feat: Add the read concern header

Add the read concern header to the top level Configuration.

Set the consistent read concern header in the cache client test fixture
if the CONSISTENT_READS env var is set.

Add a new make target for the github build to use that sets the header.

Update the test-cache-service make target to set the header so that the
canaries will use consistent reads.

.github/workflows/build.yaml

@@ -45,7 +45,7 @@ jobs:
         run: make GRPC_WEB=${{ matrix.grpc-web }} build
 
       - name: Test
-        run: make test
+        run: make prod-test
 
   build_examples:
     runs-on: ubuntu-latest

.github/workflows/on-push-to-main-branch.yaml

@@ -32,7 +32,7 @@ jobs:
         run: make GRPC_WEB=${{ matrix.grpc-web }} build
 
       - name: Test
-        run: make test
+        run: make prod-test
 
   generate_readme:
     runs-on: ubuntu-latest

Makefile

@@ -33,13 +33,11 @@ ifneq (,$(findstring NT,$(OS)))
 	BUILD_TARGETS := build-dotnet6 build-dotnet-framework
 	TEST_TARGETS := test-dotnet6 test-dotnet-framework
 	TEST_TARGETS_AUTH_SERVICE := test-dotnet6-auth-service test-dotnet-framework-auth-service
-	TEST_TARGETS_CACHE_SERVICE := test-dotnet6-cache-service test-dotnet-framework-cache-service
 	TEST_TARGETS_TOPICS_SERVICE := test-dotnet6-topics-service test-dotnet-framework-topics-service
 else
 	BUILD_TARGETS := build-dotnet6
 	TEST_TARGETS := test-dotnet6
 	TEST_TARGETS_AUTH_SERVICE := test-dotnet6-auth-service
-	TEST_TARGETS_CACHE_SERVICE := test-dotnet6-cache-service
 	TEST_TARGETS_TOPICS_SERVICE := test-dotnet6-topics-service
 endif
 
@@ -98,6 +96,16 @@ restore:
 test: ${TEST_TARGETS}
 
 
+## Run unit and integration tests with consistent reads (conditioned by OS)
+prod-test:
+	@echo "running tests with consistent reads..."
+ifeq (,$(findstring NT,$(OS)))
+	@CONSISTENT_READS=1 $(MAKE) ${TEST_TARGETS}
+else
+	@set CONSISTENT_READS=1 && $(MAKE) ${TEST_TARGETS}
+endif
+
+
 ## Run unit and integration tests on the .NET 6.0 runtime
 test-dotnet6:
 	@echo "Running unit and integration tests on the .NET 6.0 runtime..."
@@ -151,7 +159,12 @@ test-auth-service: ${TEST_TARGETS_AUTH_SERVICE}
 
 
 ## Run cache service tests
-test-cache-service: ${TEST_TARGETS_CACHE_SERVICE}
+test-cache-service:
+ifeq (,$(findstring NT,$(OS)))
+	@CONSISTENT_READS=1 $(MAKE) test-dotnet6-cache-service
+else
+	@set CONSISTENT_READS=1 && $(MAKE) test-dotnet6-cache-service test-dotnet-framework-cache-service
+endif
 
 
 ## Run leaderboard service tests

src/Momento.Sdk/Config/Configuration.cs

@@ -2,7 +2,6 @@
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.Extensions.Logging;
-using Microsoft.Extensions.Logging.Abstractions;
 using Momento.Sdk.Config.Middleware;
 using Momento.Sdk.Config.Retry;
 using Momento.Sdk.Config.Transport;
@@ -14,18 +13,41 @@ public class Configuration : IConfiguration
 {
     /// <inheritdoc />
     public ILoggerFactory LoggerFactory { get; }
+
     /// <inheritdoc />
     public IRetryStrategy RetryStrategy { get; }
+
     /// <inheritdoc />
     public IList<IMiddleware> Middlewares { get; }
+
     /// <inheritdoc />
     public ITransportStrategy TransportStrategy { get; }
 
+    /// <inheritdoc />
+    public ReadConcern ReadConcern { get; }
+
     /// <inheritdoc cref="Momento.Sdk.Config.IConfiguration" />
-    public Configuration(ILoggerFactory loggerFactory, IRetryStrategy retryStrategy, ITransportStrategy transportStrategy)
+    public Configuration(ILoggerFactory loggerFactory, IRetryStrategy retryStrategy,
+        ITransportStrategy transportStrategy)
         : this(loggerFactory, retryStrategy, new List<IMiddleware>(), transportStrategy)
     {
+    }
 
