WCF timeout exception detailed investigation

Question

We have an application that has a WCF service    svc  running on IIS7 and various clients querying the service  The server is running Win 2008 Server  The clients are running either Windows 2008 Server or Windows 2003 server  I am getting the following exception  which I have seen can in fact be related to a large number of potential WCF issues     System TimeoutException  The request channel timed out while waiting for a reply after 00 00 59 9320000  Increase the timeout value passed to the call to Request or increase the SendTimeout value on the Binding  The time allotted to this operation may have been a portion of a longer timeout  --- gt  System TimeoutException  The HTTP request to  http   www domain com WebServices myservice svc gzip  has exceeded the allotted timeout of 00 01 00  The time allotted to this operation may have been a portion of a longer timeout     I have increased the timeout to 30min and the error still occurred  This tells me that something else is at play  because the quantity of data could never take 30min to upload or download    The error comes and goes  At the moment  it is more frequent  It does not seem to matter if I have 3 clients running simultaneously or 100  it still occurs once in a while  Most of the time  there are no timeouts but I still get a few per hour  The error comes from any of the methods that are invoked  One of these methods does not have parameters and returns a bit of data  Another takes in lots of data as a parameter but executes asynchronously  The errors always originate from the client and never reference any code on the server in the stack trace  It always ends with     at System Net HttpWebRequest GetResponse     at System ServiceModel Channels HttpChannelFactory HttpRequestChannel HttpChannelRequest WaitForReply TimeSpan timeout    On the server   I ve tried  and currently have  the following binding settings   maxBufferSize  2147483647  maxReceivedMessageSize  2147483647  maxBufferPoolSize  2147483647    It does not seem to have an impact    I ve tried  and currently have  the following throttling settings    lt serviceThrottling maxConcurrentCalls  1500    maxConcurrentInstances  1500     maxConcurrentSessions  1500   gt    It does not seem to have an impact    I currently have the following settings for the WCF service     ServiceBehavior InstanceContextMode   InstanceContextMode Single  ConcurrencyMode   ConcurrencyMode Single     I ran with ConcurrencyMode Multiple for a while  and the error still occurred    I ve tried restarting IIS  restarting my underlying SQL Server  restarting the machine  All of these don t seem to have an impact    I ve tried disabling the Windows firewall  It does not seem to have an impact    On the client  I have these settings    maxReceivedMessageSize  2147483647    lt system net gt       lt connectionManagement gt       lt add address     maxconnection  16   gt   lt  connectionManagement gt    lt  system net gt    My client closes its connections   var client   new MyClient     try       return client GetConfigurationOptions      finally       client Close        I have changed the registry settings to allow more outgoing connections   MaxConnectionsPerServer 24  MaxConnectionsPer1 0Server 32    I have now just recently tried SvcTraceViewer exe  I managed to catch one exception on the client end  I see that its duration is 1 minute  Looking at the server side trace  I can see that the server is not aware of this exception  The maximum duration I can see is 10 seconds    I have looked at active database connections using exec sp who on the server  I only have a few  2-3   I have looked at TCP connections from one client using TCPview  It usually is around 2-3 and I have seen up to 5 or 6    Simply put  I am stumped  I have tried everything I could find  and must be missing something very simple that a WCF expert would be able to see  It is my gut feeling that something is blocking my clients at the low-level  TCP   before the server actually receives the message and or that something is queuing the messages at the server level and never letting them process    If you have any performance counters I should look at  please let me know   please indicate what values are bad  as some of these counters are hard to decypher   Also  how could I log the WCF message size  Finally  are there any tools our there that would allow me to test how many connections I can establish between my client and server  independently from my application   Thanks for your time   Extra information added June 20th   My WCF application does something similar to the following   while  true       Step1GetConfigurationSettingsFromServerViaWCF       can change between calls    Step2GetWorkUnitFromServerViaWCF       DoWorkLocally       takes 5-15minutes      Step3SendBackResultsToServerViaWCF        Using WireShark  I did see that when the error occurs  I have a five TCP retransmissions followed by a TCP reset later on  My guess is the RST is coming from WCF killing the connection  The exception report I get is from Step3 timing out     I discovered this by looking at the tcp stream  tcp stream eq 192   I then expanded my filter to  tcp stream eq 192 and http and http request method eq POST  and saw 6 POSTs during this stream  This seemed odd  so I checked with another stream such as tcp stream eq 100  I had three POSTs  which seems a bit more normal because I am doing three calls  However  I do close my connection after every WCF call  so I would have expected one call per stream  but I don t know much about TCP     Investigating a bit more  I dumped the http packet load to disk to look at what these six calls where   1  Step3 2  Step1 3  Step2 4  Step3 - corrupted 5  Step1 6  Step2   My guess is two concurrent clients are using the same connection  that is why I saw duplicates  However  I still have a few more issues that I can t comprehend   a  Why is the packet corrupted  Random network fluke - maybe  The load is gzipped using this sample code  http   msdn microsoft com en-us library ms751458 aspx - Could the code be buggy once in a while when used concurrently  I should test without the gzip library    b  Why would I see step 1  amp  step 2 running AFTER the corrupted operation timed out  It seems to me as if these operations should not have occurred  Maybe I am not looking at the right stream because my understanding of TCP is flawed  I have other streams that occur at the same time  I should investigate other streams - a quick glance at streams 190-194 show that the Step3 POST have proper payload data  not corrupted   Pushing me to look at the gzip library again

