Connection load balancing

Each client connection to a host in the Vertica cluster requires a small overhead in memory and processor time. If many clients connect to a single host, this overhead can begin to affect the performance of the database. You can spread the overhead of client connections by dictating that certain clients connect to specific hosts in the cluster. However, this manual balancing becomes difficult as new clients and hosts are added to your environment.

Connection load balancing helps automatically spread the overhead of client connections across the cluster by having hosts redirect client connections to other hosts. By redirecting connections, the overhead from client connections is spread across the cluster without having to manually assign particular hosts to individual clients. Clients can connect to a small handful of hosts, and they are naturally redirected to other hosts in the cluster. Load balancing does not redirect connections to draining hosts. For more information see, Drain client connections.

Native connection load balancing

Native connection load balancing is a feature built into the Vertica Analytic Database server and client libraries as well as vsql. Both the server and the client need to enable load balancing for it to function. If connection load balancing is enabled, a host in the database cluster can redirect a client's attempt to connect to it to another currently-active host in the cluster. This redirection is based on a load balancing policy. This redirection only takes place once, so a client is not bounced from one host to another.

Because native connection load balancing is incorporated into the Vertica client libraries, any client application that connects to Vertica transparently takes advantage of it simply by setting a connection parameter.

How you choose to implement connection load balancing depends on your network environment. Since native load connection balancing is easier to implement, you should use it unless your network configuration requires that clients be separated from the hosts in the Vertica database by a firewall.

For more about native connection load balancing, see About Native Connection Load Balancing.

Workload routing

Workload routing lets you create rules for routing client connections to particular subclusters based on their workloads.

The primary advantages of this type of load balancing is as follows:

• Database administrators can associate certain subclusters with certain workloads (as opposed to client IP addresses).
• Clients do not need to know anything about the subcluster they will be routed to, only the type of workload they have.
• Database administrators can change workload routing policies at any time, and these changes are transparent to all clients.

For details, see Workload routing.