Description
This alert is triggered when a transaction in the OBServer cluster is suspended in the commit phase for 1200s or longer.
Principle
The following table describes the key parameters that are involved in the monitoring and alerting logic.
| Parameter | Value |
|---|---|
| Metric | pending_trans_max_duration_seconds |
| Source |
|
| Collected metric | collect_time,ctx_create_time |
| Metric expression | max((collect_time - ctx_create_time)/1000000) |
| Collection cycle | 60 seconds |
Alert rule
| Metric | Default threshold | Source | Detection cycle | Time before clearance |
|---|---|---|---|---|
| pending_trans_max_duration_seconds | 1200 | Tenant | 60 seconds | 5 minutes |
Alert information
| Trigger method | Alert level | Scope |
|---|---|---|
| Based on the expression of the metric | Critical | Tenant |
Alert templates
Alert overview
Template: ${alarm_target} ${alarm_name}
Example: ob_cluster=obcluster-2:tenant_name=orac2:trans_hash={hash:10801753558860391353, inc:59202486, addr:"xxx.xxx.xxx.xxx:2882", t:1646993121179509} A suspended transaction exists in the OceanBase Database tenant.
Alert details
Template: Cluster: ${ob_cluster_name}; Tenant: A suspended transaction exists in the ${tenant_name} tenant. Session ID: ${session_id}; Transaction ID: ${trans_hash}; Transaction Type: ${trans_type}; Transaction Created At: ${trans_create_time}; Maximum Transaction Duration: ${value_shown}
Example: Cluster: obcluster; Tenant: A suspended transaction exists in the orac2 tenant. Session ID: 3221635048; Transaction ID: {hash:10801753558860391353, inc:59202486, addr:"xxx.xxx.xxx.xxx:2882", t:1646993121179509}; Transaction Type: distribute; Transaction Created At: 2022-03-11T18:05:21.184+08:00; Maximum Transaction Duration: 25 days 19 hours 57 minutes and 24.66 seconds
Impact on the system
When a transaction is suspended, the minor compaction of the MemStore is suspended and the application is stopped.
Possible causes
The transaction is suspended when the cluster is leaderless because the candidates fail to receive the majority of votes from other nodes in the cluster during the leader election (the "minority problem"), the disk is full, or the memory is used up.
Solutions
Check for the minority problem.
The minority problem occurs because of the OBServer exceptions or network failure. It also triggers the ob_cannot_connected alert at the same time.
In that case, you need to first solve the problem of the ob_cannot_connected alert by referring to the corresponding topic. Then, check whether the ob_server_exists_long_lived_trans alert is cleared 5 minutes later.
Check the disk space.
Insufficient disk space also triggers the following alerts at the same time. We recommend that you first solve the problems that caused the following alerts by referring to the respective topics, and then check whether the ob_server_exists_long_lived_trans alert is cleared 5 minutes later.
Check the memory.
Insufficient memory may also trigger the alert of memory usage exceeding the threshold at the same time. For more information, see ob_host_mem_percent_over_threshold.
If the problem persists despite the preceding operations, run the following commands and send the result to OceanBase Technical Support for troubleshooting.
-- View the information of all servers to see if a server is faulty. select * from __all_server; -- View the suspended transaction. SELECT * FROM __all_virtual_trans_stat WHERE is_exiting !=1 AND part_trans_action > 2 AND ctx_create_time < DATE_SUB(NOW(), INTERVAL 500 SECOND) LIMIT 100;