Address feedback

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

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

@@ -5,7 +5,19 @@ This is a Kafka `MetricsReporter` plugin that directly exposes metrics in Promet
 
 ## Current situation
 
-The Cluster Operator exposes Kafka metrics through the [Prometheus JMX Exporter](https://github.com/prometheus/jmx_exporter), which can be configured using the shared `metricsConfig` schema.
+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.
+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.
+
+```sh
+spec:
+  enableMetrics: true
+```
+
+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.
 
 ```sh
@@ -20,41 +32,20 @@ metricsConfig:
 At runtime, this configuration enables a Java agent that exposes Kafka JMX metrics in Prometheus format through an HTTP endpoint on port 9404.
 Note that this agent depends on the [Kafka JMX Reporter](https://github.com/apache/kafka/blob/3.9.0/clients/src/main/java/org/apache/kafka/common/metrics/JmxReporter.java) plugin, which is enabled by default.
 
-The only major component not using the `metricsConfig` schema is the [HTTP Bridge](https://github.com/strimzi/strimzi-kafka-bridge), as it directly instantiates the JMX Exporter's `JmxCollector` class with hard coded configuration.
-The `KafkaBridge` CRD does not support a type system for metrics configuration, but a simple boolean configuration to enable/disable metrics.
-
-```sh
-spec:
-  enableMetrics: true
-```
-
 ## Motivation
 
 We want to support the Strimzi Metrics Reporter as an alternative way of configuring metrics across all components.
-In order to provide a consistent user experience, the HTTP Bridge should align with all the other components in terms of metrics configuration. 
+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. 
 
 ## Proposal
 
-As specified in SIP-064, a new metrics config type called `strimziMetricsReporter` will be added to `metricsConfig` schema along with its configuration.
-Only the Strimzi Metrics Reporter's `prometheus.metrics.reporter.allowlist` property will be configurable by users when using the Cluster Operator.
-This configuration is a comma separated list of regex patterns that is used by the plugin to filter metrics to collect.
-All other plugin configuration properties will be locked down, including the port that will be set to 9404 to avoid conflicts with other ports.
-
-```sh
-spec:
-  kafka:
-    metricsConfig:
-      type: strimziMetricsReporter
-      values:
-        allowList:
-          - "kafka_log.*"
-          - "kafka_network.*"
-```
+The Bridge will support both JMX Exporter and Strimzi Reporter as metrics configuration types.
+It will also provide new configurations for the integration with the Cluster Operator.
 
-### HTTP Bridge
+### 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, and will only accept `jmxPrometheusExporter` and `strimziMetricsReporter`.
+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.
@@ -81,11 +72,23 @@ This script will be updated to also include `bridge.metrics` and related configu
 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.
 
-### Cluster Operator
+### Cluster Operator deploy
 
 Like for all the other major components, the `KafkaBridge` CRD will also include `metricsConfig` with support for `strimziMetricsReporter` type.
 
-Three new environment variables will be introduced to pass the metrics configuration in the HTTP Bridge container:
+This is how the Strimzi Metrics Reporter configuration will look like:
+
+```sh
+spec:
+  metricsConfig:
+    type: strimziMetricsReporter
+    values:
+      allowList:
+        - "kafka_log.*"
+        - "kafka_network.*"
+```
+
+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.
@@ -94,10 +97,11 @@ Three new environment variables will be introduced to pass the metrics configura
 The `enableMetrics` property will be deprecated and removed in a future release.
 In case they are both set, `metricsConfig` will take precedence over `enableMetrics`.
 
-All Strimzi Metrics Reporter configurations will be locked down with the exception of `allowList`.
-Unlike the other major components, the metrics endpoint port will be set to 8080, which is the one already used to expose the REST API.
+The JMX Exporter configuration file will be stored in a `ConfigMap` and mounted in the Bridge container under `/opt/strimzi/custom-config`.
+The full configuration file passed to the Bridge container will be `/opt/strimzi/custom-config/metrics-config.yml`.
 
-The JMX Exporter configuration file contained in a `ConfigMap` will be mounted in the HTTP Bridge container under `/opt/strimzi/custom-config/` to be loaded at runtime.
+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.
 
 ## Affected/not affected projects