/**
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* The `diagnostics_channel` module provides an API to create named channels
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* to report arbitrary message data for diagnostics purposes.
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*
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* It can be accessed using:
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*
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* ```js
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* import diagnostics_channel from 'diagnostics_channel';
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* ```
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*
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* It is intended that a module writer wanting to report diagnostics messages
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* will create one or many top-level channels to report messages through.
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* Channels may also be acquired at runtime but it is not encouraged
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* due to the additional overhead of doing so. Channels may be exported for
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* convenience, but as long as the name is known it can be acquired anywhere.
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*
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* If you intend for your module to produce diagnostics data for others to
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* consume it is recommended that you include documentation of what named
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* channels are used along with the shape of the message data. Channel names
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* should generally include the module name to avoid collisions with data from
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* other modules.
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* @experimental
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* @see [source](https://github.com/nodejs/node/blob/v17.0.0/lib/diagnostics_channel.js)
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*/
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declare module 'diagnostics_channel' {
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/**
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* Check if there are active subscribers to the named channel. This is helpful if
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* the message you want to send might be expensive to prepare.
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*
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* This API is optional but helpful when trying to publish messages from very
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* performance-sensitive code.
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*
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* ```js
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* import diagnostics_channel from 'diagnostics_channel';
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*
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* if (diagnostics_channel.hasSubscribers('my-channel')) {
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* // There are subscribers, prepare and publish message
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* }
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* ```
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* @since v15.1.0, v14.17.0
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* @param name The channel name
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* @return If there are active subscribers
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*/
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function hasSubscribers(name: string): boolean;
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/**
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* This is the primary entry-point for anyone wanting to interact with a named
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* channel. It produces a channel object which is optimized to reduce overhead at
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* publish time as much as possible.
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*
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* ```js
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* import diagnostics_channel from 'diagnostics_channel';
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*
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* const channel = diagnostics_channel.channel('my-channel');
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* ```
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* @since v15.1.0, v14.17.0
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* @param name The channel name
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* @return The named channel object
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*/
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function channel(name: string): Channel;
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type ChannelListener = (message: unknown, name: string) => void;
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/**
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* The class `Channel` represents an individual named channel within the data
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* pipeline. It is use to track subscribers and to publish messages when there
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* are subscribers present. It exists as a separate object to avoid channel
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* lookups at publish time, enabling very fast publish speeds and allowing
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* for heavy use while incurring very minimal cost. Channels are created with {@link channel}, constructing a channel directly
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* with `new Channel(name)` is not supported.
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* @since v15.1.0, v14.17.0
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*/
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class Channel {
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readonly name: string;
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/**
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* Check if there are active subscribers to this channel. This is helpful if
|
* the message you want to send might be expensive to prepare.
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*
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* This API is optional but helpful when trying to publish messages from very
|
* performance-sensitive code.
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*
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* ```js
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* import diagnostics_channel from 'diagnostics_channel';
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*
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* const channel = diagnostics_channel.channel('my-channel');
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*
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* if (channel.hasSubscribers) {
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* // There are subscribers, prepare and publish message
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* }
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* ```
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* @since v15.1.0, v14.17.0
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*/
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readonly hasSubscribers: boolean;
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private constructor(name: string);
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/**
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* Publish a message to any subscribers to the channel. This will
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* trigger message handlers synchronously so they will execute within
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* the same context.
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*
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* ```js
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* import diagnostics_channel from 'diagnostics_channel';
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*
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* const channel = diagnostics_channel.channel('my-channel');
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*
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* channel.publish({
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* some: 'message'
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* });
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* ```
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* @since v15.1.0, v14.17.0
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* @param message The message to send to the channel subscribers
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*/
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publish(message: unknown): void;
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/**
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* Register a message handler to subscribe to this channel. This message handler
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* will be run synchronously whenever a message is published to the channel. Any
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* errors thrown in the message handler will trigger an `'uncaughtException'`.
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*
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* ```js
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* import diagnostics_channel from 'diagnostics_channel';
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*
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* const channel = diagnostics_channel.channel('my-channel');
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*
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* channel.subscribe((message, name) => {
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* // Received data
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* });
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* ```
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* @since v15.1.0, v14.17.0
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* @param onMessage The handler to receive channel messages
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*/
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subscribe(onMessage: ChannelListener): void;
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/**
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* Remove a message handler previously registered to this channel with `channel.subscribe(onMessage)`.
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*
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* ```js
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* import diagnostics_channel from 'diagnostics_channel';
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*
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* const channel = diagnostics_channel.channel('my-channel');
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*
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* function onMessage(message, name) {
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* // Received data
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* }
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*
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* channel.subscribe(onMessage);
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*
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* channel.unsubscribe(onMessage);
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* ```
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* @since v15.1.0, v14.17.0
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* @param onMessage The previous subscribed handler to remove
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*/
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unsubscribe(onMessage: ChannelListener): void;
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}
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}
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declare module 'node:diagnostics_channel' {
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export * from 'diagnostics_channel';
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}
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