Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.Workflow.Runtime/DbRetry.cs

@@ -0,0 +1,66 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Threading;
+
+namespace System.Workflow.Runtime
+{
+    internal class DbRetry
+    {
+        private const short _defaultMaxRetries = 20;
+        private const int _defaultRetrySleep = 2000;
+        private const short _spinCount = 3;
+
+        private short _maxRetries = _defaultMaxRetries;
+        private int _retrySleep = _defaultRetrySleep;
+        private bool _enableRetries = false;
+
+        protected DbRetry()
+        {
+        }
+
+        internal DbRetry(bool enableRetries)
+        {
+            _enableRetries = enableRetries;
+        }
+
+        internal short MaxRetries
+        {
+            get { return _maxRetries; }
+        }
+
+        internal bool TryDoRetry(ref short retryCount)
+        {
+            if (CanRetry(retryCount++))
+            {
+                RetrySleep(retryCount);
+                return true;
+            }
+            else
+                return false;
+        }
+
+        internal bool CanRetry(short retryCount)
+        {
+            if (!_enableRetries)
+                return false;
+
+            if (retryCount < _maxRetries)
+                return true;
+            else
+                return false;
+        }
+
+        internal void RetrySleep(short retryCount)
+        {
+            //
+            // For the first couple of retries just spin
+            // If we fail _spinCount times start then introduce a sleep
+            if (retryCount <= _spinCount)
+                return;
+
+            int sleep = _retrySleep * retryCount;
+            Thread.Sleep(sleep);
+        }
+    }
+}