| 1 | # `@shopify/koa-metrics`
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| 2 |
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| 3 | [](https://github.com/Shopify/quilt/actions?query=workflow%3ANode-CI)
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| 4 | [](https://github.com/Shopify/quilt/actions?query=workflow%3ARuby-CI)
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| 5 | [](LICENSE.md) [](https://badge.fury.io/js/%40shopify%2Fkoa-metrics.svg)
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| 6 |
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| 7 | Opinionated performance metric tracking for Koa, implemented with DogStatsD.
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| 8 |
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| 9 | ## Installation
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| 10 |
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| 11 | ```bash
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| 12 | $ yarn add @shopify/koa-metrics
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| 13 | ```
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| 14 |
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| 15 | ## Usage
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| 16 |
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| 17 | ```javascript
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| 18 | import Koa from 'koa';
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| 19 | import metrics from '@shopify/koa-metrics';
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| 20 |
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| 21 | const app = new Koa();
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| 22 |
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| 23 | app.use(
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| 24 | metrics({
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| 25 | prefix: 'AppName',
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| 26 | host: 'some-statsd-host.com:8125',
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| 27 | }),
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| 28 | );
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| 29 | ```
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| 30 |
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| 31 | ### Options
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| 32 |
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| 33 | The passed in `options` object adheres to the following API:
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| 34 |
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| 35 | #### `prefix` (required)
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| 36 |
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| 37 | The global StatsD metric name prefix; should be provided in `PascalCase`.
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| 38 |
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| 39 | #### `host` (required)
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| 40 |
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| 41 | The url for the StatsD host; should be provided in the format: `hostname:port`.
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| 42 |
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| 43 | ## API
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| 44 |
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| 45 | An instance of the `Metrics` object will be available on `ctx.metrics` further down in the middleware stack.
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| 46 |
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| 47 | ### `Metrics`
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| 48 |
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| 49 | #### `.distribution(name: string, value: number, sampleRate?: number, tags?: Tags)`
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| 50 |
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| 51 | Sends a distribution command with the specified `value` in milliseconds.
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| 52 |
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| 53 | #### `.initTimer(): Timer`
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| 54 |
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| 55 | Returns a new `Timer` started at the current `process.hrtime()`
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| 56 |
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| 57 | ### `Timer`
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| 58 |
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| 59 | #### `.stop(): number`
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| 60 |
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| 61 | Returns the time, in milliseconds, since the `Timer` was created.
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| 62 |
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| 63 | ### `Tags`
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| 64 |
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| 65 | tags are an object keyed by the name of the corresponding tag. For example:
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| 66 |
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| 67 | ```
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| 68 | {
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| 69 | name: value,
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| 70 | name2: value2
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| 71 | }
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| 72 | ```
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| 73 |
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| 74 | ## Intelligent Defaults
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| 75 |
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| 76 | The global metric name prefix is provided through the [options object](#options).
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| 77 |
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| 78 | This package automatically provides performance metrics for HTTP requests.
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| 79 |
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| 80 | ### Standard tags
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| 81 |
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| 82 | - `path`
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| 83 | - `request_method`
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| 84 | - `response_code`
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| 85 | - `response_type` (eg. `2xx`, `3xx`, ...)
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| 86 |
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| 87 | ### Default Metrics
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| 88 |
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| 89 | #### `request_time`
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| 90 |
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| 91 | Time to complete a request, from the application perspective.
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| 92 |
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| 93 | #### `request_queuing_time`
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| 94 |
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| 95 | Time before a request actually started being processed.
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| 96 |
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| 97 | This metric is emitted when the application start processing a request. It relies on the presence of a header `X-Request-Start` set by the first HTTP hop.
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| 98 |
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| 99 | #### `request_content_length`
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| 100 |
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| 101 | This metric is based on the response header `Content-Length`. Some responses don't provide this header (chunked encoding); in those cases, this will not be reported.
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