AWS LambdaのJavaランタイムでミドルウェアのコネクションのリークでハマった件

import java.io.{InputStream, OutputStream}
import java.sql.DriverManager

import com.amazonaws.services.lambda.runtime.{Context, RequestStreamHandler}
import com.mysql.cj.jdbc.Driver
import grizzled.slf4j.Logging
import javax.jms.{DeliveryMode, Session}
import org.apache.activemq.ActiveMQConnectionFactory
import org.apache.activemq.pool.PooledConnectionFactory
import org.redisson.Redisson
import org.redisson.api.RedissonClient
import org.redisson.config.{Config, ReadMode}
import scalikejdbc.{ConnectionPool, DB, DBSession, GlobalSettings, LoggingSQLAndTimeSettings}

class App extends RequestStreamHandler with Logging {

  override def handleRequest(input: InputStream, output: OutputStream, context: Context): Unit = {
    logger.info("Execution start")
    
    val redissonClient = _redissonClient()
    val rdbConnection = _rdbConnection()
    val mqProducer = _mqProducer()
    
    // ...
    
    logger.info("Execution completed")
  }

  private def _redissonClient(): RedissonClient = {
    // prepare the Redis connection
    val config = new Config()
    config
      .useClusterServers()
      .setReadMode(ReadMode.MASTER_SLAVE)
      .addNodeAddress("redis://xxx")

    Redisson.create(config)
  }

  // RDBやAmazonMQ用のクライアントも同様にprivate defで定義していた

}

class App extends RequestStreamHandler with Logging {

  logger.info(s"Instantiate handler with PID: ${hashCode().toString}")
  
  // ...
  
}

[main] INFO App - Instantiate handler: 211024580
START RequestId: xxx Version: $LATEST
[main] INFO App - Execution start
...
[main] INFO App - Execution completed
END RequestId: xxx
REPORT RequestId: xxx Duration: ??? ms Billed Duration: ??? ms Memory Size: ??? MB Max Memory Used: ??? MB Init Duration: ??? ms 
START RequestId: yyy Version: $LATEST
[main] INFO App - Execution start
...
[main] INFO App - Execution completed
END RequestId: yyy
REPORT RequestId: yyy Duration: ??? ms Billed Duration: ??? ms Memory Size: ??? MB Max Memory Used: ??? MB Init Duration: ??? ms 
...

class App extends RequestStreamHandler with Logging {

  override def handleRequest(input: InputStream, output: OutputStream, context: Context): Unit = {
    logger.info("Execution start")
    
    // redissonClient変数などが使われる...
    
    logger.info("Execution completed")
  }

  private lazy val redissonClient: RedissonClient = {
    // prepare the Redis connection
    val config = new Config()
    config
      .useClusterServers()
      .setReadMode(ReadMode.MASTER_SLAVE)
      .addNodeAddress("redis://xxx")

    Redisson.create(config)
  }

  // RDBやAmazonMQ用のクライアントも同様にprivate lazy defで定義

}