C＃ASP .NET：如何将代码转换为更多并发？

Question

I'm making auction web application using c# asp .net.

My web application got 2 methods that I must synchronize, can't let them invoke at the same time, because they could make conflicts in my database, so I've used only lock(object) code blocks to protect these 2 methods.

I need to make this more concurrent, because this solution locking full methods makes application very slow at some moments.

I've used SignalR library to send notifications between server and clients, and MyRegistry class to make timer that ticks every second and send notifications to online clients.

In my opinion lines of code with access to database, and signalR methods for sending notifications are those lines that maybe slows system.

Here's my object that's only used as a lock object:

public static class mutex
{
    public static string lockObject = "MutEx";
}

My Hub (SignalR)

public class MyHub : Hub
{

    private static Dictionary<string, string> hashUsersConnIds = new Dictionary<string, string>(512);
    private IEP_Model db = new IEP_Model();
    public readonly log4net.ILog logger = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

    // Server Hub
    public void Send(long IDAuc, string lastBidderEmail)
    {

        AspNetUser user = db.AspNetUsers.SingleOrDefault(r => r.Email == lastBidderEmail);

        lock (mutex.lockObject)
        {

            auction auction = db.auctions.SingleOrDefault(a => a.IDAuc == IDAuc);
            long productNewPrice = auction.price + auction.increment + 1;

            // User can bid!
            if ((productNewPrice <= user.TokenNumber))
            {
                long newBidderCount = user.TokenNumber - productNewPrice;
                user.TokenNumber = newBidderCount;
                db.Entry(user).State = EntityState.Modified;

                bid newBid = new bid();
                newBid.Id = user.Id;
                newBid.IDAuc = auction.IDAuc;
                newBid.bidTime = DateTime.Now;
                newBid.tokens = productNewPrice;
                db.bids.Add(newBid);

                // Return tokens to previous client
                var previousBidder =    from o
                                        in db.UserAuctionInvested
                                        where o.AuctionId == auction.IDAuc
                                        select o.UserId;

                string previousBidderID = previousBidder.SingleOrDefault();
                AspNetUser previous = db.AspNetUsers.Find(previousBidderID);

                // Previous bidder exists
                if (previousBidderID != null)
                {
                    long tokensToReturn = (long)db.UserAuctionInvested.Where(u => u.AuctionId == auction.IDAuc && u.UserId == previousBidderID).SingleOrDefault().TokenInvested;
                    long newTokenCount = previous.TokenNumber + tokensToReturn;
                    previous.TokenNumber = newTokenCount;

                    // PUSH NOTIFICATION: SET PREVIOUS CLIENT'S TOKEN NUMBER
                    var clientSelector = "token" + previous.Email.Replace("@", "_");
                    var clientAlertSelector = "alertToken" + previous.Email.Replace("@", "_");
                    var warningAlertSelector = "warning" + previous.Email.Replace("@", "_");
                    // PREVIOUS CLIENT IS ONLINE
                    if (hashUsersConnIds.ContainsKey(previous.Email) && previous.Email != lastBidderEmail)
                    {
                        Clients.Client(hashUsersConnIds[previous.Email]).setTokenNumber(clientSelector, newTokenCount, clientAlertSelector, warningAlertSelector, auction.product_name);
                    }
                    // PUSH NOTIFICATION: CURRENT CLIENT (LAST BIDDER) NEW TOKEN COUNT
                    clientSelector = "token" + lastBidderEmail.Replace("@", "_");
                    clientAlertSelector = "alertToken" + lastBidderEmail.Replace("@", "_");
                    warningAlertSelector = "warning" + previous.Email.Replace("@", "_");
                    if (previous.Email != lastBidderEmail && hashUsersConnIds.ContainsKey(lastBidderEmail)) {
                        Clients.Client(hashUsersConnIds[lastBidderEmail]).setTokenNumber(clientSelector, newBidderCount, clientAlertSelector, "x", "x");
                    }
                    db.Entry(previous).State = EntityState.Modified;
                    UserAuctionInvested uaiPrevious = db.UserAuctionInvested.Find(previousBidderID, auction.IDAuc);
                    db.UserAuctionInvested.Remove(uaiPrevious);
                } 
                // This client is first bidder
                else
                {
                    var clientSelector = "token" + lastBidderEmail.Replace("@", "_");
                    var clientAlertSelector = "alertToken" + lastBidderEmail.Replace("@", "_");
                    // PUSH NOTIFICATION: CURRENT CLIENT (LAST BIDDER) NEW TOKEN COUNT
                    if (hashUsersConnIds.ContainsKey(lastBidderEmail))
                    {
                        Clients.Client(hashUsersConnIds[lastBidderEmail]).setTokenNumber(clientSelector, newBidderCount, clientAlertSelector, "x", "x");
                    }
                }

