Rails6.0 Ͱͷෳ਺ DB ରԠ Ebisu.rb #24

@yutadayo • ງҪ ༤ଠ • Ebisu.rb ͷΦʔΨφΠβʔ͍ͯ͠·͢ • ANGEL PORTʢhttps://angl.jpʣͱ͍ ͏αʔϏεΛ࡞͍ͬͯ·͢

ࠓ೔࿩͢͜ͱ ɾRails 6.0.0.rc2 ͕ 7/22 ʹϦϦʔε ɾMultiple Databases αϙʔτͷ঺հ

https://edgeguides.rubyonrails.org/active_record_multiple_databases.html

Ұൠతͳ Master / Slave ߏ੒ͷDB .BTUFS %# 3FQMJDB %# "QQ ϨϓϦέʔγϣϯ 8SJUF3FBE 3FBE0OMZ

• switch_point • https://github.com/eagletmt/switch_point • Octopus • https://github.com/thiagopradi/octopus • multi_db • https://github.com/schoefmann/multi_db ෳ਺DBΛѻ͏ gems

• ෳ਺ͷ Primary DB ͱͦΕͧΕʹରԠ͢Δ Replica DB • ՔಇதͷϞσϧͰͷࣗಈ઀ଓ੾Γସ͑ • HTTPಈࢺ΍ɺ௚ۙͷॻ͖ࠐΈʹԠͨ͡ Primary ͱ Replica ͷ ࣗಈ੾Γସ͑ • ෳ਺DBͷ࡞੒ɾ࡟আɾϚΠάϨʔγϣϯૢ࡞Λߦ͏ Rails Task αϙʔτ͞ΕΔ಺༰

• γϟʔσΟϯά • ΫϥελΛ·͕ͨΔJoinจͷൃߦ • Replica DB ͷϩʔυόϥϯγϯά • ෳ਺DB༻ͷ schema cache ͷ Dumping ݱ࣌఺Ͱαϙʔτ͞Εͳ͍಺༰

production: primary: database: primary_db user: root adapter: mysql primary_replica: database: secondary_db user: root_readonly adapter: mysql replica: true animals: database: animals_db user: root adapter: mysql migrations_paths: db/animals_migrate animals_replica: database: animals_secondary_db user: root_readonly adapter: mysql replica: true ෳ਺DB ͱ Replica ͷઃఆ

• Replica DB ʹ͸ replica: true Λઃఆ͢Δ • ৽͘͠௥Ճͨ͠ DB ʹ͸ϚΠάϨʔγϣϯϑΝΠϧஔ͖ ৔ͷ migrations_paths Λઃఆ͢Δ • ΨΠυϥΠϯʹ͸ replica ͸ primary ͱಉ͡DB໊ͰϢʔ βʔΛ෼͚Δ΂͖ͱ͋Δ͕ɺผDB΋໰୊ͳ͘ઃఆͰ͖Δ ཁ఺

ϞσϧͰͷࢦఆ class AnimalsBase < ApplicationRecord self.abstract_class = true connects_to database: { writing: :animals, reading: :animals_replica } end class ApplicationRecord < ActiveRecord::Base self.abstract_class = true connects_to database: { writing: :primary, reading: :primary_replica } end ֤Ϟσϧຖʹ্هͷઃఆΛߦ͏͜ͱ͸Ͱ͖Δ͕ɺυΩϡϝϯτ Ͱ͸୯ҰͷϞσϧʹઃఆΛهࡌ͠ɺͦΕΛܧঝ͢Δ͜ͱΛਪ঑ ※ DB ઀ଓ࣌ʹϞσϧͷΫϥε໊ຖʹίωΫγϣϯpool Λ࡞Δ ͷͰɺDB ΫϥΠΞϯτͷ઀ଓ਺Λফඅͯ͠͠·͏

$ rails -T rails db:create rails db:create:animals Rails db:create:primary rails db:drop rails db:drop:animals Rails db:drop:primary rails db:migrate rails db:migrate:animals Rails db:migrate:primary Rails db:migrate:status Rails db:migrate:status:animals Rails db:migrate:status:primary Migrations

• ैདྷͷ rails db:create Ͱ͸ primary ͱ animals ྆DB࡞੒͞Ε Δ • rails db:create:animals ͰࢦఆͷDBͷ࡞੒΋Մೳ • migrations_paths ͷϑΥϧμ໊ʹ͸DB໊Λ prefix ʹ͚ͭΔ ΂͖ • ෇͚ͳͯ͘΋ɺࢦఆ͞Ε͍ͯΕ͹໰୊ͳ͍Α͏Ͱ͢ ཁ఺

• rails db:create Ͱ͸ replica: true ͷDB͸࡞੒͞Ε ͳ͍ • rails db:create:primary_replica ͸ΤϥʔʹͳΔ • ಉ༷ʹෳ਺DBͷઃఆ͕ͳ͍ database.yml Ͱ rails db:create:primary ΋ΤϥʔʹͳΔ μϝͩͬͨ͜ͱ

઀ଓͷ੾Γସ͑ʢΦʔτฤʣ 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 application.rb ʹ্هઃఆΛ௥Ճ͢Δ͚ͩ

• POST / PUT / DELETE / PATCH ͷϦΫΤετ͸ primary • ॻ͖ࠐΈޙɺdelayʢσϑΥϧτ͸2ඵʣؒ͸ primary ͰҎ߱ ͸ replica ΁ • GET / HEAD ͸ delay ΑΓલʹॻ͖ࠐΈ͕ͳ͍৔߹͸ replica ΁ • ࣮૷ΛΈΔͱ session[:last_write] ͱϦΫΤετ࣌ࠁͷ͕ࠩ delay Λա͍͗ͯͳ͍͔νΣοΫ͢Δ͚ͩͷγϯϓϧͳ࣮૷ ཁ఺

઀ଓͷ੾Γସ͑ʢϚχϡΞϧฤʣ ActiveRecord::Base.connected_to(role: :reading) do # do something end ίʔυϒϩοΫ಺ͰɺroleΛࢦఆͯ͠ɺΫΤϦΛൃߦ͢Δ ActiveRecord::Base. connected_to(database: { reading_slow: :slow_replica }) do # do something end database.yml ʹఆ͕ٛ͋Ε͹ɺผͷ database Ҿ਺ΛࢦఆՄೳ

• γϯϓϧʹ Write ͸ master ΁ Read ͸ replica ΁ͷέʔεͰ͸େม༗ ޮɺطଘͷgem୤٫νϟϯε • ෳ਺DB Ͱͷ Migration ΋όονϦαϙʔτ • Slave ͷ όϥϯγϯά͸αϙʔτ֎ͳͷͰɺෳ਺ replica ͕͋Δ৔߹͸ผ ͷػߏ͕ඞཁ • RDS Auroraͷ৔߹͸ΫϥελʔΤϯυϙΠϯτΛࢦఆ͓͚ͯ͠͹ྑ͞ ͦ͏ ·ͱΊ