all: drop attribute values restrictions

CHANGELOG.md

@@ -30,6 +30,16 @@ The full list of changes can be found in the compare view for the respective rel
 - profiles: remove `has_*` debug info fields, they are moving to attributes. [#595](https://github.com/open-telemetry/opentelemetry-proto/pull/595)
 - profiles: remove `Location.is_folded`. [#690](https://github.com/open-telemetry/opentelemetry-proto/pull/690)
 
+### Changed
+
+- all: drop attribute values restrictions. [#707](https://github.com/open-telemetry/opentelemetry-proto/pull/707)<br>
+  ⚠️ **IMPORTANT**: OTLP consumers are expected to accept attribute values that were previously considered invalid.
+  All attributes can now contain:
+  - empty values,
+  - bytes values,
+  - array values different than array of string values, bool values, int values, double values,
+  - kvlist values.
+
 ## 1.7.0 - 2025-05-19
 
 ### Added

opentelemetry/proto/common/v1/common.proto

@@ -54,8 +54,10 @@ message ArrayValue {
 message KeyValueList {
   // A collection of key/value pairs of key-value pairs. The list may be empty (may
   // contain 0 elements).
+  //
   // The keys MUST be unique (it is not allowed to have more than one
   // value with the same key).
+  // The behavior of software that receives duplicated keys can be unpredictable.
   repeated KeyValue values = 1;
 }
 
@@ -76,6 +78,7 @@ message InstrumentationScope {
   // Additional attributes that describe the scope. [Optional].
   // Attribute keys MUST be unique (it is not allowed to have more than one
   // attribute with the same key).
+  // The behavior of software that receives duplicated keys can be unpredictable.
   repeated KeyValue attributes = 3;
   uint32 dropped_attributes_count = 4;
 }

opentelemetry/proto/logs/v1/logs.proto

@@ -174,6 +174,7 @@ message LogRecord {
   // Additional attributes that describe the specific event occurrence. [Optional].
   // Attribute keys MUST be unique (it is not allowed to have more than one
   // attribute with the same key).
+  // The behavior of software that receives duplicated keys can be unpredictable.
   repeated opentelemetry.proto.common.v1.KeyValue attributes = 6;
   uint32 dropped_attributes_count = 7;
 

opentelemetry/proto/metrics/v1/metrics.proto

@@ -215,6 +215,7 @@ message Metric {
   // for lossless roundtrip translation to / from another data model.
   // Attribute keys MUST be unique (it is not allowed to have more than one
   // attribute with the same key).
+  // The behavior of software that receives duplicated keys can be unpredictable.
   repeated opentelemetry.proto.common.v1.KeyValue metadata = 12;
 }
 
@@ -377,16 +378,7 @@ message NumberDataPoint {
   // where this point belongs. The list may be empty (may contain 0 elements).
   // Attribute keys MUST be unique (it is not allowed to have more than one
   // attribute with the same key).
-  //
-  // The attribute values SHOULD NOT contain empty values.
-  // The attribute values SHOULD NOT contain bytes values.
-  // The attribute values SHOULD NOT contain array values different than array of string values, bool values, int values,
-  // double values.
-  // The attribute values SHOULD NOT contain kvlist values.
-  // The behavior of software that receives attributes containing such values can be unpredictable.
-  // These restrictions can change in a minor release.
-  // The restrictions take origin from the OpenTelemetry specification:
-  // https://github.com/open-telemetry/opentelemetry-specification/blob/v1.47.0/specification/common/README.md#attribute.
+  // The behavior of software that receives duplicated keys can be unpredictable.
   repeated opentelemetry.proto.common.v1.KeyValue attributes = 7;
 