+    /// <summary>
+    /// Create a new instance of Configuration object with provided arguments: <see cref="Momento.Sdk.Config.IConfiguration.RetryStrategy" />, <see cref="Momento.Sdk.Config.IConfiguration.Middlewares" />, <see cref="Momento.Sdk.Config.IConfiguration.TransportStrategy"/>, and <see cref="Momento.Sdk.Config.IConfiguration.LoggerFactory"/>
+    /// </summary>
+    /// <param name="retryStrategy">Defines a contract for how and when to retry a request</param>
+    /// <param name="middlewares">The Middleware interface allows the Configuration to provide a higher-order function that wraps all requests.</param>
+    /// <param name="transportStrategy">This is responsible for configuring network tunables.</param>
+    /// <param name="loggerFactory">This is responsible for configuring logging.</param>
+    public Configuration(ILoggerFactory loggerFactory, IRetryStrategy retryStrategy, IList<IMiddleware> middlewares,
+        ITransportStrategy transportStrategy)
+    {
+        LoggerFactory = loggerFactory;
+        RetryStrategy = retryStrategy;
+        Middlewares = middlewares;
+        TransportStrategy = transportStrategy;
+        ReadConcern = ReadConcern.Balanced;
     }
 
     /// <summary>
@@ -34,31 +56,34 @@ public Configuration(ILoggerFactory loggerFactory, IRetryStrategy retryStrategy,
     /// <param name="retryStrategy">Defines a contract for how and when to retry a request</param>
     /// <param name="middlewares">The Middleware interface allows the Configuration to provide a higher-order function that wraps all requests.</param>
     /// <param name="transportStrategy">This is responsible for configuring network tunables.</param>
-    /// <param name="loggerFactory">This is responsible for configuraing logging.</param>
-    public Configuration(ILoggerFactory loggerFactory, IRetryStrategy retryStrategy, IList<IMiddleware> middlewares, ITransportStrategy transportStrategy)
+    /// <param name="loggerFactory">This is responsible for configuring logging.</param>
+    /// <param name="readConcern">The client-wide setting for read-after-write consistency.</param>
+    public Configuration(ILoggerFactory loggerFactory, IRetryStrategy retryStrategy, IList<IMiddleware> middlewares,
+        ITransportStrategy transportStrategy, ReadConcern readConcern)
     {
-        this.LoggerFactory = loggerFactory;
-        this.RetryStrategy = retryStrategy;
-        this.Middlewares = middlewares;
-        this.TransportStrategy = transportStrategy;
+        LoggerFactory = loggerFactory;
+        RetryStrategy = retryStrategy;
+        Middlewares = middlewares;
+        TransportStrategy = transportStrategy;
+        ReadConcern = readConcern;
     }
 
     /// <inheritdoc />
     public IConfiguration WithRetryStrategy(IRetryStrategy retryStrategy)
     {
-        return new Configuration(LoggerFactory, retryStrategy, Middlewares, TransportStrategy);
+        return new Configuration(LoggerFactory, retryStrategy, Middlewares, TransportStrategy, ReadConcern);
     }
 
     /// <inheritdoc />
     public IConfiguration WithMiddlewares(IList<IMiddleware> middlewares)
     {
-        return new Configuration(LoggerFactory, RetryStrategy, middlewares, TransportStrategy);
+        return new Configuration(LoggerFactory, RetryStrategy, middlewares, TransportStrategy, ReadConcern);
     }
 
     /// <inheritdoc />
     public IConfiguration WithTransportStrategy(ITransportStrategy transportStrategy)
     {
-        return new Configuration(LoggerFactory, RetryStrategy, Middlewares, transportStrategy);
+        return new Configuration(LoggerFactory, RetryStrategy, Middlewares, transportStrategy, ReadConcern);
     }
 
     /// <summary>
@@ -72,12 +97,13 @@ public Configuration WithAdditionalMiddlewares(IList<IMiddleware> additionalMidd
             retryStrategy: RetryStrategy,
             middlewares: Middlewares.Concat(additionalMiddlewares).ToList(),
             transportStrategy: TransportStrategy,
-            loggerFactory: LoggerFactory
+            loggerFactory: LoggerFactory,
+            readConcern: ReadConcern
         );
     }
 
