deploying metrics db during RHQ installation

John Sanda jsanda at redhat.com
Tue Sep 11 14:37:12 UTC 2012


Below is a summary of my thoughts thus far on what will be involved with deploying the new metrics database during RHQ installation. This information is available on the wiki at https://docs.jboss.org/author/display/RHQ/Acceptance+Criteria.

Let's start with the simple case involving a single node. During the RHQ installation process, the user will have to provide several pieces of information so that we can install and configure the node. For basic configuration settings that require values this includes:

* The host name of the machine on which Cassandra will be installed
* A writable directory where Cassandra will store the commit log and data files
* User credentials (more on this in the security section)
* Location for backups (more on this in the backup section)

For advanced settings for which we will supply default values, this includes:

* The various ports including rcp_port which is the port Cassandra listens on for Thrift clients
* key and row cache settings like the cache sizes and retention periods for cache entries
* Settings for the commit log which control when writes are acked and how frequently it is flushed to disk
* The JMX port which is the port on which Cassandra listens for JMX connections

Nearly all of the user-supplied configuration values will go into cassandra.yaml. The JMX port will be written into cassandra-env.sh. We will need to generate these files with the values supplied by the user. The location of backups is unique in that it pertains to how RHQ will manage the Cassandra node. That information will need to be stored in the RHQ database.

Users are not required to install and run an agent on the same machine on which the RHQ server runs. The user will however have to install an agent onto the machine on which the Cassandra node is installed so that we can fully manage it. This brings up the order of installation with respect to the Cassandra node, the RHQ server, and the RHQ agent. The key thing is that when the RHQ installer finishes, the Cassandra node should be running and fully configured for management. By that I mean that the Cassandra node should already be imported into the server's inventory, maintenance operations should already be scheduled, alert definitions should already be created, event logging configured, and so on.

If deploying multiple nodes, there are two additional properties that must be set - seeds and initial_token. seeds is a list of host names or IP addresses where nodes will be running. This list is used at start up so that a node can learn the topology of the cluster. initial_token specifies the range of the token ring for which the node is responsible. There is a simple function to use for calculating tokens. It is possible to run multiple nodes on a single machine for production use, but each node has to have its own IP address.

- John
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