WCF Performance Tuning

WCF was introduced to overcome the constraints of previous distributed technologies like ASP.NET Web Services, WSE, .NET Enterprise Services and .NET Remoting and to provide a performance boost in addition. For an introduction to WCF please read my first WCF article - WCF Tutorial .

Performance is a central goal for web or app site, expecially since Google now includes site responsiveness a factor in their ranking algorithm.  For ASP.NET optimization tips, please see  my article titled 50 Tips to Boost ASP.NET Performance.  In this article I will  discuss   WCF performance tuning techniques.

Use DataContractSerializer:

Serialization  is the process of converting an object instance into a portable and transferable format.   Xml Serialization  is popular for its interoperability and binary Serialization  is more useful for transferring objects between two .NET  applications.

System.Runtime.Serialization.DataContractSerializer is   designed for WCF but can also be used for general serialization. The DataContractSerializer has some benefits over XmlSerializer:

  1. XmlSerializer can serialize only properties but DataContractSerializer can serialize fields in addition to  properties.
  2. XmlSerializer can serialize only public members but DataContractSerializer can serialize not only public members but also private and protected members.
  3. In performance terms,  DataContractSerializer is approximately 10% faster than XmlSerializer.

Select proper WCF binding:

System-provided WCF bindings are used to specify the transport protocols, encoding, and security details required for clients and services to communicate with each other. The below are the available  system-provided WCF bindings:

1.BasicHttpBinding:

A binding   suitable for communication with WS-Basic Profile conformant Web Services such as ASMX-based services. This binding uses HTTP as the transport and Text/XML for message encoding.

2. WSHttpBinding:

A secure and interoperable binding   suitable for non-duplex service contracts.

3. WSDualHttpBinding:

A secure and interoperable binding  suitable for duplex service contracts or communication through SOAP intermediaries.

4. WSFederationHttpBinding:

A secure and interoperable binding that supports the WS-Federation protocol, enabling organizations that are in a federation to efficiently authenticate and authorize users.

5. NetTcpBinding:

A secure and optimized binding suitable for cross-machine communication between WCF applications

6. NetNamedPipeBinding:

A  reliable, secure, optimized binding suitable for on-machine communication between WCF applications.

7. NetMsmqBinding:

A queued binding suitable for cross-machine communication between WCF applications.

8. NetPeerTcpBinding :

A binding which enables secure, multi-machine communication.

9. MsmqIntegrationBinding :

A binding that is suitable for cross-machine communication between a WCF application and existing MSMQ applications.

In this context Juval Lowry has presented a nice decision making diagram:

WCF Performance Tuning

It should be noted that WCF also allows us to define our own custom bindings.

Use Tracing:

Tracing can track all the events or specified events in a  program. By default it is off. For debugging purposes we have to make enable it explicitly either through code or using a config file setting which is preferable. If  debugging is not required we should disable tracing. For more details reader can read my article titled “Tracing in WCF”.

Close Proxy:

The proxy represents a service contract. It provides the same operations as service’s contract along with some additional methods for managing the proxy life cycle and the connection to the service. It is a recommended best practice to always close the proxy when the client is finished using it. When we close the proxy, the session with the service is terminated and the connection is closed as well and thus can serve to process new requests in better way.

It should be noted that calling a proxy in a using statement (see the below code snippet) is actually not the optimal  or safest method.

using (ServiceProxy proxyClient = new ServiceProxy())
            {
                proxyClient.SomeFunction();
            }
The above code will be translated to something as follows:
    ServiceProxy proxyClient = new ServiceProxy();
            try
            {
                proxyClient.SomeFunction();
            }
            finally
            {
                if (proxyClient != null)
                    ((IDisposable)proxyClient).Dispose();
            }

The problem with this method is that proxyClient.Dispose() will throw an exception when the proxy is in a faulted state .So to close the proxy even under faulted state the below is the suggested approach:

ServiceProxy proxyClient = new ServiceProxy();
            try
            {
                proxyClient.SomeFunction();
                proxyClient.Close();
            }
            finally
            {
                if (proxyClient.State != System.ServiceModel.CommunicationState.Closed)
                {
                    proxyClient.Abort();
                }
            }

Throttling:

Throttling is a way of mitigating potential DoS (denial of service) attacks. Using ServiceThrottlingBehavior we can set smooth loading and resource allocations on the server. In WCF, there are three service-level throttles that are controlled by ServiceThrottlingBehavior.

1. MaxConcurrentCalls: The maxConcurrentCalls attribute lets us specify the maximum number of simultaneous calls for a service. When the maximum number of simultaneous calls has been met and a new call is placed, the call is queued and will be processed when the number of simultaneous calls is below the specified maximum number. The default value is 16.

2. MaxconcurrentSessions: The maxconcurrentSessions attribute specifies the maximum     number of connections

to a single service. The channels below the specified limit will be active/open. It should be noted that this throttle is effectively disabled for non-sessionful channels (such as default BasicHttpBinding).The default value is 10.

3. MaxConcurrentInstance: The maxConcurrentInstance attribute specify the maximum number of simultaneous service instances. While receiving new instance request the maximum number has already been reached, the request is queued up and will be completed when the number of instances is below the specified maximum. The default value is total of the two attributes maxConcurrentSessions and maxConcurrentCalls.

