The twelve-Factor App

前言

在研究lazy_high_charts的demo时，看到其中包含名字很奇怪的gem(rails_12factor)，然后追踪到http://12factor.net/。

看来，最近成名的工程师都热衷于写作，比如37Signals的《Reworks》以及这个Heroku的《The twelve-Factor App》。以下是其中的内容:

Introduction

In the modern era, software is commonly delivered as a service: called web apps, or software-as-a-service. The twelve-factor app is a methodology for building software-as-a-service apps that:

• Use declarative formats for setup automation, to minimize time and cost for new developers joining the project;
• Have a clean contract with the underlying operating system, offering maximum portability between execution environments;
• Are suitable for deployment on modern cloud platforms, obviating the need for servers and systems administration;
• Minimize divergence between development and production, enabling continuous deployment for maximum agility;
• And can scale up without significant changes to tooling, architecture, or development practices.

The twelve-factor methodology can be applied to apps written in any programming language, and which use any combination of backing services (database, queue, memory cache, etc). Background

The contributors to this document have been directly involved in the development and deployment of hundreds of apps, and indirectly witnessed the development, operation, and scaling of hundreds of thousands of apps via our work on the Heroku platform.

This document synthesizes all of our experience and observations on a wide variety of software-as-a-service apps in the wild. It is a triangulation on ideal practices for app development, paying particular attention to the dynamics of the organic growth of an app over time, the dynamics of collaboration between developers working on the app’s codebase, and avoiding the cost of software erosion.

Our motivation is to raise awareness of some systemic problems we’ve seen in modern application development, to provide a shared vocabulary for discussing those problems, and to offer a set of broad conceptual solutions to those problems with accompanying terminology. The format is inspired by Martin Fowler’s books Patterns of Enterprise Application Architecture and Refactoring. Who should read this document?

Any developer building applications which run as a service. Ops engineers who deploy or manage such applications.

I. Codebase

One codebase tracked in revision control, many deploys

II. Dependencies

Explicitly declare and isolate dependencies

III. Config

Store config in the environment

IV. Backing Services

Treat backing services as attached resources

V. Build, release, run

Strictly separate build and run stages

VI. Processes

Execute the app as one or more stateless processes

VII. Port binding

Export services via port binding

VIII. Concurrency

Scale out via the process model

IX. Disposability

Maximize robustness with fast startup and graceful shutdown

X. Dev/prod parity

Keep development, staging, and production as similar as possible

XI. Logs

Treat logs as event streams

XII. Admin processes

Run admin/management tasks as one-off processes

后记

偶尔，去逛了一下Rei的博客，发现其对The Twelve-Factor App有介绍，简单说，The Twelve-Factor App是用来针对部署相关的问题， 其中，提出了灵活部署的12个因素:

• 用版本管理库管理代码，例如用 git。
• 声明并且隔离依赖，例如用 Bundler。
• 把应用设置保存在环境变量中。
• 把后端服务当作附加资源。
• 明确区分 build 和 run 过程。
• 应用运行为无状态的单个或多个进程。
• 通过端口对外提供服务。
• 通过进程模型水平扩展。
• 能快速启动和安全关闭，高稳健性。
• 开发和生产环境尽可能保持一致。
• 日志通过标准流输出。
• 管理任务作为一次性流程执行