Application Master Web UI

Drill, running as a YARN application, provides the Drill-on-YARN Application Master (AM) process to manage the Drill cluster. The Drill AM provides a web UI where you can monitor cluster status and perform simple operations, such as increasing or decreasing cluster size, or stopping the cluster.

When you launch Drill using the Drill-on-YARN command line tool, the tool signals YARN to launch the AM, which in turn launches the Drillbits in the cluster. When Drill starts, you can access the web UI using the URL provided at startup.

The following sections describe the information that the Application Master web UI provides:


The main page provides the following information about the Drill cluster:

Drill Cluster Status
The Drill cluster status show the state of the Drill cluster, which is one of the following:
  • LIVE: This is the normal state and shows that the Drill cluster is running.
  • ENDING: The cluster is in the process of shutting down

There is no “ENDED.” state. When the cluster shuts down, the web UI is no longer available.

Target Drillbit Count
The target Drillbit count is the number of Drillbits to run in the cluster. The actual number may be less if Drillbits have not yet started, or if YARN cannot allocate enough containers.
Live Drillbit Count
The live Drillbit count is the number of Drillbits that are ready for use. These have successfully started, have registered with ZooKeeper, and are ready for use. You can see the detail of all Drillbits (including those in the process of starting or stopping) using the Drillbits page. Each Drillbit must run on a separate node, so this is also the number of nodes in the cluster running Drill.
Total Drillbit Memory and Virtual Cores
The total number of YARN resources currently allocated to running Drillbits.
YARN Node Count, Memory, and Virtual Cores
Reports general information about YARN itself including the number of nodes, the total cluster memory, and total number of virtual cores.
Lists the cluster groups defined in the configuration file (only one is currently supported), along with the target and actual number of Drillbits in that group.


The configuration page shows the complete set of configuration values used for the current run. The values come from the configurations you set and the Drill-provided defaults. Use this page to diagnose configuration-related issues. Names are shown in fully-expanded form. That is the name “drill.yarn.http.port” refers to the parameter defined, as follows, in your configuration file:
 http: {
   port: 8048


The Drillbits page provides the following information about each of the Drillbits:

A sequential number assigned to each new Drillbit. Numbers may not start with 1 if you have previously shut down some Drillbits.
The cluster group that started the Drillbit. Cluster groups configured in drill-on-yarn.conf.
The host name or IP address on which the Drillbit runs. If the Drillbit is in a normal operating state, this field is also a hyperlink to the Web UI for the Drillbit.
The operating state of the Drillbit. The normal state is “Running.” The Drillbit passes through a number of states as YARN allocates a container and launches a process, as the AM waits for the Drillbit to become registered in ZooKeeper, and so on. Similarly, the Drillbit passes through a different set of states during shutdown. Use this value to diagnose problems. If the Drillbit is in a live state, this field shows an “[X]” link that you can use to kill this particular Drillbit. Use this if the Drillbit has startup problems or seems unresponsive. During the shut-down process, the kill link disappears and is replaced with a “Cancelled” note.
ZK State
The ZooKeeper handshake state. Normal state is “START_ACK”, meaning that the Drillbit has registered with ZooKeeper. This state is useful when diagnosing problems.
Container ID
The YARN-assigned container ID for the Drillbit task. The ID is a link that takes you to the YARN Node Manager UI for the Drillbit task.
Memory and Virtual Cores (vcores)

The amount of resources actually allocated to the Drillbit by YARN.

Start Time
The date and time (in your local time-zone, displayed in ISO format) when the Drillbit launch started. This page also displays unmanaged Drillbits, if present. An unmanage Drillbit is one that is running, has registered with ZooKeeper, but was not started by the Application Master. Likely, the Drillbit was launched using the script directly. Use the host name to locate the machine running the Drillbit if you want to convert the Drillbit to run under YARN.


The Manage page provides options to resize or stop the Drill cluster. You can resize the cluster by adding or removing Drillbits or setting the cluster to a specific size.

Drill is a long-running application. Typlically, Drill runs indefinitely, and you would only shut down the Drill cluster to perform an upgrade of the Drill software or to change configuration options. When you terminate the Drill cluster, any in-progress queries fail. Therefore, best practice is to perform the shutdown with users so that Drill is not processing any queries at the time of the shut-down.

When removing or shutting-down the cluster, you receive a confirmation page asking if you really do want to stop Drillbit processes. Click Confirm to continue.


The History page lists all failed, killed, and restarted Drillbits. You can detect failures and diagnose problems using the information on this page. Use the YARN container ID listed on this page to locate the log files for the Drillbit.