This topic describes how to access the web UI of Hadoop Distributed File System (HDFS). This topic also describes the endpoints, UI homepage, and startup progress of the NameNode component of HDFS.
Access the web UI of HDFS
You can access the web UI of HDFS by using an SSH tunnel or in the E-MapReduce (EMR) console. For more information, see Create an SSH tunnel to access web UIs of open source components and Access the web UIs of open source components.
Endpoints of NameNode
Version | Endpoint | Description |
Hadoop 3.X | http://${namenode_hostname}:9870 | Replace ${namenode_hostname} with the hostname of the node on which NameNode is deployed. |
Hadoop 2.X | http://${namenode_hostname}:50070 | Replace ${namenode_hostname} with the hostname of the node on which NameNode is deployed. |
NameNode UI homepage
Overview
In the first line of the Overview page, the value to the right of Overview indicates the hostname of the node on which NameNode is deployed. The value active or standby that is enclosed in parentheses () specifies whether the NameNode is in the active or standby state in a high availability (HA) cluster. The following table describes the parameters.
Parameter | Description |
Namespace | The address of the namespace to which the NameNode belongs. |
NameNode ID | The service ID of the NameNode. |
Started | The start time of the NameNode. |
Version | The version number of HDFS. |
Compiled | The compilation information. |
Cluster ID | The ID of the HDFS cluster. |
Block Pool ID | The ID of the HDFS block pool. |
Summary
Description of key information in the preceding figure:
Security: indicates whether Kerberos security authentication is enabled for the cluster.
Safemode: indicates whether the cluster is in safe mode and read-only.
The numbers of files, directories, and data blocks vary based on the status of the NameNode. This is a normal scenario. In this case, the data that is provided by the active NameNode takes priority.
NameNode Journal Status
For an HA cluster, you must take note of the following items:
The active NameNode is in write mode.
You must check the ID of Written txid of each JournalNode when you view the Quorum Journal Manager (QJM) status of an active NameNode. If the ID is always 0 or the value significantly differs from the values of other JournalNodes, reset the JournalNode.
Standby NameNodes are in read mode.
The QJM status of a standby NameNode is in read mode. In most cases, you do not need to take note of the status information.
NameNode Storage
The checkpoint operations on the FsImage files of NameNodes are performed asynchronously. You must take note of the status of the image type. For example, if the image type of a standby NameNode is in the Failed state for a long period of time, the EditLog files are overstocked. If the NameNode is restarted, it takes a long time to read the EditLog files.
Startup progress of NameNode
The following operations are performed during the startup of a NameNode: load the FsImage files, load the EditLog files, and wait for reported blocks. In most cases, the operations are completed in a short period of time. If an operation takes a long period of time to complete, you can take optimization measures.
If it takes a long period of time to load the FsImage files and wait for reported blocks, you can check whether to adjust the garbage collection (GC) parameters.
If it takes a long period of time to load the EditLog files, you can check whether a large number of logs are accumulated on the JournalNode. For information about the directory that is used by a JournalNode, see Local disk directories used by HDFS components.
References
For information about issues that are related to HDFS usage, see FAQ and troubleshooting.