Update PCAP example to be async

Package.swift

@@ -409,7 +409,6 @@ extension Target {
       .nioCore,
       .nioPosix,
       .nioExtras,
-      .logging,
       .argumentParser,
     ],
     path: "Sources/Examples/PacketCapture",

Sources/Examples/PacketCapture/Empty.swift

@@ -0,0 +1,17 @@
+/*
+ * Copyright 2022, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// This file exists to workaround https://github.com/apple/swift/issues/55127.

Sources/Examples/PacketCapture/PacketCapture.swift

@@ -0,0 +1,94 @@
+/*
+ * Copyright 2020, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#if compiler(>=5.6)
+import ArgumentParser
+import EchoModel
+import GRPC
+import NIOCore
+import NIOExtras
+import NIOPosix
+
+@main
+@available(macOS 10.15, *)
+struct PCAP: AsyncParsableCommand {
+  @Option(help: "The port to connect to")
+  var port = 1234
+
+  func run() async throws {
+    // Create an `EventLoopGroup`.
+    let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+    defer {
+      try! group.syncShutdownGracefully()
+    }
+
+    // The filename for the .pcap file to write to.
+    let path = "packet-capture-example.pcap"
+    let fileSink = try NIOWritePCAPHandler.SynchronizedFileSink.fileSinkWritingToFile(
+      path: path
+    ) { error in
+      print("Failed to write with error '\(error)' for path '\(path)'")
+    }
+
+    // Ensure that we close the file sink when we're done with it.
+    defer {
+      try! fileSink.syncClose()
+    }
+
+    let channel = try GRPCChannelPool.with(
+      target: .host("localhost", port: self.port),
+      transportSecurity: .plaintext,
+      eventLoopGroup: group
+    ) {
+      $0.debugChannelInitializer = { channel in
+        // Create the PCAP handler and add it to the start of the channel pipeline. If this example
+        // used TLS we would likely want to place the handler in a different position in the
+        // pipeline so that the captured packets in the trace would not be encrypted.
+        let writePCAPHandler = NIOWritePCAPHandler(mode: .client, fileSink: fileSink.write(buffer:))
+        return channel.eventLoop.makeCompletedFuture(Result {
+          try channel.pipeline.syncOperations.addHandler(writePCAPHandler, position: .first)
+        })
+      }
+    }
+
+    // Create a client.
+    let echo = Echo_EchoAsyncClient(channel: channel)
+
+    let messages = ["foo", "bar", "baz", "thud", "grunt", "gorp"].map { text in
+      Echo_EchoRequest.with { $0.text = text }
+    }
+
+    do {
+      for try await response in echo.update(messages) {
+        print("Received response '\(response.text)'")
+      }
+      print("RPC completed successfully")
+    } catch {
+      print("RPC failed with error '\(error)'")
+    }
+
+    print("Try opening '\(path)' in Wireshark or with 'tcpdump -r \(path)'")
+
+    try await echo.channel.close().get()
+  }
+}
+#else
+@main
+enum PCAP {
+  static func main() {
+    print("This example requires Swift >= 5.6")
+  }
+}
+#endif // compiler(>=5.6)

Sources/Examples/PacketCapture/README.md

@@ -26,17 +26,7 @@ In a separate shell run:
 $ swift run PacketCapture
 ```
 
-Some logs should be emitted similar to below, including the path of the
-*.pcap* file:
-
-```sh
-2020-07-24T10:48:50+0100 info gRPC PCAP Demo : Creating fileSink for path './channel-ObjectIdentifier(0x00007f8a25604c40).pcap'
-2020-07-24T10:48:50+0100 info gRPC PCAP Demo : ✅ Successfully created fileSink for path './channel-ObjectIdentifier(0x00007f8a25604c40).pcap'
-...
-2020-07-24T10:48:50+0100 info gRPC PCAP Demo : ✅ RPC completed successfully
-...
-2020-07-24T10:48:50+0100 info gRPC PCAP Demo : Done!
-```
+The pcap file will be written to 'packet-capture-example.pcap'.
 
 The *.pcap* file can be opened with either: [Wireshark][wireshark] or `tcpdump
 -r <PCAP_FILE>`.