[monitor-opentelemetry-exporter] Serialize Span/LogRecord attributes (A…

…zure#30495)

### Packages impacted by this PR
@azure/monitor-opentelemetry-exporter

### Issues associated with this PR
Azure#30205

sdk/monitor/monitor-opentelemetry-exporter/src/utils/common.ts

@@ -44,6 +44,7 @@ import { KnownContextTagKeys, TelemetryItem as Envelope, MetricsData } from "../
 import { Resource } from "@opentelemetry/resources";
 import { Attributes, HrTime } from "@opentelemetry/api";
 import { hrTimeToNanoseconds } from "@opentelemetry/core";
+import { AnyValue } from "@opentelemetry/api-logs";
 
 export function hrTimeToDate(hrTime: HrTime): Date {
   return new Date(hrTimeToNanoseconds(hrTime) / 1000000);
@@ -255,6 +256,24 @@ export function createResourceMetricEnvelope(
   return;
 }
 
+export function serializeAttribute(value: AnyValue): string {
+  if (typeof value === "object") {
+    if (value instanceof Uint8Array) {
+      return String(value);
+    } else {
+      try {
+        // Should handle Error objects as well
+        return JSON.stringify(value, Object.getOwnPropertyNames(value));
+      } catch (err: unknown) {
+        // Failed to serialize, return string cast
+        return String(value);
+      }
+    }
+  }
+  // Return scalar and undefined values
+  return String(value);
+}
+
 export function shouldCreateResourceMetric(): boolean {
   return !(process.env.ENV_OPENTELEMETRY_RESOURCE_METRIC_DISABLED?.toLowerCase() === "true");
 }

sdk/monitor/monitor-opentelemetry-exporter/src/utils/logUtils.ts

@@ -13,7 +13,7 @@ import {
   TelemetryExceptionData,
   TelemetryExceptionDetails,
 } from "../generated";
-import { createTagsFromResource, hrTimeToDate } from "./common";
+import { createTagsFromResource, hrTimeToDate, serializeAttribute } from "./common";
 import { ReadableLogRecord } from "@opentelemetry/sdk-logs";
 import {
   SEMATTRS_EXCEPTION_MESSAGE,
@@ -135,7 +135,7 @@ function createPropertiesFromLog(log: ReadableLogRecord): [Properties, Measureme
           key === SEMATTRS_EXCEPTION_STACKTRACE
         )
       ) {
-        properties[key] = log.attributes[key] as string;
+        properties[key] = serializeAttribute(log.attributes[key]);
       }
     }
   }

sdk/monitor/monitor-opentelemetry-exporter/src/utils/spanUtils.ts

@@ -38,6 +38,7 @@ import {
   getUrl,
   hrTimeToDate,
   isSqlDB,
+  serializeAttribute,
 } from "./common";
 import { Tags, Properties, MSLink, Measurements } from "../types";
 import { parseEventHubSpan } from "./eventhub";
@@ -137,7 +138,7 @@ function createPropertiesFromSpanAttributes(attributes?: Attributes): {
           key === SEMATTRS_EXCEPTION_STACKTRACE
         )
       ) {
-        properties[key] = attributes[key] as string;
+        properties[key] = serializeAttribute(attributes[key]);
       }
     }
   }

sdk/monitor/monitor-opentelemetry-exporter/test/internal/commonUtils.test.ts

@@ -4,7 +4,7 @@ import os from "os";
 import * as assert from "assert";
 import { Resource } from "@opentelemetry/resources";
 import { Tags } from "../../src/types";
-import { createTagsFromResource } from "../../src/utils/common";
+import { createTagsFromResource, serializeAttribute } from "../../src/utils/common";
 
 describe("commonUtils.ts", () => {
   describe("#createTagsFromResource", () => {
@@ -96,5 +96,21 @@ describe("commonUtils.ts", () => {
       const tags: Tags = createTagsFromResource(resource);
       assert.ok(tags["ai.cloud.role"].startsWith("unknown_service"), "wrong ai.cloud.role");
     });
+
+    describe("#createProperties", () => {
+      it("should serialize attributes", () => {
+        let attr = serializeAttribute("test");
+        assert.strictEqual(attr, "test");
+        attr = serializeAttribute(false);
+        assert.strictEqual(attr, "false");
+        attr = serializeAttribute("123");
+        assert.strictEqual(attr, "123");
+        attr = serializeAttribute({ test: "value" });
+        assert.strictEqual(attr, '{"test":"value"}');
+        attr = serializeAttribute(new Error("testError") as any);
+        assert.ok(attr.includes('"stack":"Error: testError'));
+        assert.ok(attr.includes('"message":"testError"'));
+      });
+    });
   });
 });

sdk/monitor/monitor-opentelemetry/src/logs/batchLogRecordProcessor.ts

@@ -30,12 +30,6 @@ export class AzureBatchLogRecordProcessor extends BatchLogRecordProcessor {
         }
       }
     }
-    // Ensure nested log attributes are serialized
-    for (const [key, value] of Object.entries(logRecord.attributes)) {
-      if (typeof value === "object") {
-        logRecord.attributes[key] = JSON.stringify(value);
-      }
-    }
     super.onEmit(logRecord);
   }
 }

sdk/monitor/monitor-opentelemetry/test/internal/unit/logs/batchLogRecordProcessor.test.ts

@@ -78,28 +78,5 @@ describe("AzureBatchLogRecordProcessor", () => {
         span.end();
       });
     });
-
-    it("should serialize nested log attributes", () => {
-      const memoryLogExporter = new InMemoryLogRecordExporter();
-      const processor = new AzureBatchLogRecordProcessor(memoryLogExporter, {
-        enableTraceBasedSamplingForLogs: false,
-      });
-      const loggerProvider = new LoggerProvider();
-      loggerProvider.addLogRecordProcessor(processor);
-      const sampler = new ApplicationInsightsSampler(1);
-      const tracerProvider = new NodeTracerProvider({ sampler: sampler });
-      tracerProvider.getTracer("testTracere").startActiveSpan("test", async (span) => {
-        // Generate Log record
-        const logRecord: APILogRecord = {
-          attributes: { test: { nested: "value" } },
-          body: "testRecord",
-        };
-        loggerProvider.getLogger("testLoggere").emit(logRecord);
-        await loggerProvider.forceFlush();
-        span.end();
-      });
-      const logRecords = memoryLogExporter.getFinishedLogRecords();
-      assert.strictEqual(logRecords[0].attributes.test, '{"nested":"value"}');
-    });
   });
 });