mria VS cdk-emqx-cluster

Mria is an open source extension to Mnesia that adds eventual consistency to clusters. Most of the features described earlier still apply to it, the difference is how data is replicated between nodes. Mria switched from a full mesh topology to a mesh+star topology. Each node assumes one of two roles: core node or replicant node.

In EMQX 5.0, we attempted to mitigate this issue in a new DB backend type called RLOG (as in replication log), which is implemented in Mria. Mria is an extension to the Mnesia database that helps it scale horizontally by defining two types of nodes: i) core nodes, which behave as usual Mnesia nodes and participate in write transactions; ii) replicant nodes, which do not take part in transactions and delegate those to core nodes, while keeping a read-only replica of the data locally. This helps to reduce the risk of split-brain scenarios and lessens the coordination needed for transactions, since fewer nodes participate in it, while keeping read-only data access fast, since data is available locally for reading in all nodes.

Mria is an open-source extension to Mnesia that adds eventual consistency to the cluster.

> write-up soon as a guide for Python developers moving to Elixir

Awesome initiative!

> ETS as a KV/document store to hold user and application state and then reacting to changes in to that the way you are here

This is actually pretty interesting. I can't speak to ETS but Mnesia has replication and you can expose the replication log using something like https://github.com/emqx/mria. I've only had a cursory look at this so I could be wrong about its capabilities but it would be an awesome extension to the new Realtime if possible.

For deploying and running our cluster tests, we used AWS CDK, which allowed us to experiment with different instance types and numbers, and also trying out different development branches of EMQX. You can checkout our scripts in this Github repo. In our load generator nodes ("loadgens" for short), we used our emqtt-bench tool to generate the connection / publishing / subscribing traffic with various options. EMQX's Dashboard and Prometheus were used for monitoring the progress of the test and the instances' health.