Allow consumers to choose BoundedChannelFullMode

examples/playground/Program.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information
 
 using System.Text.Json.Serialization;
+using System.Threading.Channels;
 using Elastic.Channels;
 using Elastic.Elasticsearch.Ephemeral;
 using Elastic.Ingest.Elasticsearch;
@@ -13,7 +14,7 @@
 var ctxs = new CancellationTokenSource();
 var parallelOpts = new ParallelOptions { MaxDegreeOfParallelism = Environment.ProcessorCount, CancellationToken = ctxs.Token };
 const int numDocs = 1_000_000;
-var bufferOptions = new BufferOptions { InboundBufferMaxSize = numDocs, OutboundBufferMaxSize = 10_000 };
+var bufferOptions = new BufferOptions { InboundBufferMaxSize = 1000, OutboundBufferMaxSize = 100, ExportMaxConcurrency = 1, BoundedChannelFullMode = BoundedChannelFullMode.Wait };
 var config = new EphemeralClusterConfiguration("8.13.0");
 using var cluster = new EphemeralCluster(config);
 using var channel = SetupElasticsearchChannel();
@@ -48,10 +49,15 @@ async Task PushToChannel(DataStreamChannel<EcsDocument> c)
 	if (c == null) throw new ArgumentNullException(nameof(c));
 
 	await c.BootstrapElasticsearchAsync(BootstrapMethod.Failure);
+
+	foreach (var i in Enumerable.Range(0, numDocs))
+		await DoChannelWrite(i, ctxs.Token);
+
+	/*
 	await Parallel.ForEachAsync(Enumerable.Range(0, numDocs), parallelOpts, async (i, ctx) =>
 	{
 		await DoChannelWrite(i, ctx);
-	});
+	});*/
 
 	async Task DoChannelWrite(int i, CancellationToken cancellationToken)
 	{

src/Elastic.Channels/BufferOptions.cs

@@ -4,6 +4,7 @@
 
 using System;
 using System.Threading;
+using System.Threading.Channels;
 
 namespace Elastic.Channels;
 
@@ -62,4 +63,13 @@ public class BufferOptions
 	/// Allows you to inject a <see cref="CountdownEvent"/> to wait for N number of buffers to flush.
 	/// </summary>
 	public CountdownEvent? WaitHandle { get; set; }
+
+	/// <summary>
+	/// <inheritdoc cref="BoundedChannelFullMode" path="summary" />
+	/// <para>Defaults to <see cref="BoundedChannelFullMode.Wait"/>, this will use more memory as overproducing will need to wait to enqueue data</para>
+	/// <para>Use <see cref="BoundedChannelFullMode.DropWrite"/> to minimize memory consumption at the expense of more  likely to drop data</para>
+	/// <para>You might need to tweak <see cref="InboundBufferMaxSize"/> and <see cref="OutboundBufferMaxSize"/> to ensure sufficient allocations are available </para>
+	/// <para>The defaults for both <see cref="InboundBufferMaxSize"/> adn <see cref="OutboundBufferMaxSize"/> are quite liberal already though.</para>
+	/// </summary>
+	public BoundedChannelFullMode BoundedChannelFullMode { get; set; } = BoundedChannelFullMode.Wait;
 }

src/Elastic.Channels/BufferedChannelBase.cs

@@ -113,10 +113,10 @@ protected BufferedChannelBase(TChannelOptions options, ICollection<IChannelCallb
 			AllowSynchronousContinuations = true,
 			// wait does not block it simply signals that Writer.TryWrite should return false and be retried
 			// DropWrite will make `TryWrite` always return true, which is not what we want.
-			FullMode = BoundedChannelFullMode.Wait
+			FullMode = options.BufferOptions.BoundedChannelFullMode
 		});
 		OutChannel = Channel.CreateBounded<IOutboundBuffer<TEvent>>(
-			new BoundedChannelOptions(maxOut)
+			new BoundedChannelOptions(_maxConcurrency * 2)
 			{
 				SingleReader = false,
 				SingleWriter = true,