mirror of https://github.com/apache/druid.git
Improve doc and configuration of prometheus emitter (#13028)
* Improve doc and validation * Add configuration for peon tasks * Update doc * Update test case * Fix typo * Update docs/development/extensions-contrib/prometheus.md Co-authored-by: Kashif Faraz <kashif.faraz@gmail.com> * Update docs/development/extensions-contrib/prometheus.md Co-authored-by: Kashif Faraz <kashif.faraz@gmail.com> Co-authored-by: Kashif Faraz <kashif.faraz@gmail.com>
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Frank Chen
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@ -28,22 +28,38 @@ To use this Apache Druid extension, [include](../../development/extensions.md#lo
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## Introduction
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This extension exposes [Druid metrics](https://druid.apache.org/docs/latest/operations/metrics.html) for collection by a Prometheus server (https://prometheus.io/).
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Emitter is enabled by setting `druid.emitter=prometheus` [configs](https://druid.apache.org/docs/latest/configuration/index.html#emitting-metrics) or include `prometheus` in the composing emitter list.
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## Configuration
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All the configuration parameters for the Prometheus emitter are under `druid.emitter.prometheus`.
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|property|description|required?|default|
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|--------|-----------|---------|-------|
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|`druid.emitter.prometheus.strategy`|The strategy to expose prometheus metrics. Default strategy `exporter` would expose metrics for scraping purpose. Only peon task (short-lived jobs) need to use `pushgateway` strategy.|yes|exporter|
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|`druid.emitter.prometheus.port`|The port on which to expose the prometheus HTTPServer. Required if using exporter strategy.|no|none|
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|`druid.emitter.prometheus.namespace`|Optional metric namespace. Must match the regex `[a-zA-Z_:][a-zA-Z0-9_:]*`|no|"druid"|
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|`druid.emitter.prometheus.dimensionMapPath`|JSON file defining the Prometheus metric type, desired dimensions, help text, and conversionFactor for every Druid metric.|no|Default mapping provided. See below.|
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|`druid.emitter.prometheus.addHostAsLabel`|Flag to include the hostname as a prometheus label.|no|false|
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|`druid.emitter.prometheus.addServiceAsLabel`|Flag to include the druid service name (e.g. `druid/broker`, `druid/coordinator`, etc.) as a prometheus label.|no|false|
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|`druid.emitter.prometheus.pushGatewayAddress`|Pushgateway address. Required if using Pushgateway strategy|no|none|
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| property | description | required? | default |
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|-----------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|--------------------------------------|
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| `druid.emitter.prometheus.strategy` | The strategy to expose prometheus metrics. <br/>Should be one of `exporter` and `pushgateway`. Default strategy `exporter` would expose metrics for scraping purpose. Peon tasks (short-lived jobs) should use `pushgateway` strategy. | yes | exporter |
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| `druid.emitter.prometheus.port` | The port on which to expose the prometheus HTTPServer. Required if using `exporter` strategy. | no | none |
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| `druid.emitter.prometheus.namespace` | Optional metric namespace. Must match the regex `[a-zA-Z_:][a-zA-Z0-9_:]*` | no | druid |
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| `druid.emitter.prometheus.dimensionMapPath` | JSON file defining the Prometheus metric type, desired dimensions, help text, and conversionFactor for every Druid metric. | no | Default mapping provided. See below. |
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| `druid.emitter.prometheus.addHostAsLabel` | Flag to include the hostname as a prometheus label. | no | false |
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| `druid.emitter.prometheus.addServiceAsLabel` | Flag to include the druid service name (e.g. `druid/broker`, `druid/coordinator`, etc.) as a prometheus label. | no | false |
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| `druid.emitter.prometheus.pushGatewayAddress` | Pushgateway address. Required if using `pushgateway` strategy. | no | none |
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### Override properties for Peon Tasks
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Peon tasks are created dynamically by middle managers and have dynamic host and port addresses. Since the `exporter` strategy allows Prometheus to read only from a fixed address, it cannot be used for peon tasks.
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So, these tasks need to be configured to use `pushgateway` strategy to push metrics from Druid to prometheus gateway.
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If this emitter is configured to use `exporter` strategy globally, some of the above configurations need to be overridden in the middle manager so that spawned peon tasks can still use the `pushgateway` strategy.
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```
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#
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# Override global prometheus emitter configuration for peon tasks to use `pushgateway` strategy.
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# Other configurations can also be overridden by adding `druid.indexer.fork.property.` prefix to above configuration properties.