User · Answer

I m not a WCF expert but I m wondering if you aren t running into a DDOS protection on IIS  I know from experience that if you run a bunch of simultaneous connections from a single client to a server at some point the server stops responding to the calls as it suspects a DDOS attack  It will also hold the connections open until they time-out in order to slow the client down in his attacks   Multiple connection coming from different machines IP s should not be a problem however   There s more info in this MSDN post   http   msdn microsoft com en-us library bb463275 aspx  Check out the MaxConcurrentSession sproperty

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You will also receive this error if you are passing an object back to the client that contains a property of type enum that is not set by default and that enum does not have a value that maps to 0  i e enum MyEnum  a 1  b 2

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If you havn t tried it already - encapsulate your Server-side WCF Operations in try finally blocks  and add logging to ensure they are actually returning    If those show that the Operations are completing  then my next step would be to go to a lower level  and look at the actual transport layer    Wireshark or another similar packet capturing tool can be quite helpful at this point  I m assuming this is running over HTTP on standard port 80    Run Wireshark on the client  In the Options when you start the capture  set the capture filter to tcp http and host service example com  - this will reduce the amount of irrelevant traffic    If you can  modify your client to notify you the exact start time of the call  and the time when the timeout occurred  Or just monitor it closely    When you get an error  then you can trawl through the Wireshark logs to find the start of the call  Right click on the first packet that has your client calling out on it  Should be something like GET  service svc or POST  service svc  and select Follow TCP Stream    Wireshark will decode the entire HTTP Conversation  so you can ensure that WCF is actually sending back responses

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Did you check the WCF traces  WCF has a tendency to swallow exceptions and only return the last exception  which is the timeout that you re getting  since the end point didn t return anything meaningful

