Description
This alert is triggered when the time interval between two major compaction tasks of the OceanBase cluster managed by OceanBase Cloud Platform (OCP) exceeds the threshold. The default threshold is 108000s.
Principle
The following table describes the key parameters that are involved in the monitoring and alerting logic.
| Parameter | Value |
|---|---|
| Metric | ob_cluster_no_merge_seconds |
| Source | SQL: select zone, name, value, time_to_usec(now()) from __all_zone; Note: |
| Collected metrics (unit: us) | current_timestamp and zone_value |
| Metric expression | (max(current_timestamp{metric_group="all_zone",name="merge_start_time",@LABELS}) by (@GBLABELS) - max(zone_value{metric_group="all_zone",name="merge_start_time",@LABELS}) by (@GBLABELS)) / 1000000 |
| Collection cycle | 1 second |
The value of the metric ob_cluster_no_merge_seconds indicates the time interval between two major compaction tasks of the OceanBase cluster. When this value is greater than the threshold, this alert is triggered. The default threshold is 108000s.
Alert rule
| Metric | Default threshold (unit: s) | Duration | Detection cycle | Time before clearance |
|---|---|---|---|---|
| ob_cluster_no_merge_seconds | 108000 | 0 seconds | 60 seconds | 5 minutes |
Alert information
| Trigger method | Alert level | Scope |
|---|---|---|
| Metric expression | Critical | Cluster |
Alert templates
Overview: ${alarm_target} ${alarm_name}
Details: ${alarm_target} ${alarm_name}. The last major compaction was ${value}s ago, exceeding the threshold of ${alarm_threshold}s.
Overview example: ob_cluster=C1-1000. OceanBase cluster compaction detection failed.
Details example: ob_cluster=C1-1000. OceanBase cluster compaction detection failed. The last major compaction was 108001.0s ago, exceeding the threshold of 108000.0s.
Impact on the system
RootService of the OceanBase cluster freezes data regularly. If RootService does not freeze or compact the data for a long time, the disk usage increases, causing the disk space to be fully used and affecting writes of the application.
Possible causes
This problem is commonly found in cases where the RootService is suspended because RootService is leaderless or the process is suspended due to an exception.
Suggested solution
The solution is the same as that for the ob_cluster_no_frozen alert.
