When a Data Integration Service grid runs web service requests, the service runs jobs in the Data Integration Service process. All nodes in the grid must have both the service and compute roles.
When you enable a Data Integration Service that runs on a grid, one service process starts on each node with the service role in the grid. The Data Integration Service designates one service process as the master service process, and designates the remaining service processes as worker service processes. When a worker service process starts, it registers itself with the master service process so that the master is aware of the worker.
The worker service processes run the web service jobs. The master service process also acts as a worker service process and completes jobs.
When you submit a web service request, the Data Integration Service uses an external HTTP load balancer to distribute the request to a worker service process. When you submit multiple requests against web services, the Data Integration Service uses round robin to dispatch each query to a worker service process.