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Couchbase N1QL Transaction: An Elastic and Scalable Distributed Transaction

SQL is the only 22nd-century language available for developers today.

Abstract

In relational database systems, SQL is more than a declarative query language. It includes procedural language (T-SQL, PL/SQL, etc) and defines transactions and their semantics. SQL as a query language has been unreasonably effective even in NoSQL database systems. However, few NoSQL database systems support transactions. The ones that support come with a long list of limitations and/or were unable to support SQL operations within the transaction.  We introduce and explain transactions in Couchbase N1QL: SQL for JSON.  N1QL transactions are multi-everything: multi-document, multi-bucket, multi-scope, multi-collection, and multi-DML-statement.

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Distributed Saga and Resiliency of Microservices

Sagas are typically used for modeling long-lived transactions like those involved in workflows. It is not advisable to use two-phase transaction protocols to control long-lived transactions since the locking of resources for prolonged durations across trust boundaries is not practical, rather is not at all advisable. Sagas are similar to nested transactions. In a nested transaction, atomic transactions are embedded in other transactions. In sagas, each of these transactions has a corresponding compensating transaction. While a Saga proceeds with its steps, if any of the transactions in a saga fails, the compensating actions for each transaction that was successfully run previously will be invoked so as to nullify the effect of the previously successful transactions.

Modeling a Saga and setting up a Saga Infrastructure is rather straight forward in Local and simple deployments, however when we want to scale out in public cloud environments, and that too with multiple instances of the same type of microservice, there comes a new list of challenges. We will look at few of them in this discussion.

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Parallel Commits: An Atomic Commit Protocol for Distributed Transactions

Distributed ACID transactions form the beating heart of CockroachDB. They allow users to manipulate all of their data transactionally, no matter where it physically resides.

They're so important to CockroachDB’s goal to “Make Data Easy” that we spend a lot of time thinking about how to make them as fast as possible. Specifically, CockroachDB specializes in globally distributed deployments, so we put a lot of effort into optimizing CockroachDB’s transaction protocol for clusters with high inter-node latencies.

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Distributed Transactions and Microservices Still Don’t Mix

I’m talking as someone who has actually implemented multiple distributed transaction systems. People moving to microservices are now discovering a lot of the challenges and hurdles of distributed systems and it is only natural to want to go back to the cozy transactional world, where you can reason about things properly.

This post is in response to this article: Microservices and distributed transactions, which I read with interest, because it isn’t often that a post will refute it’s own premise with the very first statement.