Default Trend behaviour: N/A or Exception Values -VS- TimeOut Gaps

Solved117 viewsadl2099 exception values Trend Graphs Trending monitoring vertical line
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Hello Dojo,

I'm looking for a clarification in terms of trend behaviour normally implemented in DM connectors: when is a vertical line added in trend graphs between values?

Typically, if an element is in timeout, a gap is presented in trend graphs as no data was being polled for the
duration of the timeout (No line connecting the discontinuity, this is well known and expected behaviour in DM).

At times, a "Not Available" (typically "-1" mapped as "Not Available") can be defined
e.g. in case a process disappears: would this present the same gap as a timeout (no vertical line)?

Or would this need to produce a vertical line down to a "Not available" on the Y-axis?

Asking in the context of "exception values" too, e.g. all those values that any polled device can use to signal a state that is not a valid measurement, such as:

  • Large constants used as “out-of-range” placeholders

    • 9999, 65535, 2147483647, -999

  • Special strings

    • "N/A", "Not Available", "Invalid", "Unknown"

  • Hex values

    • 0xFFFF (often used in SNMP MIBs to indicate no value)

Trying to streamline the behaviour for different connectors & cases from different vendors - any steer will be helpful.

Alberto De Luca [DevOps Enabler] Selected answer as best 5 days ago

1 Answer

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861 3 Comments

Hi Alberto,

My understanding is that whenever the trended parameter changes to one of its exception values (e.g., N/A, -999, 0xFFFF, etc., as defined in the protocol), this change is treated as a discontinuity, and therefore no vertical line is expected.

This seems consistent with your second graph: note that the vertical line indicated by the green arrow represents a transition between normal values, which is different from the transitions to or from N/A.

That said, it’s possible I didn’t fully capture your point—please correct me if I misunderstood.

Paulo Henriques [SLC] [DevOps Advocate] Posted new comment 4 days ago
Alberto De Luca [DevOps Enabler] commented

Thanks for your feedback Paulo – it makes sense now – so I'd have a vertical line only when there is a transition across normal values.

In case of discontinuity (no vertical line), what is the default behaviour for connectors?

Should a horizontal "gap" be always present in case of element timeout?

Asking to be able to tell the difference between an "exception value" discontinuity VS a timeout discontinuity.
Paulo Henriques [SLC] [DevOps Advocate] commented

Hi Alberto,
I read your previous comment and your last question but I'm still trying to find what is the current behavior versus what is expected. Good that you put the question on a new post, it will get a better visibility I think.
Thanks.