Create 2024-09-02-connection-resiliency-for-ef-core-and-sql-data.md

_posts/2024-09-02-connection-resiliency-for-ef-core-and-sql-data.md

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+---
+layout: post
+title: "Connection Resiliency for Entity Framework Core and SqlClient"
+description: "Retry... retry... argh."
+date: 2024-09-02 23:59
+author: Robert Muehsig
+tags: [Entity Framework Core, Cloud, SQL Azure, TIL]
+language: en
+---
+
+{% include JB/setup %}
+
+*This is more of a "Today-I-Learned" post and not a "full-blown How-To article." If something is completely wrong, please let me know - thanks!* 
+
+If you work with SQL Azure you might find this familiar:
+
+> Unexpected exception occurred: An exception has been raised that is likely due to a transient failure. Consider enabling transient error resiliency by adding 'EnableRetryOnFailure' to the 'UseSqlServer' call.
+
+# EF Core Resiliency
+
+The above error already shows a very simple attempt to "stabilize" your application. If you are using Entity Framework Core, this could look like this:
+
+```
+protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
+{
+    optionsBuilder
+        .UseSqlServer(
+            @"Server=(localdb)\mssqllocaldb;Database=EFMiscellanous.ConnectionResiliency;Trusted_Connection=True;ConnectRetryCount=0",
+            options => options.EnableRetryOnFailure());
+}
+```
+
+The [EnableRetryOnFailure-Method](https://learn.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.infrastructure.sqlserverdbcontextoptionsbuilder.enableretryonfailure?view=efcore-8.0) has a couple of options, like a retry count or the retry delay. 
+
+If you don't use the `UseSqlServer`-method to configure your context, there are other ways to enable this behavior: [See Microsoft Docs](https://learn.microsoft.com/en-us/ef/core/miscellaneous/connection-resiliency)
+
+# Microsoft.Data.SqlClient - Retry Provider
+
+If you use the "plain" `Microsoft.Data.SqlClient` NuGet Package to connect to your database have a look at [Retry Logic Providers](https://learn.microsoft.com/en-us/sql/connect/ado-net/configurable-retry-logic?view=sql-server-ver16)
+
+A basic implementation would look like this:
+
+```
+// Define the retry logic parameters
+var options = new SqlRetryLogicOption()
+{
+    // Tries 5 times before throwing an exception
+    NumberOfTries = 5,
+    // Preferred gap time to delay before retry
+    DeltaTime = TimeSpan.FromSeconds(1),
+    // Maximum gap time for each delay time before retry
+    MaxTimeInterval = TimeSpan.FromSeconds(20)
+};
+
+// Create a retry logic provider
+SqlRetryLogicBaseProvider provider = SqlConfigurableRetryFactory.CreateExponentialRetryProvider(options);
+
+// Assumes that connection is a valid SqlConnection object 
+// Set the retry logic provider on the connection instance
+connection.RetryLogicProvider = provider;
+// Establishing the connection will retry if a transient failure occurs.
+connection.Open();
+```
+
+You can set a `RetryLogicProvider` on a [Connection](https://learn.microsoft.com/en-us/dotnet/api/microsoft.data.sqlclient.sqlconnection.retrylogicprovider?view=sqlclient-dotnet-standard-5.2) and on a [SqlCommand](https://learn.microsoft.com/en-us/dotnet/api/microsoft.data.sqlclient.sqlcommand.retrylogicprovider?view=sqlclient-dotnet-standard-5.2).
+
+# Some more links and tips
+
+These two options seem to be the "low-level-entry-points".
+Of course could you wrap each action with a library like [Polly](https://github.com/App-vNext/Polly).
+
+During my research I found a good overview: [__Implementing Resilient Applications__](https://learn.microsoft.com/en-us/dotnet/architecture/microservices/implement-resilient-applications/).
+
+Hope this helps!