MySQL 5.7.18 and memory ...

[Adam Nelson]

I have a 5.7.18 MySQL instance configured and setup on a rather dedicated large box. It's running InnoDB only with Group Replication. From a query perspective it's running without any problems or hiccups ... from a Admin perspective ... it's consuming way to much memory and it never seems to stop. The current setup has ...

InnoDB bufffer set to 256G
Open innodb files limited to 1000
Open tables limited to 3000
Join buffer set to 8m
sort buffer set to 2m
tmp-table limited to 128m (however, global stats shows very few created)
There are on average around 300 active connections
only 5k - 6k writes per/s
reads vary between 5 - 15 mil per/s

I would expect the memory to be running around 300GB ... When I restarted the MySQL instance on Thursday it was using over 500GB of RAM ... what I'm seeing is that after the warm up period it slowly starts increasing every day till it consumes all memory on the box and then crashes because there is zero free memory .. as an example ...

Thursday last week, system was restarted
After an hour it was around 275G
After six hours it was around 300GB
By Friday afternoon it was 350GB
By Saturday afternoon it was 380GB
By Sunday afternoon it was 390GB
By this afternoon it is up to 410GB

That's not virtual memory, that's physical memory it's consuming. I've limited every thing I would normally limit ... open tables, open files, join/sort buffers, to no avail ... it still increases and never seems to release it. Here's the real confusing part to me. After the first time this happened I turned on performance stats for memory to see if I could find where the memory is being consumed at. According to memory_summary_by_user_by_event_name only 292 GBs of memory is being used. According to memory_summary_global_by_event_name only 292 GBs of memory is being used. According to everything I know to check in MySQL, it's not using the amount of memory the OS is allocating to it. I'm not sure where to check or where to go with this ... does anyone have any suggestions?