Adding Change Feed Processor code migration sample (#782)

* Adding migration sample

* Adding more options

* Code comments

* comments

Microsoft.Azure.Cosmos.Samples/Usage/ChangeFeed/ChangeFeed.csproj

@@ -9,6 +9,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.Azure.Cosmos" Version="3.1.1" />
+    <PackageReference Include="Microsoft.Azure.DocumentDB.ChangeFeedProcessor" Version="2.2.7" />
     <PackageReference Include="Microsoft.Extensions.Configuration" Version="2.2.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.FileExtensions" Version="2.2.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="2.2.0" />

Microsoft.Azure.Cosmos.Samples/Usage/ChangeFeed/Program.cs

@@ -6,7 +6,9 @@
     using System.Threading;
     using System.Threading.Tasks;
     using Microsoft.Azure.Cosmos;
+    using Microsoft.Azure.Documents.ChangeFeedProcessor.FeedProcessing;
     using Microsoft.Extensions.Configuration;
+    using ChangeFeedProcessorLibrary = Microsoft.Azure.Documents.ChangeFeedProcessor;
 
     // ----------------------------------------------------------------------------------------------------------
     // Prerequisites - 
@@ -26,6 +28,8 @@
     // 3. Listening for changes that happen since the container was created.
     //
     // 4. Generate Estimator metrics to expose current Change Feed Processor progress
+    //
+    // 5. Code migration template from existing Change Feed Processor library V2
     //-----------------------------------------------------------------------------------------------------------
 
 
@@ -66,6 +70,8 @@
                     await Program.RunStartFromBeginningChangeFeed("changefeed-beginning", client);
                     Console.WriteLine($"\n4. Generate Estimator metrics to expose current Change Feed Processor progress.");
                     await Program.RunEstimatorChangeFeed("changefeed-estimator", client);
+                    Console.WriteLine($"\n5. Code migration template from existing Change Feed Processor library V2.");
+                    await Program.RunMigrationSample("changefeed-migration", client, configuration);
                 }
             }
             finally
@@ -243,6 +249,89 @@
             await changeFeedEstimator.StopAsync();
         }
 
+        /// <summary>
+        /// Example of a code migration template from Change Feed Processor V2 to SDK V3.
+        /// </summary>
+        /// <returns></returns>
+        public static async Task RunMigrationSample(
+            string databaseId,
+            CosmosClient client,
+            IConfigurationRoot configuration)
+        {
+            await Program.InitializeAsync(databaseId, client);
+
+            Console.WriteLine("Generating 10 items that will be picked up by the old Change Feed Processor library...");
+            await Program.GenerateItems(10, client.GetContainer(databaseId, Program.monitoredContainer));
+
+            // This is how you would initialize the processor in V2
+            // <ChangeFeedProcessorLibrary>
+            ChangeFeedProcessorLibrary.DocumentCollectionInfo monitoredCollectionInfo = new ChangeFeedProcessorLibrary.DocumentCollectionInfo()
+            {
+                DatabaseName = databaseId,
+                CollectionName = Program.monitoredContainer,
+                Uri = new Uri(configuration["EndPointUrl"]),
+                MasterKey = configuration["AuthorizationKey"]
+            };
+
+            ChangeFeedProcessorLibrary.DocumentCollectionInfo leaseCollectionInfo = new ChangeFeedProcessorLibrary.DocumentCollectionInfo()
+            {
+                DatabaseName = databaseId,
+                CollectionName = Program.leasesContainer,
+                Uri = new Uri(configuration["EndPointUrl"]),
+                MasterKey = configuration["AuthorizationKey"]
+            };
+
+            ChangeFeedProcessorLibrary.ChangeFeedProcessorBuilder builder = new ChangeFeedProcessorLibrary.ChangeFeedProcessorBuilder();
+            var oldChangeFeedProcessor = await builder
+                .WithHostName("consoleHost")
+                .WithProcessorOptions(new ChangeFeedProcessorLibrary.ChangeFeedProcessorOptions {
+                    StartFromBeginning = true,
+                    LeasePrefix = "MyLeasePrefix" })
+                 .WithProcessorOptions(new ChangeFeedProcessorLibrary.ChangeFeedProcessorOptions()
+                 {
+                     MaxItemCount = 10,
+                     FeedPollDelay = TimeSpan.FromSeconds(1)
+                 })
+                .WithFeedCollection(monitoredCollectionInfo)
+                .WithLeaseCollection(leaseCollectionInfo)
+                .WithObserver<ChangeFeedObserver>()
+                .BuildAsync();
+            // </ChangeFeedProcessorLibrary>
+
+            await oldChangeFeedProcessor.StartAsync();
+
+            // Wait random time for the delegate to output all messages after initialization is done
+            await Task.Delay(5000);
+            Console.WriteLine("Now we will stop the V2 Processor and start a V3 with the same parameters to pick up from the same state, press any key to continue...");
+            Console.ReadKey();
+            await oldChangeFeedProcessor.StopAsync();
+
+            Console.WriteLine("Generating 5 items that will be picked up by the new Change Feed Processor...");
+            await Program.GenerateItems(5, client.GetContainer(databaseId, Program.monitoredContainer));
+
+            // This is how you would do the same initialization in V3
+            // <ChangeFeedProcessorMigrated>
+            Container leaseContainer = client.GetContainer(databaseId, Program.leasesContainer);
+            Container monitoredContainer = client.GetContainer(databaseId, Program.monitoredContainer);
+            ChangeFeedProcessor changeFeedProcessor = monitoredContainer
+                .GetChangeFeedProcessorBuilder<ToDoItem>("MyLeasePrefix", Program.HandleChangesAsync)
+                    .WithInstanceName("consoleHost")
+                    .WithLeaseContainer(leaseContainer)
+                    .WithMaxItems(10)
+                    .WithPollInterval(TimeSpan.FromSeconds(1))
+                    .WithStartTime(DateTime.MinValue.ToUniversalTime())
+                    .Build();
+            // </ChangeFeedProcessorMigrated>
+
+            await changeFeedProcessor.StartAsync();
+
+            // Wait random time for the delegate to output all messages after initialization is done
+            await Task.Delay(5000);
+            Console.WriteLine("Press any key to continue with the next demo...");
+            Console.ReadKey();
+            await changeFeedProcessor.StopAsync();
+        }
+
         /// <summary>
         /// The delegate receives batches of changes as they are generated in the change feed and can process them.
         /// </summary>
@@ -322,4 +411,27 @@
         public DateTime creationTime { get; set; }
     }
     // </Model>
+
+    internal class ChangeFeedObserver : IChangeFeedObserver
+    {
+        public Task CloseAsync(IChangeFeedObserverContext context, ChangeFeedObserverCloseReason reason)
+        {
+            return Task.CompletedTask;
+        }
+
+        public Task OpenAsync(IChangeFeedObserverContext context)
+        {
+            return Task.CompletedTask;
+        }
+
+        public Task ProcessChangesAsync(IChangeFeedObserverContext context, IReadOnlyList<Microsoft.Azure.Documents.Document> docs, CancellationToken cancellationToken)
+        {
+            foreach (var doc in docs)
+            {
+                Console.WriteLine($"\t[OLD Processor] Detected operation for item with id {doc.Id}, created at {doc.GetPropertyValue<DateTime>("creationTime")}.");
+            }
+
+            return Task.CompletedTask;
+        }
+    }
 }