fix(otlp-transformer): trunc hrTime to int for nanos converting

experimental/CHANGELOG.md

@@ -13,6 +13,7 @@ For notes on migrating to 2.x / 0.200.x see [the upgrade guide](doc/upgrade-to-2
 ### :bug: Bug Fixes
 
 * fix(instrumentation-http): respect requireParent flag when INVALID_SPAN_CONTEXT is used [#4788](https://github.com/open-telemetry/opentelemetry-js/pull/4788) @reberhardt7
+* fix(otlp-transformer): trunc hrTime to int for nanos converting [#5924](https://github.com/open-telemetry/opentelemetry-js/pull/5924) @blumamir
 
 ### :books: Documentation
 

experimental/packages/otlp-transformer/src/common/utils.ts

@@ -21,7 +21,9 @@ import { hexToBinary } from './hex-to-binary';
 
 export function hrTimeToNanos(hrTime: HrTime): bigint {
   const NANOSECONDS = BigInt(1_000_000_000);
-  return BigInt(hrTime[0]) * NANOSECONDS + BigInt(hrTime[1]);
+  return (
+    BigInt(Math.trunc(hrTime[0])) * NANOSECONDS + BigInt(Math.trunc(hrTime[1]))
+  );
 }
 
 export function toLongBits(value: bigint): LongBits {

experimental/packages/otlp-transformer/test/trace.test.ts

@@ -544,6 +544,12 @@ describe('Trace', () => {
       assert.deepStrictEqual(JSON.parse(decoder.decode(serialized)), expected);
     });
 
+    it('hrtime contains float value', () => {
+      const span = createSpanWithResource(resource);
+      (span as any).startTime = [1640715557.5, 342725388.5];
+      JsonTraceSerializer.serializeRequest([span]);
+    });
+
     it('deserializes a response', () => {
       const expectedResponse = {
         partialSuccess: {