Clarify SDK processor processed metric boundary

.chloggen/clarify-sdk-processor-processed-boundary.yaml

@@ -0,0 +1,11 @@
+change_type: enhancement
+
+component: otel
+
+note: >
+  Clarify when SDK processors record successful processing and distinguish it
+  from queue acceptance and exporter completion.
+
+issues: [1921]
+
+subtext:

docs/otel/sdk-metrics.md

@@ -265,7 +265,11 @@ This metric is [recommended][MetricRecommended].
 **[1]:** For successful processing, `error.type` MUST NOT be set. For failed processing, `error.type` MUST contain the failure cause.
 SDK Batching Span Processors MUST use `queue_full` as the value of `error.type` for spans dropped due to a full queue.
 SDK Span Processors MUST use `already_shutdown` as the value of `error.type` for spans dropped because the processor has already been shut down.
-For the SDK Simple and Batching Span Processor a span is considered to be processed already when it has been submitted to the exporter, not when the corresponding export call has finished.
+For the SDK Simple and Batching Span Processors, successful processing finishes when the processor invokes the export operation.
+For batching processors, all spans in the invoked batch are considered processed at this point; spans that were accepted and remain
+queued have not yet been processed. Implementations MUST record successful processing when the export operation is invoked, regardless
+of whether the invocation returns normally or throws, and MUST NOT delay recording until the export operation completes. The outcome
+of the export operation MUST NOT affect this metric.
 
 **Attributes:**
 
@@ -705,8 +709,11 @@ This metric is [recommended][MetricRecommended].
 **[1]:** For successful processing, `error.type` MUST NOT be set. For failed processing, `error.type` MUST contain the failure cause.
 SDK Batching Log Record Processors MUST use `queue_full` as the value of `error.type` for log records dropped due to a full queue.
 SDK Log Record Processors MUST use `already_shutdown` as the value of `error.type` for log records dropped because the processor has already been shut down.
-For the SDK Simple and Batching Log Record Processor a log record is considered to be processed already when it has been submitted to the exporter,
-not when the corresponding export call has finished.
+For the SDK Simple and Batching Log Record Processors, successful processing finishes when the processor invokes the export operation.
+For batching processors, all log records in the invoked batch are considered processed at this point; log records that were accepted
+and remain queued have not yet been processed. Implementations MUST record successful processing when the export operation is invoked,
+regardless of whether the invocation returns normally or throws, and MUST NOT delay recording until the export operation completes.
+The outcome of the export operation MUST NOT affect this metric.
 
 **Attributes:**
 

model/otel/metrics.yaml

@@ -74,7 +74,11 @@ groups:
       For successful processing, `error.type` MUST NOT be set. For failed processing, `error.type` MUST contain the failure cause.
       SDK Batching Span Processors MUST use `queue_full` as the value of `error.type` for spans dropped due to a full queue.
       SDK Span Processors MUST use `already_shutdown` as the value of `error.type` for spans dropped because the processor has already been shut down.
-      For the SDK Simple and Batching Span Processor a span is considered to be processed already when it has been submitted to the exporter, not when the corresponding export call has finished.
+      For the SDK Simple and Batching Span Processors, successful processing finishes when the processor invokes the export operation.
+      For batching processors, all spans in the invoked batch are considered processed at this point; spans that were accepted and remain
+      queued have not yet been processed. Implementations MUST record successful processing when the export operation is invoked, regardless
+      of whether the invocation returns normally or throws, and MUST NOT delay recording until the export operation completes. The outcome
+      of the export operation MUST NOT affect this metric.
     instrument: counter
     unit: "{span}"
     attributes:
@@ -191,8 +195,11 @@ groups:
       For successful processing, `error.type` MUST NOT be set. For failed processing, `error.type` MUST contain the failure cause.
       SDK Batching Log Record Processors MUST use `queue_full` as the value of `error.type` for log records dropped due to a full queue.
       SDK Log Record Processors MUST use `already_shutdown` as the value of `error.type` for log records dropped because the processor has already been shut down.
-      For the SDK Simple and Batching Log Record Processor a log record is considered to be processed already when it has been submitted to the exporter,
-      not when the corresponding export call has finished.
+      For the SDK Simple and Batching Log Record Processors, successful processing finishes when the processor invokes the export operation.
+      For batching processors, all log records in the invoked batch are considered processed at this point; log records that were accepted
+      and remain queued have not yet been processed. Implementations MUST record successful processing when the export operation is invoked,
+      regardless of whether the invocation returns normally or throws, and MUST NOT delay recording until the export operation completes.
+      The outcome of the export operation MUST NOT affect this metric.
     instrument: counter
     unit: "{log_record}"
     attributes: