告诉Datastax Java Cassandra驱动程序超时集群连接

Question

How do you tell the Datastax Java Cassandra driver to time-out when it attempts to connect to your cluster?

I'm particularly interested in the case when the hosts are reachable, but the Cassandra ports are blocked or the Cassandra daemons are not running. I'm writing a command-line client that ought to exit and report a suitable error message if it can not connect in a reasonable time. At present it seems that the driver will wait forever for a contact point to response, if the contact point is reachable.

That is, I want Cluster.build() to throw a NoHostAvailableException if the driver can not communicate with the Cassandra daemon of any of the contact points within a given maximum time.

• Creating my own RetryPolicy won't work: that is for retrying queries, and I want the timeout to apply before we are ready to run queries.
• Creating my own ReconnectinoPolicy initially looked promising, but the contract for the interface gives no means for indicating "consider this node to be dead forever more"

Answer 1

That is, I want Cluster.build() to throw a NoHostAvailableException if the driver can not communicate with the Cassandra daemon of any of the contact points within a given maximum time.

This is supposed to be the case. The driver will try to connect to each of the contact points and throw an exception if it fails to connect to any. You can control the maximum time the driver will try connecting (to each node) through SocketOptions.setConnectTimeoutMillis() (the default is 5 seconds).

My experience is that Cluster.build() does return an exception if no node can be connected to, but if your experience differs, you might want to report it as a bug (but a bit more detail on how you reproduce this would help).

That being said:

• The timeout above is per host. So if you pass a list of 100 contact points, you could in theory have to wait 500 seconds (by default) before getting the NoHostAvailableException. But there is no real point in providing that many contact points, and in practice, if Cassandra is not running on the node tried, the connection attempt will usually fail right away (you won't wait the timeout).
• There is currently no real query timeout on the driver side. Which mean that if the driver does connect to a node (which means that some process is listening on that port and accept the connection), but get no answer to his initial messages, then it can indeed hold forever. That should probably be fixed, and I encourage you to open a ticket for that on https://datastax-oss.atlassian.net/browse/JAVA . However, this doesn't seem to be the case you are describing, since if "Cassandra ports are blocked or the Cassandra daemons are not running" then the driver shouldn't be able to connect in the first place.