Add SDK span telemetry metrics

.chloggen/sdk-telemetry-span-metrics.yaml

@@ -0,0 +1,22 @@
+# Use this changelog template to create an entry for release notes.
+#
+# If your change doesn't affect end users you should instead start
+# your pull request title with [chore] or use the "Skip Changelog" label.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: 'enhancement'
+
+# The name of the area of concern in the attributes-registry, (e.g. http, cloud, db)
+component: 'telemetry'
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Adds SDK self-monitoring metrics for span processing
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+# The values here must be integers.
+issues: [1631]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

docs/attributes-registry/telemetry.md

@@ -14,20 +14,36 @@ This document defines attributes for telemetry SDK.
 |---|---|---|---|---|
 | <a id="telemetry-distro-name" href="#telemetry-distro-name">`telemetry.distro.name`</a> | string | The name of the auto instrumentation agent or distribution, if used. [1] | `parts-unlimited-java` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
 | <a id="telemetry-distro-version" href="#telemetry-distro-version">`telemetry.distro.version`</a> | string | The version string of the auto instrumentation agent or distribution, if used. | `1.2.3` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
+| <a id="telemetry-sdk-component-id" href="#telemetry-sdk-component-id">`telemetry.sdk.component.id`</a> | string | A name uniquely identifying the instance of the OpenTelemetry SDK component within its containing SDK instance. [2] | `batch-span-0`; `custom-name` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
+| <a id="telemetry-sdk-exporter-type" href="#telemetry-sdk-exporter-type">`telemetry.sdk.exporter.type`</a> | string | A name identifying the type of the OpenTelemetry SDK exporter. [3] | `otlp-grpc`; `jaeger` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
 | <a id="telemetry-sdk-language" href="#telemetry-sdk-language">`telemetry.sdk.language`</a> | string | The language of the telemetry SDK. | `cpp`; `dotnet`; `erlang` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
-| <a id="telemetry-sdk-name" href="#telemetry-sdk-name">`telemetry.sdk.name`</a> | string | The name of the telemetry SDK as defined above. [2] | `opentelemetry` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
+| <a id="telemetry-sdk-name" href="#telemetry-sdk-name">`telemetry.sdk.name`</a> | string | The name of the telemetry SDK as defined above. [4] | `opentelemetry` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
+| <a id="telemetry-sdk-processor-type" href="#telemetry-sdk-processor-type">`telemetry.sdk.processor.type`</a> | string | A name identifying the type of the OpenTelemetry SDK processor. [5] | `batch-span`; `MyCustomProcessor` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
 | <a id="telemetry-sdk-version" href="#telemetry-sdk-version">`telemetry.sdk.version`</a> | string | The version string of the telemetry SDK. | `1.2.3` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
 
 **[1] `telemetry.distro.name`:** Official auto instrumentation agents and distributions SHOULD set the `telemetry.distro.name` attribute to
 a string starting with `opentelemetry-`, e.g. `opentelemetry-java-instrumentation`.
 
-**[2] `telemetry.sdk.name`:** The OpenTelemetry SDK MUST set the `telemetry.sdk.name` attribute to `opentelemetry`.
+**[2] `telemetry.sdk.component.id`:** The SDK MAY allow users to provide an id for the component instances. If no id is provided by the user,
+the SDK SHOULD automatically assign an id. Because this attribute is used in metrics, the SDK MUST ensure a low cardinality in that case.
+E.g. it MUST NOT use a UUID.
+It instead MAY do that by using the following pattern as value: `<telemetry.sdk.processor/exporter.type>-<instance-counter>`:
+Hereby, `<instance-counter>` is a monotonically increasing counter (starting with `0`), which is incremented every time an
+instance of the given component type is created.
+For example, the first Batch Span Processor will have `batch-span-0` as `telemetry.sdk.component.id`, the second one `batch-span-1` and so one.
+These values will therefore be reused in the case of an application restart.
+
+**[3] `telemetry.sdk.exporter.type`:** For OTLP, the values `otlp-grpc`, `otlp-http` or `otlp-http-json` MUST be used, based on the transport and serialization format.
+
+**[4] `telemetry.sdk.name`:** The OpenTelemetry SDK MUST set the `telemetry.sdk.name` attribute to `opentelemetry`.
 If another SDK, like a fork or a vendor-provided implementation, is used, this SDK MUST set the
 `telemetry.sdk.name` attribute to the fully-qualified class or module name of this SDK's main entry point
 or another suitable identifier depending on the language.
 The identifier `opentelemetry` is reserved and MUST NOT be used in this case.
 All custom identifiers SHOULD be stable across different versions of an implementation.
 
+**[5] `telemetry.sdk.processor.type`:** The value `batch-span` MUST be used for the SDK builtin Batch Span Processor.
+
 ---
 
 `telemetry.sdk.language` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

docs/general/metrics.md

@@ -38,6 +38,7 @@ The following semantic conventions surrounding metrics are defined:
   * [Hardware](/docs/system/hardware-metrics.md): For hardware-related metrics.
   * [Process](/docs/system/process-metrics.md): For standard process metrics.
   * [Runtime Environment](/docs/runtime/README.md#metrics): For runtime environment metrics.
+* [SDK Telemetry](/docs/telemetry/telemetry-sdk-metrics.md): Metrics emitted by the OpenTelemetry SDK components.
 
 Apart from semantic conventions for metrics, [traces](trace.md), [logs](logs.md), and [events](events.md), OpenTelemetry also
 defines the concept of overarching [Resources](https://github.com/open-telemetry/opentelemetry-specification/tree/v1.39.0/specification/resource/sdk.md) with