node:diagnostics_channel

node:diagnostics_channel provides channel, subscribe, tracingChannel, bindStore and runStores from Node’s diagnostics_channel.

Example

// dc.mjs
import diagnostics from "node:diagnostics_channel";

const channel = diagnostics.channel("app:query");
diagnostics.subscribe("app:query", (message, name) => console.log(name, message.sql));
console.log("subscribers:", channel.hasSubscribers);
channel.publish({ sql: "select 1" });

const tracing = diagnostics.tracingChannel("app:job");
tracing.subscribe({
  start: () => console.log("start"),
  end: () => console.log("end"),
});
console.log(tracing.traceSync(() => 42));

utf-8 · js · Lines: 14

elide run dc.mjs prints:

text

subscribers: true
app:query select 1
start
end
42

utf-8 · text · Lines: 5

Differences from Node

Elide adds boundedChannel and BoundedChannel.
Channel stores follow the propagation rules in node:async_hooks.
net.server.socket, tracing:module.import, http2.*, tls.* and Web Locks channels are not published.

Built-in modules publish on these channels:

Module	Publishes
`node:http`	client and server request channels
`node:net`	`net.client.socket`, `tracing:net.server.listen`
`node:dgram`, `node:child_process`, `node:worker_threads`	their Node channels
`require()`	`tracing:module.require`

Reference

Status: Full · 42 of 67 suite tests pass (62.7%) · since 1.1.0

Exports

Export	Kind	Status	Notes
`Channel`	class	Full	`name`, `hasSubscribers`, `publish()`, `subscribe()`, `unsubscribe()`
`channel()`	function	Full	Returns a Channel object for the given name, creating one if it does not exist
`hasSubscribers()`	function	Full	Returns whether the named channel has active subscribers
`subscribe()`	function	Full	Subscribe a handler to the named channel
`unsubscribe()`	function	Full	Unsubscribe a handler from the named channel

Tests: node-api node:diagnostics-channel: 42 pass, 25 fail, 0 error, 1 skipped. Failing: test-diagnostics-channel-http2-client-stream-body-multiple-buffers-and-strings.js, test-diagnostics-channel-http2-client-stream-body-multiple-buffers.js, test-diagnostics-channel-http2-client-stream-body-no-chunks.js, test-diagnostics-channel-http2-client-stream-body-single-buffer.js, test-diagnostics-channel-http2-client-stream-body-single-string.js, test-diagnostics-channel-http2-client-stream-close-error.js, test-diagnostics-channel-http2-client-stream-close.js, test-diagnostics-channel-http2-client-stream-created.js, and 17 more.