https://github.com/takeyuweb/rails6-multidb-sample
Rails 6.0 の DatabaseSelector middleware を理解する
https://github.com/takeyuweb/rails6-multidb-sample
Last synced: about 2 months ago
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Rails 6.0 の DatabaseSelector middleware を理解する
- Host: GitHub
- URL: https://github.com/takeyuweb/rails6-multidb-sample
- Owner: takeyuweb
- Created: 2019-09-20T13:36:27.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2023-01-19T14:56:31.000Z (over 3 years ago)
- Last Synced: 2025-03-15T15:12:58.315Z (over 1 year ago)
- Language: Ruby
- Homepage: https://qiita.com/takeyuweb/items/e33db948e69c7e4420cc
- Size: 1.42 MB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 32
-
Metadata Files:
- Readme: README.md
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README
# rails6-multidb-sample
次のことを確認するためのサンプルアプリケーションです。
- PostgreSQL の非同期レプリケーション
- Rails 6.0 の Multiple DBs 機能
- DatabaseSelector を使った HTTP Method による接続先自動切り替え
## 試す
```bash
$ docker-compose up
```
```bash
$ docker-compose exec app bundle exec rails db:setup
```
Open http://localhost:3000/posts
## PostgreSQL の非同期レプリケーション
Docker Compose を使って、2 つの PostgreSQL コンテナを立ち上げます。
一方をレプリケーションの parimary に、もう一方を readonly (Hot Standby) として使います。
## Rails 6.0 の Multiple DBs 機能
[Active Record で複数のデータベース利用](https://railsguides.jp/active_record_multiple_databases.html)
次のようにレプリケーションの parimary （読み書き可能）と readonly （読み込み専用）を `host` で指定します。
YAML 中の `primary` `primary_readonly` は後で参照するのに使う識別子で任意に設定可能です。
```yaml
development:
primary:
<<: *default
database: MyApp_development
host: pg_primary
primary_readonly:
<<: *default
database: MyApp_development
host: pg_readonly
replica: true # この接続はレプリカであることRailsに伝える
```
```ruby
class ApplicationRecord < ActiveRecord::Base
self.abstract_class = true
connects_to database: { writing: :primary, reading: :primary_readonly }
end
```
```ruby
ActiveRecord::Base.connected_to(role: :writing) do
# このブロック内のコードはすべて writing ロールで接続される
ActiveRecord::Base.current_role #=> :writing
end
ActiveRecord::Base.connected_to(role: :reading) do
# このブロック内のコードはすべて reading ロールで接続される
ActiveRecord::Base.current_role #=> :reading
end
```
## DatabaseSelector を使った HTTP Method による接続先自動切り替え
`config/environments/development.rb` で以下を設定しています。
```ruby
config.active_record.database_selector = { delay: 2.seconds }
config.active_record.database_resolver = ActiveRecord::Middleware::DatabaseSelector::Resolver
config.active_record.database_resolver_context = ActiveRecord::Middleware::DatabaseSelector::Resolver::Session
```
[コネクションの自動切り替えを有効にする - Active Record で複数のデータベース利用](https://railsguides.jp/active_record_multiple_databases.html#%E3%82%B3%E3%83%8D%E3%82%AF%E3%82%B7%E3%83%A7%E3%83%B3%E3%81%AE%E8%87%AA%E5%8B%95%E5%88%87%E3%82%8A%E6%9B%BF%E3%81%88%E3%82%92%E6%9C%89%E5%8A%B9%E3%81%AB%E3%81%99%E3%82%8B)
### 試してみる
http://localhost:3000/posts で記事を登録したり、表示したりすると次のようなログが表示され、どちらのデータベースにクエリが送信されたか確認できます。
```
app_1 | Started PATCH "/posts/1" for 172.21.0.1 at 2019-10-03 18:37:22 +0000
app_1 | Cannot render console from 172.21.0.1! Allowed networks: 127.0.0.0/127.255.255.255, ::1
