Update Collector configuration telemetry section (#3483)

content/en/docs/collector/configuration.md

@@ -496,10 +496,10 @@ extensions:
 
 ## Service section {#service}
 
-The service section is used to configure what components are enabled in the
+The `service` section is used to configure what components are enabled in the
 Collector based on the configuration found in the receivers, processors,
 exporters, and extensions sections. If a component is configured, but not
-defined within the service section, then it's not enabled.
+defined within the `service` section, then it's not enabled.
 
 The service section consists of three subsections:
 
@@ -509,8 +509,8 @@ The service section consists of three subsections:
 
 ### Extensions {#service-extensions}
 
-The `extensions` subsection consists of a list of all extensions to enable. For
-example:
+The `extensions` subsection consists of a list of desired extensions to be
+enabled. For example:
 
 ```yaml
 service:
@@ -519,8 +519,8 @@ service:
 
 ### Pipelines
 
-Pipelines are defined in the `pipelines` subsection and can be of the following
-types:
+The `pipelines` subsection is where the pipelines are configured, which can be
+of the following types:
 
 - `traces` collect and processes trace data.
 - `metrics` collect and processes metric data.
@@ -552,38 +552,99 @@ service:
 
 ### Telemetry
 
-You can configure telemetry for the Collector itself in the `telemetry`
-subsection inside the `service` section. Collector telemetry can be useful when
-troubleshooting Collector issues.
-
-The `logs` subsection lets you configure logs generated by the Collector. By
-default, the Collector writes its logs to stderr with a log level of `INFO`. You
-can also add static key-value pairs to all logs using the `initial_fields`
-section. See the full list of `logs` options
-[here.](https://github.com/open-telemetry/opentelemetry-collector/blob/7666eb04c30e5cfd750db9969fe507562598f0ae/config/service.go#L41-L97)
-
-The `metrics` subsection lets you configure metrics generated by the Collector.
-By default, the Collector generates basic metrics about itself and expose them
-for scraping at <http://localhost:8888/metrics>. For the full list of options
-for the `metrics` subsection, see the
-[`ServiceTelemetryMetrics struct`](https://github.com/open-telemetry/opentelemetry-collector/blob/7666eb04c30e5cfd750db9969fe507562598f0ae/config/service.go#L99-L111)
-comments.
-
-The following example shows Collector telemetry configuration:
+The `telemetry` is where the telemetry for the Collector itself can be
+configured. Collector's own telemetry can be useful when troubleshooting
+Collector issues. It consists of two subsections: `logs` and `metrics`.
+
+The `logs` subsection lets you configure how the logs can be generated by the
+Collector. By default, the Collector writes its logs to `stderr` with a log
+level of `INFO`. You can also add static key-value pairs to all log entries with
+the `initial_fields` to enrich the logging context. As per the `LogsConfig`
+defined in v{{%
+param vers %}} [here](https://github.com/open-telemetry/opentelemetry-collector/blob/v{{%
+param vers %}}/service/telemetry/config.go), the `logs` configuration options are:
+
+- `level`: sets the minimum enabled logging level, default `INFO`.
+- `development`: puts the logger in development mode, default `false`.
+- `encoding`: sets the logger's encoding, default `console`. Example values are
+  `json`, `console`.
+- `disable_caller`: stops annotating logs with the calling function's file name
+  and line number. By default `false`, all logs are annotated.
+- `disable_stacktrace`: disables automatic stacktrace capturing, default
+  `false`. By default, stacktraces are captured for `WARN` level and above logs
+  in development and `ERROR` level and above in production.
+- `sampling`: sets a sampling policy.
+- `output_paths`: a list of URLs or file paths to write logging output to,
+  default `["stderr"]`.
+- `error_output_paths`: a list of URLs or file paths to write logger errors to,
+  default `["stderr"]`.
+- `initial_fields`: a collection of fields to add to the root logger. By
+  default, there is no initial field.
+
+The `metrics` subsection lets you configure how the metrics can be generated and
+exposed by the Collector. By default, the Collector generates basic metrics
+about itself and expose them for scraping at <http://127.0.0.1:8888/metrics>.
+You can expose the endpoint to a specific or even all network interfaces when
+needed. As per the `MetricsConfig` defined in v{{%
+param vers %}} [here](https://github.com/open-telemetry/opentelemetry-collector/blob/v{{%
+param vers %}}/service/telemetry/config.go), the `metrics` configuration options
+are:
+
+- `level`: the level of telemetry metrics, default `basic`. The possible values
+  are:
+  - "none" indicates that no telemetry data should be collected.
+  - "basic" is the recommended and covers the basics of the service telemetry.
+  - "normal" adds some other indicators on top of basic.
+  - "detailed" adds dimensions and views to the previous levels.
+- `address`: the `[address]:port` formatted URL that metrics exposition should
+  be bound to. Default `127.0.0.1:8888`.
+
+The following example shows the Collector telemetry configuration:
 
 ```yaml
 service:
   telemetry:
     logs:
-      level: debug
+      level: DEBUG
       initial_fields:
         service: my-instance
     metrics:
       level: detailed
       address: 0.0.0.0:8888
 ```
 
-## Additional information
+Note that it's possible to scrape the metrics by using a
+[Prometheus receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/prometheusreceiver)
+within the Collector configuration so that we can consume the Collector's
+metrics at the backend. For example:
+
+```yaml
+receivers:
+  prometheus:
+    trim_metric_suffixes: true
+    use_start_time_metric: true
+    start_time_metric_regex: .*
+    config:
+      scrape_configs:
+        - job_name: 'otel-collector'
+          scrape_interval: 5s
+          static_configs:
+            - targets: ['127.0.0.1:8888']
+
+exporters:
+  otlp:
+    endpoint: my.company.com:4317
+    tls:
+      insecure: true
+
+service:
+  pipelines:
+    metrics:
+      receivers: [prometheus]
+      exporters: [otlp]
+```
+
+## Other Information
 
 ### Environment variables