Update documentation and code snippets

Author: ismaelhamed

docs/articles/streams/error-handling.md

@@ -96,6 +96,16 @@ when a WebSocket connection fails due to the HTTP server it's running on going d
 By using an exponential backoff, we avoid going into a tight reconnect look, which both gives the HTTP server some time
 to recover, and it avoids using needless resources on the client side.
 
+The various restart shapes mentioned all expect an `Akka.Stream.RestartSettings` which configures the restart behavior.
+
+Configurable parameters are:
+
+* `minBackoff` is the initial duration until the underlying stream is restarted
+* `maxBackoff` caps the exponential backoff
+* `randomFactor` allows addition of a random delay following backoff calculation
+* `maxRestarts` caps the total number of restarts
+* `maxRestartsWithin` sets a timeframe during which restarts are counted towards the same total for `maxRestarts`
+
 The following snippet shows how to create a backoff supervisor using `Akka.Streams.Dsl.RestartSource` 
 which will supervise the given `Source`. The `Source` in this case is a 
 `HttpResponseMessage`, produced by `HttpCLient`. If the stream fails or completes at any point, the request will

src/core/Akka.Docs.Tests/Streams/RestartDocTests.cs

@@ -8,12 +8,9 @@
 using System;
 using System.Linq;
 using System.Net.Http;
-using System.Threading.Tasks;
-using Akka;
 using Akka.Streams;
 using Akka.Streams.Dsl;
 using Akka.TestKit.Xunit2;
-using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
@@ -39,19 +36,21 @@ public void Restart_stages_should_demonstrate_a_restart_with_backoff_source()
             #region restart-with-backoff-source
             var httpClient = new HttpClient();
 
-            var restartSource = RestartSource.WithBackoff(() =>
-                {
-                    // Create a source from a task
-                    return Source.FromTask(
-                        httpClient.GetAsync("http://example.com/eventstream") // Make a single request
-                    )
-                    .Select(c => c.Content.ReadAsStringAsync())
-                    .Select(c => c.Result);
-                }, 
+            var settings = RestartSettings.Create(
                 minBackoff: TimeSpan.FromSeconds(3), 
                 maxBackoff: TimeSpan.FromSeconds(30),
                 randomFactor: 0.2 // adds 20% "noise" to vary the intervals slightly
-            );
+            ).WithMaxRestarts(20, TimeSpan.FromMinutes(5)); // limits the amount of restarts to 20 within 5 minutes
+
+            var restartSource = RestartSource.WithBackoff(() =>
+            {
+                // Create a source from a task
+                return Source.FromTask(
+                    httpClient.GetAsync("http://example.com/eventstream") // Make a single request
+                )
+                .Select(c => c.Content.ReadAsStringAsync())
+                .Select(c => c.Result);
+            }, settings);
             #endregion
 
             #region with-kill-switch