This topic describes the monitoring metrics related to clog synchronization delay of an OceanBase Database tenant. The metrics include full_clog_sync_delay for clog synchronization delay of full-featured replicas, readonly_clog_sync_delay for clog synchronization delay of read-only replicas, and logly_clog_sync_delay for clog synchronization delay of log replicas. You can specify a statistical range to query statistics about the clog synchronization delay in a single zone or on a single OBServer of an OceanBase Database tenant.
OceanBase Database supports the following types of replicas:
Full-featured replica: A standard replica type that contains all the data categories and all the features, including MemTables, SSTables, and transaction logs. A full-featured replica can switch to the leader role in an efficient manner to provide services.
Log replica: A replica that contains only logs. It does not have a MemTable or an SSTable. It provides log services for external applications and participates in log voting. It can facilitate the recovery of other replicas, but it cannot become the leader to provide database services.
Read-only replica: A replica that contains full logs, MemTables, and SSTables. Its logging feature is special. It does not participate in elections as a Paxos group member. Instead, it tracks in real time the logs of Paxos group members and locally plays back the logs. If an application does not require high consistency in data reading, these replicas can provide read-only services. They are not part of the Paxos group. Therefore, they do not increase the latency of transaction commit because the voting membership is not expanded.
A clog synchronization delay is a delay in the synchronization of the clogs of these replicas.
full_clog_sync_delay
Definition
The maximum clog synchronization delay of the full-featured replicas in the specified statistical range.
Description
| Metric | Metric name | Unit |
|---|---|---|
| full_clog_sync_delay | max_full_clog_sync_delay_second | Seconds |
Calculation expression
max(ob_clog_max_sync_delay_seconds{replica_type="0",@LABELS}) by (@GBLABELS)
readonly_clog_sync_delay
Definition
The maximum clog synchronization delay of the read-only replicas in the specified statistical range.
Description
| Metric | Metric name | Unit |
|---|---|---|
| readonly_clog_sync_delay | max_readonly_clog_sync_delay_seconds | Seconds |
Calculation expression
max(ob_clog_max_sync_delay_seconds{replica_type="5",@LABELS}) by (@GBLABELS)
logonly_clog_sync_delay
Definition
The maximum clog synchronization delay of the log replicas in the specified statistical range.
Description
| Metric | Metric name | Unit |
|---|---|---|
| logonly_clog_sync_delay | max_logonly_clog_sync_delay_seconds | Seconds |
Calculation expression
max(ob_clog_max_sync_delay_seconds{replica_type="16",@LABELS}) by (@GBLABELS)