Cloudera Manager Health Tests
This section provides information on health tests supported by Cloudera Manager.
- Pass-fail tests - there are two types:
- Compare a property to a yes-no value. For example, whether a service or role started as expected, a DataNode is connected to its NameNode, or a TaskTracker is (or is not) blacklisted.
- Exercise a service lightly to confirm it is working and responsive. HDFS (NameNode role), HBase, and ZooKeeper services perform these tests, which are referred to as "canary" tests.
- Metric tests - compare a property to a numeric value. For example, the number of file descriptors in use, the amount of disk space used or free, how much time spent in garbage collection, or how many pages were swapped to disk in the previous 15 minutes. In these tests the property is compared to a threshold that determine whether everything is Good, (for example, plenty of disk space available), whether it is Concerning (disk space getting low), or is Bad (a critically low amount of disk space).
By default most health tests are enabled and (if appropriate) configured with reasonable thresholds. You can modify threshold values by editing the monitoring properties under the entity's Configuration tab. You can also enable or disable individual or summary health tests, and in some cases specify what should be included in the calculation of overall health for the service, role instance, or host. See Configuring Monitoring Settings for more information.