   // StartTimeUnixNano is optional but strongly encouraged, see the
@@ -435,16 +427,7 @@ message HistogramDataPoint {
   // where this point belongs. The list may be empty (may contain 0 elements).
   // Attribute keys MUST be unique (it is not allowed to have more than one
   // attribute with the same key).
-  //
-  // The attribute values SHOULD NOT contain empty values.
-  // The attribute values SHOULD NOT contain bytes values.
-  // The attribute values SHOULD NOT contain array values different than array of string values, bool values, int values,
-  // double values.
-  // The attribute values SHOULD NOT contain kvlist values.
-  // The behavior of software that receives attributes containing such values can be unpredictable.
-  // These restrictions can change in a minor release.
-  // The restrictions take origin from the OpenTelemetry specification:
-  // https://github.com/open-telemetry/opentelemetry-specification/blob/v1.47.0/specification/common/README.md#attribute.
+  // The behavior of software that receives duplicated keys can be unpredictable.
   repeated opentelemetry.proto.common.v1.KeyValue attributes = 9;
 
   // StartTimeUnixNano is optional but strongly encouraged, see the
@@ -529,16 +512,7 @@ message ExponentialHistogramDataPoint {
   // where this point belongs. The list may be empty (may contain 0 elements).
   // Attribute keys MUST be unique (it is not allowed to have more than one
   // attribute with the same key).
-  //
-  // The attribute values SHOULD NOT contain empty values.
-  // The attribute values SHOULD NOT contain bytes values.
-  // The attribute values SHOULD NOT contain array values different than array of string values, bool values, int values,
-  // double values.
-  // The attribute values SHOULD NOT contain kvlist values.
-  // The behavior of software that receives attributes containing such values can be unpredictable.
-  // These restrictions can change in a minor release.
-  // The restrictions take origin from the OpenTelemetry specification:
-  // https://github.com/open-telemetry/opentelemetry-specification/blob/v1.47.0/specification/common/README.md#attribute.
+  // The behavior of software that receives duplicated keys can be unpredictable.
   repeated opentelemetry.proto.common.v1.KeyValue attributes = 1;
 
   // StartTimeUnixNano is optional but strongly encouraged, see the
@@ -655,16 +629,7 @@ message SummaryDataPoint {
   // where this point belongs. The list may be empty (may contain 0 elements).
   // Attribute keys MUST be unique (it is not allowed to have more than one
   // attribute with the same key).
-  //
-  // The attribute values SHOULD NOT contain empty values.
-  // The attribute values SHOULD NOT contain bytes values.
-  // The attribute values SHOULD NOT contain array values different than array of string values, bool values, int values,
-  // double values.
-  // The attribute values SHOULD NOT contain kvlist values.
-  // The behavior of software that receives attributes containing such values can be unpredictable.
-  // These restrictions can change in a minor release.
-  // The restrictions take origin from the OpenTelemetry specification:
-  // https://github.com/open-telemetry/opentelemetry-specification/blob/v1.47.0/specification/common/README.md#attribute.
+  // The behavior of software that receives duplicated keys can be unpredictable.
   repeated opentelemetry.proto.common.v1.KeyValue attributes = 7;
 
   // StartTimeUnixNano is optional but strongly encouraged, see the

opentelemetry/proto/profiles/v1development/profiles.proto

@@ -129,16 +129,6 @@ message ProfilesDictionary {
   //     "/http/server_latency": 300
   //     "abc.com/myattribute": true
   //     "abc.com/score": 10.239
-  //
-  // The attribute values SHOULD NOT contain empty values.
-  // The attribute values SHOULD NOT contain bytes values.
-  // The attribute values SHOULD NOT contain array values different than array of string values, bool values, int values,
-  // double values.
-  // The attribute values SHOULD NOT contain kvlist values.
-  // The behavior of software that receives attributes containing such values can be unpredictable.
-  // These restrictions can change in a minor release.
-  // The restrictions take origin from the OpenTelemetry specification:
-  // https://github.com/open-telemetry/opentelemetry-specification/blob/v1.47.0/specification/common/README.md#attribute.
   repeated KeyValueAndUnit attribute_table = 6;
 
   // Stacks referenced by samples via Sample.stack_index.

