docs: Add telemetry documentation page

modules/concepts/nav.adoc

@@ -22,7 +22,8 @@
 *** xref:operations/graceful_shutdown.adoc[]
 *** xref:operations/temporary_credentials_lifetime.adoc[]
 ** Observability
-*** xref:labels.adoc[]
-*** xref:logging.adoc[]
-*** xref:containerdebug.adoc[]
+*** xref:labels.adoc[Labels]
+*** xref:logging.adoc[Logging]
+*** xref:containerdebug.adoc[Container environment]
+*** xref:observability/telemetry.adoc[Telemetry]
 ** xref:container-images.adoc[]

modules/concepts/pages/observability/telemetry.adoc

@@ -0,0 +1,73 @@
+= Telemetry signals in operators
+
+Since SDP 25.7.0, all Stackable operators emit telemetry data in the following ways:
+
+* logs (via console, file, and OTLP export)
+* metrics (not yet available, will most likely be an OTLP export)
+* traces (via OTLP export)
+
+Every signal can be toggled and customized using Helm values.
+All fields are grouped under the top-level `telemetry` section.
+
+NOTE: The following sections describe the available fields their default and supported values.
+
+== Console logs
+
+This signal prints log messages at the selected level and in the selected format to STDOUT.
+These logs are useful for quick debugging.
+For a more complete debugging experience, we recommend the OpenTelemetry signals.
+
+[source,yaml]
+----
+telemetry:
+  consoleLog:
+    enabled: true # <1>
+    level: null   # <2>
+    format: null  # <3>
+----
+
+<1> Boolean: `true, false`
+<2> Enum: `error, warning, info, debug, trace` - operator defaults to `info`
+<3> Enum: `plain, json` - operator defaults to `plain`
+
+== File logs
+
+This signal writes log messages at the selected level in JSON to (rolling) log file(s).
+These logs can be picked up by log aggregation systems, like Vector.
+
+[source,yaml]
+----
+telemetry:
+  fileLog:
+    enabled: false         # <1>
+    level: null            # <2>
+    rotationPeriod: hourly # <3>
+    maxFiles: 6            # <4>
+----
+
+<1> Boolean: `true, false`
+<2> Enum: `error, warning, info, debug, trace` - operator defaults to `info`
+<3> Enum: `never, daily, hourly, minutely`
+<4> Unsigned Integer
+
+== OpenTelemetry logs and traces
+
+These two signal export OpenTelemetry logs and traces to OTLP enabled collectors.
+These signals can be visualized using tools, like Grafana, Loki, and Jaeger.
+
+[source,yaml]
+----
+telemetry:
+  otelLogExporter:
+    enabled: false # <1>
+    level: null    # <2>
+    endpoint: null # <3>
+  otelTraceExporter:
+    enabled: false # <1>
+    level: null    # <2>
+    endpoint: null # <3>
+----
+
+<1> Boolean: `true, false`
+<2> Enum: `error, warning, info, debug, trace` - operator defaults to `info`
+<3> String: E.g. `my-collector:4317`