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#
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druid.indexer.fork.property.druid.emitter.prometheus.strategy=pushgateway
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druid.indexer.fork.property.druid.emitter.prometheus.pushGatewayAddress=http://<push-gateway-address>
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```
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### Metric names
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@ -58,15 +74,34 @@ be provided as a JSON file. Additionally, this mapping specifies which dimensio
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histogram timers to use Seconds as the base unit. Timers which do not use seconds as a base unit can use the `conversionFactor` to set
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the base time unit. If the user does not specify their own JSON file, a default mapping is used. All
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metrics are expected to be mapped. Metrics which are not mapped will not be tracked.
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Prometheus metric path is organized using the following schema:
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`<druid metric name> : { "dimensions" : <dimension list>, "type" : <timer|counter|gauge>, conversionFactor: <conversionFactor>, "help" : <help text>,}`
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e.g.
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`query/time" : { "dimensions" : ["dataSource", "type"], "conversionFactor": 1000.0, "type" : "timer", "help": "Seconds taken to complete a query."}`
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```json
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<druid metric name> : {
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"dimensions" : <dimension list>,
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"type" : <timer|counter|gauge>,
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"conversionFactor": <conversionFactor>,
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"help" : <help text>
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}
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```
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For example:
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```json
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"query/time" : {
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"dimensions" : ["dataSource", "type"],
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"type" : "timer",
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"conversionFactor": 1000.0,
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"help": "Seconds taken to complete a query."
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}
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```
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For metrics which are emitted from multiple services with different dimensions, the metric name is prefixed with
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the service name.
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e.g.
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`"coordinator-segment/count" : { "dimensions" : ["dataSource"], "type" : "gauge" },
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"historical-segment/count" : { "dimensions" : ["dataSource", "tier", "priority"], "type" : "gauge" }`
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the service name. For example:
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```json
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"coordinator-segment/count" : { "dimensions" : ["dataSource"], "type" : "gauge" },
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"historical-segment/count" : { "dimensions" : ["dataSource", "tier", "priority"], "type" : "gauge" }
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```
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For most use-cases, the default mapping is sufficient.
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For most use cases, the default mapping is sufficient.
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@ -70,15 +70,16 @@ public class PrometheusEmitterConfig
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@JsonProperty("addServiceAsLabel") boolean addServiceAsLabel
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)
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{
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this.strategy = strategy != null ? strategy : Strategy.exporter;
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this.namespace = namespace != null ? namespace : "druid";
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Preconditions.checkArgument(PATTERN.matcher(this.namespace).matches(), "Invalid namespace " + this.namespace);
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if (strategy == Strategy.exporter) {
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Preconditions.checkArgument(port != null, "For `exporter` strategy, port must be specified.");
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} else if (strategy == Strategy.pushgateway) {
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Preconditions.checkArgument(pushGatewayAddress != null, "For `pushgateway` strategy, pushGatewayAddress must be specified.");
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}
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this.dimensionMapPath = dimensionMapPath;
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this.port = port;
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if (this.strategy == Strategy.pushgateway) {
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Preconditions.checkNotNull(pushGatewayAddress, "Invalid pushGateway address");
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}
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this.pushGatewayAddress = pushGatewayAddress;
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this.addHostAsLabel = addHostAsLabel;
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this.addServiceAsLabel = addServiceAsLabel;
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@ -137,7 +137,30 @@ public class PrometheusEmitterTest
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@Test
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public void testEmitterConfigCreationWithNullAsAddress()
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{
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Assert.assertThrows(NullPointerException.class, () -> new PrometheusEmitterConfig(PrometheusEmitterConfig.Strategy.pushgateway, "namespace4", null, 0, null, true, true));
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// pushGatewayAddress can be null if it's exporter mode
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new PrometheusEmitterConfig(
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PrometheusEmitterConfig.Strategy.exporter,
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"namespace5",
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null,
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1,
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null,
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true,
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true
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);
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Assert.assertThrows(
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"For `pushgateway` strategy, pushGatewayAddress must be specified.",
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IllegalArgumentException.class,
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() -> new PrometheusEmitterConfig(
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PrometheusEmitterConfig.Strategy.pushgateway,
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"namespace5",
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null,
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null,
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null,
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true,
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true
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)
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);
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}
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@Test
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@ -157,4 +180,33 @@ public class PrometheusEmitterTest
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pushEmitter.start();
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Assert.assertNotNull(pushEmitter.getPushGateway());
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}
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@Test
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public void testEmitterConfig()
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{
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Assert.assertThrows(
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"For `exporter` strategy, port must be specified.",
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IllegalArgumentException.class,
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() -> new PrometheusEmitterConfig(
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PrometheusEmitterConfig.Strategy.exporter,
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"namespace5",
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null,
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null,
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"https://pushgateway",
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true,
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true
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)
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);
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// For pushgateway strategy, port can be null
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new PrometheusEmitterConfig(
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PrometheusEmitterConfig.Strategy.pushgateway,
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"namespace5",
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null,
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null,
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"https://pushgateway",
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true,
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true
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);
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}
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}
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