Fix initial randomization of nodes (#4112)

This commit fixes the initial randomization of nodes in a StaticConnectionPool. Instead of calling the protected ctor,
the initialization logic has been pulled out into a separate method that is now called from the ctor that accepts a randomize parameter.

Fixes #4055

Author: russcam

src/Elasticsearch.Net/ConnectionPool/SniffingConnectionPool.cs

@@ -17,7 +17,7 @@ public SniffingConnectionPool(IEnumerable<Node> nodes, bool randomize = true, ID
 			: base(nodes, randomize, dateTimeProvider) { }
 
 		public SniffingConnectionPool(IEnumerable<Node> nodes, Func<Node, float> nodeScorer, IDateTimeProvider dateTimeProvider = null)
-			: base(nodes, nodeScorer, dateTimeProvider) { }
+			: base(nodes, nodeScorer, false, dateTimeProvider) { }
 
 		/// <inheritdoc />
 		public override IReadOnlyCollection<Node> Nodes

src/Elasticsearch.Net/ConnectionPool/StaticConnectionPool.cs

@@ -15,24 +15,29 @@ public StaticConnectionPool(IEnumerable<Uri> uris, bool randomize = true, IDateT
 			: this(uris.Select(uri => new Node(uri)), randomize, dateTimeProvider) { }
 
 		public StaticConnectionPool(IEnumerable<Node> nodes, bool randomize = true, IDateTimeProvider dateTimeProvider = null)
-			: this(nodes, null, dateTimeProvider) => Randomize = randomize;
+			: this(nodes, null, randomize, dateTimeProvider) { }
 
 		//this constructor is protected because nodeScorer only makes sense on subclasses that support reseeding
 		//otherwise just manually sort `nodes` before instantiating.
-		protected StaticConnectionPool(IEnumerable<Node> nodes, Func<Node, float> nodeScorer, IDateTimeProvider dateTimeProvider = null)
+		protected StaticConnectionPool(IEnumerable<Node> nodes, Func<Node, float> nodeScorer = null, bool randomize = true, IDateTimeProvider dateTimeProvider = null)
 		{
 			nodes.ThrowIfEmpty(nameof(nodes));
-			DateTimeProvider = dateTimeProvider ?? Net.DateTimeProvider.Default;
-
-			var nn = nodes.ToList();
-			var uris = nn.Select(n => n.Uri).ToList();
-			if (uris.Select(u => u.Scheme).Distinct().Count() > 1)
-				throw new ArgumentException("Trying to instantiate a connection pool with mixed URI Schemes");
-
-			UsingSsl = uris.Any(uri => uri.Scheme == "https");
+			string scheme = null;
+			foreach (var node in nodes)
+			{
+				if (scheme == null)
+				{
+					scheme = node.Uri.Scheme;
+					UsingSsl = scheme == "https";
+				}
+				else if (scheme != node.Uri.Scheme)
+					throw new ArgumentException("Trying to instantiate a connection pool with mixed URI Schemes");
+			}
 
+			DateTimeProvider = dateTimeProvider ?? Net.DateTimeProvider.Default;
+			Randomize = randomize;
 			_nodeScorer = nodeScorer;
-			InternalNodes = SortNodes(nn)
+			InternalNodes = SortNodes(nodes)
 				.DistinctBy(n => n.Uri)
 				.ToList();
 			LastUpdate = DateTimeProvider.Now();

src/Tests/Tests/ClientConcepts/ConnectionPooling/BuildingBlocks/ConnectionPooling.doc.cs

@@ -1,6 +1,8 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using System.Text;
+using System.Threading;
 using Elastic.Xunit.XunitPlumbing;
 using Elasticsearch.Net;
 using FluentAssertions;
@@ -214,6 +216,33 @@ [U] public void Static()
 			}
 		}
 
+		// hide
+		[U] public void RandomizedInitialNodes()
+		{
+			IEnumerable<StaticConnectionPool> CreatStaticConnectionPools()
+			{
+				Thread.Sleep(1);
+
+				var uris = new[]
+				{
+					new Uri("https://10.0.0.1:9200/"),
+					new Uri("https://10.0.0.2:9200/"),
+					new Uri("https://10.0.0.3:9200/")
+				};
+
+				yield return new StaticConnectionPool(uris);
+			}
+
+			// assertion works on the probability of seeing a Uri other than https://10.0.0.1:9200/
+			// as the first value over 50 runs, when randomized.
+			CreatStaticConnectionPools()
+				.Take(50)
+				.Select(p => p.CreateView().First().Uri.ToString())
+				.All(uri => uri == "https://10.0.0.1:9200/")
+				.Should()
+				.BeFalse();
+		}
+
 		/**[[sniffing-connection-pool]]
 		* ==== SniffingConnectionPool
 		*