Use hex encoding for trace id and span id fields in OTLP JSON encoding (

open-telemetry#911) Resolves: open-telemetry#786 See discussion and motivation for the change in the issue linked above. Co-authored-by: Sergey Kanzhelev <[email protected]>
carlosalberto · Sep 8, 2020 · ae0257b · ae0257b
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -52,6 +52,8 @@ Updates:
   ([#611](https://github.com/open-telemetry/opentelemetry-specification/pull/611))
 - Version attributes no longer have a prefix such as semver:
   ([#873](https://github.com/open-telemetry/opentelemetry-specification/pull/873))
+- Use hex encoding for trace id and span id fields in OTLP JSON encoding:
+  ([#911](https://github.com/open-telemetry/opentelemetry-specification/pull/911))
 - Explicitly specify the SpanContext APIs IsValid and IsRemote as required
   ([#914](https://github.com/open-telemetry/opentelemetry-specification/pull/914))
 

diff --git a/specification/protocol/otlp.md b/specification/protocol/otlp.md
@@ -332,8 +332,13 @@ sides.
 
 JSON-encoded Protobuf payloads use proto3 standard defined
 [JSON Mapping](https://developers.google.com/protocol-buffers/docs/proto3#json)
-for mapping between Protobuf and JSON. `trace_id` and `span_id` is base64
-encoded, not hex.
+for mapping between Protobuf and JSON, with one deviation from that mapping: the
+`trace_id` and `span_id` byte arrays are represented as
+[case-insensitive hex-encoded strings](https://tools.ietf.org/html/rfc4648#section-8),
+they are not base64-encoded like it is defined in the standard
+[JSON Mapping](https://developers.google.com/protocol-buffers/docs/proto3#json).
+The hex encoding is used for `trace_id` and `span_id` fields in all OTLP
+Protobuf messages, e.g. the `Span`, `Link`, `LogRecord`, etc. messages.
 
 #### Response