Added WaitForReloadToComplete method for Lambda functions to call so that the config is reloaded before the Lambda compute environment is frozen.

Author: normj

src/Amazon.Extensions.Configuration.SystemsManager/SystemsManagerConfigurationProvider.cs

@@ -35,6 +35,8 @@ public class SystemsManagerConfigurationProvider : ConfigurationProvider
         private ISystemsManagerProcessor SystemsManagerProcessor { get; }
         private IParameterProcessor ParameterProcessor { get; }
 
+        private ManualResetEvent ReloadTaskEvent { get; } = new ManualResetEvent(true);
+
         /// <inheritdoc />
         /// <summary>
         /// Initializes a new instance with the specified source.
@@ -66,10 +68,33 @@ public SystemsManagerConfigurationProvider(SystemsManagerConfigurationSource sou
                     var cancellationTokenSource = new CancellationTokenSource(source.ReloadAfter.Value);
                     var cancellationChangeToken = new CancellationChangeToken(cancellationTokenSource.Token);
                     return cancellationChangeToken;
-                }, async () => await LoadAsync(true).ConfigureAwait(false));
+                }, async () =>
+                {
+                    ReloadTaskEvent.Reset();
+                    try
+                    {
+                        await LoadAsync(true).ConfigureAwait(false);
+                    }
+                    finally
+                    {
+                        ReloadTaskEvent.Set();
+                    }
+                });
             }
         }
 
+        /// <summary>
+        /// If this configuration provider is currently performing a reload of the config data this method will block until
+        /// the reload is called.
+        /// 
+        /// This method is not meant for general use. It is exposed so a Lambda function can wait for the reload to complete
+        /// before completing the event causing the Lambda compute environment to be frozen.
+        /// </summary>
+        public void WaitForReloadToComplete(TimeSpan timeout)
+        {
+            ReloadTaskEvent.WaitOne(timeout);
+        }
+
         /// <inheritdoc />
         /// <summary>
         /// Loads the AWS Systems Manager Parameters.