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79 lines
3.3 KiB
Plaintext
79 lines
3.3 KiB
Plaintext
# Debug
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<!--type=misc-->
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Undici emits human-readable debug logs through Node.js' built-in
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[`util.debuglog()`][]. The logs are disabled by default and are turned on by
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listing one or more namespaces in the `NODE_DEBUG` environment variable. Because
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`util.debuglog()` reads `NODE_DEBUG` once, when the namespace is first used, the
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variable must be set before the process starts.
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Each log line is prefixed with the namespace (uppercased) and the process id,
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for example `UNDICI 16241: connecting to nodejs.org using https:h1`. Multiple
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namespaces can be enabled at once by separating them with commas, for example
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`NODE_DEBUG=undici,websocket`.
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The following sections describe the namespaces exposed by undici.
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## `undici`
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Enables debug logs for the core undici library, covering connection setup,
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request dispatch, responses, and trailers. The `fetch` and `websocket` APIs are
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built on top of this core, so enabling `undici` also surfaces activity that
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originates from them.
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```console
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$ NODE_DEBUG=undici node script.js
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UNDICI 16241: connecting to nodejs.org using https:h1
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UNDICI 16241: connecting to nodejs.org using https:h1
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UNDICI 16241: connected to nodejs.org using https:h1
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UNDICI 16241: sending request to GET https://nodejs.org/
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UNDICI 16241: received response to GET https://nodejs.org/ - HTTP 307
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UNDICI 16241: connecting to nodejs.org using https:h1
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UNDICI 16241: trailers received from GET https://nodejs.org/
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UNDICI 16241: connected to nodejs.org using https:h1
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UNDICI 16241: sending request to GET https://nodejs.org/en
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UNDICI 16241: received response to GET https://nodejs.org/en - HTTP 200
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UNDICI 16241: trailers received from GET https://nodejs.org/en
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```
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## `fetch`
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Enables debug logs scoped to the `fetch` API. The output mirrors the `undici`
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namespace but is emitted only for requests made through [`fetch()`][], which
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makes it useful for isolating `fetch` traffic from other undici activity.
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```console
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$ NODE_DEBUG=fetch node script.js
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FETCH 16241: connecting to nodejs.org using https:h1
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FETCH 16241: connecting to nodejs.org using https:h1
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FETCH 16241: connected to nodejs.org using https:h1
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FETCH 16241: sending request to GET https://nodejs.org/
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FETCH 16241: received response to GET https://nodejs.org/ - HTTP 307
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FETCH 16241: connecting to nodejs.org using https:h1
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FETCH 16241: trailers received from GET https://nodejs.org/
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FETCH 16241: connected to nodejs.org using https:h1
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FETCH 16241: sending request to GET https://nodejs.org/en
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FETCH 16241: received response to GET https://nodejs.org/en - HTTP 200
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FETCH 16241: trailers received from GET https://nodejs.org/en
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```
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## `websocket`
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Enables debug logs scoped to the [`WebSocket`][] API, covering the opening
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handshake and connection lifecycle. When the `undici` or `fetch` namespace is
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also enabled, some lines may appear under both namespaces because the handshake
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is performed through the core library.
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```console
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$ NODE_DEBUG=websocket node script.js
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WEBSOCKET 18309: connecting to echo.websocket.org using https:h1
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WEBSOCKET 18309: connected to echo.websocket.org using https:h1
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WEBSOCKET 18309: sending request to GET https://echo.websocket.org/
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WEBSOCKET 18309: connection opened <ip_address>
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```
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[`WebSocket`]: WebSocket.md#class-websocket
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[`fetch()`]: Fetch.md
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[`util.debuglog()`]: https://nodejs.org/api/util.html#utildebuglogsection-callback
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