Don't use parallel execution within plug-ins and workflow activities

Category: Design, Performance, Security, Supportability

Impact potential: High

Symptoms

Multi-threading or parallel calls within plug-ins or custom workflow activities can cause corruption of those the connections. As an example, executing parallel threads can log exceptions such as:

Generic SQL error. The transaction active in this session has been committed or aborted by another session.

Also, nonthread safe objects such as items in the System.Collections Namespace can become corrupted by parallel threads.

Guidance

The sandbox service is designed to execute calls in a specific order as part of a transaction. Developing plug-ins or custom workflow activities to make parallel or multi-threaded calls isn't supported. Develop your plug-ins and custom workflow activities knowing that the calls are performed sequentially and might need to be rolled back.

Problematic patterns

Plug-ins and custom workflow activities run within a single transaction and multiple threads introduced by parallel execution can corrupt the transaction. The following are examples of patterns and practices that shouldn't be used within plug-ins and custom workflow activities:

• Using Task-based asynchronous pattern (TAP)
• Using Task Parallel Library (TPL)
• Using Managed Threading

Additional information

Using and updating shared pipeline context objects could cause these objects to contain unexpected results or become corrupted. The affect of this would be a failure in the plug-in or custom workflow activity.

See also

Parallel Processing, Concurrency, and Async Programming in .NET