Accumulo

Appendix C. Data Stored in ZooKeeper

Under the /accumulo node in ZooKeeper, there is a node for each instance of Accumulo keyed by instance ID. There is also an instances node that contains a node for each Accumulo instance name, with the data for each instance name being the instance ID currently associated with that name.

The following nodes can exist under each instance ID node.

masters, tservers, gc, monitor, and tracers Nodes

These nodes contain the locations of the various Accumulo processes.

The masters/lock node contains an ephemeral sequential master lock whose data is the master location. The masters/goal_state node contains the master’s goal state (NORMAL, SAFE_MODE, or CLEAN_STOP).

The tservers/tablet_server_host:port nodes contain an ephemeral sequential lock for the specified tablet server. The data for the lock is TSERV_CLIENT=host:port.

The gc/lock node contains an ephemeral sequential lock for the garbage collector. The data for the lock is GC_CLIENT=IP:port.

The data for the monitor node is the location (IP:port) of the monitor server. There is also a child node monitor/log4j_port, whose data is the port of the monitor server used for collecting error logs from other Accumulo processes.

The data for the tracers/trace-ID nodes is the location (IP:port) for the tracer process. The ID is a one-up counter for the tracer processes.

problems/problem_info Nodes

These nodes are created when a problem has occurred with a resource of the metadata table. Problems with ...