From general feedback it is has been noted that the default settings for the above mentioned three attributes are very conservative and are insufficient in real production scenarios and thus developers need to increase those default settings.

Hence Microsoft has increased the default settings in WCF4.0 as follows:

1. MaxConcurrentSessions: default is 100 * ProcessorCount

2. MaxConcurrentCalls: default is 16 * ProcessorCount

3. MaxConcurrentInstances: default is the total of MaxConcurrentSessions and MaxConcurrentCalls

Now we have a new parameter which is the multiplier “ProcessorCount” for the settings. The main reason for this is that we do not need to change the settings in deployment from a low end system to a multiple processor based system. The value for MaxConcurrentSessions is also increased from 10 to 100.

Quotas:

There are three types of quotas in WCF transports:

1. Timeouts. Timeouts are used for the mitigation of DOS attacks which rely on tying up resources for an extended period of time.

2. Memory allocation limits: Memory allocation limits prevent a single connection from exhausting the system resources and denying service to other connections.

3. Collection size limits: Collection size limits restrict the consumption of resources which indirectly allocate memory or are in limited supply.

As per MSDN the transport quotas available for the standard WCF transports: HTTP(S), TCP/IP, and named pipes are

as follows:

Sl.No

Name

Type

Min Value

Default Value

Description

1

CloseTimeout

TimeSpan

0

1 min

Maximum time to wait for a connection to

close before the transport will raise an exception.

2

ConnectionBufferSize

Integer

0

8 KB

Size in bytes of the transmit and receive

buffers of the underlying transport.  Increasing this buffer size can

improve throughput when sending large messages.

3

ConnectionLeaseTimeout

Timespan

0

5 Min

Maximum lifetime of an active pooled

connection.  After the specified time elapses, the connection will close

once the current request is serviced.

This setting only applies to pooled

connections.

4

IdleTimeout

Timespan

0

2 Min

Maximum time a pooled connection can remain

idle before being closed.

This setting only applies to pooled connections.

5

ListenBacklog

Integer

0

10

Maximum number of unserviced connections

that can queue at an endpoint before additional connections are denied.

6

MaxBufferPoolSize

Long

0

512 KB

Maximum amount in bytes of memory that the

transport will devote pooling reusable message buffers.  When the pool

cannot supply a message buffer, a new buffer is allocated for temporary use.

Installations that create many channel

factories or listeners can allocate large amounts of memory for buffer

pools.  Reducing this buffer size can greatly reduce memory usage in

this scenario.

7

MaxBufferSize

Integer

1

64 KB

Maximum size in bytes of a buffer used for

streaming data.  If this transport quota is not set or the transport is

not using streaming, then the quota value is the same as the smaller of the

MaxReceivedMessageSize quota value and Integer.MaxValue.

8

MaxInboundConnections

1

10

Maximum number of incoming connections that

can be serviced.  Increasing this collection size can improve

scalability for large installations.

Connection features such as message

security can cause a client to open more than one connection.  Service

administrators should account for these additional connections when setting

this quota value.

Connections waiting to complete a transfer

operation can occupy a connection slot for an extended period of time.

Reducing the timeouts for send and receive operations can free up connection

slots quicker by disconnecting slow and idle clients.

9

MaxOutboundConnectionsPerEndpoint

Integer

1

10

Maximum number of outgoing connections that

can be associated with a particular endpoint.

This setting only applies to pooled

connections.

10

MaxOutputDelay

Timespan

0

200 ms

Maximum time to wait after a send operation

for batching additional messages in a single operation.  Messages are

sent earlier if the buffer of the underlying transport becomes full.

Sending additional messages does not reset the delay period.

11

MaxPendingAccepts

Integer

1

1

Maximum number of channels that the

listener can have waiting to be accepted.

There is an interval of time between a

channel completing an accept and the next channel beginning to wait to be

accepted.  Increasing this collection size can prevent clients that

connect during this interval from being dropped.

12

MaxReceivedMessageSize

Long

0

64 KB

Maximum size in bytes of a received

message, including headers, before the transport will raise an exception

13

OpenTimeout

Timespan

0

1 Min

Maximum time to wait for a connection to be

established before the transport will raise an exception.

14

ReceiveTimeout

Timespan

0

1 Min

Maximum time to wait for a read operation

to complete before the transport will raise an exception.

15

SendTimeout

Timespan

0

1 Min

Maximum time to wait for a write operation

to complete before the transport will raise an exception.

Without  proper settings of quotas (see the below configuration settings) the exceptions will rise which may cause to terminate the service.

 xxx

Other quotas of the ReaderQuotas property that can be used to restrict message complexity to provide protection from denial of service (DOS) attacks, these are:

  1. MaxDepth: The maximum nested no depth per read. The default is 32.
  2. MaxStringContentLength: The maximum string length allowed by the reader.  The default is 8192.
  3. MaxArrayLength: The maximum allowed array length of data being received by WCF from a client. The default is 16384.
  4. MaxBytesPerRead: The maximum allowed bytes returned per readThe default is 4096.
  5. MaxNameTableCharCount: The maximum characters in a table name. The default is 16384.

Continues…

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