[Bundle] Parallel bundle perf improvements (#3727)

* Switch from Task.WaitAll to Task.WhenAll
* Removing calls to GC

src/Microsoft.Health.Fhir.Core/Features/Persistence/Orchestration/BundleOrchestratorOperation.cs

@@ -316,7 +316,7 @@ private async Task<IDictionary<DataStoreOperationIdentifier, DataStoreOperationO
                     // The database will be responsible for handling it internally.
                     MergeOptions mergeOptions = new MergeOptions(enlistTransaction: false);
 
-                    // 2 - Merge all resources in the data base.
+                    // 2 - Merge all resources in the database.
                     IDictionary<DataStoreOperationIdentifier, DataStoreOperationOutcome> response = await _dataStore.MergeAsync(_resources.Values.ToList(), mergeOptions, cancellationToken);
 
                     SetStatusSafe(BundleOrchestratorOperationStatus.Completed);

src/Microsoft.Health.Fhir.Shared.Api/Features/Resources/Bundle/BundleHandler.cs

@@ -589,15 +589,8 @@ private static void AddHeaderIfNeeded(string headerKey, string headerValue, Http
 
         private async Task<EntryComponent> ExecuteRequestsWithSingleHttpVerbInSequenceAsync(Hl7.Fhir.Model.Bundle responseBundle, HTTPVerb httpVerb, EntryComponent throttledEntryComponent, BundleHandlerStatistics statistics, CancellationToken cancellationToken)
         {
-            const int GCCollectTrigger = 150;
-
             foreach (ResourceExecutionContext resourceContext in _requests[httpVerb])
             {
-                if (resourceContext.Index % GCCollectTrigger == 0 && resourceContext.Index > 0)
-                {
-                    RunGarbageCollection();
-                }
-
                 EntryComponent entryComponent;
 
                 Stopwatch watch = Stopwatch.StartNew();
@@ -873,25 +866,6 @@ private void PopulateReferenceIdDictionary(IEnumerable<EntryComponent> bundleEnt
             }
         }
 
-        private void RunGarbageCollection()
-        {
-            try
-            {
-                _logger.LogInformation("{Origin} - MemoryWatch - Memory used before collection: {MemoryInUse:N0}", nameof(BundleHandler), GC.GetTotalMemory(forceFullCollection: false));
-
-                // Collecting memory up to Generation 2 using default collection mode.
-                // No blocking, allowing a collection to be performed as soon as possible, if another collection is not in progress.
-                // SOH compacting is set to true.
-                GC.Collect(GC.MaxGeneration, GCCollectionMode.Default, blocking: false, compacting: true);
-
-                _logger.LogInformation("{Origin} - MemoryWatch - Memory used after full collection: {MemoryInUse:N0}", nameof(BundleHandler), GC.GetTotalMemory(forceFullCollection: false));
-            }
-            catch (Exception ex)
-            {
-                _logger.LogInformation(ex, "{Origin} - MemoryWatch - Error running garbage collection.", nameof(BundleHandler));
-            }
-        }
-
         private static OperationOutcome CreateOperationOutcome(OperationOutcome.IssueSeverity issueSeverity, OperationOutcome.IssueType issueType, string diagnostics)
         {
             return new OperationOutcome

src/Microsoft.Health.Fhir.Shared.Api/Features/Resources/Bundle/BundleHandlerParallelOperations.cs

@@ -72,8 +72,6 @@ private async Task<EntryComponent> ExecuteRequestsInParallelAsync(
                 return await Task.FromResult(throttledEntryComponent);
             }
 
-            const int GCCollectTrigger = 150;
-
             using (CancellationTokenSource requestCancellationToken = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken))
             {
                 IAuditEventTypeMapping auditEventTypeMapping = _auditEventTypeMapping;
@@ -84,11 +82,6 @@ private async Task<EntryComponent> ExecuteRequestsInParallelAsync(
                 // Parallel Resource Handling Function.
                 Func<ResourceExecutionContext, CancellationToken, Task> handleRequestFunction = async (ResourceExecutionContext resourceExecutionContext, CancellationToken ct) =>
                 {
-                    if (resourceExecutionContext.Index > 0 && resourceExecutionContext.Index % GCCollectTrigger == 0)
-                    {
-                        RunGarbageCollection();
-                    }
-
                     _logger.LogInformation("BundleHandler - Running '{HttpVerb}' Request #{RequestNumber} out of {TotalNumberOfRequests}.", resourceExecutionContext.HttpVerb, resourceExecutionContext.Index, bundleOperation.OriginalExpectedNumberOfResources);
 
                     // Creating new instances per record in the bundle, and making their access thread-safe.
@@ -147,12 +140,11 @@ private async Task<EntryComponent> ExecuteRequestsInParallelAsync(
 
                 try
                 {
-                    // The following Task.WaitAll should wait for all requests to finish.
+                    // The following Task.WhenAll should wait for all requests to finish.
 
-                    // Parallel requests are not supossed to raise exceptions, unless they are FhirTransactionFailedExceptions.
+                    // Parallel requests are not supposed to raise exceptions, unless they are FhirTransactionFailedExceptions.
                     // FhirTransactionFailedExceptions are a special case to invalidate an entire bundle.
-
-                    Task.WaitAll(requestsPerResource.ToArray(), cancellationToken);
+                    await Task.WhenAll(requestsPerResource);
                 }
                 catch (AggregateException age)
                 {