[example] Fix a few nitpicks

Lets clarify a few things better, and fix a couple of bugs:

- In one example a member wasn't initialized in the constructor.

- In another a task didn't set deadline when waiting for a signal.
  It led to a busy loop.

Follow up #21

Author: Gerold103

examples/iocore_01_tcp_hello/main.cpp

@@ -33,6 +33,9 @@ class MyClient final
 		mySock->Open({});
 		mg::aio::TCPSocketConnectParams connParams;
 		connParams.myEndpoint = mg::net::HostMakeLocalIPV4(aPort).ToString();
+
+		// From PostConnect() moment the socket runs in IOCore and its event-callbacks
+		// will start firing.
 		mySock->PostConnect(connParams, this);
 	}
 
@@ -58,6 +61,7 @@ class MyClient final
 	{
 		MG_LOG_INFO("Client.OnRecv", "%d: got response", myID);
 		MG_BOX_ASSERT(aStream.GetReadSize() > 0);
+		// Closure is asynchronous as well. You get OnClose() event when it is complete.
 		mySock->PostClose();
 	}
 
@@ -74,6 +78,11 @@ class MyClient final
 	void
 	OnClose() final
 	{
+		// Here the socket should be deleted, ideally. But also you can reopen it and
+		// reuse. The socket will stay valid anyway. Moreover, the socket still can be
+		// used for deadlines and wakeups, even when it is closed. This allows to
+		// implement automatic reconnect with a fallback period like 1 second or so.
+
 		MG_LOG_INFO("Client.OnClose", "%d", myID);
 		// Try to always have all deletions in a single place. And the only suitable place
 		// is on-close. This is the only place where you can safely assume that the socket
@@ -185,6 +194,8 @@ class MyServer final
 	Start()
 	{
 		mg::box::Error::Ptr err;
+		// From Listen() moment the server's socket runs in IOCore and its event-callbacks
+		// start firing.
 		bool ok = myServer->Listen(mg::net::SocketMaxBacklog(), this, err);
 		MG_BOX_ASSERT(ok);
 	}
@@ -209,6 +220,8 @@ class MyServer final
 	void
 	OnClose() final
 	{
+		// The server will not run anymore after this event. It is still valid, but won't
+		// fire any events.
 		MG_LOG_INFO("Server.OnClose", "");
 	}
 

examples/iocore_03_pipeline/main.cpp

@@ -77,6 +77,13 @@ class CalcClient final
 		std::function<void(int64_t)>&& aOnComplete)
 	{
 		MG_LOG_INFO("Client.Submit", "new request");
+		// This function can be called by any thread in our code. Not only by IOCore
+		// worker serving this client's socket right now. Need to be careful with thread
+		// safety here.
+		//
+		// The solution we can do is have a thread-safe queue of requests submitted to the
+		// client. When the queue gets populated, we wakeup the client to pop the queue
+		// and handle the requests.
 		CalcRequest* req = new CalcRequest();
 		req->myOp = aOp;
 		req->myArg1 = aArg1;
@@ -119,12 +126,14 @@ class CalcClient final
 	{
 		CalcRequest* tail;
 		CalcRequest* head = myFrontQueue.PopAll(tail);
+		// Check if spurious wakeup.
 		if (head == nullptr)
 			return;
 
-		// Save the requests for later response handling.
+		// Move the requests from the thread-safe front queue to the local plain simple
+		// list. For later response handling.
 		myQueue.Append(head, tail);
-		// Send requests in bulk.
+		// Send requests in bulk, in one stream of bytes.
 		mg::net::BufferStream data;
 		while (head != nullptr)
 		{
@@ -181,9 +190,14 @@ class CalcClient final
 	}
 
 	mg::aio::TCPSocket* mySock;
-	// Queue of sent requests waiting for their responses.
+
+	// Queue of sent requests waiting for their responses. It is not thread-safe, just a
+	// normal list. But it is only accessed inside client's socket context. Hence never is
+	// touched by more than one thread. No need for a mutex.
 	mg::box::ForwardList<CalcRequest> myQueue;
-	// Queue if requests submitted by other threads. Not yet sent to the network.
+
+	// Queue if requests submitted by other threads. Not yet sent to the network. It is
+	// thread-safe.
 	mg::box::MultiProducerQueueIntrusive<CalcRequest> myFrontQueue;
 };
 
@@ -360,7 +374,8 @@ class MyRequest
 			aSelf->myTask.PostSignal();
 		});
 		// Wait for the signal in a yielding loop, to handle potential spurious wakeups.
-		while (!co_await aSelf->myTask.AsyncReceiveSignal());
+		while (!co_await aSelf->myTask.AsyncReceiveSignal())
+			aSelf->myTask.SetWait();
 		// 
 		MG_LOG_INFO("MyRequest.Execute", "%d: got response %lld", myID, (long long)res);
 
@@ -371,7 +386,8 @@ class MyRequest
 			res = aRes;
 			aSelf->myTask.PostSignal();
 		});
-		while (!co_await aSelf->myTask.AsyncReceiveSignal());
+		while (!co_await aSelf->myTask.AsyncReceiveSignal())
+			aSelf->myTask.SetWait();
 		MG_LOG_INFO("MyRequest.Execute", "%d: got response %lld", myID, (long long)res);
 
 		// 'delete this' + co_return wouldn't work here. Because deletion of the self

examples/iocore_04_tcp_periodic/main.cpp

@@ -135,6 +135,7 @@ class MyPeer final
 		mg::net::Socket aSock)
 		: myID(aID)
 		, mySock(new mg::aio::TCPSocket(aCore))
+		, mySendSize(0)
 		, mySendDeadline(0)
 	{
 		mySock->Open({});
@@ -203,11 +204,12 @@ class MyPeer final
 		if (mySendSize != 0)
 			return;
 
-		// Finally all is sent. Send the next one in 1 second.
+		// Finally all is sent. Send the next one in 1 second. For that need to actually
+		// do socket->SetDeadline(), but we will do it in OnEvent().
 		mySendDeadline = mg::box::GetMilliseconds() + 1000;
-		// OnEvent() is going to be executed again ASAP, but this is ok. It is simpler
-		// for us to implement all the logic in one function. It will handle this
-		// reschedule a spurious wakeup.
+		// Reschedule() basically means 'reschedule the socket right away'. Same as saying
+		// SetDeadline(0). OnEvent() is going to be executed again ASAP. This way it is
+		// simpler for us to implement all the logic in one function.
 		mySock->Reschedule();
 	}