[GitHub] [incubator-druid] himanshug commented on a change in pull request #7363: Implementing dropwizard emitter for druid

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himanshug commented on a change in pull request #7363: Implementing dropwizard emitter for druid
URL: https://github.com/apache/incubator-druid/pull/7363#discussion_r321012640
 
 

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 File path: docs/design/extensions-contrib/dropwizard.md
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+---
+layout: doc_page
+title: "Dropwizard metrics emitter"
+---
+
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+
+# Dropwizard Emitter
+
+To use this extension, make sure to [include](../../development/extensions.md#loading-extensions) `dropwizard-emitter` extension.
+
+## Introduction
+
+This extension integrates [Dropwizard](http://metrics.dropwizard.io/3.1.0/getting-started/#) metrics library with druid so that dropwizard users can easily absorb druid into their monitoring ecosystem.
+It accumulates druid metrics as dropwizard metrics, and emits them to various sinks via dropwizard supported reporters.
+Currently supported dropwizard metrics types counter, gauge, meter, timer and histogram. 
+These metrics can be emitted using either Console or JMX reporter. 
+
+## Configuration
+
+All the configuration parameters for Dropwizard emitter are under `druid.emitter.dropwizard`.
+    
+|property|description|required?|default|
+|--------|-----------|---------|-------|
+|`druid.emitter.dropwizard.reporters`|List of dropwizard reporters to be used. Here is a list of [Supported Reporters](#supported-dropwizard-reporters)|yes|none|
+|`druid.emitter.dropwizard.prefix`|Optional prefix to be used for metrics name|no|none|
+|`druid.emitter.dropwizard.includeHost`|Flag to include the host and port as part of the metric name.|no|yes|
+|`druid.emitter.dropwizard.dimensionMapPath`|Path to JSON file defining the dropwizard metric type, and desired dimensions for every Druid metric|no|Default mapping provided. See below.|
+|`druid.emitter.dropwizard.alertEmitters`| List of emitters where alerts will be forwarded to. |no| empty list (no forwarding)|
+|`druid.emitter.dropwizard.maxGaugeCount`| Maximum size of distinct gauge metrics to be cached at any time. |no| 100K|
+
+
+### Druid to Dropwizard Event Conversion
+
+Each metric emitted using Dropwizard must specify a type, one of `[timer, counter, guage, meter, histogram]`. Dropwizard Emitter expects this mapping to
+be provided as a JSON file.  Additionally, this mapping specifies which dimensions should be included for each metric.
+If the user does not specify their own JSON file, a [default mapping](#default-metrics-mapping) is used.
+All metrics are expected to be mapped. Metrics which are not mapped will be ignored.
+Dropwizard metric path is organized using the following schema:
+
+`<druid metric name> : { "dimensions" : <dimension list>, "type" : <Dropwizard metric type>, "timeUnit" : <For timers, timeunit in which metric is emitted>}`
+
+e.g.
+```json
+"query/time" : { "dimensions" : ["dataSource", "type"], "type" : "timer", "timeUnit": "MILLISECONDS"},
+"segment/scan/pending" : { "dimensions" : [], "type" : "gauge"}
+```
+
+For most use-cases, the default mapping is sufficient.
+
+### Supported Dropwizard reporters
+
+#### JMX Reporter
+Used to report druid metrics via JMX.
+```
+
+druid.emitter.dropwizard.reporter={"type":"jmx"}
 
 Review comment:
   ```suggestion
   druid.emitter.dropwizard.reporters=[{"type":"jmx"}]
   ```

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