opentelemetry/proto/resource/v1/resource.proto

@@ -29,16 +29,7 @@ message Resource {
   // Set of attributes that describe the resource.
   // Attribute keys MUST be unique (it is not allowed to have more than one
   // attribute with the same key).
-  //
-  // The attribute values SHOULD NOT contain empty values.
-  // The attribute values SHOULD NOT contain bytes values.
-  // The attribute values SHOULD NOT contain array values different than array of string values, bool values, int values,
-  // double values.
-  // The attribute values SHOULD NOT contain kvlist values.
-  // The behavior of software that receives attributes containing such values can be unpredictable.
-  // These restrictions can change in a minor release.
-  // The restrictions take origin from the OpenTelemetry specification:
-  // https://github.com/open-telemetry/opentelemetry-specification/blob/v1.47.0/specification/common/README.md#attribute.
+  // The behavior of software that receives duplicated keys can be unpredictable.
   repeated opentelemetry.proto.common.v1.KeyValue attributes = 1;
 
   // dropped_attributes_count is the number of dropped attributes. If the value is 0, then

opentelemetry/proto/trace/v1/trace.proto

@@ -208,16 +208,7 @@ message Span {
   //
   // Attribute keys MUST be unique (it is not allowed to have more than one
   // attribute with the same key).
-  //
-  // The attribute values SHOULD NOT contain empty values.
-  // The attribute values SHOULD NOT contain bytes values.
-  // The attribute values SHOULD NOT contain array values different than array of string values, bool values, int values,
-  // double values.
-  // The attribute values SHOULD NOT contain kvlist values.
-  // The behavior of software that receives attributes containing such values can be unpredictable.
-  // These restrictions can change in a minor release.
-  // The restrictions take origin from the OpenTelemetry specification:
-  // https://github.com/open-telemetry/opentelemetry-specification/blob/v1.47.0/specification/common/README.md#attribute.
+  // The behavior of software that receives duplicated keys can be unpredictable.
   repeated opentelemetry.proto.common.v1.KeyValue attributes = 9;
 
   // dropped_attributes_count is the number of attributes that were discarded. Attributes
@@ -238,16 +229,7 @@ message Span {
     // attributes is a collection of attribute key/value pairs on the event.
     // Attribute keys MUST be unique (it is not allowed to have more than one
     // attribute with the same key).
-    //
-    // The attribute values SHOULD NOT contain empty values.
-    // The attribute values SHOULD NOT contain bytes values.
-    // The attribute values SHOULD NOT contain array values different than array of string values, bool values, int values,
-    // double values.
-    // The attribute values SHOULD NOT contain kvlist values.
-    // The behavior of software that receives attributes containing such values can be unpredictable.
-    // These restrictions can change in a minor release.
-    // The restrictions take origin from the OpenTelemetry specification:
-    // https://github.com/open-telemetry/opentelemetry-specification/blob/v1.47.0/specification/common/README.md#attribute.
+    // The behavior of software that receives duplicated keys can be unpredictable.
     repeated opentelemetry.proto.common.v1.KeyValue attributes = 3;
 
     // dropped_attributes_count is the number of dropped attributes. If the value is 0,
@@ -278,18 +260,10 @@ message Span {
     string trace_state = 3;
 
     // attributes is a collection of attribute key/value pairs on the link.
+    //
     // Attribute keys MUST be unique (it is not allowed to have more than one
     // attribute with the same key).
-    //
-    // The attribute values SHOULD NOT contain empty values.
-    // The attribute values SHOULD NOT contain bytes values.
-    // The attribute values SHOULD NOT contain array values different than array of string values, bool values, int values,
-    // double values.
-    // The attribute values SHOULD NOT contain kvlist values.
-    // The behavior of software that receives attributes containing such values can be unpredictable.
-    // These restrictions can change in a minor release.
-    // The restrictions take origin from the OpenTelemetry specification:
-    // https://github.com/open-telemetry/opentelemetry-specification/blob/v1.47.0/specification/common/README.md#attribute.
+    // The behavior of software that receives duplicated keys can be unpredictable.
     repeated opentelemetry.proto.common.v1.KeyValue attributes = 4;
 
     // dropped_attributes_count is the number of dropped attributes. If the value is 0,