[ZBX-4884] incorrect value of a delta (speed per second) item after being NOTSUPPORTED Created: 2012 Apr 17  Updated: 2017 May 30  Resolved: 2012 Apr 25

Status: Closed
Project: ZABBIX BUGS AND ISSUES
Component/s: Server (S)
Affects Version/s: 1.8.11
Fix Version/s: 1.8.13rc1, 2.0.0rc4

Type: Incident report Priority: Major
Reporter: Kodai Terashima Assignee: Unassigned
Resolution: Fixed Votes: 0
Labels: delta, spike
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Attachments: PNG File after-fix.png     PNG File before-fix.png    
Issue Links:
Duplicate

 Description   

Sometimes, after some period of time when no data collection is made for a particular SNMP item (defined as delta speed per second), we may notice very unusual spikes in graphs. Looking at the trend data stored in the database we may actually see those values like 125086928993896.

It seems that it happens when unsupported item (that's why there was not data collected) becomes available again.



 Comments   
Comment by Alexander Vladishev [ 2012 Apr 18 ]

Fixed in the development branch svn://svn.zabbix.com/branches/dev/ZBX-4884

Comment by dimir [ 2012 Apr 24 ]

This is not directly related to snmp so fixing title and labels.

Comment by dimir [ 2012 Apr 24 ]

When delta (speed per second) item becomes NOTSUPPORTED we still update lastclock which results in incorrect delta value (big difference in data, small difference in time) after item becomes supported. In the graph one would see spikes in such situation.

Comment by dimir [ 2012 Apr 24 ]

before-fix.png and after-fix.png to indicate the spike. The item was UNSUPPORTED at the end of the graph for about 10 minutes. The actual data (speed per second) was around 1 for the whole time.

Comment by dimir [ 2012 Apr 25 ]

Successfully tested. Please review my changes in r27083, r27094.

<Sasha> CLOSED

Comment by Alexander Vladishev [ 2012 Apr 25 ]

Fixed in versions pre-1.8.13 r27100 and pre-2.0.0 r27102.

Comment by Oleksii Zagorskyi [ 2012 Apr 25 ]

meh, this change has to be documented ! At least in at the "what_s_new_1.8.13" page and maybe somewhere else (Martins could try to find some place ).
Am I right that now "Last check" column at the zabbix frontend page "Latest data" will not be updated for cases when an item becomes unsupported?
It could be an unexpected news for users.
REOPENED

<zalex> I was wrong, all is fine.
CLOSED

Comment by dimir [ 2012 Apr 25 ]

lastcheck will be updated as before, even if item is NOTSUPPORTED, lastvalue will be listed as real previous value. The only thing that is new is that after item becomes supported there will be a value only after 2 orig values received (in order to calculate difference). If item becomes NOTSUPPORTED lastorgvalue (used only for deltas) becomes NULL instead of keeping the previous value, but users will not see this. I think we have nothing to document here unless we want to note that the bug, causing invalid deltas (resulting in spikes in graph), was fixed.

<Sasha> Has a typo: lastorgvalue => prevorgvalue.

I close this issue.

Comment by richlv [ 2012 Jul 11 ]

interestingly, ZBX-5310 seems to report a very similar issue for 2.0.1

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