Starting and stopping processes using Cloudera Manager.
In a Cloudera Manager managed
cluster, you can only start or stop role instance processes using Cloudera
Manager. Cloudera Manager uses an open source process management tool
starts processes, takes care of redirecting log files, notifying of
process failure, setting the effective user ID of the calling process to
the right user, and so on. Cloudera Manager supports automatically
restarting a crashed process. It will also flag a role instance with a bad
health flag if its process crashes repeatedly right after start up.
Stopping the Cloudera Manager Server and the Cloudera Manager Agents will not bring down your services; any running role instances keep running.
The Agent is started by
init.d at start-up. It, in turn,
contacts the Cloudera Manager Server and determines which processes should be running. The
Agent is monitored as part of Cloudera Manager's host monitoring. If the Agent stops
heartbeating, the host is marked as having bad health.
One of the Agent's main responsibilities is to start
and stop processes. When the Agent detects a new process from the Server
heartbeat, the Agent creates a directory for it in
/var/run/cloudera-scm-agent and unpacks the
configuration. It then contacts
starts the process.
These actions reinforce an important point: a Cloudera Manager process never travels alone. In other words, a process is more than just the arguments to exec()—it also includes configuration files, directories that need to be created, and other information.