Add an option to limit length of values of attributes and metric values

spec-compliance-matrix.md

@@ -48,6 +48,7 @@ status of the feature is not known.
 |links collection size limit                   |   |    | + |      |    |      |   |    |   |    |
 |[Span attributes](https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/trace/api.md#set-attributes)|
 |SetAttribute                                  | + | +  | + | +    | +  | +    | + | +  | + | +  |
+|Span attribute size limit                     |   | +  |   |      |    |      |   |    |   |    |
 |Set order preserved                           | + | -  | + | +    | +  | +    | + | +  | + | +  |
 |String type                                   | + | +  | + | +    | +  | +    | + | +  | + | +  |
 |Boolean type                                  | + | +  | + | +    | +  | +    | + | +  | + | +  |
@@ -81,7 +82,7 @@ status of the feature is not known.
 
 |Feature                                       |Go|Java|JS |Python|Ruby|Erlang|PHP|Rust|C++|.Net|
 |----------------------------------------------|--|----|---|------|----|------|---|----|---|----|
-|TBD|
+|Metric label value size limit                 |  |    |   |      |    |      |   |    |   |    |
 
 ## Resource
 
@@ -128,6 +129,8 @@ status of the feature is not known.
 |OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT               |   |    |   |      |    |      |   |    |   |    |
 |OTEL_SPAN_EVENT_COUNT_LIMIT                   |   |    |   |      |    |      |   |    |   |    |
 |OTEL_SPAN_LINK_COUNT_LIMIT                    |   |    |   |      |    |      |   |    |   |    |
+|OTEL_SPAN_ATTRIBUTE_SIZE_LIMIT                |   |    |   |      |    |      |   |    |   |    |
+|OTEL_METRIC_LABEL_SIZE_LIMIT                  |   |    |   |      |    |      |   |    |   |    |
 
 ## Exporters
 

specification/metrics/sdk.md

@@ -494,3 +494,22 @@ and Sketch.
 
 TODO: T.B.D.: DDSketch considered a good choice for ValueRecorder
 instrument default aggregation.
+
+## Limits on Metrics
+
+Erroneous code can add unintended labels to a span. If they are unbounded, they 
+can quickly exhaust available memory, resulting in crashes that are difficult to
+recover from safely.
+
+To protect against such errors, SDKs MAY be configured to truncate label values.
+By default, label values SHOULD NOT be truncated. If an SDK provides a way to set
+this limit and the limit is set, then for each Metric label value, if its length
+exceeds that limit, SDK Spans SHOULD truncate that value, so that its length is 
+at most equal to the limit.
+
+If there is a configurable limit, the SDK SHOULD honor the environment variables
+specified in [SDK environment variables](../sdk-environment-variables.md#metric-limits).
+
+There SHOULD be a log emitted to indicate to the user that any value was discarded
+or truncated due to such a limit. To prevent excessive logging, the log should 
+not be emitted more than once per metric or value.

specification/sdk-environment-variables.md

@@ -23,12 +23,23 @@ Additional values can be specified in the respective SDK's documentation, in cas
 | OTEL_BSP_MAX_EXPORT_BATCH_SIZE | Maximum batch size                             | 512     | Must be less than or equal to OTEL_BSP_MAX_QUEUE_SIZE |
 
 ## Span Collection Limits
+Moved [here](#span-limits). This section serves as
+a permalink.
 
-| Name                            | Description                          | Default | Notes |
-| ------------------------------- | ------------------------------------ | ------- | ----- |
-| OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT | Maximum allowed span attribute count | 1000    |       |
-| OTEL_SPAN_EVENT_COUNT_LIMIT     | Maximum allowed span event count     | 1000    |       |
-| OTEL_SPAN_LINK_COUNT_LIMIT      | Maximum allowed span link count      | 1000    |       |
+## Span Limits
+
+| Name                            | Description                           | Default | Notes |
+| ------------------------------- | ------------------------------------- | ------- | ----- |
+| OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT | Maximum allowed span attribute count  | 1000    |       |
+| OTEL_SPAN_EVENT_COUNT_LIMIT     | Maximum allowed span event count      | 1000    |       |
+| OTEL_SPAN_LINK_COUNT_LIMIT      | Maximum allowed span link count       | 1000    |       |
+| OTEL_SPAN_ATTRIBUTE_SIZE_LIMIT  | Maximum allowed span attribute length |         | Empty value is treated as infinity. Non-integer and negative values are invalid. |
+
+## Metric Limits
+
+| Name                         | Description                         | Default | Notes |
+| ---------------------------- | ----------------------------------- | ------- | ----- |
+| OTEL_METRIC_LABEL_SIZE_LIMIT | Maximum allowed metric value length |         | Empty value is treated as infinity. Non-integer and negative values are invalid. |
 
 ## OTLP Exporter
 

specification/trace/sdk.md

@@ -8,6 +8,7 @@
 * [Tracer Provider](#tracer-provider)
 * [Additional Span Interfaces](#additional-span-interfaces)
 * [Limits on Span Collections](#limits-on-span-collections)
+* [Limits on Span Collections and Attributes](#limits-on-span-collections-and-attributes)
 * [Span Processor](#span-processor)
 * [Span Exporter](#span-exporter)
 
@@ -265,6 +266,10 @@ Thus, the SDK specification defines sets of possible requirements for
   or a getter could be provided).
 
 ## Limits on Span Collections
+Moved [here](#limits-on-span-collections-and-attributes). This section serves as
+a permalink.
+
+## Limits on Span Collections and Attributes
 
 Erroneous code can add unintended attributes, events, and links to a span. If
 these collections are unbounded, they can quickly exhaust available memory,
@@ -274,12 +279,18 @@ To protect against such errors, SDK Spans MAY discard attributes, links, and
 events that would increase the number of elements of each collection beyond
 the recommended limit of 1000 elements. SDKs MAY provide a way to change this limit.
 
+Similarly, SDKs MAY be configured to truncate attribute values. By default, attribute
+values SHOULD NOT be truncated. If an SDK provides a way to set this limit and the
+limit is set, then for each span attribute value, serialized into a string,
+if it exceeds that limit, SDK Spans SHOULD truncate that value, so that its length
+is at most equal to the limit.
+
 If there is a configurable limit, the SDK SHOULD honor the environment variables
-specified in [SDK environment variables](../sdk-environment-variables.md#span-collection-limits).
+specified in [SDK environment variables](../sdk-environment-variables.md#span-limits).
 
 There SHOULD be a log emitted to indicate to the user that an attribute, event,
 or link was discarded due to such a limit. To prevent excessive logging, the log
-should not be emitted once per span, or per discarded attribute, event, or links.
+should not be emitted more than once per span, attribute, event, or link.
 
 ## Span processor