PADRE: A Policy Architecture for building Data REplication systems

This paper presents Padre, a new policy architecture for developing data replication systems. Padre simplifies design and implementation by embodying the right abstractions for replication in widely distributed systems. In particular, Padre cleanly separates the problem of building a replication system into the subproblems of specifying liveness policy and specifying safety policy, and it identifies a small set of primitives that are sufficient to specify sophisticated systems. As a result, building a replication system is reduced to writing a few liveness rules in a domain-specific language to trigger communication among nodes and specifying safety predicates that define when the system must block requests. We demonstrate the flexibility and simplicity of Padre by constructing a dozen substantial and diverse systems, each using just a few dozen system-specific policy rules. We demonstrate the agility that Padre enables by adding new features to several systems, yielding significant performance improvements; each addition required fewer than ten additional rules and took less than a day.