71 lines
2.9 KiB
Markdown
71 lines
2.9 KiB
Markdown
cowboy_telemetry
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=====
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[](https://hex.pm/packages/cowboy_telemetry)
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[](https://github.com/beam-telemetry/cowboy_telemetry/actions)
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[Telemetry](https://github.com/beam-telemetry/telemetry) instrumentation for the [Cowboy](https://github.com/ninenines/cowboy) HTTP server.
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This package contains a [`cowboy_stream`](https://ninenines.eu/docs/en/cowboy/2.8/manual/cowboy_stream/) handler that will instrument each request and emit `telemetry` events.
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## Usage
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Configure your cowboy server with the `cowboy_telemetry_h` stream handler first.
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```erlang
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cowboy:start_clear(http, [{port, Port}], #{
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env => #{dispatch => Dispatch},
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stream_handlers => [cowboy_telemetry_h, cowboy_stream_h]
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}.
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```
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## Telemetry Events
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#### `[cowboy, request, start]`
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A span event emitted at the beginning of a request.
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* `measurements`: `#{system_time => erlang:system_time()}`
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* `metadata`: `#{stream_id => cowboy_stream:streamid(), req => cowboy_req:req()}`
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#### `[cowboy, request, stop]`
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A span event emitted at the end of a request.
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* `measurements`: `measurements()`
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* `metadata`: `metadata()`
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If the request is terminated early - by the client or by the server - before a response is sent, the metadata will also contain an `error`:
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* `metadata`: `metadata()` + `#{error => cowboy_stream:reason()}`
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#### `[cowboy, request, exception]`
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A span event emitted if the request process exits.
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* `measurements`: `measurements()`
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* `metadata`: `metadata()` + `#{kind => exit, stacktrace => list()}`
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#### `[cowboy, request, early_error]`
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A single event emitted when Cowboy itself returns an `early_error` response before executing any handlers.
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* `measurements`: `#{system_time => erlang:system_time(), resp_body_length => non_neg_integer()}`
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* `metadata`: `metadata()` without `procs` or `informational`
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### Types
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* `measurements()`:
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* `duration :: req_start - req_end` see [`cowboy_metrics_h`](https://github.com/ninenines/cowboy/blob/master/src/cowboy_metrics_h.erl#L75)
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* `req_body_duration :: req_body_start - req_body_end` see [`cowboy_metrics_h`](https://github.com/ninenines/cowboy/blob/master/src/cowboy_metrics_h.erl#L80)
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* `resp_duration :: resp_start - resp_end` see [`cowboy_metrics_h`](https://github.com/ninenines/cowboy/blob/master/src/cowboy_metrics_h.erl#L87)
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* `req_body_length :: non_neg_integer()`
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* `resp_body_length :: non_neg_integer()`
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* `metadata()`:
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* `pid`, `streamid`, `req`, `resp_headers`, `resp_status`, and `ref` from `cowboy_metrics_h:metrics()`
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* `cowboy_metrics_h:metrics()`: Defined in [`cowboy_metrics_h`](https://github.com/ninenines/cowboy/blob/master/src/cowboy_metrics_h.erl#L46)
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Note:
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* The `telemetry` handlers are executed from the cowboy connection process, not from the request process.
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