The current state of a host component resource can be determined by looking at the ServiceComponentInfo/state property.
GET api/v1/clusters/c1/services/HDFS/components/NAMENODE?fields=ServiceComponentInfo/state
200 OK
{
"href" : "http://your.ambari.server/api/v1/clusters/c1/services/HDFS/components/NAMENODE?fields=ServiceComponentInfo/state",
"ServiceComponentInfo" : {
"cluster_name" : "c1",
"component_name" : "NAMENODE",
"state" : "INSTALLED",
"service_name" : "HDFS"
}
}
The following table lists the possible values of the service resource ServiceComponentInfo/state property.
A component can be started through the API by setting its state to be STARTED (see update host component).
A component can be stopped through the API by setting its state to be INSTALLED (see update host component).
The user can update the desired state of a host component through the API to be MAINTENANCE (see update host component). When a host component is into maintenance state it is basically taken off line. This state can be used, for example, to move a component like NameNode. The NameNode component can be put in MAINTENANCE mode and then a new NameNode can be created for the service.