[C#] FasterLog CommitAsync wait if no new commit done (#753)

Author: badrishc

cs/src/core/FasterLog/FasterLog.cs

@@ -931,14 +931,29 @@ public bool CommitStrongly(out long commitTail, out long actualCommitNum, bool s
         public async ValueTask CommitAsync(CancellationToken token = default)
         {
             token.ThrowIfCancellationRequested();
+
+            // Take a lower-bound of the content of this commit in case our request is filtered but we need to wait
+            var tail = TailAddress;
+            var lastCommit = commitNum;
+
             var task = CommitTask;
-            if (!CommitInternal(out var tailAddress, out var actualCommitNum, true, null, -1, null))
-                return;
+            var success = CommitInternal(out var actualTail, out var actualCommitNum, true, null, -1, null);
 
-            while (CommittedUntilAddress < tailAddress || persistedCommitNum < actualCommitNum)
+            if (success)
             {
-                var linkedCommitInfo = await task.WithCancellationAsync(token).ConfigureAwait(false);
-                task = linkedCommitInfo.NextTask;
+                while (CommittedUntilAddress < actualTail || persistedCommitNum < actualCommitNum)
+                {
+                    var linkedCommitInfo = await task.WithCancellationAsync(token).ConfigureAwait(false);
+                    task = linkedCommitInfo.NextTask;
+                }
+            }
+            else
+            {
+                while (CommittedUntilAddress < tail || persistedCommitNum < lastCommit)
+                {
+                    var linkedCommitInfo = await task.WithCancellationAsync(token).ConfigureAwait(false);
+                    task = linkedCommitInfo.NextTask;
+                }
             }
         }
 
@@ -951,18 +966,37 @@ public async ValueTask CommitAsync(CancellationToken token = default)
         public async ValueTask<Task<LinkedCommitInfo>> CommitAsync(Task<LinkedCommitInfo> prevCommitTask, CancellationToken token = default)
         {
             token.ThrowIfCancellationRequested();
+
+            // Take a lower-bound of the content of this commit in case our request is filtered but we need to spin
+            var tail = TailAddress;
+            var lastCommit = commitNum;
+
             if (prevCommitTask == null) prevCommitTask = CommitTask;
 
-            if (!CommitInternal(out var tailAddress, out var actualCommitNum, true, null, -1, null))
-                return prevCommitTask;
+            var success = CommitInternal(out var actualTail, out var actualCommitNum, true, null, -1, null);
 
-            while (CommittedUntilAddress < tailAddress || persistedCommitNum < actualCommitNum)
+
+            if (success)
             {
-                var linkedCommitInfo = await prevCommitTask.WithCancellationAsync(token).ConfigureAwait(false);
-                if (linkedCommitInfo.CommitInfo.UntilAddress < tailAddress || persistedCommitNum < actualCommitNum)
-                    prevCommitTask = linkedCommitInfo.NextTask;
-                else
-                    return linkedCommitInfo.NextTask;
+                while (CommittedUntilAddress < actualTail || persistedCommitNum < actualCommitNum)
+                {
+                    var linkedCommitInfo = await prevCommitTask.WithCancellationAsync(token).ConfigureAwait(false);
+                    if (linkedCommitInfo.CommitInfo.UntilAddress < actualTail || persistedCommitNum < actualCommitNum)
+                        prevCommitTask = linkedCommitInfo.NextTask;
+                    else
+                        return linkedCommitInfo.NextTask;
+                }
+            }
+            else
+            {
+                while (CommittedUntilAddress < tail || persistedCommitNum < lastCommit)
+                {
+                    var linkedCommitInfo = await prevCommitTask.WithCancellationAsync(token).ConfigureAwait(false);
+                    if (linkedCommitInfo.CommitInfo.UntilAddress < actualTail || persistedCommitNum < actualCommitNum)
+                        prevCommitTask = linkedCommitInfo.NextTask;
+                    else
+                        return linkedCommitInfo.NextTask;
+                }
             }
 
             return prevCommitTask;