     /// <summary>
-    /// Add the specified client timeout to an existing instance of Configuration object as an addiion to the existing transport strategy.
+    /// Add the specified client timeout to an existing instance of Configuration object as an addition to the existing transport strategy.
     /// </summary>
     /// <param name="clientTimeout">The amount of time to wait before cancelling the request.</param>
     /// <returns>Configuration object with client timeout provided</returns>
@@ -87,7 +113,20 @@ public Configuration WithClientTimeout(TimeSpan clientTimeout)
             retryStrategy: RetryStrategy,
             middlewares: Middlewares,
             transportStrategy: TransportStrategy.WithClientTimeout(clientTimeout),
-            loggerFactory: LoggerFactory
+            loggerFactory: LoggerFactory,
+            readConcern: ReadConcern
+        );
+    }
+
+    /// <inheritdoc />
+    public IConfiguration WithReadConcern(ReadConcern readConcern)
+    {
+        return new Configuration(
+            retryStrategy: RetryStrategy,
+            middlewares: Middlewares,
+            transportStrategy: TransportStrategy,
+            loggerFactory: LoggerFactory,
+            readConcern: readConcern
         );
     }
 
@@ -106,14 +145,15 @@ public override bool Equals(object obj)
 
         var other = (Configuration)obj;
         return RetryStrategy.Equals(other.RetryStrategy) &&
-            Middlewares.SequenceEqual(other.Middlewares) &&
-            TransportStrategy.Equals(other.TransportStrategy) &&
-            LoggerFactory.Equals(other.LoggerFactory);
+               Middlewares.SequenceEqual(other.Middlewares) &&
+               TransportStrategy.Equals(other.TransportStrategy) &&
+               LoggerFactory.Equals(other.LoggerFactory) &&
+               ReadConcern.Equals(other.ReadConcern);
     }
 
     /// <inheritdoc />
     public override int GetHashCode()
     {
         return base.GetHashCode();
     }
-}
+}

src/Momento.Sdk/Config/IConfiguration.cs

@@ -21,6 +21,8 @@ public interface IConfiguration
     public IList<IMiddleware> Middlewares { get; }
     /// <inheritdoc cref="Momento.Sdk.Config.Transport.ITransportStrategy" />
     public ITransportStrategy TransportStrategy { get; }
+    /// <inheritdoc cref="Momento.Sdk.Config.ReadConcern" />
+    public ReadConcern ReadConcern { get; }
 
     /// <summary>
     /// Creates a new instance of the Configuration object, updated to use the specified retry strategy.
@@ -49,4 +51,11 @@ public interface IConfiguration
     /// <param name="clientTimeout">The amount of time to wait before cancelling the request.</param>
     /// <returns>Configuration object with custom client timeout provided</returns>
     public IConfiguration WithClientTimeout(TimeSpan clientTimeout);
+
+    /// <summary>
+    /// Creates a new instance of the Configuration object, updated to use the specified read concern.
+    /// </summary>
+    /// <param name="readConcern">The read concern setting.</param>
+    /// <returns>Configuration object with custom read concern provided</returns>
+    public IConfiguration WithReadConcern(ReadConcern readConcern);
 }

src/Momento.Sdk/Config/ReadConcern.cs

@@ -0,0 +1,41 @@
+using System;
+
+namespace Momento.Sdk.Config;
+
+/// <summary>
+/// The read consistency setting for the cache client. Consistent guarantees read after write consistency, but applies a
+/// 6x multiplier to your operation usage. 
+/// </summary>
+public enum ReadConcern
+{
+    /// <summary>
+    /// Balanced is the default read concern for the cache client.
+    /// </summary>
+    Balanced,
+    /// <summary>
+    /// Consistent read concern guarantees read after write consistency.
+    /// </summary>
+    Consistent
+}
+
+/// <summary>
+/// Extension methods for the ReadConcern enum.
+/// </summary>
+public static class ReadConcernExtensions
+{
+    /// <summary>
+    /// Converts the read concern to a string value.
+    /// </summary>
+    /// <param name="readConcern">to convert to a string</param>
+    /// <returns></returns>
+    /// <exception cref="ArgumentOutOfRangeException">if given an unknown read concern</exception>
+    public static string ToStringValue(this ReadConcern readConcern)
+    {
+        return readConcern switch
+        {
+            ReadConcern.Balanced => "balanced",
+            ReadConcern.Consistent => "consistent",
+            _ => throw new ArgumentOutOfRangeException()
+        };
+    }
+}

src/Momento.Sdk/Internal/DataGrpcManager.cs

@@ -4,11 +4,6 @@
 using System.Linq;
 using System.Threading.Tasks;
 using Grpc.Core;
-using Grpc.Net.Client;
-using System.Net.Http;
-#if USE_GRPC_WEB
-using Grpc.Net.Client.Web;
-#endif
 using Microsoft.Extensions.Logging;
 using Momento.Protos.CacheClient;
 using Momento.Protos.CachePing;
@@ -17,7 +12,6 @@
 using Momento.Sdk.Config.Retry;
 using Momento.Sdk.Exceptions;
 using Momento.Sdk.Internal.Middleware;
-using static System.Reflection.Assembly;
 
 namespace Momento.Sdk.Internal;
 
@@ -256,10 +250,13 @@ public class DataGrpcManager : GrpcManager
 
     internal DataGrpcManager(IConfiguration config, string authToken, string endpoint): base(config.TransportStrategy.GrpcConfig, config.LoggerFactory, authToken, endpoint, "DataGrpcManager")
     {
+        var readConcernHeader = new Header(Header.ReadConcern, config.ReadConcern.ToStringValue());
+        headers.Add(readConcernHeader);
+
         var middlewares = config.Middlewares.Concat(
             new List<IMiddleware> {
                 new RetryMiddleware(config.LoggerFactory, config.RetryStrategy),
-                new HeaderMiddleware(config.LoggerFactory, this.headers),
+                new HeaderMiddleware(config.LoggerFactory, headers),
                 new MaxConcurrentRequestsMiddleware(config.LoggerFactory, config.TransportStrategy.MaxConcurrentRequests)
             }
         ).ToList();
@@ -280,7 +277,7 @@ await pingClient.PingAsync(new _PingRequest(),
         catch (RpcException ex)
         {
             MomentoErrorTransportDetails transportDetails = new MomentoErrorTransportDetails(
-                new MomentoGrpcErrorDetails(ex.StatusCode, ex.Message, null)
+                new MomentoGrpcErrorDetails(ex.StatusCode, ex.Message)
             );
             throw new ConnectionException("Eager connection to server failed", transportDetails, ex);
         }

src/Momento.Sdk/Internal/Middleware/HeaderMiddleware.cs

@@ -5,6 +5,7 @@
 using Grpc.Core;
 using Grpc.Core.Interceptors;
 using Microsoft.Extensions.Logging;
+using Momento.Sdk.Config;
 using Momento.Sdk.Config.Middleware;
 
 namespace Momento.Sdk.Internal.Middleware
@@ -14,6 +15,7 @@ internal class Header
         public const string AuthorizationKey = "authorization";
         public const string AgentKey = "agent";
         public const string RuntimeVersionKey = "runtime-version";
+        public const string ReadConcern = "read-concern";
         public readonly List<string> onceOnlyHeaders = new List<string> { Header.AgentKey, Header.RuntimeVersionKey };
         public string Name;
         public string Value;

tests/Integration/Momento.Sdk.Tests/Fixtures.cs

@@ -20,19 +20,29 @@ public class CacheClientFixture : IDisposable
     public CacheClientFixture()
     {
         AuthProvider = new EnvMomentoTokenProvider("MOMENTO_API_KEY");
+
+        // Enable consistent reads if the CONSISTENT_READS env var is set to anything
+        var consistentReads = !string.IsNullOrEmpty(Environment.GetEnvironmentVariable("CONSISTENT_READS"));
+
+        var config = Configurations.Laptop.Latest(LoggerFactory.Create(builder =>
+        {
+            builder.AddSimpleConsole(options =>
+            {
+                options.IncludeScopes = true;
+                options.SingleLine = true;
+                options.TimestampFormat = "hh:mm:ss ";
+            });
+            builder.AddFilter("Grpc.Net.Client", LogLevel.Error);
+            builder.SetMinimumLevel(LogLevel.Information);
+        }));
+
+        if (consistentReads)
+        {
+            config = config.WithReadConcern(ReadConcern.Consistent);
+        }
+
         CacheName = $"dotnet-integration-{Utils.NewGuidString()}";
-        Client = new TestCacheClient(Configurations.Laptop.Latest(LoggerFactory.Create(builder =>
-                {
-                    builder.AddSimpleConsole(options =>
-                    {
-                        options.IncludeScopes = true;
-                        options.SingleLine = true;
-                        options.TimestampFormat = "hh:mm:ss ";
-                    });
-                    builder.AddFilter("Grpc.Net.Client", LogLevel.Error);
-                    builder.SetMinimumLevel(LogLevel.Information);
-                })),
-                AuthProvider, defaultTtl: DefaultTtl);
+        Client = new TestCacheClient(config, AuthProvider, defaultTtl: DefaultTtl);
         Utils.CreateCacheForTest(Client, CacheName);
     }