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POC# TCP Asynchronous connection actively refused with low CPU utilization
 

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  1. POC# TCP Asynchronous connection actively refused with low CPU utilization
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    <p>I have a C# TCP Asynchronous socket server.</p> <p>Testing locally, I can accept 5K connections over 35 seconds. I am running a quad core hyper threaded PC (8 threads) and the utilization is ~20-40% on each core. As the connections are accepted, the server asks the client for a bunch of data and then performas a bunch of database entries.</p> <p>I moved the server application and SQL database to a small database and medium server instance on Amazon AWS.</p> <p>The Amazon Medium server(EC2) is 1 virtual core and 2 ECU's. From what I can tell it only has 1 thread.(from performance monitor)</p> <p>If I try to connect 1000 clients over 35 seconds to the medium server. After ~650 connections i start to receive <em>Connect failed(b) No connection could be made because the target machine actively refused it</em>. </p> <p>Looking at performance monitor, I noticed that the CPU utilization is only ~10-15%. </p> <p>I am guessing that the core is not getting loaded because it is trying to handle a huge queue of connections, of small operations and does not provide enough load to increase CPU usage, since the server only has 1 virtual core.</p> <p>Does anyone have any experience with this, does my theory make sense? I am stuck at a hardware limitation? (need to bump up the server size?)</p> <p>If not, any ideas how to get more utilization and support more/quicker connections?</p> <p>Does anyone have experience with this?</p> <p>EDIT: </p> <p>I upgraded my instance on Amazon EC2 to the High CPU Extra Large instance.</p> <p>The Instance now has 8 cores and 20 ECU's. </p> <p>I am experiencing the same problem, I get No connection could be made because the target machine actively refused it after ~600 connections.</p>
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    1. USMausimo
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    1. COAre you handling the "asks the client for a bunch of data and then performas a bunch of database entries" part on a seperate thread? If not then you could be backlogged just from the db I/O time.
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      1. UStcarvin
    2. COLatency to the database may be the cause, try disabling the database access and just return dummy data, that may show you if it's the network/machine or the database.
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      1. POC# TCP Asynchronous connection actively refused with low CPU utilization
      1. USJoachim Isaksson
    3. COI will double check. As soon as I get the socket I call EndAccept() and get the client socket. I call BeginAccept() right away. Then I call waitForData() which is asych and when wait for data receives data from the client is does db processing on a separate thread. I am thinking the Medium instance from EC2 (1 virtual core and 2 ECU's) only has 1 thread. Which might be the problem. But my CPU utilization is very low on the core..
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