Define your choice of ports by setting properties dfs.http.address for Namenode and mapred.job.tracker.http.address for Jobtracker in conf/core-site.xml:
<configuration>

    <property>
        <name>dfs.http.address</name>
        <value>50070</value>
    </property>

    <property>
        <name>mapred.job.tracker.http.address</name>
        <value>50030</value>
    </property>

</configuration>


Web UIs for the Common User

The default Hadoop ports are as follows:

 Daemon Default Port Configuration Parameter
HDFS Namenode 50070 dfs.http.address
Datanodes 50075 dfs.datanode.http.address
Secondarynamenode 50090 dfs.secondary.http.address
Backup/Checkpoint node? 50105 dfs.backup.http.address
MR Jobracker 50030 mapred.job.tracker.http.address
Tasktrackers 50060 mapred.task.tracker.http.address
? Replaces secondarynamenode in 0.21.
Hadoop daemons expose some information over HTTP. All Hadoop daemons expose the following:
/logs
Exposes, for downloading, log files in the Java system property hadoop.log.dir.
/logLevel
Allows you to dial up or down log4j logging levels. This is similar to hadoop daemonlog on the command line.
/stacks
Stack traces for all threads. Useful for debugging.
/metrics
Metrics for the server. Use /metrics?format=json to retrieve the data in a structured form. Available in 0.21.
Individual daemons expose extra daemon-specific endpoints as well. Note that these are not necessarily part of Hadoop’s public API, so they tend to change over time.
The Namenode exposes:
/
Shows information about the namenode as well as the HDFS. There’s a link from here to browse the filesystem, as well.
/dfsnodelist.jsp?whatNodes=(DEAD|LIVE)
Shows lists of nodes that are disconnected from (DEAD) or connected to (LIVE) the namenode.
/fsck
Runs the “fsck” command. Not recommended on a busy cluster.
/listPaths
Returns an XML-formatted directory listing. This is useful if you wish (for example) to poll HDFS to see if a file exists. The URL can include a path (e.g., /listPaths/user/philip) and can take optional GET arguments: /listPaths?recursive=yes will return all files on the file system; /listPaths/user/philip?filter=s.* will return all files in the home directory that start with s; and /listPaths/user/philip?exclude=.txt will return all files except text files in the home directory. Beware that filter and exclude operate on the directory listed in the URL, and they ignore the recursive flag.
/data and /fileChecksum
These forward your HTTP request to an appropriate datanode, which in turn returns the data or the checksum.
Datanodes expose the following:
/browseBlock.jsp, /browseDirectory.jsp, tail.jsp, /streamFile, /getFileChecksum
These are the endpoints that the namenode redirects to when you are browsing filesystem content. You probably wouldn’t use these directly, but this is what’s going on underneath.
/blockScannerReport
Every datanode verifies its blocks at configurable intervals. This endpoint provides a listing of that check.
The secondarynamenode exposes a simple status page with information including which namenode it’s talking to, when the last checkpoint was, how big it was, and which directories it’s using.
The jobtracker‘s UI is commonly used to look at running jobs, and, especially, to find the causes of failed jobs. The UI is best browsed starting at /jobtracker.jsp. There are over a dozen related pages providing details on tasks, history, scheduling queues, jobs, etc.
Tasktrackers have a simple page (/tasktracker.jsp), which shows running tasks. They also expose /taskLog?taskid=<id> to query logs for a specific task. They use /mapOutput to serve the output of map tasks to reducers, but this is an internal API.
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