add DTFx sample and use simple credential resolver

DurableTask.Netherite.sln

@@ -36,7 +36,9 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "LoadGeneratorApp", "test\Lo
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "HelloDTFx", "samples\HelloDTFx\HelloDTFx\HelloDTFx.csproj", "{EC293D85-91E3-4F78-8B1E-2C691315CE96}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "TokenCredentialDF", "samples\TokenCredentialDF\TokenCredentialDF.csproj", "{B99AB043-47DC-467C-93CB-D6C69D3B1AD4}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "TokenCredentialDF", "samples\TokenCredentialDF\TokenCredentialDF.csproj", "{B99AB043-47DC-467C-93CB-D6C69D3B1AD4}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "TokenCredentialDTFx", "samples\TokenCredentialDTFx\TokenCredentialDTFx.csproj", "{FBFF0814-E6C0-489A-ACCF-9D0699219621}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -84,6 +86,10 @@ Global
 		{B99AB043-47DC-467C-93CB-D6C69D3B1AD4}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{B99AB043-47DC-467C-93CB-D6C69D3B1AD4}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{B99AB043-47DC-467C-93CB-D6C69D3B1AD4}.Release|Any CPU.Build.0 = Release|Any CPU
+		{FBFF0814-E6C0-489A-ACCF-9D0699219621}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{FBFF0814-E6C0-489A-ACCF-9D0699219621}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{FBFF0814-E6C0-489A-ACCF-9D0699219621}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{FBFF0814-E6C0-489A-ACCF-9D0699219621}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -99,6 +105,7 @@ Global
 		{78B360B8-3A41-4DC0-A300-94A0FABC1FB0} = {4A7226CF-57BF-4CA3-A4AC-91A398A1D84B}
 		{EC293D85-91E3-4F78-8B1E-2C691315CE96} = {AB958467-9236-402E-833C-B8DE4841AB9F}
 		{B99AB043-47DC-467C-93CB-D6C69D3B1AD4} = {AB958467-9236-402E-833C-B8DE4841AB9F}
+		{FBFF0814-E6C0-489A-ACCF-9D0699219621} = {AB958467-9236-402E-833C-B8DE4841AB9F}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {238A9613-5411-41CF-BDEC-168CCD5C03FB}

samples/TokenCredentialDF/FunctionsStartup.cs

@@ -8,6 +8,7 @@ namespace PerformanceTests
     using System;
     using Azure.Identity;
     using DurableTask.Netherite;
+    using DurableTask.Netherite.AzureFunctions;
     using Microsoft.Azure.Functions.Extensions.DependencyInjection;
     using Microsoft.Azure.WebJobs;
     using Microsoft.Extensions.DependencyInjection;
@@ -15,7 +16,7 @@ namespace PerformanceTests
 
     public class Startup : FunctionsStartup
     {
-        public class MyConnectionResolver : TokenCredentialResolver
+        public class MyConnectionResolver : CredentialBasedConnectionNameResolver
         {
             readonly INameResolver nameResolver;
 
@@ -29,7 +30,7 @@ namespace PerformanceTests
                 ?? Environment.GetEnvironmentVariable(name)
                 ?? throw new InvalidOperationException($"missing configuration setting '{name}'");
 
-            public override string GetStorageAccountName(string connectionName) => this.Resolve($"{connectionName}__storageAccountName");
+            public override string GetStorageAccountName(string connectionName) => this.Resolve($"{connectionName}__accountName");
 
             public override string GetEventHubsNamespaceName(string connectionName) => this.Resolve($"{connectionName}__eventHubsNamespaceName");
         }

samples/TokenCredentialDF/host.json

@@ -17,7 +17,7 @@
       "routePrefix": ""
     },
     "durableTask": {
-      "hubName": "tokentest",
+      "hubName": "tokencredentialsample",
       "UseGracefulShutdown": true,
       "storageProvider": {
         "type": "Netherite",

samples/TokenCredentialDTFx/HelloCities.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
- 
 using System;
 using DurableTask.Core;
 
