Summary

This is a follow-up to ZBX-27423 and ZBX-16162. Even with the latest version 7.0.25 graphs are still showing dots instead of lines for items which are using "discard unchanged" in some way. In my current case the items are configured as follows:

• Master item:
  • Update interval:   1m
  • Discard unchanged without heartbeat
    • Usually there's actually only a change every 5m
• Items in the graph
  • Dependent from master item
  • JSONPath preprocessing

Tests

For testing I already tried adding "discard unchanged with heartbeat" for the graph items to see if the graph drawing reflects the discard option only if it is configured for those items:

• 5s heartbeat:   Still only dots
• 5m heartbeat:   Dots are connected
• 150s heartbeat:   Dots are connected

This shows that the discard option it is really only reflected in the graph if it is used for the graph items. Additionally this seems only to work if the heartbeat interval is at least half of the actual interval of item values.

So it's difficult not very intuitive to get the expected result. I also think that it can be hard to configure an item to behave as needed while also leading to the expected graph drawing.

Solution proposal

The first idea would be to also take the master item's throttling configuration into account when drawing the graph. But since a master item can also have its own master item this would make it necessary to look it up recursively which probably won't be that easy.

I'd therefore prefer another approach which is also very common with other tools providing such graph drawings. In my opinion it would be better to configure the desired behavior on the graph level. I can imagine the following options for this:

• For the whole graph:
  • Connect values
  • Connect values with specified max. time interval between the values
• For the items in the graph
  • Use graph default
  • Connect values
  • Connect values with specified max. time interval between the values
• For ad-hoc graphs:
  • Provide similar configuration options or keep using the current behavior

In the first moment this solution may seem to be complex. But this would replace the need to look into the items' throttling configuration. In the end this would make it possible to configure items as needed while having expected graphs drawings.