eG Monitoring
 

Measures reported by ZkpStatTest

This test monitors the current state and the packet transmission and reception of the target Apache Zookeeper server. This test helps administrators figure out the number of znodes, followers, watches of the znodes, synchronized followers etc connected to the target Apache Zookeeper server. Using this test, administrators can figure out the file descriptors that are currently open. This way, administrators can figure out the responsiveness of the server.

Outputs of the test : One set of results for the target Apache Zookeeper server being monitored.

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
Status Indicates the current state of the Apache Zookeeper server.   The values reported by this measure and its numeric equivalents are mentioned in the table below:

State Numeric Value
STANDALONE 0
LEADER 1
FOLLOWER 2
Note:

By default, this measure reports the Measure Values listed in the table above to indicate the current state of the server. The graph of this measure however, represents the state of the server using the numeric equivalents only.
Packet_trans_rate Indicates the rate at which packets were transmitted through the server during the last measurement period. Packets/sec  
Packet_rec_rate Indicates the rate at which packets were received by the server during the last measurement period. Packets/sec  
Open_file_desc_count Indicates the number of file descriptors that are currently open. Number A file descriptor is a number that uniquely identifies an open file in a computer's operating system. It describes a data resource, and how that resource may be accessed.

A low value is desired for this measure.
Open_file_desc_usage Indicates the percentage of file descriptors that are currently open. Percent  
Max_file_desc Indicates the maximum number of file descriptors that can be opened concurrently. Number  
Data_size Indicates the amount of data available on the data tree of the server. Bytes  
Znode_count Indicates the number of znodes in the Zookeeper namespace/ensemble. Number  
Ephermal_node_count Indicates the number of ephemeral nodes on the server. Number Ephemeral znodes are active until the client is alive. When a client gets disconnected from the ZooKeeper ensemble, then the ephemeral znodes get deleted automatically. For this reason, only ephemeral znodes are not allowed to have a children further. If an ephemeral znode is deleted, then the next suitable node will fill its position. Ephemeral znodes play an important role in Leader election.
Watch_count Indicates the number of watches on the Znodes of the server. Number Watches are a simple mechanism for the client to get notifications about the changes in the ZooKeeper ensemble. Clients can set watches while reading a particular znode. Watches send a notification to the registered client for any of the znode (on which client registers) changes.

Znode changes are modification of data associated with the znode or changes in the znode’s children. Watches are triggered only once. If a client wants a notification again, it must be done through another read operation. When a connection session is expired, the client will be disconnected from the server and the associated watches are also removed.
Followers Indicates the number of followers in a Zookeeper ensemble. Number Followers receive write requests from the clients and forward them to the leader znode.
Zynced_followers Indicates the number of synchronized followers. Number  
Pending_syncs Indicates the number of synchronization operations that are pending on the server. Number This measure is applicable only if the target Apache Zookeeper server is a leader in a Zookeeper ensemble.