Connecting to Virtual DataPort Through a Load Balancer¶
Read this section when the JDBC client is connecting to Virtual DataPort through a load balancer or another intermediate resource that holds a pool of connections to Virtual DataPort.
The table Parameters of the JDBC driver useful to set-up a cluster of Denodo servers lists the parameters of the URL that are useful when connecting to Virtual DataPort through a load balancer:
|Parameter of the URL||Description|
Important: set this property to
|pingQuery and pingQueryTimeout||
Important: only use these two properties if the load balancer or the client will execute a ping query without support to set a timeout for that query.
When a client executes the query set
on the parameter
See below for a more detailed explanation of these properties.
Default value for both parameters: <empty>
Sample URL for JDBC applications that connect to Virtual DataPort through a load balancer:
Sample URL for JDBC applications with the parameters
With the URL above, if the query
SELECT 1 does not finish in one
second, the driver returns an error.
You need to add the parameters
the connection URL if the load balancer or the client meet these
- It will execute a ping query to check that the Virtual DataPort server is alive, or a connection to it is still valid.
- And it does not support setting a timeout for that ping query.
At runtime, when the JDBC driver receives the query set on the parameter
pingQuery, it will wait for a maximum of
milliseconds for the query to finish. If the query does not finish in
that time, the driver will return an error, which will indicate the
client or the load balancer that the connection is no longer valid. A
connection to a Virtual DataPort server can become invalid when it has
timed out or dropped by a firewall.