                // Creating new bid userAuctionInvested -> [dbo].[userAuctionInvested] (user, auction, tokenNo)
                UserAuctionInvested uai = new UserAuctionInvested();
                uai.AuctionId = auction.IDAuc;
                uai.UserId = user.Id;
                uai.TokenInvested = productNewPrice;
                db.UserAuctionInvested.Add(uai);

                // Update Auction
                auction.increment += 1;
                auction.lastbidder = lastBidderEmail;

                // Seconds to end of auction
                var secondsDifference = ((DateTime)auction.close_date_time - DateTime.Now).TotalSeconds;
                if (secondsDifference <= 10)
                {
                    DateTime oldCloseDateTime = (DateTime)auction.close_date_time;
                    DateTime newCloseDateTime = oldCloseDateTime.AddSeconds(10);
                    auction.close_date_time = newCloseDateTime;
                    auction.duration += 10;
                }

                db.Entry(auction).State = EntityState.Modified;
                string remainingToEnd = ((DateTime)auction.close_date_time - DateTime.Now).ToString(@"dd\:hh\:mm\:ss");
                Clients.All.clientBidsUpdate(IDAuc, auction.state, remainingToEnd, lastBidderEmail, auction.price + auction.increment, "false");
                // Update details auction page // clientWarningSelector, auctionNameWarning
                Clients.All.auctionDetailsUpdate(IDAuc, lastBidderEmail, auction.price + auction.increment, newBid.bidTime.ToString(@"dd\:hh\:mm\:ss"), "Open");
                db.SaveChanges();
                return;

            }
            // Client was previous bidder needs to pay +1 on actual price
            else if (auction.lastbidder == user.Email)
            {
                if (user.TokenNumber > 0) // can place next bid
                {
                    user.TokenNumber = user.TokenNumber - 1;
                    db.Entry(user).State = EntityState.Modified;
                    bid newBid = new bid();
                    newBid.Id = user.Id;
                    newBid.IDAuc = auction.IDAuc;
                    newBid.bidTime = DateTime.Now;
                    newBid.tokens = auction.price + auction.increment + 1;
                    db.bids.Add(newBid);
                    if (hashUsersConnIds.ContainsKey(lastBidderEmail))
                    {
                        var clientSelector = "token" + lastBidderEmail.Replace("@", "_");
                        var clientAlertSelector = "alertToken" + lastBidderEmail.Replace("@", "_");
                        var clientWarningSelector = "warning" + lastBidderEmail.Replace("@", "_");
                        Clients.Client(hashUsersConnIds[lastBidderEmail]).setTokenNumber(clientSelector, user.TokenNumber, clientAlertSelector, "x", "x");
                    }
                    // Updating userAuctionInvested -> [dbo].[userAuctionInvested] (user, auction, tokenNo)
                    UserAuctionInvested uai = db.UserAuctionInvested.Where(u => u.AuctionId == auction.IDAuc && u.UserId == user.Id).SingleOrDefault();
                    uai.TokenInvested += 1;
                    db.Entry(uai).State = EntityState.Modified;
                    // Update Auction
                    auction.increment += 1;
                    // Seconds to end of auction
                    var secondsDifference = ((DateTime)auction.close_date_time - DateTime.Now).TotalSeconds;
                    if (secondsDifference <= 10)
                    {
                        DateTime oldCloseDateTime = (DateTime)auction.close_date_time;
                        DateTime newCloseDateTime = oldCloseDateTime.AddSeconds(10);
                        auction.close_date_time = newCloseDateTime;
                        auction.duration += 10;
                    }
                    db.Entry(auction).State = EntityState.Modified;
                    string remainingToEnd = ((DateTime)auction.close_date_time - DateTime.Now).ToString(@"dd\:hh\:mm\:ss");
                    Clients.All.clientBidsUpdate(IDAuc, auction.state, remainingToEnd, lastBidderEmail, auction.price + auction.increment, "false");
                    Clients.All.auctionDetailsUpdate(IDAuc, lastBidderEmail, auction.price + auction.increment, newBid.bidTime.ToString(@"dd\:hh\:mm\:ss"), "Open");

                    db.SaveChanges();
                    return;
                }
            }
            // No tokens - Warn user!
            string remaining = ((DateTime)auction.close_date_time - DateTime.Now).ToString(@"dd\:hh\:mm\:ss");
            Clients.All.clientBidsUpdate(IDAuc, auction.state, remaining, lastBidderEmail, auction.price + auction.increment, "true");
        }
    }

    // Registring client
    public void registerConId(string email)
    {
        hashUsersConnIds[email] = Context.ConnectionId;
    }