pg_primary_1 | 2019-10-03 18:37:22.227 UTC [66] LOG: statement: SELECT 1
app_1 | Processing by PostsController#update as HTML
app_1 | Parameters: {"authenticity_token"=>"tJBhu5R3jC6vI+SubacKMK4bAyLUi62Tq5GkXpI/jhwPPLlpzC546Nwmaurjgp45kFieKwScCboGzkXgsC71cw==", "post"=>{"title"=>"Hello world!!", "body"=>"one two three"}, "commit"=>"Update Post", "id"=>"1"}
pg_primary_1 | 2019-10-03 18:37:22.229 UTC [66] LOG: statement: SHOW search_path
pg_primary_1 | 2019-10-03 18:37:22.230 UTC [66] LOG: execute a1: SELECT "posts".* FROM "posts" WHERE "posts"."id" = $1 LIMIT $2
pg_primary_1 | 2019-10-03 18:37:22.230 UTC [66] DETAIL: parameters: $1 = '1', $2 = '1'
app_1 | Post Load (0.4ms) SELECT "posts".* FROM "posts" WHERE "posts"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
app_1 | ↳ app/controllers/posts_controller.rb:67:in `set_post'
app_1 | Redirected to http://localhost:3000/posts/1
app_1 | Completed 302 Found in 4ms (ActiveRecord: 0.8ms | Allocations: 1373)
app_1 |
app_1 |
app_1 | Started GET "/posts/1" for 172.21.0.1 at 2019-10-03 18:37:22 +0000
app_1 | Cannot render console from 172.21.0.1! Allowed networks: 127.0.0.0/127.255.255.255, ::1
pg_primary_1 | 2019-10-03 18:37:22.237 UTC [66] LOG: statement: SELECT 1
app_1 | Processing by PostsController#show as HTML
app_1 | Parameters: {"id"=>"1"}
pg_primary_1 | 2019-10-03 18:37:22.238 UTC [66] LOG: execute a1: SELECT "posts".* FROM "posts" WHERE "posts"."id" = $1 LIMIT $2
pg_primary_1 | 2019-10-03 18:37:22.238 UTC [66] DETAIL: parameters: $1 = '1', $2 = '1'
app_1 | Post Load (0.3ms) SELECT "posts".* FROM "posts" WHERE "posts"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
app_1 | ↳ app/controllers/posts_controller.rb:67:in `set_post'
app_1 | Rendering posts/show.html.erb within layouts/application
app_1 | Rendered posts/show.html.erb within layouts/application (Duration: 0.2ms | Allocations: 95)
app_1 | Completed 200 OK in 6ms (Views: 4.7ms | ActiveRecord: 0.3ms | Allocations: 6369)
app_1 |
app_1 |
app_1 | Started GET "/posts/1" for 172.21.0.1 at 2019-10-03 18:37:36 +0000
app_1 | Cannot render console from 172.21.0.1! Allowed networks: 127.0.0.0/127.255.255.255, ::1
pg_primary_1 | 2019-10-03 18:37:36.607 UTC [66] LOG: statement: SELECT 1
app_1 | Processing by PostsController#show as HTML
app_1 | Parameters: {"id"=>"1"}
pg_readonly_1 | 2019-10-03 18:37:36.609 UTC [30] LOG: statement: SELECT 1
pg_readonly_1 | 2019-10-03 18:37:36.609 UTC [30] LOG: execute a1: SELECT "posts".* FROM "posts" WHERE "posts"."id" = $1 LIMIT $2
pg_readonly_1 | 2019-10-03 18:37:36.609 UTC [30] DETAIL: parameters: $1 = '1', $2 = '1'
app_1 | Post Load (0.5ms) SELECT "posts".* FROM "posts" WHERE "posts"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
app_1 | ↳ app/controllers/posts_controller.rb:67:in `set_post'
app_1 | Rendering posts/show.html.erb within layouts/application
app_1 | Rendered posts/show.html.erb within layouts/application (Duration: 0.2ms | Allocations: 92)
app_1 | Completed 200 OK in 8ms (Views: 5.3ms | ActiveRecord: 0.5ms | Allocations: 6356)
```