Clustering

Moleculer framework supports several software architectures.

Monolith architecture

In this version, all services are running on the same node like a monolith. There is no network latency and no transporter module. The local calls are the fastest.

Microservices architecture

This is the well-known microservices architecture when all services are running on individual nodes and communicates via transporter. In this case, the network latency is not negligible. But your services can be scaled to be resilient and fault-tolerant.

Mixed architecture

In this case, we are running coherent services in a group on the same node. It combines the advantages of monolith and microservices architectures.
For example, if the posts service calls the users service multiple times, we put them to the same node, so that we can cut down the network latency between these services. If the node is overloaded, we will scale it up.

Tip

The ServiceBroker first tries to call the local instances of service (if exists) to reduce network latencies. This logic can be turned off in broker options with preferLocal: false property under the registry key.

How choose

Don’t you choose between monolith and microservices? Would you choose monolith because easy to develop? Would you choose microservice because reliable and easy to scale?
Choose both. With Moleculer it is available. When you develop your services, load all services in one node. Easy to debug and test. When your are ready, separate services to multiple nodes. No need to change service codes. Just select a transporter and load one service per node. Your app is running in microservices architecture.