Clear MDC context after each task (#2545)

Author: Quinn-With-Two-Ns

temporal-sdk/src/main/java/io/temporal/internal/worker/PollTaskExecutor.java

@@ -81,8 +81,7 @@ public void process(@Nonnull T task) {
                   .uncaughtException(Thread.currentThread(), handler.wrapFailure(task, e));
             }
           } finally {
-            MDC.remove(LoggerTag.NAMESPACE);
-            MDC.remove(LoggerTag.TASK_QUEUE);
+            MDC.clear();
           }
         });
   }

temporal-sdk/src/test/java/io/temporal/worker/MdcClearedBetweenTasksTest.java

@@ -0,0 +1,71 @@
+package io.temporal.worker;
+
+import static org.junit.Assert.assertNull;
+
+import io.temporal.activity.ActivityInterface;
+import io.temporal.activity.ActivityMethod;
+import io.temporal.testing.internal.SDKTestOptions;
+import io.temporal.testing.internal.SDKTestWorkflowRule;
+import io.temporal.workflow.Workflow;
+import io.temporal.workflow.shared.TestWorkflows;
+import org.junit.Rule;
+import org.junit.Test;
+import org.slf4j.MDC;
+
+public class MdcClearedBetweenTasksTest {
+  @Rule
+  public SDKTestWorkflowRule testWorkflowRule =
+      SDKTestWorkflowRule.newBuilder()
+          .setWorkflowTypes(TestWorkflowImpl.class)
+          .setActivityImplementations(new SetMdcActivityImpl(), new GetMdcActivityImpl())
+          .build();
+
+  @Test
+  public void testMdcClearedBetweenActivities() {
+    TestWorkflows.TestWorkflowReturnString workflow =
+        testWorkflowRule.newWorkflowStub(TestWorkflows.TestWorkflowReturnString.class);
+    String result = workflow.execute();
+    assertNull(result);
+  }
+
+  public static class TestWorkflowImpl implements TestWorkflows.TestWorkflowReturnString {
+    private final SetMdcActivity setMdcActivity =
+        Workflow.newActivityStub(
+            SetMdcActivity.class, SDKTestOptions.newActivityOptions20sScheduleToClose());
+    private final GetMdcActivity getMdcActivity =
+        Workflow.newActivityStub(
+            GetMdcActivity.class, SDKTestOptions.newActivityOptions20sScheduleToClose());
+
+    @Override
+    public String execute() {
+      setMdcActivity.execute();
+      return getMdcActivity.execute();
+    }
+  }
+
+  @ActivityInterface
+  public interface SetMdcActivity {
+    @ActivityMethod(name = "setMdc")
+    void execute();
+  }
+
+  public static class SetMdcActivityImpl implements SetMdcActivity {
+    @Override
+    public void execute() {
+      MDC.put("mdcTest", "value");
+    }
+  }
+
+  @ActivityInterface
+  public interface GetMdcActivity {
+    @ActivityMethod(name = "getMdc")
+    String execute();
+  }
+
+  public static class GetMdcActivityImpl implements GetMdcActivity {
+    @Override
+    public String execute() {
+      return MDC.get("mdcTest");
+    }
+  }
+}