Circonus doesn’t ever roll-up or aggregate any of your data, so you can do some interesting real-time analytics. The “+” button in the upper-right corner of any graph lets you add overlays for data analysis to the graph you are viewing. There are overlays for showing historical data, comparisons with other graphs, identifying anomalies, or extrapolating into the future.


For instance, if you have a graph of disk space utilization on a server, it may be growing at a fairly consistent, yet slow pace. Adding a Linear Regression overlay to this data can show the trend of your current usage. If you expand the time frame for your graph into the future, the Linear Regression overlay will predict when you’ll hit your limit for disk space, allowing you to plan your capacity before you need it.


Let's look at a simple example of how to add an overlay to an existing graph to compare it with historical data:

  1. Open the graph to which you would like to add an overlay.

  2. Click the "+" button in the upper-right corner. This will display the "Add Data Overlay" menu.
         
  3. There are tabs for several categories of overlays; Capacity Planning, Anomaly Detection, Service Level Monitoring (which handles percentiles), Graph Comparison, and Other Analytics. For this example, we'll use the Graph Comparison tab.
                                 
  4. The Graph Comparison tab can also be used to overlay other graphs from this account, but for this example, we're going to make an overlay of the current graph. "Current Graph" is the default option in the graph field.

  5. When comparing the current graph with itself, the x axis can be shifted to show a prior time frame and the Y axis can optionally be locked to the main graph’s Y axis. For this example, we'll compare the graph to data from the previous week. Note the drop down menus for "Shift the x axis to show" and "Lock this graph's Y axis to the main graph's Y axis:" We will set the first drop down to "1 week prior" and the second drop down to "Yes".

  6. Once you've made your selections, click the "Add Overlay" button.

  7. The original graph now has the comparison graph overlayed over it. Notice the tabs at the top of the graph and the new information in the legend. Once an overlay has been added to a graph, tabs will appear directly above the graph indicating each of the overlays added. You can drag-and-drop the tabs to reorder them.
         
    The legend has titles that include both the date (useful for understanding time comparisons) and the tab letter indicator (A, B, C, etc.). This helps keep the frame of reference so we know which column is which.

    As you hover, the legend automatically updates the current values with an additional indicator describing the variance between the two graphs for each corresponding data point. An icon pointing up or down indicates if the value is above or below the reference value. A percentage difference is available below the icon. The intensity of the arrow will change (becoming darker or lighter) as the difference increases or decreases.

    The graphs are overlaid from left to right (B "on top of" A and so on). This means that the right-most tab will be the clearest graph and each subsequent graph "underneath" it will be faded. To pull graph data to the front, you can hover over a tab and it will intensify just that overlay.

  8. A graph overlay or a set of overlays can be saved to quickly recall it later. Click on the menu button next to the plus button to manage your overlay sets.

  9. Name the overlay and click the "Save" button:
         
  10. Once an Overlay Set has been saved, it can be recalled at any time by clicking on the menu icon and selecting it from the list of existing sets. Just click "view" to recall your saved overlays.
         


For more information about Analytics, refer to the User Documentation for Graph Overlays and Analytics Overlays.


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