@@ -28,4 +27,3 @@ public class SayHello : TaskActivity<string, string>
     }
 }
 
- 

samples/TokenCredentialDTFx/Program.cs

@@ -1,12 +1,12 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using Azure.Identity;
 using DurableTask.Core;
 using DurableTask.Netherite;
 using Microsoft.Extensions.Logging;
 using Newtonsoft.Json;
 
-
 // ----------- construct the Netherite orchestration service
 
 Console.WriteLine("Starting Netherite...");
@@ -15,14 +15,13 @@ var netheriteSettings = new NetheriteOrchestrationServiceSettings()
 {
     HubName = "myhub",
     PartitionCount = 4,
-
-    // we explicitly specify the two required connection strings here.
-    // Another option would be to use a connection name resolver when calling Validate().
-    ResolvedStorageConnectionString = "UseDevelopmentStorage=true;",
-    ResolvedTransportConnectionString = "SingleHost",
 };
 
-netheriteSettings.Validate();
+netheriteSettings.Validate(new SimpleCredentialResolver(
+    new DefaultAzureCredential(),
+    Environment.GetEnvironmentVariable("AccountName") ?? throw new Exception("missing env var: AccountName"),
+    Environment.GetEnvironmentVariable("NamespaceName") ?? throw new Exception("missing env var: NamespaceName")
+));
 
 var loggerFactory = LoggerFactory.Create(builder =>
 {

samples/TokenCredentialDTFx/TokenCredentialDTFx.csproj

@@ -8,8 +8,11 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Azure.DurableTask.Netherite" Version="1.1.1" />
     <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="6.0.0" />
   </ItemGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\DurableTask.Netherite\DurableTask.Netherite.csproj" />
+  </ItemGroup>
+
 </Project>

src/DurableTask.Netherite.AzureFunctions/TokenCredentialResolver.cs

@@ -1,16 +1,17 @@
-namespace DurableTask.Netherite
+namespace DurableTask.Netherite.AzureFunctions
 {
     using System;
     using System.Collections.Generic;
     using System.Text;
     using Azure.Identity;
-    using Microsoft.Azure.Storage.Blob.Protocol;
     using Microsoft.Extensions.Logging.Abstractions;
 
+#if !NETCOREAPP2_2
+
     /// <summary>
     /// Resolves connections using a token credential and a mapping from connection names to resource names.
     /// </summary>
-    public abstract class TokenCredentialResolver : ConnectionResolver
+    public abstract class CredentialBasedConnectionNameResolver : DurableTask.Netherite.ConnectionResolver
     {
         readonly Azure.Core.TokenCredential tokenCredential;
 
@@ -18,7 +19,7 @@
         /// Create a connection resolver that uses an Azure token credential.
         /// </summary>
         /// <param name="tokenCredential">The token credential to use.</param>
-        public TokenCredentialResolver(Azure.Core.TokenCredential tokenCredential)
+        public CredentialBasedConnectionNameResolver(Azure.Core.TokenCredential tokenCredential)
         {      
             this.tokenCredential = tokenCredential;
         }
@@ -71,4 +72,6 @@
             }
         }
     }
+
+#endif
 }

