Add clarification and cleanups

Signed-off-by: Federico Valeri <[email protected]>

090-integrate-bridge-with-metrics-reporter.md

@@ -1,15 +1,15 @@
 # Integrate Bridge with Metrics Reporter
 
 In [SIP-064](https://github.com/strimzi/proposals/blob/main/064-prometheus-metrics-reporter.md) we introduced the [Strimzi Metrics Reporter](https://github.com/strimzi/metrics-reporter).
-This is a Kafka `MetricsReporter` plugin that directly exposes metrics in Prometheus format via an HTTP endpoint.
+This is a Kafka MetricsReporter plugin that directly exposes metrics in Prometheus format via an HTTP endpoint.
 
 ## Current situation
 
 The HTTP Bridge allow users to enable or disable the metrics endpoint using the `KAFKA_BRIDGE_METRICS_ENABLED` environment variable.
-When this variable is set to true, the Bridge creates the JMX Exporter's `JmxCollector` class with hard coded configuration.
+When this variable is set to true, the Bridge creates the JMX Exporter's JmxCollector class with hard coded configuration.
 This configuration is a JMX metrics exporter YAML distributed as an embedded resource within the Bridge JAR file.
 
-When deploying the Bridge through the Cluster Operator, a similar configuration is available in the `KafkaBridge` CRD.
+When deploying the Bridge through the Cluster Operator, a similar configuration is available in the KafkaBridge CRD:
 
 ```sh
 spec:
@@ -18,14 +18,15 @@ spec:
 
 This is different from how the metrics endpoint is enabled in all the other major components deployed bu the Cluster Operator.
 The Cluster Operator exposes metrics through the [Prometheus JMX Exporter](https://github.com/prometheus/jmx_exporter), which can be configured using the shared `metricsConfig` schema.
-This schema has a `type` property that only allows the `jmxPrometheusExporter` value, and a reference to a `ConfigMap` containing its configuration.
+
+This schema has a type property that only allows the `jmxPrometheusExporter` value, and a reference to a ConfigMap containing its configuration:
 
 ```sh
 metricsConfig:
   type: jmxPrometheusExporter
   valueFrom:
     configMapKeyRef:
-      name: <component>-metrics
+      name: $COMPONENT_NAME-metrics
       key: metrics-config.yml
 ```
 
@@ -34,8 +35,8 @@ Note that this agent depends on the [Kafka JMX Reporter](https://github.com/apac
 
 ## Motivation
 
-We want to support the Strimzi Metrics Reporter as an alternative way of configuring metrics across all components.
-When deploying configuring major components through the Cluster Operator, we want to provide a consistent user experience, so the HTTP Bridge should also support the `metricsConfig` schema. 
+We want to support the Strimzi Reporter as an alternative way of configuring metrics across all components.
+When deploying configuring major components through the Cluster Operator, we want to provide a consistent user experience, so the Bridge should also support the `metricsConfig` schema. 
 
 ## Proposal
 
@@ -44,13 +45,13 @@ It will also provide new configurations for the integration with the Cluster Ope
 
 ### Metrics configuration types
 
-The HTTP Bridge project will be updated to support multiple types of metrics configurations.
-A new `bridge.metrics` property will be available within the `application.properties` configuration file, and will only accept `jmxPrometheusExporter` and `strimziMetricsReporter`.
+The Bridge project will be updated to support multiple types of metrics configurations.
+A new `bridge.metrics` property will be available within the application.properties configuration file, and will only accept `jmxPrometheusExporter` and `strimziMetricsReporter`.
 Any other value will raise an error and the application will fail to start with an appropriate error message.
 
-When running in standalone mode with `strimziMetricsReporter`, the user will be able to configure any Strimzi Metrics Reporter property using the `kafka.` prefix.
-At a minimum `kafka.metric.reporters=io.strimzi.kafka.metrics.KafkaPrometheusMetricsReporter` and `kafka.prometheus.metrics.reporter.listener.enable=false` will be needed.
-The following example will be provided as a comment in the default properties file.
+When running in standalone mode with `strimziMetricsReporter`, the user will be able to configure any Strimzi Reporter property using the "kafka." prefix.
+
+The following example will be provided as a comment in the default application.properties file:
 
