Diagnostics Channel
自 v15.1.0 版本开始新增
源代码: 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:
MJS
CJS
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.
MJS
CJS
M diagnostics_channel.hasSubscribers(name)
自 v15.1.0, v14.17.0 版本开始新增
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.
MJS
CJS
M diagnostics_channel.channel(name)
自 v15.1.0, v14.17.0 版本开始新增
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.
MJS
CJS
M diagnostics_channel.subscribe(name, onMessage)
自 v18.7.0, v16.17.0 版本开始新增
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'
.
MJS
CJS
M diagnostics_channel.unsubscribe(name, onMessage)
自 v18.7.0, v16.17.0 版本开始新增
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)
.
MJS
CJS
C Channel
自 v15.1.0, v14.17.0 版本开始新增
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.
M channel.hasSubscribers
自 v15.1.0, v14.17.0 版本开始新增
- 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.
MJS
CJS
M channel.publish(message)
自 v15.1.0, v14.17.0 版本开始新增
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.
MJS
CJS
M channel.subscribe(onMessage)
自 v18.7.0, v16.17.0 版本开始弃用
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'
.
MJS
CJS
M channel.unsubscribe(onMessage)
历史
版本 | 历史变更 |
---|---|
v17.1.0, v16.14.0, v14.19.0 | Added return value. Added to channels without subscribers. |
v18.7.0, v16.17.0 | 自 v18.7.0, v16.17.0 版本开始新增 |
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)
.
MJS
CJS
Built-in Channels
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
自 v16.18.0 版本开始新增
child_process
process
ChildProcess
Emitted when a new process is created.
Worker Thread
自 v16.18.0 版本开始新增
worker_threads
worker
Worker
Emitted when a new thread is created.