From 00ad16e79644efdfd2ffce5c7f979a7cd5fd5181 Mon Sep 17 00:00:00 2001
From: Alex Ma <alma1@microsoft.com>
Date: Tue, 6 Sep 2022 13:42:43 -0700
Subject: [PATCH] Alex/fixforretrysleeping (#1669)

* added getResponseConnect function

* added WIP changes to getResponseConnect

* changed retry number to be smaller number

* added comments and changed max tries

* added changes

* added more changes

* added notification class

* made changes to fix

* added null fix
---
 .../Connection/ConnectionService.cs           | 31 ++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/src/Microsoft.SqlTools.ServiceLayer/Connection/ConnectionService.cs b/src/Microsoft.SqlTools.ServiceLayer/Connection/ConnectionService.cs
index dd0897cb..80cf7c71 100644
--- a/src/Microsoft.SqlTools.ServiceLayer/Connection/ConnectionService.cs
+++ b/src/Microsoft.SqlTools.ServiceLayer/Connection/ConnectionService.cs
@@ -35,6 +35,8 @@ namespace Microsoft.SqlTools.ServiceLayer.Connection
         private const string SqlAzureEdition = "SQL Azure";
         public const int MaxTolerance = 2 * 60; // two minutes - standard tolerance across ADS for AAD tokens
 
+        public const int MaxServerlessReconnectTries = 5; // Max number of tries to wait for a serverless database to start up when its paused before giving up.
+
         /// <summary>
         /// Singleton service instance
         /// </summary>
@@ -377,7 +379,7 @@ namespace Microsoft.SqlTools.ServiceLayer.Connection
             }
 
             // Try to open a connection with the given ConnectParams
-            ConnectionCompleteParams response = await TryOpenConnection(connectionInfo, connectionParams);
+            ConnectionCompleteParams? response = await this.TryOpenConnectionWithRetry(connectionInfo, connectionParams);
             if (response != null)
             {
                 return response;
@@ -400,6 +402,33 @@ namespace Microsoft.SqlTools.ServiceLayer.Connection
             return completeParams;
         }
 
+        private async Task<ConnectionCompleteParams?> TryOpenConnectionWithRetry(ConnectionInfo connectionInfo, ConnectParams connectionParams)
+        {
+            int counter = 0;
+            ConnectionCompleteParams? response = null;
+            while (counter <= MaxServerlessReconnectTries)
+            {
+                // The OpenAsync function used in TryOpenConnection does not retry when a database is sleeping.
+                // SqlClient will be implemented at a later time, which will have automatic retries.  
+                response = await TryOpenConnection(connectionInfo, connectionParams);
+                // If a serverless database is sleeping, it will return this error number and will need to be retried.
+                // See here for details: https://docs.microsoft.com/en-us/azure/azure-sql/database/serverless-tier-overview?view=azuresql#connectivity
+                if (response?.ErrorNumber == 40613)
+                {
+                    counter++;
+                    if(counter != MaxServerlessReconnectTries) {
+                        Logger.Information($"Database for connection {connectionInfo.OwnerUri} is paused, retrying connection. Attempt #{counter}");
+                    }
+                }
+                else
+                {
+                    // Every other response, we can stop.
+                    break;
+                }
+            }
+            return response;
+        }
+
         private void TryCloseConnectionTemporaryConnection(ConnectParams connectionParams, ConnectionInfo connectionInfo)
         {
             try