Define transient error in OTLP exporter specification

CHANGELOG.md

@@ -33,6 +33,11 @@ release.
 
 ### Resource
 
+### Protocol
+
+- Fix and clarify definition of "transient error" in the OTLP exporter specification.
+  ([#3653](https://github.com/open-telemetry/opentelemetry-specification/pull/3653))
+
 ### Compatibility
 
 - Prometheus exporters SHOULD provide configuration to disable the addition of `_total` suffixes.

specification/protocol/exporter.md

@@ -162,7 +162,17 @@ The `OTEL_EXPORTER_OTLP_HEADERS`, `OTEL_EXPORTER_OTLP_TRACES_HEADERS`, `OTEL_EXP
 
 Transient errors MUST be handled with a retry strategy. This retry strategy MUST implement an exponential back-off with jitter to avoid overwhelming the destination until the network is restored or the destination has recovered.
 
-For OTLP/HTTP, the errors `408 (Request Timeout)` and `5xx (Server Errors)` are defined as transient, detailed information about errors can be found in the [HTTP failures section](https://github.com/open-telemetry/opentelemetry-proto/blob/main/docs/specification.md#failures). For the OTLP/gRPC, the full list of the gRPC retryable status codes can be found in the [gRPC response section](https://github.com/open-telemetry/opentelemetry-proto/blob/main/docs/specification.md#otlpgrpc-response).
+Transient errors are defined by a set of retryable response status codes
+received from the server. Refer to the
+[protocol specification][protocol-spec] for the set of retryable status codes:
+
+* [OTLP/HTTP retryable status codes][retryable-http-status-codes]
+* [OTLP/gRPC retryable status codes][retryable-grpc-status-codes]
+
+For OTLP/HTTP, the following scenarios are also considered a transient error:
+
+* The server disconnects without returning a response.
+* The exporter cannot connect to the server.
 
 ## User Agent
 
@@ -177,3 +187,6 @@ The format of the header SHOULD follow [RFC 7231][rfc-7231]. The conventions use
 [resource-semconv]: ../resource/semantic_conventions/README.md#telemetry-sdk
 [otlphttp-req]: https://github.com/open-telemetry/opentelemetry-proto/blob/main/docs/specification.md#otlphttp-request
 [rfc-7231]: https://datatracker.ietf.org/doc/html/rfc7231#section-5.5.3
+[protocol-spec]: https://github.com/open-telemetry/opentelemetry-proto/blob/main/docs/specification.md
+[retryable-grpc-status-codes]: https://github.com/open-telemetry/opentelemetry-proto/blob/main/docs/specification.md#failures
+[retryable-http-status-codes]: https://github.com/open-telemetry/opentelemetry-proto/blob/main/docs/specification.md#failures-1