be triggered. If an error
is received asynchronously through a callback or promise rejection it will also
be assigned to the error
field of the event and trigger the error
event.
It is possible for a single traceable function call to produce errors multiple
times so this should be considered when consuming this event. For example, if
another async task is triggered internally which fails and then the sync part
of the function then throws and error two error
events will be emitted, one
for the sync error and one for the async error.
Built-in Channels#
While the diagnostics_channel API is now considered stable, the built-in channels currently available are not. Each channel must be declared stable independently.
HTTP#
http.client.request.start
request
<http.ClientRequest>
Emitted when client starts a request.
http.client.response.finish
request
<http.ClientRequest>response
<http.IncomingMessage>
Emitted when client receives a response.
http.server.request.start
request
<http.IncomingMessage>response
<http.ServerResponse>socket
<net.Socket>server
<http.Server>
Emitted when server receives a request.
http.server.response.finish
request
<http.IncomingMessage>response
<http.ServerResponse>socket
<net.Socket>server
<http.Server>
Emitted when server sends a response.
NET#
net.client.socket
socket
<net.Socket>
Emitted when a new TCP or pipe client socket is created.
net.server.socket
socket
<net.Socket>
Emitted when a new TCP or pipe connection is received.
UDP#
udp.socket
socket
<dgram.Socket>
Emitted when a new UDP socket is created.
Process#
child_process
process
<ChildProcess>
Emitted when a new process is created.
Worker Thread#
worker_threads
worker
Worker
Emitted when a new thread is created.