Value widget is improved to enable displaying values in sync with the time range and displaying trends

Hello, this is id:kmuto from Mackerel team CRE. I'm here to inform you about recent updates.

The newly added features in this update were implemented by the students participating in the Hatena remote internship program.

We added the following three features to the Value widget you can place on the custom dashboard.

  • The value displayed is now in sync with the time range.
  • The metric trend can now be displayed.
  • Full screen graphs can now be opened from the Value widget.

I will cover them individually below.

The value displayed is now in sync with the time range

The Value widget can be placed on the custom dashboard to show a given metric or the product of a function as an easy-to-understand number, so it is useful for displaying the value of a metric or an SLI obtained using a function, such as availability or latency.

However, it was limited by the fact that the graph would sync with the time range specified on the dashboard properly, but the Value widget would end up displaying the most recent value at that point in time, irrespective of the time range.

We improved this feature so that the Value widget properly displays the value depending on the selected time range.

When you select a time range in a graph, the value in the Value widget also changes
The value synchronizes with the time range

The widget will now display the end value (for a running average or linear regression, it will be calculated based on this end value) for the selected time range.

Because this behavior is incompatible with the prior Value widget, so at this time, this feature improvement is only enabled when the “Display a value in sync with the time range” box is checked in the Value widget options. (Checking this box is also required for the other features covered below as well.)

Enable “Display a value in sync with the time range” on the widget's Edit screen.
Enable “Display a value in sync with the time range”

The metric trend can now be displayed

This also appeared in the image in the previous paragraph, but when you check the “Show metric trend” box in the Value widget options, the trend will also be displayed in the widget.

An end value of 90.50%, with the average value of 88.43% and the difference of 2.06% displayed as the trend
Show the metric trend

The trend is displayed as the average value during the selected time range (“Avg 88.43” in the image) and the difference between this average value and the end value (“+2.06” in the image).

In many cases it was probably difficult to determine if anything had or had not changed about the current conditions based on the values alone, so they would be compared against the graph to figure it out. Showing the amount of the change at a glance like this should speed up assessing the situation.

Full screen graphs can now be opened from the Value widget

While this feature is currently only compatible with expression graphs, the button is located to the right of the expression for the widget. Clicking this will open a new browser window and display the expression graph.

Expression graph based on the Value widget value
Full size expression graph

This should come in handy for cases such as SLO where you want to be able to see the fluctuations as necessary, but without going so far as to put the expression graph on the dashboard.

These feature improvements to the Value widget originated from a request of Mackerel team's SRE, so as the “experimental” label indicates, we regard them as experimental features at this time, but they are complete enough for practical use. Going forward, we plan to improve the level of polish and make them standard behavior, so please be sure to try them out!