HBase is a distributed, NoSQL, open-source database, initially conceived as an open-source alternative to Google’s proprietary BigTable. Originally, HBase was part of the Hadoop project, but was eventually spun off as a subproject. Given this legacy, it is not surprising that most often HBase is deployed on top of a Hadoop cluster (it used HDFS as its underlying storage), however a case study suggests that it can run on top of Amazon Elastic Block Store (EBS) as well. These days HBase is used by companies such as Adobe, Facebook, Twitter and Yahoo – and many others to process large amounts of data in real time, since it is ideally placed to store the input and/or the output of MapReduce jobs.
Like most products written in Java, both HBase and Hadoop contain built-in JMX instrumentation, which theoretically allows us to use any JMX client to view their performance metrics. Naturally, Monitis has just what the doctor ordered – a generic JMX agent that can be configured to monitor any JMX-enabled process through a point-and-click web interface.
By default the HBase JMX interface is disabled, but it can be enabled with relatively few configuration changes as explained in the official HBase documentation. (For security reasons and especially since we are not going to use JMX to modify the metric values or invoke administrative operations on the MBeans, I highly recommend that you do not add controlRole to jmxremote.passwd and jmxremote.access as the document suggests. Also, make sure these two files are owned by the login under which the HBase daemons will run, and that their permissions are 600, otherwise HBase will not start).
The agent is implemented as a JEE web application and is packaged accordingly as a .war file. To download, log on to your Monitis account and select Monitors -> Manage Monitors -> JMX Monitors:
The JMX Monitors window will open. At the bottom of it, you will find a link to download the JMX Agent:
The .war file should be deployed in a standard JEE servlet container. While I recommend Tomcat due to its small footprint and ease of use, there are other options. If you already use an application server such as JBoss or WebSphere, you can deploy the JMX agent in it. While Tomcat offers many ways to deploy a .war file, the easiest one is to copy the .war file to Tomcat’s deploy folder. If Tomcat is already running, you don’t need to restart it – it will pick up and deploy the new .war file automatically.
Another consideration is which machine to deploy the monitor on. The HBase master would be the natural choice but your decision is going to be influenced by your specific network topology and corporate standards. In any case, the JMX agent should be able to accessthe HBase master on TCP port 10101 and optionally the Region Servers (data nodes) on port 10102. Aditionaly, Tomcat needs to be accessible on port 8080 (default).
Once the JMX agent .war file is deployed, go to http://<server_name>:8080/mon_jmx_agent. You should see the JMX agent’s login page which looks like this:
Enter your Monitis credentials – the same ones you use to login to your account on monitis.com – and click Login.
Once it logs you in, the JMX Agent will prompt you to enter an Agent Name:
The Agent Name is used to uniquely identify the JMX Agent instance within Monitis. The metadata about the monitors is associated with your acount on monitis.com and the JMX agent will automatically download and run any existing monitors previously defined for this agent name. For this reason, you want to choose a unique name for each JMX agent deployment. Once you enter a meaningful name and click Save, you should see the JMX Parameters page:
Make sure you enter the correct JMX port number and credentials you configured in HBase and click Submit to go to the next page:
Select the hadoop domain from the drop down – HBase’s MBeans live there for historical reasons. (You may also want to explore other domains – such as java.lang, which provides important information on JVM’s internals). Within the hadoop domain, select the HBase service -> RPC Statistics. The next screen shows an impressive number of metrics:
Under Monitor Name enter something meaningful. This is how your monitor will appear on monitis.com. Check interval is in minutes. Select the following attributes:
While most attribute names are self-explanatory, the MBean does not provide a meaningful description for the attributes, so feel free to examine the JMX section of the HBase book. Once you have selected all the metrics you are interested in, click on the Add Monitor button at the bottom of the page.
We are now ready to log on to Monitis and examine the data collected by our newly created monitor. If you are just logging on, Monitis will prompt you to add the new monitor, otherwise go to Monitors -> Manage Monitors -> JMX Monitors to open the familiar JMX Monitors screen:
Select the check box next to the new monitor and click Add to Window to open a new monitor window:
That’s it! As with any monitor, you can choose between multiple views and define notifications for your HBase performance metrics:
And finally, a few words about architecture. First, the JMX agent’s collector is implemented in the web application (war file). For this reason, you want to make sure that Tomcat (or whatever application server you deployed the agent’s war file on) keeps running for as long as you need to collect data. You may want to monitor the application server process itself and make sure it starts up automatically when the system is booted. Second, when you log on to the JMX Agent’s web interface, your credentials are submitted over an unencrypted HTTP connection (at least with the default Tomcat setup). This might be OK if you are viewing over the corporate LAN, otherwise you should look into enabling HTTPS on Tomcat. Alternatively, you could front Tomcat with Apache and let it do the heavy lifting.
In this installment we introduced the Monitis JMX Agent and hopefully convinced you how easy it is to monitor your HBase cluster. In a future post you will how you can use the agent to monitor JBoss. Happy monitoring!