Add subscriber only benchmark and order test

Signed-off-by: Tomasz Pietrek <tomasz@nats.io>

Package.swift

@@ -23,7 +23,8 @@ let package = Package(
         .testTarget(name: "NatsSwiftTests", dependencies: ["NatsSwift"]),
 
         .executableTarget(name: "Benchmark", dependencies: ["NatsSwift"]),
-        .executableTarget(name: "BenchmarkPubSub", dependencies: ["NatsSwift"])
+        .executableTarget(name: "BenchmarkPubSub", dependencies: ["NatsSwift"]),
+        .executableTarget(name: "BenchmarkSub", dependencies: ["NatsSwift"])
     ]
 )
 

Sources/BenchmarkSub/main.swift

@@ -0,0 +1,44 @@
+import NatsSwift
+import Foundation
+
+let nats = Client(url: URL(string: "nats://localhost:4222")!)
+print("Connecting...")
+try! await nats.connect()
+print("Connected!")
+
+let data = "foo".data(using: .utf8)!
+// Warmup
+print("Starting benchmark...")
+print("Waiting for first message...")
+var now = DispatchTime.now()
+let numMsgs = 1_000_000
+let sub = try await nats.subscribe(to: "foo")
+var hm = HeaderMap()
+hm.append(try! HeaderName("foo"), HeaderValue("bar"))
+hm.append(try! HeaderName("foo"), HeaderValue("baz"))
+for i in 1...numMsgs {
+    let msg = await sub.next()
+    if i == 0 {
+        print("Received first message! Starting the timer")
+        now = DispatchTime.now()
+    }
+    guard let payload = msg?.payload else {
+        print("empty payload!")
+        continue
+    }
+    if String(data: payload, encoding: .utf8) != "\(i)" {
+        print("invalid payload; expected: \(i); got: \(String(data: payload, encoding: .utf8))")
+    }
+    guard let headers = msg?.headers else {
+        print("empty headers!")
+        continue
+    }
+    if i%1000 == 0 {
+        print("received \(i) msgs")
+    }
+}
+
+let elapsed = DispatchTime.now().uptimeNanoseconds - now.uptimeNanoseconds
+let msgsPerSec: Double = Double(numMsgs)/(Double(elapsed)/1_000_000_000)
+print("Elapsed: \(elapsed / 1000000)ms")
+print("\(msgsPerSec) msgs/s")