In the Cluster area of OpsCenter, you select different views of the nodes comprising your Cassandra cluster, and then, perform node management.
OpsCenter Enterprise Edition 3.0 can monitor and administer Cassandra 1.0 and later, but with Cassandra 1.2 it will not work as described in these procedures if you enable virtual nodes. When you enable virtual nodes, OpsCenter chooses a single token for each node for operations, such as collecting metrics. Attempting to move nodes, rebalance nodes, and perform other tasks involving token ranges is not supported.
Each of the cluster views--ring, physical, and list--has an Actions button.
Click the Actions button to access a drop-down list of node management operations. To avoid impacting cluster performance, perform actions that move data between nodes at low-usage times. Examples of such actions are move, decommission, and repair.
This table describes actions on the drop-down list:
|View Metrics||Redirects you to the Performance area of OpsCenter where you can select metrics graphs and configure performance views for the selected node.|
|View Replication||Shows the replication relationships between the selected node and other nodes in the cluster. Visible in Ring View and Physical View.|
|Configure||Allows you to change the configuration of the node.|
|Start||Starts the DSE / Cassandra process on the node.|
|Stop||Stops the DSE / Cassandra process on the node.|
|Restart||Restarts the DSE / Cassandra process on the node.|
|Cleanup||Removes rows that the node is no longer responsible for. This is usually done after changing the partitioner tokens or the replication options for a cluster.|
|Compact||Performs a major compaction, which is not a recommended procedure in most Cassandra clusters.|
|Flush||Causes the recent writes currently stored in memory (memtables) to be flushed to disk as persistent SSTables.|
|Repair||Makes a node consistent with its replicas by doing an in-memory comparison of all the rows of a column family, and resolving any discrepancies between replicas by updating outdated rows with the current data.|
|Perform GC||Forces the Java Virtual Machine (JVM) on the selected node to perform a garbage collection (GC). This reclaims physical disk space occupied by obsolete SSTables, such as those that have been truncated or compacted (merged) into new SSTables.|
|Decommission||Removes a node from the cluster and streams its data to neighboring replicas.|
|Drain||Causes the recent writes currently stored in memory (memtables) to be flushed to disk as persistent SSTables, and then makes the node read-only (the node will stop accepting new writes). This is usually done when upgrading a node.|
|Move||Changes the partitioner token assignment for the node, thus changing the range of data that the node is responsible for.|