fix: redis instrumentation loses context when using callbacks (open-t…

…elemetry#580)

* fix: redis instrumentation loses context when using callbacks

* fix: rename test

* fix: merge new test into existing describe

* fix: refactor context.with as requested

* fix: remove redundant callbackThis const

* fix: move originalContext to inside if

plugins/node/opentelemetry-instrumentation-redis/src/utils.ts

@@ -127,6 +127,7 @@ export const getTracedInternalSendCommand = (
 
     const originalCallback = arguments[0].callback;
     if (originalCallback) {
+      const originalContext = context.active();
       (arguments[0] as RedisCommand).callback = function callback<T>(
         this: unknown,
         err: Error | null,
@@ -146,7 +147,12 @@ export const getTracedInternalSendCommand = (
         }
 
         endSpan(span, err);
-        return originalCallback.apply(this, arguments);
+        return context.with(
+          originalContext,
+          originalCallback,
+          this,
+          ...arguments
+        );
       };
     }
     try {

plugins/node/opentelemetry-instrumentation-redis/test/redis.test.ts

@@ -212,6 +212,16 @@ describe('redis@2.x', () => {
           });
         });
       });
+
+      it('should invoke callback with original command context', () => {
+        const rootSpan = tracer.startSpan('test span');
+        context.with(trace.setSpan(context.active(), rootSpan), () => {
+          client.set('callbacksTestKey', 'value', () => {
+            const activeSpan = trace.getSpan(context.active());
+            assert.strictEqual(activeSpan, rootSpan);
+          });
+        });
+      });
     });
 
     describe('Removing instrumentation', () => {