Web Services (ASMX 1.1) Performance Guidelines

- J.D. Meier, Srinath Vasireddy, Ashish Babbar, and Alex Mackman

Design Considerations

• Design chunky interfaces to reduce round trips.
• Prefer message-based programming over RPC style.
• Use literal message encoding for parameter formatting.
• Prefer primitive types for Web services parameters.
• Avoid maintaining server state between calls.
• Consider input validation for costly Web methods.
• Consider your approach to caching.
• Consider approaches for bulk data transfer and attachments.
• Avoid calling local Web services.

Asynchronous Invocation

• Consider calling Web services asynchronously when you have additional parallel work.
• Use asynchronous invocation to call multiple unrelated Web services.
• Call Web services asynchronously for UI responsiveness.

Asynchronous Web Methods

• Use Asynchronous Web Methods for I/O Operations.
• Do Not Use Asynchronous Web Methods When You Depend on Worker Threads.

Attachments

• Consider your attachment options.

Bulk Data Transfer

• Consider using a byte array Web method parameter.
• Consider returning a URL from the Web service.
• Consider using streaming.

Caching

• Consider output caching for less volatile data.
• Consider providing cache-related information to clients.
• Consider perimeter caching.

COM Interop

• Avoid calling single-threaded apartment objects.

Connections

• Configure the maxconnection attribute.
• Prioritize and allocate connections across discrete Web services.
• Use a single identity for outbound calls.
• Consider UnsafeAuthenticatedConnectionSharing with Windows Integrated Authentication.
• Use PreAuthenticate with Basic authentication.

One-Way (Fire-and-Forget) Communication

• Consider using the OneWay attribute if you do not require a response.

Serialization

• Reduce serialization with XmlIgnore.
• Reduce round trips.
• Consider XML compression.

State Management

• Use session state only where it is needed.
• Avoid server affinity.

Threading

• Tune the thread pool using the Formula for Reducing Contention.
• Consider minIoThreads and minWorkerThreads for intermittent burst load.

Timeouts

• Set your proxy timeout appropriately.
• Set your ASP.NET timeout greater than your Web service timeout.
• Abort connections for ASP.NET pages that timeout before a Web services call completes.
• Consider the responseDeadlockInterval attribute.

WebMethods

• Prefer primitive parameter types.
• Consider caching responses.
• Enable session state only for Web methods that need it.