src/DurableTask.Netherite/Connections/SimpleCredentialResolver.cs

@@ -0,0 +1,71 @@
+namespace DurableTask.Netherite
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Text;
+    using Azure.Identity;
+    using Microsoft.Extensions.Logging.Abstractions;
+
+    /// <summary>
+    /// Resolves connections using a token credential, a storage account name, and an eventhubs namespace name.
+    /// </summary>
+    public class SimpleCredentialResolver : ConnectionResolver
+    {
+        readonly Azure.Core.TokenCredential tokenCredential;
+        readonly string storageAccountName;
+        readonly string eventHubNamespaceName;
+
+        /// <summary>
+        /// Create a connection resolver that uses an Azure token credential.
+        /// </summary>
+        /// <param name="tokenCredential">The token credential to use.</param>
+        /// <param name="storageAccountName">The name of the storage account, or null if using in-memory emulation.</param>
+        /// <param name="eventHubNamespaceName">The name of the event hub namespace, or null if using the singlehost configuration.</param>
+        public SimpleCredentialResolver(Azure.Core.TokenCredential tokenCredential, string storageAccountName = null, string eventHubNamespaceName = null)
+        {
+            this.tokenCredential = tokenCredential;
+            this.storageAccountName = storageAccountName;
+            this.eventHubNamespaceName = eventHubNamespaceName;
+        }
+
+        /// <inheritdoc/>
+        public override ConnectionInfo ResolveConnectionInfo(string taskHub, string connectionName, ResourceType recourceType)
+        {
+            switch (recourceType)
+            {
+                case ResourceType.BlobStorage:
+                case ResourceType.TableStorage:
+                    return ConnectionInfo.FromTokenCredential(this.tokenCredential, this.storageAccountName, recourceType);
+
+                case ResourceType.PageBlobStorage:
+                    return null; // same as blob storage
+
+                case ResourceType.EventHubsNamespace:
+                    return ConnectionInfo.FromTokenCredential(this.tokenCredential, this.eventHubNamespaceName, recourceType);
+
+                default:
+                    throw new NotImplementedException("unknown resource type");
+            }
+        }
+
+        /// <inheritdoc/>
+        public override void ResolveLayerConfiguration(string connectionName, out StorageChoices storageChoice, out TransportChoices transportChoice)
+        {
+            if (string.IsNullOrEmpty(this.storageAccountName))
+            {
+                storageChoice = StorageChoices.Memory;
+                transportChoice = TransportChoices.SingleHost;
+            }
+            else if (string.IsNullOrEmpty(this.eventHubNamespaceName))
+            {
+                storageChoice = StorageChoices.Faster;
+                transportChoice = TransportChoices.SingleHost;
+            }
+            else
+            {
+                storageChoice = StorageChoices.Faster;
+                transportChoice = TransportChoices.EventHubs;
+            }
+        }
+    }
+}

src/DurableTask.Netherite/TransportLayer/EventHubs/EventHubsTransport.cs

@@ -28,7 +28,6 @@ namespace DurableTask.Netherite.EventHubsTransport
     {
         readonly TransportAbstraction.IHost host;
         readonly NetheriteOrchestrationServiceSettings settings;
-        readonly CloudStorageAccount cloudStorageAccount;
         readonly ILogger logger;
         readonly EventHubsTraceHelper traceHelper;
         readonly IStorageLayer storage;
@@ -380,14 +379,36 @@ namespace DurableTask.Netherite.EventHubsTransport
             {
                 byte[] taskHubGuid = this.parameters.TaskhubGuid.ToByteArray();
                 TimeSpan longPollingInterval = TimeSpan.FromMinutes(1);
+                var backoffDelay = TimeSpan.Zero;
 
                 await this.clientConnectionsEstablished[index];
 
                 while (!this.shutdownSource.IsCancellationRequested)
+                {
+                    IEnumerable<EventData> eventData;
+
+                    try
                     {
                         this.traceHelper.LogTrace("Client{clientId}.ch{index} waiting for new packets", Client.GetShortId(this.ClientId), index);
 
-                    IEnumerable<EventData> eventData = await receiver.ReceiveAsync(1000, longPollingInterval);
+                        eventData = await receiver.ReceiveAsync(1000, longPollingInterval);
+
+                        backoffDelay = TimeSpan.Zero;
+                    }
+                    catch (Exception exception) when (!this.shutdownSource.IsCancellationRequested)
+                    {
+                        if (backoffDelay < TimeSpan.FromSeconds(30))
+                        {
+                            backoffDelay = backoffDelay + backoffDelay + TimeSpan.FromSeconds(2);
+                        }
+
+                        // if we lose access to storage temporarily, we back off, but don't quit
+                        this.traceHelper.LogError("Client{clientId}.ch{index} backing off for {backoffDelay} after error in receive loop: {exception}", Client.GetShortId(this.ClientId), index, backoffDelay, exception);
+
+                        await Task.Delay(backoffDelay);
+
+                        continue; // retry
+                    }
 
                     if (eventData != null)
                     {