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I m having a very similar problem   In the past  this has been related to serialization problems   If you are still having this problem  can you verify that you can correctly serialize the objects you are returning   Specifically  if you are using Linq-To-Sql objects that have relationships  there are known serialization problems if you put a back reference on a child object to the parent object and mark that back reference as a DataMember   You can verify serialization by writing a console app that serializes and deserializes your objects using the DataContractSerializer on the server side and whatever serialization methods your client uses   For example  in our current application  we have both WPF and Compact Framework clients   I wrote a console app to verify that I can serialize using a DataContractSerializer and deserialize using an XmlDesserializer   You might try that   Also  if you are returning Linq-To-Sql objects that have child collections  you might try to ensure that you have eagerly loaded them on the server side   Sometimes  because of lazy loading  the objects being returned are not populated and may cause the behavior you are seeing where the request is sent to the service method multiple times   If you have solved this problem  I d love to hear how because I m stuck with it too   I have verified that my issue is not serialization so I m at a loss   UPDATE  I m not sure if it will help you any but the Service Trace Viewer Tool just solved my problem after 5 days of very similar experience to yours   By setting up tracing and then looking at the raw XML  I found the exceptions that were causing my serialization problems   It was related to Linq-to-SQL objects that occasionally had more child objects than could be successfully serialized   Adding the following to your web config file should enable tracing    lt sharedListeners gt       lt add name  sharedListener           type  System Diagnostics XmlWriterTraceListener           initializeData  c  Temp servicetrace svclog    gt     lt  sharedListeners gt     lt sources gt       lt source name  System ServiceModel  switchValue  Verbose  ActivityTracing   gt         lt listeners gt           lt add name  sharedListener    gt         lt  listeners gt       lt  source gt       lt source name  System ServiceModel MessageLogging  switchValue  Verbose  gt         lt listeners gt           lt add name  sharedListener    gt         lt  listeners gt       lt  source gt     lt  sources gt    The resulting file can be opened with the Service Trace Viewer Tool or just in IE to examine the results

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I ve just solved the problem I found that the nodes in the App config file have configed wrong    lt client gt   lt endpoint name  WCF QtrwiseSalesService  binding  wsHttpBinding  bindingConfiguration  ws  address  http   cntgbs1131 9005 MyService TGE ISupplierClientManager  contract     gt   lt  endpoint gt   lt  client gt    lt bindings gt       lt wsHttpBinding gt           lt binding name  ws  maxBufferPoolSize  2147483647  maxReceivedMessageSize  2147483647  messageEncoding  Text  gt               lt readerQuotas maxDepth  2147483647  maxStringContentLength  2147483647  maxArrayLength  2147483647  maxBytesPerRead  2147483647  maxNameTableCharCount  2147483647   gt               lt   security mode  None  gt                     lt transport clientCredentialType  None  gt  lt  transport gt               lt  security gt           lt  binding gt       lt  wsHttpBinding gt   lt  bindings gt    Confirm your config in the node  lt security gt  the attribute  mode  value is  None   If your value is  Transport  the error occurs

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from  http   www codeproject com KB WCF WCF Operation Timeout  aspx     To avoid this timeout error  we need   to configure the OperationTimeout   property for Proxy in the WCF client   code  This configuration is something   new unlike other configurations such   as Send Timeout  Receive Timeout etc     which I discussed early in the   article  To set this operation timeout   property configuration  we have to   cast our proxy to IContextChannel in   WCF client application before calling   the operation contract methods

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Are you closing the connection to the WCF service in between requests  If you don t  you ll see this exact timeout  eventually

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Looks like this exception message is quite generic and can be received due to a variety of reasons  We ran into this while deploying the client on Windows 8 1 machines  Our WCF client runs inside of a windows service and continuously polls the WCF service  The windows service runs under a non-admin user  The issue was fixed by setting the clientCredentialType to  Windows  in the WCF configuration to allow the authentication to pass-through  as in the following          lt security mode  None  gt           lt transport clientCredentialType  Windows  proxyCredentialType  None            realm      gt           lt message clientCredentialType  UserName  algorithmSuite  Default    gt         lt  security gt

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Did you try using clientVia to see the message sent  using SOAP toolkit or something like that  This could help to see if the error is coming from the client itself or from somewhere else

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If you are using  Net client then you may not have set     This says how many outgoing connection you can make to a single endpoint  Default Value is 2 System Net ServicePointManager DefaultConnectionLimit   200    here is the original question and answer WCF Service Throttling  Update    This config goes in  Net client application may be on start up or whenever but before starting your tests    Moreover you can have it in app config file as well like following    lt system net gt       lt connectionManagement gt         lt add maxconnection    200  address        gt       lt  connectionManagement gt     lt  system net gt

[wcf] WCF timeout exception detailed investigation

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