Introducting component lifecycle management

[practicalli-johnny]

Overview of lifecycle management in Clojure,

Discuss why and when livecycle management is required

Briefly covering the different approaches taken by Mount, Component and Integrant.

Link to a section and examples of each

component

• ?

integrant

• duct
• ?

Check to see which luminus and pedestal templates use.

Write section on application lifecycle management tools

Application lifecycle management tools configure the many components that are part of an application, such as HTTP server, persistence store access, cache management, passing configuration to routing (db connections, security, etc)

When running an application, lifecycle tools ensure components are configured and started correctly, to provide a consistent startup and clean shutdown of all components.

Some tools also have specific REPL libraries (e.g. Integrant REPL, Component REPL) to support a REPL driven development workflow. These tools can start, restart and stop components in the system or the whole system itself, without requiring the Clojure REPL process to be restarted.

Commonly used projects

• https://github.com/tolitius/mount - simple, atom based, lightweight

• https://github.com/weavejester/integrant - data focus, more involved, separate Integrant REPL project, most common for new projects with multiple components, works well with JUXT aero

• https://github.com/stuartsierra/component - classic component approach, less used for new projects, but still many projects using this approach

Projects to evaluate

• https://github.com/juxt/clip - combination of code and configuration in one structure
• https://github.com/donut-power/system - combination of code and configuration in one structure
• https://github.com/tolitius/yurt - manage stateful components in isolation (related to Mount)

Semi-related projects

• https://github.com/kepler16/gx.cljc - a data-oriented library for defining and manipulating directed acyclic graph's of state machines

Resources

Related issues

• Introduce Integrant #13
• Lifecycle management: mount clojure#48
• Lifecycle management: integrant clojure#47
• Lifecycle management: roll your own clojure#46
• Lifecycle management: Component clojure#45