feat: add lambda configuration (#427)

Adds a configuration optimized for Lambda environments. This is the
same as the InRegion.Default config but also eagerly connects the
client. This avoids the cold start penalty from before where we
established the connection on the first request, leading to
first-request timeouts.

src/Momento.Sdk/Config/Configurations.cs

@@ -163,5 +163,33 @@ public static IConfiguration V1(ILoggerFactory? loggerFactory = null)
                 return new LowLatency(finalLoggerFactory, retryStrategy, transportStrategy);
             }
         }
+
+        /// <summary>
+        /// This config optimizes for lambda environments. In addition to the in region settings of
+        /// <see cref="Default"/>, this configures the clients to eagerly connect to the Momento service
+        /// to avoid the cold start penalty of establishing a connection on the first request.
+        /// </summary>
+        public class Lambda : Configuration
+        {
+            private Lambda(ILoggerFactory loggerFactory, IRetryStrategy retryStrategy, ITransportStrategy transportStrategy)
+                : base(loggerFactory, retryStrategy, transportStrategy)
+            {
+
+            }
+
+            /// <summary>
+            /// Provides the latest recommended configuration for a lambda environment.
+            /// </summary>
+            /// <param name="loggerFactory"></param>
+            /// <returns></returns>
+            public static IConfiguration Latest(ILoggerFactory? loggerFactory = null)
+            {
+                var config = Default.V1(loggerFactory);
+                var transportStrategy = config.TransportStrategy.WithEagerConnectionTimeout(
+                    TimeSpan.FromSeconds(30)
+                );
+                return config.WithTransportStrategy(transportStrategy);
+            }
+        }
     }
 }

tests/Unit/Momento.Sdk.Tests/ConfigTest.cs

@@ -19,4 +19,11 @@ public void V1VConfigs_EqualLatest_HappyPath()
         Assert.Equal(Configurations.InRegion.Default.Latest(), Configurations.InRegion.Default.V1());
         Assert.Equal(Configurations.InRegion.LowLatency.Latest(), Configurations.InRegion.LowLatency.V1());
     }
+
+    [Fact]
+    public void LambdaLatest_HasEagerConnectionTimeout_HappyPath()
+    {
+        var config = Configurations.InRegion.Lambda.Latest();
+        Assert.Equal(TimeSpan.FromSeconds(30), config.TransportStrategy.EagerConnectionTimeout);
+    }
 }