[Beta] Serialize Logged Errors

src/logs/api.ts

@@ -1,7 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT license.
 
 import { Logger as OtelLogger, LogRecord, logs } from "@opentelemetry/api-logs";
 import { LogRecord as SDKLogRecord } from "@opentelemetry/sdk-logs";
 import { Attributes } from "@opentelemetry/api";
 import { IdGenerator, RandomIdGenerator } from "@opentelemetry/sdk-trace-base";
@@ -119,9 +119,21 @@
             const attributes: Attributes = {};
             if (telemetry.properties) {
                 for (const [key, value] of Object.entries(telemetry.properties)) {
-                    attributes[key] = typeof value === 'object'
+                    // Serialize Error objects as strings to avoid serialization errors
+                    if (value?.constructor.name === "Error") {
+                        attributes[key] = Util.getInstance().stringify(
+                            {
+                                name: value.name,
+                                message: value.message,
+                                stack: value.stack,
+                                cause: value.cause,
+                            }
+                        );
+                    } else {
+                        attributes[key] = typeof value === 'object'
                         ? Util.getInstance().stringify(value)
                         : value;
+                    }
                 }
             }
 

test/unitTests/logs/api.tests.ts

@@ -63,6 +63,26 @@ describe("logs/API", () => {
             assert.equal(logRecord.attributes["_MS.baseType"], "TestData");
         });
 
+        it("should serialize errors", () => {
+            let testLogger = new TestLogger();
+            let logApi = new LogApi(testLogger);
+            let error = new Error("test error");
+            const telemetry: Telemetry = {
+                properties: { "testAttribute": "testValue", "error": error }
+            };
+            const data: MonitorDomain = {};
+            const logRecord = logApi["_telemetryToLogRecord"](
+                telemetry,
+                "TestData",
+                data,
+            ) as LogRecord;
+            assert.equal(logRecord.body, "{}");
+            assert.equal(logRecord.attributes["testAttribute"], "testValue");
+            const errorStr: string = logRecord.attributes["error"] as string;
+            assert.ok(errorStr.includes("test error"));
+            assert.equal(logRecord.attributes["_MS.baseType"], "TestData");
+        });
+
         it("trackAvailability", () => {
             let testLogger = new TestLogger();
             let logApi = new LogApi(testLogger);