Configure TCP keepalive with AWS network load balancer
AWS supports three types of elastic load balancers (ELBs):
Vertica strongly recommends the AWS Network Load Balancer (NLB), which provides the best performance with your Vertica database. The Network Load Balancer acts as a proxy between clients (such as JDBC) and Vertica servers. The Classic and Application Load Balancers do not work with Vertica, in Enterprise Mode or Eon Mode.
To avoid timeouts and hangs when connecting to Vertica through the NLB, it is important to understand how AWS NLB handles idle timeouts for connections. For the NLB, AWS sets the idle timeout value to 350 seconds and you cannot change this value. The timeout applies to both connection points.
For a long-running query, if either the client or the server fails to send a timely keepalive, that side of the connection is terminated. This can lead to situations where a JDBC client hangs waiting for results that would never be returned because the server fails to send a keepalive within 350 seconds.
To identify an idle timeout/keepalive issue, run a query like this via a client such as JDBC:
=> SELECT SLEEP(355);
If there’s a problem, one of the following situations occurs:
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The client connection terminates before 355 seconds. In this case, lower the JDBC keepalive setting so that keepalives are sent less than 350 seconds apart.
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The client connection doesn’t return a result after 355 seconds. In this case, you need to adjust the server keepalive settings (tcp_keepalive_time and tcp_keepalive_intvl) so that keepalives are sent less than 350 seconds apart.
You can adjust the keepalive settings on the server, or you can adjust them in Vertica.
For detailed information about AWS Network Load Balancers, see the AWS documentation.