stablise 1000 TCP connections alloc test (#1566)

Motivation:

The 1000 TCP connections allocation counter test did way too many thread
crosses and other things that allocated for unrelated reasons.

Modifications:

Remove those.

Result:

Much more stable

IntegrationTests/tests_04_performance/test_01_resources/test_1000_tcpconnections.swift

@@ -23,14 +23,23 @@ fileprivate final class ReceiveAndCloseHandler: ChannelInboundHandler {
         precondition(byteBuffer.readableBytes == 1)
         context.channel.close(promise: nil)
     }
+
+    func errorCaught(context: ChannelHandlerContext, error: Error) {
+        fatalError("unexpected \(error)")
+    }
 }
 
 func run(identifier: String) {
+    let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+    defer {
+        try! group.syncShutdownGracefully()
+    }
+
     let serverChannel = try! ServerBootstrap(group: group)
             .serverChannelOption(ChannelOptions.socketOption(.so_reuseaddr), value: 1)
             .childChannelInitializer { channel in
                 channel.pipeline.addHandler(ReceiveAndCloseHandler())
-            }.bind(to: localhostPickPort).wait()
+            }.bind(host: "127.0.0.1", port: 0).wait()
     defer {
         try! serverChannel.close().wait()
     }
@@ -39,16 +48,19 @@ func run(identifier: String) {
 
     measure(identifier: identifier) {
         let numberOfIterations = 1000
+        let serverAddress = serverChannel.localAddress!
+        let buffer = ByteBuffer(integer: 1, as: UInt8.self)
+        let el = group.next()
 
         for _ in 0 ..< numberOfIterations {
-            let clientChannel = try! clientBootstrap.connect(to: serverChannel.localAddress!)
+            try! el.flatSubmit {
-                    .wait()
+                clientBootstrap.connect(to: serverAddress).flatMap { clientChannel in
                     // Send a byte to make sure everything is really open.
-            var buffer = clientChannel.allocator.buffer(capacity: 1)
+                    clientChannel.writeAndFlush(buffer).flatMap {
-            buffer.writeInteger(1, as: UInt8.self)
+                        clientChannel.closeFuture
-            clientChannel.writeAndFlush(NIOAny(buffer), promise: nil)
+                    }
-            // Wait for the close to come from the server side.
+                }
-            try! clientChannel.closeFuture.wait()
+            }.wait()
         }
         return numberOfIterations
     }

docker/docker-compose.1604.52.yaml

@@ -37,7 +37,7 @@ services:
       - MAX_ALLOCS_ALLOWED_udp_1000_reqs_1_conn=16250
       - MAX_ALLOCS_ALLOWED_udp_1_reqs_1000_conn=226050
       - MAX_ALLOCS_ALLOWED_1000_tcpbootstraps=4100
-      - MAX_ALLOCS_ALLOWED_1000_tcpconnections=196800
+      - MAX_ALLOCS_ALLOWED_1000_tcpconnections=178010
       - MAX_ALLOCS_ALLOWED_1000_udpbootstraps=4000
       - MAX_ALLOCS_ALLOWED_1000_udpconnections=115050
       - MAX_ALLOCS_ALLOWED_1000_udp_reqs=16050

docker/docker-compose.1604.53.yaml

@@ -36,7 +36,7 @@ services:
       - MAX_ALLOCS_ALLOWED_udp_1000_reqs_1_conn=16250
       - MAX_ALLOCS_ALLOWED_udp_1_reqs_1000_conn=226050
       - MAX_ALLOCS_ALLOWED_1000_tcpbootstraps=4100
-      - MAX_ALLOCS_ALLOWED_1000_tcpconnections=194050
+      - MAX_ALLOCS_ALLOWED_1000_tcpconnections=177010
       - MAX_ALLOCS_ALLOWED_1000_udpbootstraps=4000
       - MAX_ALLOCS_ALLOWED_1000_udpconnections=113050
       - MAX_ALLOCS_ALLOWED_1000_udp_reqs=16050

docker/docker-compose.1804.50.yaml

@@ -37,7 +37,7 @@ services:
       - MAX_ALLOCS_ALLOWED_udp_1000_reqs_1_conn=18250
       - MAX_ALLOCS_ALLOWED_udp_1_reqs_1000_conn=235050
       - MAX_ALLOCS_ALLOWED_1000_tcpbootstraps=3100
-      - MAX_ALLOCS_ALLOWED_1000_tcpconnections=205800
+      - MAX_ALLOCS_ALLOWED_1000_tcpconnections=186050
       - MAX_ALLOCS_ALLOWED_1000_udpbootstraps=3000
       - MAX_ALLOCS_ALLOWED_1000_udpconnections=120050
       - MAX_ALLOCS_ALLOWED_1000_udp_reqs=18050

docker/docker-compose.1804.51.yaml

@@ -37,7 +37,7 @@ services:
       - MAX_ALLOCS_ALLOWED_udp_1000_reqs_1_conn=16250
       - MAX_ALLOCS_ALLOWED_udp_1_reqs_1000_conn=224050
       - MAX_ALLOCS_ALLOWED_1000_tcpbootstraps=3100
-      - MAX_ALLOCS_ALLOWED_1000_tcpconnections=196800
+      - MAX_ALLOCS_ALLOWED_1000_tcpconnections=178050
       - MAX_ALLOCS_ALLOWED_1000_udpbootstraps=3000
       - MAX_ALLOCS_ALLOWED_1000_udpconnections=115050
       - MAX_ALLOCS_ALLOWED_1000_udp_reqs=16050