Yarn (Yet Another Resource negotiator) is a data operating system and distributed Resource Manager, also known as Hadoop 2 as it is the evolution of Hadoop Map-Reduce.
The most significant changes of Hadoop 2 over Hadoop 1 is that the thread technology is included, this technology provides an effective allocation of resources, for it runs two demons:
Resource Manager: responsible for managing the resources on their multiple nodes.
Application Master: responsible for negotiating resources with the resource manager on the one hand and with the node manager to run and monitor for another. There will be a master application for each “job” sent to the cluster.
View Yarn Processes
The service of Yarn in cloudy or Hortoworks is usually configured in Port 8088
http://localhost:8088 or http://127.0.0.1:8088
Commands used in the Hortonworks shell:
sudo service Ambari-server restart
View the Process list
yarn application -list -appStates ALL
Note You can specify the processes by the state by changing ALL by: NEW, NEW_SAVING, submitted, accepted, RUNNING, finished, failed, killed.
Kill applications ripped off
yarn application -kill
View Logs Concrete Application
yarn logs -applicationId <id-aplicación>
Source: Official website