Performing global computation in distributed database systems

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for instrumentation and control of workloads in a massively parallel processing database. Deployment is in a cluster which mirrors the cluster of the database to be controlled. The system includes data publishing modules, action agents, rules processing modules, deployment managers, rule compilation and management tools. Together these provide a distributed, fault tolerant system for the automated rules-based control of work in a database cluster. A first calculation master, upon receiving a request, performs local calculation on a first node, and directs a second calculation master to perform local calculation on a second node. The first calculation master then performs global calculation using intermediate results from the first node and the second node.