 ```sh
 bridge.metrics=strimziMetricsReporter
@@ -59,24 +60,25 @@ kafka.prometheus.metrics.reporter.listener.enable=false
 kafka.prometheus.metrics.reporter.allowlist=.*
 ```
 
-The `KAFKA_BRIDGE_METRICS_ENABLED` env var will be deprecated and removed in a future release.
-When set, the user will get a warning suggesting to use the new `bridge.metrics` configuration.
-In case they are both set, the `bridge.metrics` configuration will take precedence over `KAFKA_BRIDGE_METRICS_ENABLED`.
+The `KAFKA_BRIDGE_METRICS_ENABLED` environment variable will be deprecated and removed in a future release.
+When set, the user will get a warning suggesting to use the `bridge.metrics` property.
+In case they are both set, `bridge.metrics` will take precedence over `KAFKA_BRIDGE_METRICS_ENABLED`.
 
-The `MetricsReporter` class will be updated to also include a new `StrimziCollectorRegistry` that will work similarly to the `JmxCollectorRegistry`.
-The `StrimziCollectorRegistry` will include a reference to `PrometheusRegistry.defaultRegistry`, which is the same instance used by the Strimzi Metrics Reporter to collect metrics.
+The MetricsReporter class will be updated to also include a new StrimziCollectorRegistry that will work similarly to the JmxCollectorRegistry.
+The StrimziCollectorRegistry will include a reference to PrometheusRegistry.defaultRegistry, which is the same instance used by the Strimzi Reporter to collect metrics.
 
-The `kafka_bridge_config_generator.sh` script is used to generate the image configuration based on environment variables.
+The kafka_bridge_config_generator.sh script is used to generate the image configuration based on environment variables.
 This script will be updated to also include `bridge.metrics` and related configurations (see the following section).
 
-The Bridge will also try to load the JMX Exporter configuration file from the path specified by the `bridge.metrics.jmx.exporter.config.path` property.
-If not specified or not found, it will fall back to the hard coded configuration.
+The Bridge will try to load the JMX Exporter configuration file from the path specified by the `bridge.metrics.jmx.exporter.config.path` property.
+If the property is not specified or the file is not found, the Bridge will fall back to the hard coded configuration.
+This feature is not strictly required for the Strimzi Reporter support, but will be used by the Cluster Operator.
 
 ### Cluster Operator deploy
 
-Like for all the other major components, the `KafkaBridge` CRD will also include `metricsConfig` with support for `strimziMetricsReporter` type.
+Like the other major components, the KafkaBridge CRD will also support `metricsConfig` with support for `strimziMetricsReporter` type.
 
-This is how the Strimzi Metrics Reporter configuration will look like:
+This is how the Strimzi Reporter configuration will look like:
 
 ```sh
 spec:
@@ -90,18 +92,19 @@ spec:
 
 Three new environment variables will be introduced to pass the metrics configuration to the Bridge's container:
 
-1. `STRIMZI_METRICS`: This will contain the `metricsConfig` types to enable (one of `jmxPrometheusExporter` and `strimziMetricsReporter`).
-2. `KAFKA_BRIDGE_METRICS_JMX_CONFIG`: Used with `STRIMZI_METRICS=jmxPrometheusExporter` to pass the configuration file path.
-3. `KAFKA_BRIDGE_METRICS_SMR_CONFIG`: Used with `STRIMZI_METRICS=strimziMetricsReporter` to pass the plugin configuration.
+- `STRIMZI_METRICS`: This will contain the `metricsConfig` types to enable (one of `jmxPrometheusExporter` and `strimziMetricsReporter`).
+- `KAFKA_BRIDGE_METRICS_JMX_CONFIG`: Used with JMX Exporter to pass the configuration file path.
+- -`KAFKA_BRIDGE_METRICS_SMR_CONFIG`: Used with Strimzi Reporter to pass the plugin configuration.
 
 The `enableMetrics` property will be deprecated and removed in a future release.
+When set, the user will get a warning suggesting to use the `metricsConfig` configuration.
 In case they are both set, `metricsConfig` will take precedence over `enableMetrics`.
 
-The JMX Exporter configuration file will be stored in a `ConfigMap` and mounted in the Bridge container under `/opt/strimzi/custom-config`.
+The JMX Exporter configuration file will be stored in a ConfigMap and mounted in the Bridge container.
 The full configuration file passed to the Bridge container will be `/opt/strimzi/custom-config/metrics-config.yml`.
 
-Metrics will be exposed through the Bridge HTTP server, so the reporter's listener will be disabled with `kafka.prometheus.metrics.reporter.listener.enable=false`.
-The Strimzi Metrics Reporter configurations will be locked down with the exception of the `allowlist` property.
+Metrics will be exposed through the Bridge HTTP server, so the Strimzi Reporter's listener will be disabled.
+Other configurations will be locked down with the exception of the `prometheus.metrics.reporter.allowlist` property.
 
 ## Affected/not affected projects
 
@@ -113,5 +116,5 @@ All changes will be backwards compatible, but there will be some deprecations as
 
 ## Rejected alternatives
 
-Lock down and automate the Strimzi Metrics Reporter configurations for the standalone HTTP Bridge.
-Historically, the HTTP Bridge allows user to customize Kafka clients and plugins using its properties file and providing commented examples.
+Lock down and automate the Strimzi Reporter configurations for the standalone Bridge.
+Historically, the Bridge allows user to customize Kafka clients and plugins using its properties file and providing commented examples.