When running a simple workload like:
If the network connectivity between pmm-client and pmm-server is interrupted (e.g. by blocking port 443 on pmm-server) for a few minutes, when it is re-established, the queries are inserted but with the wrong timestamp.
That is, all queries seem to be inserted, but they show up as having been executed at ingest time, not at the time registered on the slow query log.
This can be seen in the "load" column on the query ranking, as a spike in QPS right after the network connection is established (the spike doesn't really happen, on mysqld's side, the simple select loop has been running constantly). Please refer to the attachment to see what I mean.
I can further verify this by feeding the agent a pre-existing slow query log.
That is, use the agent as normal, but on the fly, replace mysql's slow query log for a file with older queries. These queries will show up in QAN but will be timestamped as having executed at ingest time, not at the time on the slow query log entries.