moving acquiring of the extended session lock before execution of the first work item to ensure that the worker does not store the extended session state unnecessarily in the isolated model

Author: Sophia Tevosyan

src/DurableTask.Core/TaskOrchestrationDispatcher.cs

@@ -242,8 +242,10 @@ async Task OnProcessWorkItemSessionAsync(TaskOrchestrationWorkItem workItem)
                         // If the provider provided work items, execute them.
                         if (workItem.NewMessages?.Count > 0)
                         {
-                            // As long as we are in this execution loop, the extended session is maintained.
-                            workItem.IsExtendedSession = true;
+                            concurrencyLockAcquired = this.concurrentSessionLock.Acquire();
+                            workItem.IsExtendedSession = concurrencyLockAcquired;
+                            // Regardless of whether or not we acquired the concurrent session lock, we will make sure to execute this work item.
+                            // If we failed to acquire it, we will end the extended session after this execution.
                             bool isCompletedOrInterrupted = await this.OnProcessWorkItemAsync(workItem);
                             if (isCompletedOrInterrupted)
                             {
@@ -253,15 +255,11 @@ async Task OnProcessWorkItemSessionAsync(TaskOrchestrationWorkItem workItem)
                             processCount++;
                         }
 
-                        // Fetches beyond the first require getting an extended session lock, used to prevent starvation.
+                        // If we failed to acquire the concurrent session lock, we will end the extended session after the execution of the first work item
                         if (processCount > 0 && !concurrencyLockAcquired)
                         {
-                            concurrencyLockAcquired = this.concurrentSessionLock.Acquire();
-                            if (!concurrencyLockAcquired)
-                            {
-                                TraceHelper.Trace(TraceEventType.Verbose, "OnProcessWorkItemSession-MaxOperations", "Failed to acquire concurrent session lock.");
-                                break;
-                            }
+                            TraceHelper.Trace(TraceEventType.Verbose, "OnProcessWorkItemSession-MaxOperations", "Failed to acquire concurrent session lock.");
+                            break;
                         }
 
                         TraceHelper.Trace(TraceEventType.Verbose, "OnProcessWorkItemSession-StartFetch", "Starting fetch of existing session.");