kemal_pool_db_test.cr

require "kemal"
require "mysql"

module KemalPoolDBTest
  DB_URL = "mysql://javier@localhost/customers?initial_pool_size=10"
  
  dbpool = DB:open DB_URL
  
  get "/" do
    dbpool.using_connection do |db|
      temp = db.query_all "SELECT id, name, created_at FROM customers", as: { Int64, String, Time }
      temp.inspect
    end
  end
  
  Kemal.run
end

mysql> SHOW PROCESSLIST;

+-----+--------+-----------------+-----------+---------+------+----------+------------------+
| Id  | User   | Host            | db        | Command | Time | State    | Info             |
+-----+--------+-----------------+-----------+---------+------+----------+------------------+
| 211 | javier | localhost       | NULL      | Query   |    0 | starting | SHOW PROCESSLIST |
| 222 | javier | localhost:53684 | customers | Sleep   |   14 |          | NULL             |
| 223 | javier | localhost:53684 | customers | Sleep   |   14 |          | NULL             |
| 224 | javier | localhost:53686 | customers | Sleep   |   14 |          | NULL             |
| 225 | javier | localhost:53688 | customers | Sleep   |   14 |          | NULL             |
| 226 | javier | localhost:53690 | customers | Sleep   |   14 |          | NULL             |
| 227 | javier | localhost:53692 | customers | Sleep   |   14 |          | NULL             |
| 228 | javier | localhost:53694 | customers | Sleep   |   14 |          | NULL             |
| 229 | javier | localhost:53696 | customers | Sleep   |   14 |          | NULL             |
| 230 | javier | localhost:53698 | customers | Sleep   |   14 |          | NULL             |
| 231 | javier | localhost:53700 | customers | Sleep   |   14 |          | NULL             |
+-----+--------+-----------------+-----------+---------+------+----------+------------------+
11 rows in set (0,00 sec)