ALM-45480 Tablet Leaders of a Tserver Process Are Unevenly Distributed

Alarm Description

The system checks the Kudu service status every 60 seconds. This alarm is generated when the ratio of tablet leaders of a Tserver process to total tablet leaders in the cluster exceeds the threshold.

This alarm is cleared when the ratio of tablet leaders of a Tserver process to total tablet leaders in the cluster becomes normal.

Alarm Attributes

Alarm ID	Alarm Severity	Auto Cleared
45480	Minor	Yes

Alarm Parameters

Type	Parameter	Description
Location Information	Source	Specifies the cluster for which the alarm was generated.
	ServiceName	Specifies the service for which the alarm was generated.
	RoleName	Specifies the role for which the alarm was generated.
	HostName	Specifies the host for which the alarm was generated.

Impact on the System

If Tserver tablet leaders are unevenly distributed, the query performance of the Kudu engine deteriorates.

Possible Causes

Tserver instances are added or restarted.
The threshold is not properly set.

Handling Procedure

Handle the uneven distribution of tablet leaders.

On FusionInsight Manager, choose O&M > Alarm > Alarms, and check whether alarm ALM-45480 Tablet Leaders of a Tserver Process Are Unevenly Distributed exists.
- If yes, go to 2.
- If no, go to 8.
Log in to the Kudu node where the number of tablet leaders exceeds the threshold.
Run the following commands to manually adjust the number of tablet leaders:
su omm

cd /opt/Bigdata/FusionInsight_Kudu_xxx/install/FusionInsight-Kudu-xxx/kudu/bin

./kudu tablet leader_step_down <master_addresses> <tablet_id> [-new_leader_uuid=<new_tablet_server_uuid>]
- master_addresses: The value is in the format of KuduMaster service IP address 1:7051,KuduMaster service IP address 2:7051,KuduMaster service IP address 3:7051.
  KuduMaster service IP address: You can log in to FusionInsight Manager and choose Cluster > Services > Kudu > Instances to view the service IP address of the KuduMaster instance.
- tablet_id: tablet ID to be adjusted.
  You can log in to Manager, choose Cluster > Services > Kudu, and click KuduMaster(KuduMaster) next to KuduMaster WebUI to access the KuduMaster web UI. Choose Tables on the menu bar, click the ID in the Table Id column, and obtain the target tablet ID in Detail.
- new_tablet_server_uuid: ID of the target tablet servers.
  You can log in to the KuduMaster web UI, choose Tablet Servers on the menu bar, and view the UUID.
- new_leader_uuid: You are advised to set the UUID of the node with a small number of tablet leaders.
Choose O&M > Alarm > Alarms and check whether the alarm is cleared.
- If yes, no further action is required.
- If no, go to 5.

Change the threshold.

On FusionInsight Manager, choose O&M > Alarm > Alarms, and check whether alarm ALM-45480 Tablet Leaders of a Tserver Process Are Unevenly Distributed exists.
- If yes, go to 6.
- If no, go to 8.
Choose Cluster > Kudu > Configurations > All Configurations > KuduMaster, locate the alarm threshold parameter TABLET_LEADER_UNBALANCE_SCALE, change the value, and rolling-restart all Kudu Masters to make the configuration take effect.
Choose O&M > Alarm > Alarms and check whether the alarm is cleared.
- If yes, no further action is required.
- If no, go to 8.

Collect fault information.

On FusionInsight Manager, choose O&M. In the navigation pane on the left, choose Log > Download.
Expand the Service drop-down list, and select Kudu for the target cluster.
Click the edit icon 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.
Contact O&M personnel and provide the collected logs.