DSL For Common Patterns In Distributed Protocols

DSL For Common Patterns In Distributed Protocols

Two common patterns at the moment recur across the body of examples we have demonstrating the applicability of the DiSeL framework.

• A 2-way communication channel in which one end asks a question and waits for the answer, and the other end does some upon receiving the question and computing the answer. In some sense this corresponds to a remote procedure call: we are interested in some property of another node, so invoke some code on it to obtain this information.
• A 1-way communication channel in which one end notifies the other of some event occurring. In some sense this corresponds to an event-listener pattern.

Setting up an RPC in DiSeL requires a total of 4 separate transitions to be defined, along with transformations on states, pre- and post-conditions and messages, etc.

Conceivably we can invent a notation for describing such a system of communication channels, or perhaps just parts of it - and mechanically compute the definitions of the required transitions, lifting the examples size for DiSeL examples a notch.

Example

As part of the Lease based locking protocol, a resource guarded by a lock must verify the sequence number offered by a client to be the active sequence number. So we can specify this 'transaction' as an RPC, invoked by the resource 'on' the lock.