2514: Add row version to packages table to detect concurrency conflic…

…ts when updating IsLatest

src/NuGetGallery.Core/Entities/Package.cs

@@ -118,6 +118,12 @@ public Package()
 
         public bool RequiresLicenseAcceptance { get; set; }
 
+        /// <summary>
+        /// Timestamp for optimistic concurrency checks to prevent conflicting IsLatest updates from multiple uploads
+        /// </summary>
+        [Timestamp]
+        public byte[] RowVersion { get; set; }
+
         /// <remarks>
         ///     Has a max length of 4000. Is not indexed and not used for searches. Db column is nvarchar(max).
         /// </remarks>

src/NuGetGallery/Controllers/PackagesController.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Data;
+using System.Data.Entity.Infrastructure;
 using System.Diagnostics;
 using System.Globalization;
 using System.IO;
@@ -1178,9 +1179,18 @@ public virtual async Task<ActionResult> VerifyPackage(VerifyPackageRequest formD
                 // save package to blob storage
                 uploadFile.Position = 0;
                 await _packageFileService.SavePackageFileAsync(package, uploadFile.AsSeekableStream());
-
-                // commit all changes to database as an atomic transaction
-                await _entitiesContext.SaveChangesAsync();
+
+                try
+                {
+                    // commit all changes to database as an atomic transaction
+                    await _entitiesContext.SaveChangesAsync();
+                }
+                catch (DbUpdateConcurrencyException)
+                {
+                    // another package upload modified IsLatest state for packages in this registration
+                    TempData["Message"] = "Your attempt to verify the package submission failed, because of a conflict with another upload. Please try again.";
+                    return new RedirectResult(Url.VerifyPackage());
+                }
 
                 // tell Lucene to update index for the new package
                 _indexingService.UpdateIndex();

src/NuGetGallery/Migrations/201612091849195_PackagesRowVersion.cs

@@ -0,0 +1,18 @@
+namespace NuGetGallery.Migrations
+{
+    using System;
+    using System.Data.Entity.Migrations;
+
+    public partial class PackagesRowVersion : DbMigration
+    {
+        public override void Up()
+        {
+            AddColumn("dbo.Packages", "RowVersion", c => c.Binary(nullable: false, fixedLength: true, timestamp: true, storeType: "rowversion"));
+        }
+
+        public override void Down()
+        {
+            DropColumn("dbo.Packages", "RowVersion");
+        }
+    }
+}