Let it recover: multiparty protocol-induced recovery

Fault-tolerant communication systems rely on recovery strategies which are often error-prone (e.g. a programmer manually specifies recovery strategies) or inefficient (e.g. the whole system is restarted from the beginning). This paper proposes a static analysis based on multiparty session types that can efficiently compute a safe global state from which a system of interacting processes should be recov- ered. We statically analyse the communication flow of a program, given as a multiparty protocol, to extract the causal dependencies between processes and to localise failures. We formalise our re- covery algorithm and prove its safety. A recovered communication system is free from deadlocks, orphan messages and reception er- rors. Our recovery algorithm incurs less communication cost (only affected processes are notified) and overall execution time (only required states are repeated). On top of our analysis, we design and implement a runtime framework in Erlang where failed pro- cesses and their dependencies are soundly restarted from a com- puted safe state. We evaluate our recovery framework on message- passing benchmarks and a use case for crawling webpages. The experimental results indicate our framework outperforms a built-in static recovery strategy in Erlang when a part of the protocol can be safely recovered