Architecture

SHAR server uses NATS Message Pull combined with a Stateless Decoupled Monolith pattern to achieve linear scaling.

Each instance pulls a number of concurrent messages from NATS, performs tasks based on the messages and sends messages back to NATS for further processing.

The advantages of this are:

• SHAR server instances are unaware of their participation in a cluster.
• No configuration is needed to cluster SHAR servers.
• The topology is driven from NATS configuration.
• Any instance can handle any message.
• Failed processing is retried automatically.
• Servers only pull as many messages as they can handle.
• Removing or adding servers provides immediate performance alterations.

SHAR is split into 3 components:

• The Client which wraps API calls to the server, can send workflow messages, registers tasks, and runs tasks.
• The Engine which handles workflow processing, storage and orchestration.
• The Server which thinly wraps the engine, and provides API access, and lifecycle management.