AttributeMap does not respect last-value-wins semantics for duplicate keys (SpanBuilder.setAttribute vs Attributes.builder) #7897
Description
Describe the bug
According to the OpenTelemetry specification:
-
Attribute keys are strings
https://opentelemetry.io/docs/specs/otel/common/#attribute“The attribute key MUST be a non-null and non-empty string… Keys that differ in casing are treated as distinct keys.”
-
Setting an attribute with the same key SHOULD overwrite the existing value
https://opentelemetry.io/docs/specs/otel/trace/api/#set-attributes“Setting an attribute with the same key as an existing attribute SHOULD overwrite the existing attribute’s value.”
However, in OpenTelemetry Java 1.56.0, last-value-wins semantics are not consistently applied.
Attributes.builder().put("key", ...) behaves correctly, but SpanBuilder.setAttribute("key", ...) produces different observable results when the same key name is reused with different types.
The core issue:
AttributeMap does not treat duplicate string keys consistently, violating spec last-value-wins semantics.
Steps to reproduce
JUnit 5 test (Java):
import static org.junit.jupiter.api.Assertions.assertEquals;
import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.sdk.OpenTelemetrySdk;
import io.opentelemetry.sdk.trace.SdkTracerProvider;
import io.opentelemetry.sdk.trace.data.SpanData;
import io.opentelemetry.sdk.trace.export.SimpleSpanProcessor;
import io.opentelemetry.sdk.testing.exporter.InMemorySpanExporter;
import java.util.ArrayList;
import java.util.List;
import org.junit.jupiter.api.Test;
class AttributeLastWinsTest {
@Test
void lastWinSemanticConvention() {
InMemorySpanExporter exporter = InMemorySpanExporter.create();
SdkTracerProvider tracerProvider =
SdkTracerProvider.builder()
.addSpanProcessor(SimpleSpanProcessor.create(exporter))
.build();
OpenTelemetrySdk telemetry =
OpenTelemetrySdk.builder()
.setTracerProvider(tracerProvider)
.build();
// Span 1: Attributes.builder() with same key, different types
telemetry
.getTracer("test")
.spanBuilder("okSpan")
.setAllAttributes(
Attributes.builder()
.put("key", "value")
.put("key", false)
.build())
.startSpan()
.end();
// Span 2: SpanBuilder.setAttribute(...) with same key, different types
telemetry
.getTracer("test")
.spanBuilder("test")
.setAttribute("key", "value")
.setAttribute("key", false)
.startSpan()
.end();
List<SpanData> finished = exporter.getFinishedSpanItems();
// Span 1: last-wins behavior (correct)
assertEquals(
List.of(false),
new ArrayList<>(finished.get(0).getAttributes().asMap().values()));
// Span 2: last-wins behavior is incorrect
assertEquals(
List.of(false),
new ArrayList<>(finished.get(1).getAttributes().asMap().values()));
}
}What did you expect to see?
For both spans:
Only one attribute with key "key" should appear.
The final value should be the last assigned value: false.
What did you see instead?
Attributes.builder() → correct last-value-wins behavior.
SpanBuilder.setAttribute(String, ...) → incorrect last-value-wins behavior.
This contradicts the specification requirement that setting the same key SHOULD overwrite the existing value.
What version and what artifacts are you using?
Artifacts:
io.opentelemetry:opentelemetry-api
io.opentelemetry:opentelemetry-sdk
io.opentelemetry:opentelemetry-sdk-testing
org.junit.jupiter:junit-jupiter
Version: 1.56.0
dependencies {
testImplementation("io.opentelemetry:opentelemetry-api:1.56.0")
testImplementation("io.opentelemetry:opentelemetry-sdk:1.56.0")
testImplementation("io.opentelemetry:opentelemetry-sdk-testing:1.56.0")
testImplementation("org.junit.jupiter:junit-jupiter:5.10.0")
}Environment
Compiler: openjdk 17.0.8.1 2023-08-24
OS: MacOs 15.6.1
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