Aspects of microservices communication when using saga template

Microservices architectural pattern «saga» is a common approach that addresses the problem of eventual consistency in modern back-end cloud solutions. However, sagas approach does not define a fault tolerant way of solving the data consistency problem of distributed systems that can lead to business data inconsistency. In this paper we analysed a number of scientific publications in order to determine the most common ways of sagas definition from the cross-service communication point of view. The defined set of communication protocols was split on client-server protocols and message queues. For them we collected potential pitfalls of data consistency guarantee as well as ways to provide fault tolerance in these environments. It was shown how to adopt these protocols for both synchronous and asynchronous communication approaches in sagas. The applicability of CQRS and DQL in communication within saga was also studied in the paper.