YARN-6098. Add documentation for Delete Queue. (Suma Shivaprasad via wangda)

Change-Id: I23bf7ca0acbe1168a7f805ceccdd62fe41bfeb35

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/CapacityScheduler.md

@@ -54,7 +54,7 @@ The `CapacityScheduler` supports the following features:
 
 * **Operability**
 
-    * Runtime Configuration - The queue definitions and properties such as capacity, ACLs can be changed, at runtime, by administrators in a secure manner to minimize disruption to users. Also, a console is provided for users and administrators to view current allocation of resources to various queues in the system. Administrators can *add additional queues* at runtime, but queues cannot be *deleted* at runtime.
+    * Runtime Configuration - The queue definitions and properties such as capacity, ACLs can be changed, at runtime, by administrators in a secure manner to minimize disruption to users. Also, a console is provided for users and administrators to view current allocation of resources to various queues in the system. Administrators can *add additional queues* at runtime, but queues cannot be *deleted* at runtime unless the queue is STOPPED and nhas no pending/running apps.
 
     * Drain applications - Administrators can *stop* queues at runtime to ensure that while existing applications run to completion, no new applications can be submitted. If a queue is in `STOPPED` state, new applications cannot be submitted to *itself* or *any of its child queues*. Existing applications continue to completion, thus the queue can be *drained* gracefully. Administrators can also *start* the stopped queues.
 
@@ -441,6 +441,18 @@ Changing queue/scheduler properties and adding/removing queues can be done in tw
     $ vi $HADOOP_CONF_DIR/capacity-scheduler.xml
     $ $HADOOP_YARN_HOME/bin/yarn rmadmin -refreshQueues
 
+#### Deleting queue via file
+
+  Step 1: Stop the queue
+
+  Before deleting a leaf queue, the leaf queue should not have any running/pending apps and has to BE STOPPED by changing `yarn.scheduler.capacity.<queue-path>.state`. See the
+  [Queue Administration & Permissions](CapacityScheduler.html#Queue Properties) section. 
+  Before deleting a parent queue, all its child queues should not have any running/pending apps and have to BE STOPPED. The parent queue also needs to be STOPPED
+
+  Step 2: Delete the queue
+
+  Remove the queue configurations from the file and run refresh as described above
+
 ### Changing queue configuration via API
 
   Editing by API uses a backing store for the scheduler configuration. To enable this, the following parameters can be configured in yarn-site.xml.