an activeRecord::connection TimeoutError occurred in redirect#show all pooled connections were in use
ActiveRecord::ConnectionTimeoutError:无法在5000秒内从池中获得连接。所有的集合连接都在使用中。

修改config/database.yml, 原来pool是１０，　修改成２０了。

production:
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 20 } %>
  host: 127.0.0.1
  port: 5432
  user: postgres
  password:
  database: db_production