Monitor Lag Using Automatic Heartbeat Tables

You can use the default automatic heartbeat table functionality to monitor end-to-end replication lag. Automatic heartbeats are sent from each source database into the replication streams, by updating the records in a heartbeat seed table and a heartbeat table, and constructing a heartbeat history table. Each of the replication processes in the replication path process these heartbeat records and update the information in them. These heartbeat records are inserted or updated into the heartbeat table at the target databases.

The heartbeat tables contain the following information:

• Source database

• Destination database

• Information about the outgoing replication streams:

  • Names of the Extract, Distribution Service, and or Replicat processes in the path

  • Timestamps when heartbeat records were processed by the replication processes.

• Information about the incoming replication streams:

  • Names of the Extract, Distribution Service, and or Replicat processes in the path

  • Timestamps when heartbeat records were processed by the replication processes.

Using the information in the heartbeat table and the heartbeat history table, the current and historical lags in each of the replication can be computed.

Replicat can track the current restart position of Extract with automatic heartbeat tables (LOGBSN). This allows regenerating the trail files from the source database, if required and minimizes the redo log retention period of the source database. Also, by tracking the most recent Extract restart position, the tombstone tables for automatic Conflict Detection and Resolution (ACDR) tables can be purged more frequently.

In a bidirectional configuration, the heartbeat table has as many entries as the number of replication paths to neighbors that the database has and in a unidirectional setup, the table at the source is empty. The outgoing columns have the timestamps and the outgoing path, the local Extract and the downstream processes. The incoming columns have the timestamps and path of the upstream processes and local Replicat.

In a unidirectional configuration, the target database will populate only the incoming columns in the heartbeat table.

Note:

The Automatic Heartbeat functionality is not supported on MySQL version 5.5.