Current File : //usr/share/nodejs/@types/node/diagnostics_channel.d.ts
/**
* The `diagnostics_channel` module provides an API to create named channels
* to report arbitrary message data for diagnostics purposes.
*
* It can be accessed using:
*
* ```js
* import diagnostics_channel from '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.
* @experimental
* @see [source](https://github.com/nodejs/node/blob/v18.0.0/lib/diagnostics_channel.js)
*/
declare module "diagnostics_channel" {
/**
* 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.
*
* ```js
* import diagnostics_channel from 'diagnostics_channel';
*
* if (diagnostics_channel.hasSubscribers('my-channel')) {
* // There are subscribers, prepare and publish message
* }
* ```
* @since v15.1.0, v14.17.0
* @param name The channel name
* @return If there are active subscribers
*/
function hasSubscribers(name: string | symbol): boolean;
/**
* This is the primary entry-point for anyone wanting to interact with a named
* channel. It produces a channel object which is optimized to reduce overhead at
* publish time as much as possible.
*
* ```js
* import diagnostics_channel from 'diagnostics_channel';
*
* const channel = diagnostics_channel.channel('my-channel');
* ```
* @since v15.1.0, v14.17.0
* @param name The channel name
* @return The named channel object
*/
function channel(name: string | symbol): Channel;
type ChannelListener = (message: unknown, name: string | symbol) => void;
/**
* 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'.
*
* ```js
* import diagnostics_channel from 'diagnostics_channel';
*
* diagnostics_channel.subscribe('my-channel', (message, name) => {
* // Received data
* });
* ```
*
* @since v18.7.0, v16.17.0
* @param name The channel name
* @param onMessage The handler to receive channel messages
*/
function subscribe(name: string | symbol, onMessage: ChannelListener): void;
/**
* Remove a message handler previously registered to this channel with diagnostics_channel.subscribe(name, onMessage).
*
* ```js
* import diagnostics_channel from 'diagnostics_channel';
*
* function onMessage(message, name) {
* // Received data
* }
*
* diagnostics_channel.subscribe('my-channel', onMessage);
*
* diagnostics_channel.unsubscribe('my-channel', onMessage);
* ```
*
* @since v18.7.0, v16.17.0
* @param name The channel name
* @param onMessage The previous subscribed handler to remove
* @returns `true` if the handler was found, `false` otherwise
*/
function unsubscribe(name: string | symbol, onMessage: ChannelListener): boolean;
/**
* The class `Channel` represents an individual named channel within the data
* pipeline. It is use 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 {@link channel}, constructing a channel directly
* with `new Channel(name)` is not supported.
* @since v15.1.0, v14.17.0
*/
class Channel {
readonly name: string | symbol;
/**
* 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.
*
* ```js
* import diagnostics_channel from 'diagnostics_channel';
*
* const channel = diagnostics_channel.channel('my-channel');
*
* if (channel.hasSubscribers) {
* // There are subscribers, prepare and publish message
* }
* ```
* @since v15.1.0, v14.17.0
*/
readonly hasSubscribers: boolean;
private constructor(name: string | symbol);
/**
* Publish a message to any subscribers to the channel. This will
* trigger message handlers synchronously so they will execute within
* the same context.
*
* ```js
* import diagnostics_channel from 'diagnostics_channel';
*
* const channel = diagnostics_channel.channel('my-channel');
*
* channel.publish({
* some: 'message'
* });
* ```
* @since v15.1.0, v14.17.0
* @param message The message to send to the channel subscribers
*/
publish(message: unknown): void;
/**
* 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'`.
*
* ```js
* import diagnostics_channel from 'diagnostics_channel';
*
* const channel = diagnostics_channel.channel('my-channel');
*
* channel.subscribe((message, name) => {
* // Received data
* });
* ```
* @since v15.1.0, v14.17.0
* @param onMessage The handler to receive channel messages
*/
subscribe(onMessage: ChannelListener): void;
/**
* Remove a message handler previously registered to this channel with `channel.subscribe(onMessage)`.
*
* ```js
* import diagnostics_channel from 'diagnostics_channel';
*
* const channel = diagnostics_channel.channel('my-channel');
*
* function onMessage(message, name) {
* // Received data
* }
*
* channel.subscribe(onMessage);
*
* channel.unsubscribe(onMessage);
* ```
* @since v15.1.0, v14.17.0
* @param onMessage The previous subscribed handler to remove
* @return `true` if the handler was found, `false` otherwise.
*/
unsubscribe(onMessage: ChannelListener): void;
}
}
declare module "node:diagnostics_channel" {
export * from "diagnostics_channel";
}
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