Graphite

Gaps in graph while using high update freq, data volume

Asked by Dimitry Braznichenko on 2008-07-24

I have changed the auto-update frequency to update the graph every 1 second. The problem I am having is that I have gaps in my lines when I try to plot data. The retention is set to 1:3600 (1 point per second for 3600 points). I send in data at very high volumes, maybe 10 points per second, all with the same timestamp. Do additional points on the same timestamp overwrite the original ones - how is this handled? Even at a scale of only showing the graph for the past 1 minute, there are still small (5 second wide) gaps in the lines where it is not connected.

In addition, when all of the y values are around, say, 12450ish, why does graphite not rescale the y axis to something like 12440 to 12460? The scale remains at about 12400 to 13500, making my line nearly horizontal. Please let me know if these are bugs, or simply settings that can be configured with some modification to the source code. I can email you a screenshot of the gaps if you like.

Question information

Language:: English Edit question

Status:: Solved

For:: Graphite Edit question

Assignee:: No assignee Edit question

Solved by:: chrismd

Solved:: 2008-07-29

Last query:: 2008-07-29

Last reply:: 2008-07-28

Revision history for this message

Dimitry Braznichenko (dimab0) said on 2008-07-24:

Nevermind, realized gaps occur when there is no data for the interval that graphite is expecting. For example, if you expect data once a second, but don't send data one of the seconds, or send data every other second to graphite, there will be gaps...

Still no progress why there is no rescaling on the y axis at large numbers...

Revision history for this message

chrismd (chrismd) said on 2008-07-25:

The Y-axis is supposed to be scaled to span the nearest "nice looking" values that cover your graph's value range. So for instance if your graph is of a bunch of values between 103 and 117, the Y-axis labels should be something like 100, 105, 110, 115, 120.

If the Y-axis you are getting is from 12,400 to 13,500, then there should be at least one value outside of the 12,440-12,460 range (or else we may have a bug). Two things will make this easy to troubleshoot: a graph, and its raw data.

To get the raw data for a graph, simply edit its URL and add a "rawData=true" query string parameter. This will return CSV data instead of an image. Could you attach a graph image and its corresponding raw data to this question? (I assume launchpad lets you attach files, if not please email them to me).

Revision history for this message

Dimitry Braznichenko (dimab0) said on 2008-07-25:

I feel that this must be some sort of bug...I don't know what other explanation there can be. I have searched the raw data for anything beginning with 124-- or 127-- and there is nothing there. I have attached both the graph and the raw data for you to take a look at. Please let me know if you have any ideas.
~Dimitry

----- Original Message ----
From: chrismd <email address hidden>
To: <email address hidden>
Sent: Thursday, July 24, 2008 7:49:09 PM
Subject: Re: [Question #40164]: Gaps in graph while using high update freq, data volume

Your question #40164 on Graphite changed:
https://answers.launchpad.net/graphite/+question/40164

Status: Open => Needs information

chrismd requested for more information:
The Y-axis is supposed to be scaled to span the nearest "nice looking"
values that cover your graph's value range. So for instance if your
graph is of a bunch of values between 103 and 117, the Y-axis labels
should be something like 100, 105, 110, 115, 120.

If the Y-axis you are getting is from 12,400 to 13,500, then there
should be at least one value outside of the 12,440-12,460 range (or else
we may have a bug). Two things will make this easy to troubleshoot: a
graph, and its raw data.

To get the raw data for a graph, simply edit its URL and add a
"rawData=true" query string parameter. This will return CSV data instead
of an image. Could you attach a graph image and its corresponding raw
data to this question? (I assume launchpad lets you attach files, if not
please email them to me).

--
To answer this request for more information, you can either reply to
this email or enter your reply at the following page:
https://answers.launchpad.net/graphite/+question/40164

You received this question notification because you are a direct
subscriber of the question.

Revision history for this message

chrismd (chrismd) said on 2008-07-28:

I have found the bug that caused this and committed a fix to trunk. Thanks for the info.

If you want to you can wait until the 0.9.4 release in a week or two, or if you want to get this fix right away you can bzr pull the latest trunk and run the misc/build_release.sh script to create a new release tarball from trunk.