Introduction

This book aims to describe a superior approach to build heavily asynchronous and distributed applications based on the actor model using the elfo framework.

Goals

• Facilitate the development of resilient, fault-tolerant systems.
• Maintain enough performance to meet the needs of low-latency systems.
• Enhance observability through extensive metrics to identify and rectify issues promptly.
• Offer built-in support for exposing log events, dumps, metrics, and trace events.
• Simplify the process of distributing actors across multiple machines.

Non-goals

• Provide the most performant way to communicate between actors.
• Provide any HTTP/WS server functionalities.

Features

• Asynchronous actors equipped with supervision and a customizable life cycle.
• Two-level routing system: between actor groups (pipelining) and inside them (sharding).
• Protocol diversity: actors have the capability to process messages from various protocols, defined in different places.
• Varied communication patterns: regular messages, request-response (TODO: subscriptions).
• Dynamic configuration updates and distribution.
• Suitable for tasks requiring both low latency and high throughput.
• Tracing: every message is assigned a trace_id which spreads system-wide implicitly.
• Telemetry through the metrics crate.
• Dumping: messages can be archived for subsequent debugging.
• Effortless distribution across nodes.
• Utilities for straightforward testing.

The term "observability" could be better understood through demonstration. Consider, for example, the concept of metrics: