Make UDP connection allocation test more like best practice code. (#1583)

Motivation:

There is at least a theoretical race to flush before close in prior version.
Having terrible code in the NIO repo is asking for someone to copy it.

Modifications:

flatMap the various parts of the client together which also ensures the
flush is complete before close is called.

Result:

Slightly nicer code, slightly fewer allocations.

IntegrationTests/tests_04_performance/test_01_resources/test_1000_udpconnections.swift

@@ -60,14 +60,13 @@ func run(identifier: String) {
     measure(identifier: identifier) {
         let buffer = ByteBuffer(integer: 1, as: UInt8.self)
         for _ in 0 ..< numberOfIterations {
-            let clientChannel = try! clientBootstrap.bind(to: localhostPickPort).wait()
-            defer {
-                try! clientChannel.close().wait()
-            }
-            
-            // Send a byte to make sure everything is really open.
-            let envelope = AddressedEnvelope<ByteBuffer>(remoteAddress: remoteAddress, data: buffer)
-            clientChannel.writeAndFlush(envelope, promise: nil)
+            try! clientBootstrap.bind(to: localhostPickPort).flatMap { clientChannel -> EventLoopFuture<Void> in 
+                // Send a byte to make sure everything is really open.
+                let envelope = AddressedEnvelope<ByteBuffer>(remoteAddress: remoteAddress, data: buffer)
+                return clientChannel.writeAndFlush(envelope).flatMap {
+                    clientChannel.close()
+                }
+            }.wait()
         }
         try! serverHandler.completionFuture.wait()
         return numberOfIterations

docker/docker-compose.1604.52.yaml

@@ -39,7 +39,7 @@ services:
       - MAX_ALLOCS_ALLOWED_1000_tcpbootstraps=4100
       - MAX_ALLOCS_ALLOWED_1000_tcpconnections=181010
       - MAX_ALLOCS_ALLOWED_1000_udpbootstraps=2000
-      - MAX_ALLOCS_ALLOWED_1000_udpconnections=105050
+      - MAX_ALLOCS_ALLOWED_1000_udpconnections=103050
       - MAX_ALLOCS_ALLOWED_1000_udp_reqs=16050
       - SANITIZER_ARG=--sanitize=thread
       - INTEGRATION_TESTS_ARG=-f tests_0[013-9]

docker/docker-compose.1604.53.yaml

@@ -38,7 +38,7 @@ services:
       - MAX_ALLOCS_ALLOWED_1000_tcpbootstraps=4100
       - MAX_ALLOCS_ALLOWED_1000_tcpconnections=180010
       - MAX_ALLOCS_ALLOWED_1000_udpbootstraps=2000
-      - MAX_ALLOCS_ALLOWED_1000_udpconnections=103050
+      - MAX_ALLOCS_ALLOWED_1000_udpconnections=102050
       - MAX_ALLOCS_ALLOWED_1000_udp_reqs=16050
       - SANITIZER_ARG=--sanitize=thread
 

docker/docker-compose.1804.50.yaml

@@ -39,7 +39,7 @@ services:
       - MAX_ALLOCS_ALLOWED_1000_tcpbootstraps=3100
       - MAX_ALLOCS_ALLOWED_1000_tcpconnections=189050
       - MAX_ALLOCS_ALLOWED_1000_udpbootstraps=2000
-      - MAX_ALLOCS_ALLOWED_1000_udpconnections=110050
+      - MAX_ALLOCS_ALLOWED_1000_udpconnections=108050
       - MAX_ALLOCS_ALLOWED_1000_udp_reqs=18050
 
 

docker/docker-compose.1804.51.yaml

@@ -39,7 +39,7 @@ services:
       - MAX_ALLOCS_ALLOWED_1000_tcpbootstraps=3100
       - MAX_ALLOCS_ALLOWED_1000_tcpconnections=181050
       - MAX_ALLOCS_ALLOWED_1000_udpbootstraps=2000
-      - MAX_ALLOCS_ALLOWED_1000_udpconnections=105050
+      - MAX_ALLOCS_ALLOWED_1000_udpconnections=103050
       - MAX_ALLOCS_ALLOWED_1000_udp_reqs=16050