netdata/docs/developer-and-contributor-corner/monitor-hadoop-cluster.md

Monitor a Hadoop cluster with Netdata

Hadoop is an Apache project is a framework for processing large sets of data across a distributed cluster of systems.

And while Hadoop is designed to be a highly available and fault-tolerant service, those who operate a Hadoop cluster will want to monitor the health and performance of their Hadoop Distributed File System (HDFS) and Zookeeper implementations.

Netdata comes with built-in and pre-configured support for monitoring both HDFS and Zookeeper.

This guide assumes you have a Hadoop cluster, with HDFS and Zookeeper, running already. If you don't, please follow the official Hadoop instructions or an alternative, like the guide available from DigitalOcean.

For more specifics on the collection modules used in this guide, read the respective pages in our documentation:

• HDFS
• Zookeeper

Set up your HDFS and Zookeeper installations

As with all data sources, Netdata can auto-detect HDFS and Zookeeper nodes if you installed them using the standard installation procedure.

For Netdata to collect HDFS metrics, it needs to be able to access the node's /jmx endpoint. You can test whether an JMX endpoint is accessible by using curl HDFS-IP:PORT/jmx. For a NameNode, you should see output similar to the following:

{
  "beans" : [ {
    "name" : "Hadoop:service=NameNode,name=JvmMetrics",
    "modelerType" : "JvmMetrics",
    "MemNonHeapUsedM" : 65.67851,
    "MemNonHeapCommittedM" : 67.3125,
    "MemNonHeapMaxM" : -1.0,
    "MemHeapUsedM" : 154.46341,
    "MemHeapCommittedM" : 215.0,
    "MemHeapMaxM" : 843.0,
    "MemMaxM" : 843.0,
    "GcCount" : 15,
    "GcTimeMillis" : 305,
    "GcNumWarnThresholdExceeded" : 0,
    "GcNumInfoThresholdExceeded" : 0,
    "GcTotalExtraSleepTime" : 92,
    "ThreadsNew" : 0,
    "ThreadsRunnable" : 6,
    "ThreadsBlocked" : 0,
    "ThreadsWaiting" : 7,
    "ThreadsTimedWaiting" : 34,
    "ThreadsTerminated" : 0,
    "LogFatal" : 0,
    "LogError" : 0,
    "LogWarn" : 2,
    "LogInfo" : 348
  }, 
  { ... }
  ]
}

The JSON result for a DataNode's /jmx endpoint is slightly different:

{
  "beans" : [ {
    "name" : "Hadoop:service=DataNode,name=DataNodeActivity-dev-slave-01.dev.local-9866",
    "modelerType" : "DataNodeActivity-dev-slave-01.dev.local-9866",
    "tag.SessionId" : null,
    "tag.Context" : "dfs",
    "tag.Hostname" : "dev-slave-01.dev.local",
    "BytesWritten" : 500960407,
    "TotalWriteTime" : 463,
    "BytesRead" : 80689178,
    "TotalReadTime" : 41203,
    "BlocksWritten" : 16,
    "BlocksRead" : 16,
    "BlocksReplicated" : 4,
    ...
  },
  { ... }
  ]
}

If Netdata can't access the /jmx endpoint for either a NameNode or DataNode, it will not be able to auto-detect and collect metrics from your HDFS implementation.

Zookeeper auto-detection relies on an accessible client port and an allow-listed mntr command. For more details on mntr, see Zookeeper's documentation on cluster options and Zookeeper commands.

Configure the HDFS and Zookeeper modules

To configure Netdata's HDFS module, navigate to your Netdata directory (typically at /etc/netdata/) and use edit-config to initialize and edit your HDFS configuration file.

cd /etc/netdata/
sudo ./edit-config go.d/hdfs.conf

At the bottom of the file, you will see two example jobs, both of which are commented out:

# [ JOBS ]
#jobs:
#  - name: namenode
#    url: http://127.0.0.1:9870/jmx
#
#  - name: datanode
#    url: http://127.0.0.1:9864/jmx

Uncomment these lines and edit the url value(s) according to your setup. Now's the time to add any other configuration details, which you can find inside the hdfs.conf file itself. Most production implementations will require TLS certificates.

The result for a simple HDFS setup, running entirely on localhost and without certificate authentication, might look like this:

# [ JOBS ]
jobs:
  - name: namenode
    url: http://127.0.0.1:9870/jmx

  - name: datanode
    url: http://127.0.0.1:9864/jmx

At this point, Netdata should be configured to collect metrics from your HDFS servers. Let's move on to Zookeeper.

Next, use edit-config again to initialize/edit your zookeeper.conf file.

cd /etc/netdata/
sudo ./edit-config go.d/zookeeper.conf

As with the hdfs.conf file, head to the bottom, uncomment the example jobs, and tweak the address values according to your setup. Again, you may need to add additional configuration options, like TLS certificates.

jobs:
  - name    : local
    address : 127.0.0.1:2181

  - name    : remote
    address : 203.0.113.10:2182

Finally, restart Netdata.

sudo systemctl restart netdata

Upon restart, Netdata should recognize your HDFS/Zookeeper servers, enable the HDFS and Zookeeper modules, and begin showing real-time metrics for both in your Netdata dashboard. 🎉

Configuring HDFS and Zookeeper alerts

The Netdata community helped us create sane defaults for alerts related to both HDFS and Zookeeper. You may want to investigate these to ensure they work well with your Hadoop implementation.

• HDFS alerts

You can also access/edit these files directly with edit-config:

sudo /etc/netdata/edit-config health.d/hdfs.conf
sudo /etc/netdata/edit-config health.d/zookeeper.conf

For more information about editing the defaults or writing new alert entities, see our health monitoring documentation.