Alexander Radzin created CASSANDRA-7299:
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Summary: Cluster.Builder throws UnknownHostException when adding
not existing host
Key: CASSANDRA-7299
URL: https://issues.apache.org/jira/browse/CASSANDRA-7299
Project: Cassandra
Issue Type: Bug
Components: API
Reporter: Alexander Radzin
Priority: Trivial
Connection to Cassandra cluster from client side is typically done using
{{Cluster.Builder}} class that allows to configure the connection and then
build cluster by invocation of method {{build()}}. Not all contact points must
be available at creation time. If some of them start after the connection has
been established they client continue its work using the newly connected
endpoints.
However if specific hostname is not available at the moment when builder is
being created {{UnknownHostException}} is thrown.
IMHO Typically applications tend to create builder on start-up when reading
configuration parameters and then connect to Cassandra. For example in Spring
based applications this happens during context creation.
This issue prevents the application to start.
This does not happen when using IP address even if it is not available at the
moment.
The problem is that {{Builder.addContactPoint()}} invokes
{{InetAddress.getByName()}} when creating the builder.
{noformat}
public Builder addContactPoint(String address) {
try {
this.addresses.add(InetAddress.getByName(address));
return this;
} catch (UnknownHostException e) {
throw new IllegalArgumentException(e.getMessage());
}
}
{noformat}
IMHO it should do this only when building the cluster.
My current work around is to extend {{Cluster.Builder}} (fortunately it is
public and not final) and store addresses in their textual for transforming the
to instances of {{InetAddress}} only when {{build()}} is called. This is
however not full solution because the {{Cluster}} itself also requires list of
{{InetAddress}}.
The point here is that we can create builder and cluster with unavailable
contact points if string representation of IP address is supplied but cannot
use symbolic computer name. This is because {{InetAddress.getByName()}} throws
{{UnknownHostException}} only if host identified by name is not available:
{quote}
If a literal IP address is supplied, only the validity of the address format is
checked.
{quote}
(from Javadoc of {{InetAddress.getByName()}}.
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