Help Center/ MapReduce Service/ User Guide/ MRS Cluster O&M/ MRS Cluster Alarm Handling Reference/ ALM-14015 DataNode GC Time Exceeds the Threshold
Updated on 2024-09-23 GMT+08:00
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ALM-14015 DataNode GC Time Exceeds the Threshold

Description

The system checks the garbage collection (GC) duration of the DataNode process every 60 seconds. This alarm is generated when the GC duration exceeds the threshold (12 seconds by default).

This alarm is cleared when the GC duration is less than the threshold.

Attribute

Alarm ID

Alarm Severity

Automatically Cleared

14015

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

A long GC duration of the DataNode process may interrupt the services and users cannot read or write files.

Possible Causes

The heap memory of the DataNode instance is overused or the heap memory is inappropriately allocated. As a result, GCs occur frequently.

Procedure

Check the GC duration.

  1. On the FusionInsight Manager portal, choose O&M > Alarm > Alarms. On the displayed interface, click the drop-down button of ALM-14015 DataNode GC Time Exceeds the Threshold. Then check the role name in Location and confirm the IP adress of the instance.
  2. On the FusionInsight Manager portal, choose Cluster > Name of the desired cluster > Services > HDFS > Instance > DataNode (IP address for which the alarm is generated). Click the drop-down menu in the upper right corner of Chart, choose Customize > Garbage Collection, and select DataNode Garbage Collection (GC) to check the GC duration statistics of the DataNode process collected every minute.

    Figure 1 DataNode Garbage Collection (GC)

  3. Check whether the GC duration of the DataNode process collected every minute exceeds the threshold (12 seconds by default).

    • If yes, go to 4.
    • If no, go to 7.

  4. On the FusionInsight Manager portal, choose Cluster > Name of the desired cluster > Services > HDFS > Configurations > All Configurations > DataNode > System to increase the value of GC_OPTS parameter as required.

    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

  5. Save the configuration and restart the DataNode instance.

    Services may be affected or interrupted during the restart. You are advised to perform this operation during off-peak hours.

  6. Check whether the alarm is cleared.

    • If yes, no further action is required.
    • If no, go to 7.

Collect fault information.

  1. On the FusionInsight Manager portal, choose O&M > Log > Download.
  2. Select DataNode 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