discourse/config/initializers/002-rails_failover.rb

# frozen_string_literal: true

message_bus_keepalive_interval = nil

RailsFailover::Redis.on_failover do
  message_bus_keepalive_interval = MessageBus.keepalive_interval
  MessageBus.keepalive_interval = -1 # Disable MessageBus keepalive_interval
  Discourse.received_redis_readonly!
end

RailsFailover::Redis.on_fallback do
  Discourse.clear_redis_readonly!
  Discourse.request_refresh!
  MessageBus.keepalive_interval = message_bus_keepalive_interval
end

if Rails.configuration.multisite
  if ActiveRecord::Base.current_role == ActiveRecord::Base.reading_role
    RailsMultisite::ConnectionManagement.default_connection_handler =
      ActiveRecord::Base.connection_handlers[ActiveRecord::Base.reading_role]
  end
end

RailsFailover::ActiveRecord.on_failover do
  RailsMultisite::ConnectionManagement.each_connection do
    Discourse.enable_readonly_mode(Discourse::PG_READONLY_MODE_KEY)
    Sidekiq.pause!("pg_failover") if !Sidekiq.paused?
  end
end

RailsFailover::ActiveRecord.on_fallback do
  RailsMultisite::ConnectionManagement.each_connection do
    Discourse.disable_readonly_mode(Discourse::PG_READONLY_MODE_KEY)
    Sidekiq.unpause! if Sidekiq.paused?
  end

  if Rails.configuration.multisite
    RailsMultisite::ConnectionManagement.default_connection_handler =
      ActiveRecord::Base.connection_handlers[ActiveRecord::Base.writing_role]
  end
end

RailsFailover::ActiveRecord.register_force_reading_role_callback do
  Discourse.redis.exists?(
    Discourse::PG_READONLY_MODE_KEY,
    Discourse::PG_FORCE_READONLY_MODE_KEY
  )
rescue => e
  Rails.logger.warn "#{e.class} #{e.message}: #{e.backtrace.join("\n")}"
  false
end