By default, `orchestrator` uses `SHOW SLAVE STATUS` and takes a 1-second granularity value for lag. However this lag does not take into account cascading lags in the event of chained replication. Many use custom heartbeat mechanisms such as `pt-heartbeat`. This provides with "absolute" lag from master, as well as sub-second resolution.
`ReplicationLagQuery` allows you to setup your own query.``~~~~``
`ReplicationLagQuery` allows you to setup your own query.
