Invalid scraped values in HA-->MySQL replication summary

[Luke03011]

I am frequently seeing invalid values in HA–>MySQL replication summary.
e.g.

You can see the lag value suddenly increasing from 0 to a very big value 14377389, I am sure this is not the real lag value for this instance. It’s like some kind of numerical value overflow, could someone can help with this? Thanks

PMM I used is the latest version 2.26.0.

[Michael_Coburn]

Hi @Luke03011 , thank you for posting to the Percona forums

These artifacts are safe to ignore, and are due to the way Seconds_Behind_Source variable is generated. From the docs:

It is also possible that transient values for Seconds_Behind_Source may not reflect the situation accurately. When the replication SQL (applier) thread has caught up on I/O, Seconds_Behind_Source displays 0; but when the replication I/O (receiver) thread is still queuing up a new event, Seconds_Behind_Source may show a large value until the replication applier thread finishes executing the new event. This is especially likely when the events have old timestamps; in such cases, if you execute SHOW REPLICA STATUS several times in a relatively short period, you may see this value change back and forth repeatedly between 0 and a relatively large value.

https://dev.mysql.com/doc/refman/8.0/en/replication-administration-status.html

An alternative method to tracking replication delay is to use the pt-heartbeat

[Luke03011]

@Michael_Coburn Thanks for your quick response.