Check that server version is greater than or equal to the client (#5111)

Co-authored-by: Brandon Ording <[email protected]>

Author: ramonsmits

src/ServiceControl.RavenDB/StartupChecks.cs

@@ -9,15 +9,26 @@ public static class StartupChecks
     {
         public static async Task EnsureServerVersion(IDocumentStore store, CancellationToken cancellationToken = default)
         {
+            // RavenDB compatibility policy is that the major/minor version of the server must be
+            // equal or higher than the client and ignores the patch version.
+            //
+            // https://docs.ravendb.net/6.2/client-api/faq/backward-compatibility/#compatibility---ravendb-42-and-higher
+            //
+            // > Starting with version 4.2, RavenDB clients are compatible with any server of their own version and higher.
+            // > E.g. -
+            // >
+            // > Client 4.2 is compatible with Server 4.2, Server 4.5, Server 5.2, and any other server of a higher version.
+
             var build = await store.Maintenance.Server.SendAsync(new GetBuildNumberOperation(), cancellationToken);
+            var serverProductVersion = new Version(build.ProductVersion);
 
             var clientVersion = typeof(Raven.Client.Constants).Assembly.GetCustomAttributes<AssemblyInformationalVersionAttribute>().First().InformationalVersion;
             var parts = clientVersion.Split('.');
-            var clientProductVersion = $"{parts[0]}.{parts[1]}";
+            var clientProductVersion = new Version($"{parts[0]}.{parts[1]}");
 
-            if (clientProductVersion != build.ProductVersion)
+            if (clientProductVersion > serverProductVersion)
             {
-                throw new Exception($"ServiceControl expects RavenDB Server version {clientProductVersion} but the server is using {build.ProductVersion}.");
+                throw new Exception($"ServiceControl expects RavenDB Server version {clientProductVersion} or higher, but the server is using {serverProductVersion}.");
             }
         }
     }