}

And finally here's my Registry class that acts like a Timer on my web application, ticks every one seconds and updates database:

public class MyRegistry : Registry
{

    public readonly log4net.ILog logger = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

    public MyRegistry()
    {

        Schedule(() =>
        {

            // Check if some auction is over each 1 sec
            lock (mutex.lockObject)
            {

                IEP_Model db = new IEP_Model();
                var hubContext = GlobalHost.ConnectionManager.GetHubContext<MyHub>();

                var auctions = from o 
                               in db.auctions
                               where o.state == "Open"
                               select o;

                var auctionsList = auctions.ToList();

                foreach (var auction in auctionsList)
                {

                    DateTime now = DateTime.Now;
                    DateTime end = (DateTime)auction.close_date_time;

                    // Time is up! Auction is "Expired" or "Sold"
                    if (now >= end)
                    {
                        var edited = db.auctions.Find(auction.IDAuc);
                        // NO Winner
                        if (edited.increment == 0)
                        {
                            edited.state = "Expired";
                            db.Entry(edited).State = EntityState.Modified;
                            TimeSpan timeEnd = new TimeSpan(0);
                            string newDurationExpired = timeEnd.ToString(@"dd\:hh\:mm\:ss");

                            hubContext.Clients.All.timerUpdate(auction.IDAuc, edited.state, newDurationExpired, " - ", edited.price, "false", "odd", "true");
                            db.SaveChanges();
                        }
                        // YES Winner
                        else
                        {
                            edited.state = "Sold";
                            db.Entry(edited).State = EntityState.Modified;
                            db.SaveChanges();

                            // Refresh client
                            long soldPrice = edited.price + edited.increment;
                            TimeSpan timeEnd = new TimeSpan(0);
                            string newDurationSold = timeEnd.ToString(@"dd\:hh\:mm\:ss");
                            hubContext.Clients.All.timerUpdate(auction.IDAuc, edited.state, newDurationSold, edited.lastbidder, soldPrice, "false", "odd", "true");

                            // Return tokens to non-winners
                            string winnerId = db.AspNetUsers.Where(a => a.Email == edited.lastbidder).SingleOrDefault().Id;
                            //var bids = db.bids.Where(b => b.IDAuc == auction.IDAuc && b.Id != winnerId).ToList();
                            var userInvested = db.UserAuctionInvested.Where(i => i.AuctionId == auction.IDAuc);

                            foreach (var item in userInvested.ToList())
                            {
                                if (item.UserId != winnerId) // Not winner - return money
                                {
                                    AspNetUser FetchUser = db.AspNetUsers.Find(item.UserId);
                                    FetchUser.TokenNumber += (long)item.TokenInvested;
                                    db.Entry(FetchUser).State = EntityState.Modified;
                                }
                                db.UserAuctionInvested.Remove(item);
                            }

                            db.SaveChanges();

                        }
                    }

                    // Update auction - is still active
                    long actualPrice = auction.price + auction.increment;
                    TimeSpan difference = end.Subtract(now);
                    string newDuration = difference.ToString(@"dd\:hh\:mm\:ss");

                    string lastTenSeconds__ = "false";
                    string numberOddEven__ = "odd";
                    string end__ = "false";
                    if (difference.TotalSeconds <= 10)
                    {
                        lastTenSeconds__ = "true";
                        if (difference.TotalSeconds <= 1)
                        {
                            end__ = "true";
                        }
                        if ((int)Math.Ceiling(difference.TotalSeconds) % 2 == 0) 
                        {
                            numberOddEven__ = "even";
                        }
                    }
                    hubContext.Clients.All.timerUpdate(auction.IDAuc, auction.state, newDuration, auction.lastbidder, actualPrice, lastTenSeconds__, numberOddEven__, end__);


                }

            }
        }).ToRunNow().AndEvery(1).Seconds();
    }

}

I'd need a help to get an idea how could I transform a bit this code, so I could make it more concurrent. I've seen that c# also supports Monitors, wondering if I would benefit from using it?

Answer 1

Looking at your code, the first thing I would suggest is reducing your db calls to be a few as possible, front load your current auctions, logged in users, and anything else that is fairly static, and either cache them using something like Redis (in memory caching tool) or in dictionaries. (for the binary search performance)

Secondly I would suggest a multi-threaded process that uses a ConcurrentDictionary for your live auction tracking, it has the speed you are looking for, and you can wrap it on a BlockingCollection if you need the thread to wait for changes. That way you do not have to use locks. Also you can off load persisting the data to storage using a Queue.

If you have Pluralsight I would suggest this course:

https://app.pluralsight.com/library/courses/csharp-concurrent-collections/table-of-contents