fix: add locking around the auto-install of SQL Server objects so that multiple hubs don't try to enable service broker or create the initial schema at the same time.

Author: ascott18

src/IntelliTect.AspNetCore.SignalR.SqlServer/Internal/SqlServer/SqlInstaller.cs

@@ -10,37 +10,27 @@
 
 namespace IntelliTect.AspNetCore.SignalR.SqlServer.Internal
 {
-    internal class SqlInstaller
+    internal class SqlInstaller(SqlServerOptions options, ILogger logger, string messagesTableNamePrefix, string tracePrefix)
     {
         private const int SchemaVersion = 1;
 
-        private readonly string _messagesTableNamePrefix;
-        private readonly ILogger _logger;
-        private readonly SqlServerOptions _options;
-
-        public SqlInstaller(SqlServerOptions options, ILogger logger, string messagesTableNamePrefix)
-        {
-            _logger = logger;
-            _options = options;
-            _messagesTableNamePrefix = messagesTableNamePrefix;
-        }
-
         public async Task Install()
         {
-            if (!_options.AutoEnableServiceBroker && !_options.AutoInstallSchema)
+            if (!options.AutoEnableServiceBroker && !options.AutoInstallSchema)
             {
-                _logger.LogInformation("Skipping install of SignalR SQL objects");
+                logger.LogInformation("{HubName}: Skipping install of SignalR SQL objects", tracePrefix);
                 return;
             }
 
-            _logger.LogInformation("Start installing SignalR SQL objects");
+            await options.InstallLock.WaitAsync();
+            logger.LogInformation("{HubName}: Start installing SignalR SQL objects", tracePrefix);
             try
             {
-                using var connection = new SqlConnection(_options.ConnectionString);
+                using var connection = new SqlConnection(options.ConnectionString);
                 await connection.OpenAsync();
                 using var command = connection.CreateCommand();
 
-                if (_options.AutoEnableServiceBroker)
+                if (options.AutoEnableServiceBroker)
                 {
                     try
                     {
@@ -49,31 +39,34 @@ public async Task Install()
                     }
                     catch (Exception ex)
                     {
-                        _logger.LogError(ex, "Unable to automatically enable SQL Server Service Broker.");
+                        logger.LogError(ex, "Unable to automatically enable SQL Server Service Broker.");
                     }
                 }
 
-                if (_options.AutoInstallSchema)
+                if (options.AutoInstallSchema)
                 {
                     var script = GetType().Assembly.StringResource("install.sql");
 
-                    script = script.Replace("SET @SCHEMA_NAME = 'SignalR';", "SET @SCHEMA_NAME = '" + _options.SchemaName + "';");
+                    script = script.Replace("SET @SCHEMA_NAME = 'SignalR';", "SET @SCHEMA_NAME = '" + options.SchemaName + "';");
                     script = script.Replace("SET @TARGET_SCHEMA_VERSION = 1;", "SET @TARGET_SCHEMA_VERSION = " + SchemaVersion + ";");
-                    script = script.Replace("SET @MESSAGE_TABLE_COUNT = 1;", "SET @MESSAGE_TABLE_COUNT = " + _options.TableCount + ";");
-                    script = script.Replace("SET @MESSAGE_TABLE_NAME = 'Messages_YourHubName';", "SET @MESSAGE_TABLE_NAME = '" + _messagesTableNamePrefix + "';");
+                    script = script.Replace("SET @MESSAGE_TABLE_COUNT = 1;", "SET @MESSAGE_TABLE_COUNT = " + options.TableCount + ";");
+                    script = script.Replace("SET @MESSAGE_TABLE_NAME = 'Messages_YourHubName';", "SET @MESSAGE_TABLE_NAME = '" + messagesTableNamePrefix + "';");
 
                     command.CommandText = script;
                     await command.ExecuteNonQueryAsync();
 
-                    _logger.LogInformation("SignalR SQL objects installed");
+                    logger.LogInformation("{HubName}: SignalR SQL objects installed", messagesTableNamePrefix);
                 }
             }
             catch (Exception ex)
             {
-                _logger.LogError(ex, "Unable to install SignalR SQL objects");
+                logger.LogError(ex, "{HubName}: Unable to install SignalR SQL objects", messagesTableNamePrefix);
                 throw;
             }
-
+            finally
+            {
+                options.InstallLock.Release();
+            }
         }
     }
 }

src/IntelliTect.AspNetCore.SignalR.SqlServer/SqlServerHubLifetimeManager.cs

@@ -371,14 +371,14 @@ private async Task EnsureSqlServerConnection()
                 {
                     if (_streams.Count == 0)
                     {
-                        var installer = new SqlInstaller(_options, _logger, _tableNamePrefix);
+                        var installer = new SqlInstaller(_options, _logger, _tableNamePrefix, typeof(THub).FullName!);
                         await installer.Install();
 
                         for (var i = 0; i < _options.TableCount; i++)
                         {
                             var streamIndex = i;
                             var tableName = string.Format(CultureInfo.InvariantCulture, "{0}_{1}", _tableNamePrefix, streamIndex);
-                            var tracePrefix = $"{typeof(THub).FullName}:{streamIndex}: ";
+                            var tracePrefix = $"{typeof(THub).FullName}:{streamIndex}";
 
                             var stream = new SqlStream(
                                 _options,

src/IntelliTect.AspNetCore.SignalR.SqlServer/SqlServerOptions.cs

@@ -14,6 +14,13 @@ namespace IntelliTect.AspNetCore.SignalR.SqlServer
     /// </summary>
     public class SqlServerOptions
     {
+        /// <summary>
+        /// Shared lock to prevent multiple concurrent installs against the same DB.
+        /// This prevents auto-enable of service broker from deadlocking 
+        /// when an application has multiple hubs.
+        /// </summary>
+        internal readonly SemaphoreSlim InstallLock = new SemaphoreSlim(1);
+
         /// <summary>
         /// The SQL Server connection string to use.
         /// </summary>