Erlang OTP: Distributed & Fault-Tolerant Systems Programming · レッスン

リリースのバージョン管理とデプロイ

本番環境でリリースのバージョン管理、更新のデプロイ、ロールバックを行うためのベストプラクティスを理解します。

「リリースのバージョン管理とデプロイ」はCoddyKit上の無料Erlang OTP: Distributed & Fault-Tolerant Systems Programmingレッスンです。これはレッスン3/4です。下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。これはErlang OTP: Distributed & Fault-Tolerant Systems Programming学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Erlang OTP: Distributed & Fault-Tolerant Systems Programmingコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

Why Version Your Releases?

When you build an Erlang application for production, it's bundled into a release. Just like any software, releases need clear version numbers.

Versioning helps you:

Track changes over time.
Identify specific builds.
Manage compatibility with other systems.
Plan for upgrades and rollbacks.

Erlang's Versioning System

In Erlang, versioning happens at different levels. Each individual application (an .app file) has its own version. The overall release (the .rel file) also has a version that typically reflects the entire bundle.

The vsn key in an .app file defines an application's version.

% my_app.app file (conceptual)
{application, my_app,
 [{description, "My Erlang Application"},
  {vsn, "1.0.0"},
  {modules, [my_app_app, my_app_sup]},
  {registered, []},
  {applications, [kernel, stdlib]},
  {mod, {my_app_app, []}},
  {env, []}]}.

Semantic Versioning (SemVer)

A widely adopted standard is Semantic Versioning (SemVer), typically formatted as MAJOR.MINOR.PATCH. It's a great practice to follow for your Erlang applications.

MAJOR: Incremented for incompatible API changes.
MINOR: Incremented for new functionality in a backward-compatible way.
PATCH: Incremented for backward-compatible bug fixes.

This helps users understand the impact of an upgrade.

Applying SemVer in Erlang

You'll typically apply SemVer to your application's vsn in the .app file. When you create a release, its version (relvsn) often matches the main application's version or follows a similar scheme.

Tools like rebar3 manage these versions when building releases.

% my_app.app file
{application, my_app,
 [{description, "My Erlang Service"},
  {vsn, "1.2.3"},
  {modules, [my_app_app, my_app_sup]},
  {registered, []},
  {applications, [kernel, stdlib]},
  {mod, {my_app_app, []}},
  {env, []}]}.

Deployment Strategies Overview

Once you have a versioned Erlang release, how do you get it running in production? There are several strategies, depending on your system's requirements for uptime and complexity.

Cold Deployment: Simplest, involves downtime.
Hot Upgrades: Zero-downtime (covered in previous lesson).
Blue/Green or Canary Deployments: More advanced, often used with orchestration tools.

Cold Deployment: Simple Restart

A cold deployment is the most straightforward method. You stop your currently running Erlang system completely, replace its files with the new release, and then start the new version.

This method always incurs downtime, making it suitable for systems where brief interruptions are acceptable.

# Stop the old release
/path/to/my_app/bin/my_app stop

# (Replace files with new release)

# Start the new release
/path/to/my_app/bin/my_app start

Hot Upgrades vs. Full Deployment

Recall from the previous lesson that hot code loading allows you to upgrade a running Erlang system without stopping it.

While powerful for applying patches or minor feature additions, hot upgrades are specific to changing *parts* of a running system. A full deployment often refers to the initial setup or a complete replacement of the entire release, sometimes involving a cold restart or more advanced traffic management.

The Importance of Rollbacks

Even with careful testing, new deployments can introduce unexpected issues. A robust deployment strategy always includes a plan for rollbacks.

A rollback means reverting your system to a previous, stable version if the new deployment fails or causes problems. This minimizes the impact of failures and restores service quickly.

Erlang's Rollback Mechanism

Erlang releases are designed to support rollbacks. When you perform a hot upgrade, Erlang generates an .relup script that describes how to move between versions. Crucially, it also knows how to reverse that script to go back.

Even with cold deployments, you can switch back to a previous release by managing your release directories and restarting the desired version.

# Example of a rollback command using release_handler
# This would typically be part of a custom script or release tool

% release_handler:install_release("my_app-1.1.0").
% release_handler:make_permanent("my_app-1.1.0").

# Alternatively, for cold deployment:
# /path/to/my_app_1.1.0/bin/my_app start

Test Your Understanding

Order the steps for a typical cold deployment of an Erlang release.

Summary: Versioning & Deployment

You've learned about the critical aspects of release versioning and deployment in Erlang:

Versioning: Use vsn in .app files, ideally following SemVer (MAJOR.MINOR.PATCH), to track and manage changes.
Deployment: Understand cold deployment (with downtime) and its distinction from hot upgrades.
Rollbacks: Always plan for reverting to a stable previous version to ensure system resilience.

These practices are key to managing robust Erlang applications in production!

よくある質問

「リリースのバージョン管理とデプロイ」レッスンは無料ですか？

はい。「リリースのバージョン管理とデプロイ」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Erlang OTP: Distributed & Fault-Tolerant Systems Programmingコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Erlang OTP: Distributed & Fault-Tolerant Systems Programmingコースには全4レッスンが含まれています。

「リリースのバージョン管理とデプロイ」で何を学びますか？

本番環境でリリースのバージョン管理、更新のデプロイ、ロールバックを行うためのベストプラクティスを理解します。ブラウザで直接実行するハンズオンコードでErlang OTP: Distributed & Fault-Tolerant Systems Programmingを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Erlang OTP: Distributed & Fault-Tolerant Systems Programmingを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのErlang OTP: Distributed & Fault-Tolerant Systems Programmingは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。これはレッスン3/4です。

「リリースのバージョン管理とデプロイ」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このErlang OTP: Distributed & Fault-Tolerant Systems Programmingレッスンでコードを書いて実行できますか？

はい。すべてのErlang OTP: Distributed & Fault-Tolerant Systems Programmingレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

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