Help Center/ MapReduce Service/ User Guide/ MRS Cluster O&M/ MRS Cluster Alarm Handling Reference/ ALM-14008 DataNode Heap Memory Usage Exceeds the Threshold
Updated on 2024-09-23 GMT+08:00
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ALM-14008 DataNode Heap Memory Usage Exceeds the Threshold

Description

The system checks the HDFS DataNode Heap Memory usage every 30 seconds and compares the actual Heap Memory usage with the threshold. The HDFS DataNode Heap Memory usage has a default threshold. This alarm is generated when the HDFS DataNode Heap Memory usage exceeds the threshold.

You can change the threshold in O&M > Alarm > Thresholds > Name of the desired cluster > HDFS.

When the Trigger Count is 1, this alarm is cleared when the HDFS DataNode Heap Memory usage is less than or equal to the threshold. When the Trigger Count is greater than 1, this alarm is cleared when the HDFS DataNode Heap Memory usage is less than or equal to 90% of the threshold.

Attribute

Alarm ID

Alarm Severity

Automatically Cleared

14008

Major

Yes

Parameters

Name

Meaning

Source

Specifies the cluster for which the alarm is generated.

ServiceName

Specifies the service for which the alarm is generated.

RoleName

Specifies the role for which the alarm is generated.

HostName

Specifies the host for which the alarm is generated.

Trigger condition

Specifies the threshold triggering the alarm. If the current indicator value exceeds this threshold, the alarm is generated.

Impact on the System

The HDFS DataNode Heap Memory usage is too high, which affects the data read/write performance of the HDFS.

Possible Causes

The HDFS DataNode Heap Memory is insufficient.

Procedure

Delete unnecessary files.

  1. Log in to the HDFS client as user root. Run cd to switch to the client installation directory, and run source bigdata_env.

    If the cluster uses the security mode, perform security authentication.

    Run the kinit hdfs command and enter the password as prompted. Obtain the password from the administrator.

  2. Run the hdfs dfs -rm -r file or directory command to delete unnecessary files.
  3. Check whether the alarm is cleared.

    • If yes, no further action is required.
    • If no, go to 4.

Check the DataNode JVM memory usage and configuration.

  1. On the FusionInsight Manager portal, choose Cluster > Name of the desired cluster > Services > HDFS.
  2. In the Basic Information area, click NameNode(Active) to go to the HDFS WebUI.

    By default, the admin user does not have the permissions to manage other components. If the page cannot be opened or the displayed content is incomplete when you access the native UI of a component due to insufficient permissions, you can manually create a user with the permissions to manage that component.

  3. On the HDFS WebUI, click the DataNodes tab, and check the number of blocks of all DataNodes related to the alarm.
  4. On the FusionInsight Manager portal, choose Cluster > Name of the desired cluster > Services > HDFS > Configurations > All Configurations. In Search, enter GC_OPTS to check the GC_OPTS memory parameter of HDFS->DataNode.

Adjust the configuration in the system.

  1. Check whether the memory is configured properly based on the number of block in 6 and the DataNode Heap Memory parameters in 7.

    • If yes, go to 9.
    • If no, go to 11.

    The mapping between the average number of blocks of a DataNode instance and the DataNode memory is as follows:

    • If the average number of blocks of a DataNode instance reaches 2,000,000, the reference values of the JVM parameters of the DataNode are as follows: -Xms6G -Xmx6G -XX:NewSize=512M -XX:MaxNewSize=512M
    • If the average number of blocks of a DataNode instance reaches 5,000,000, the reference values of the JVM parameters of the DataNode are as follows: -Xms12G -Xmx12G -XX:NewSize=1G -XX:MaxNewSize=1G

  2. Modify the heap memory parameters of the DataNode based on the mapping between the number of blocks and the memory. Click Save and choose Dashboard > More > Restart Service.

    The service will be unavailable during the restart. In addition, upper-layer services that depend on the service are affected.

  3. Check whether the alarm is cleared.

    • If yes, no further action is required.
    • If no, go to 11.

Collect fault information.

  1. On the FusionInsight Manager portal, choose O&M > Log > Download.
  2. Select HDFS in the required cluster from the Service.
  3. Click in the upper right corner, and set Start Date and End Date for log collection to 10 minutes ahead of and after the alarm generation time, respectively. Then, click Download.
  4. Contact the O&M personnel and send the collected logs.

Alarm Clearing

After the fault is rectified, the system automatically clears this alarm.

Related Information

None