RrdGraphJS

by Tobi Oetiker, OETIKER+PARTNER AG

The purpose of RrdGraphJS is to allow live interaction with RRD graphs. There are two approaches to accomplish this. The simple one, where we just have the browser request freshly rendered images from the server, according to the users interactions. And the more complex one where the images are drawn at the browser end.

After initial experiments with jQuery, I have switched to qooxdoo Website as a base library. It is a bit larger than jQuery, but the advantage is, that it provides a host of features I would have had to source from third party libraries or write myself otherwise. Notably the event normalization which made the implementation of the chart interaction much simpler.

rrdGraphPng.js

RrdGraphPng.js kicks your RRD graphs into life by requesting new bitmaps from the server as you interact with the chart in the browser. The only thing required on the server side to make this work, is the ability to specify a start and end time for the chart you are requesting from the server.

Depending on the number of people playing with your charts, the load on the server can be significant as it will have to draw several graphs a second as the user interacts with the graphs.

Instantiation

var g = q(selector).rrdGraphPng(configMap);

The selector is expected to pick up <img> tags with a data-src-template attribute. The template can contain the following mustache tags:

<img class="rrd"  data-src-template="graphA?start={{start}}&amp;end={{end}}" />

{{start}}, {{end}}

the start and end time of the chart in epoch seconds.

{{width}}, {{height}}

The size of you image tag as input for the back end chart renderer (make sure to provide img sizing instructions via css).

{{random}}

A random number for every chart requested. Use this to make sure to get a current image if you run into trouble with an eager cache.

{{zoom}}

If you set the moveZoom property. It will show up here while the chart is being moved. Causing a lower resolution (faster) chart to be rendered during animation operations.

Configuration Properties

canvasPadding

For zooming the pointer position on the graph canvas is relevant. Since the JS can not see where the actual chart is on the png image, this option allows you to provide a hint. Default: 100

initialStart

Epoch time for the start of the chart as it is initially loaded. Default: (new Date()).getTime() / 1000 - 24*3600. If you don't want an initial graph to get loaded, set this to 'null'. This is especially usefull if you want to use rrdGraphPng in connection with rrdGraphCtrl.

initialRange

Initial time range for the chart in seconds. Default: 24*3600

moveZoom

The moveZoom value will show up in {{zoom}} while the chart is being moved. Causing a lower resolution (faster) chart to be rendered during animation operations.

autoUpdate

When the current time is in view on the chart, reload the chart automatically and shift it, so that it moves with the time. Default: true

gridFillStyleA, gridFillStyleB

While interacting with the graph, rrdGraphPng will overlay it with a generated grid, providing immediate visual response even when the server is not as fast in generating new images. With this setting, you can modify the color of the grid. Default: rgba(0,0,0,0.08) and rgba(255,255,255,0.08) respectively.

cursorUrl

The package comes with custom cursor images. The images are activated with inline styles on the dom node. This means that the location of the cursor image must be expressed relative to the location of the index.html file. We use some magic in rrdGraphPng.js to deterime this location. But if it fails you may just want to explicitly configure it.

Methods

g.setStart(start), g.setRange(range), g.setStartRange(start,range)

Actively set the time and zoom level for the chart. This will also update the chart.

g.getStart(), g.getRange()

Request the current time and zoom level.

g.update()

Cause the chart to be updated even when neither start nor range are changed.

g.dispose()

Remove ourselves from the img.

Events

changeStartRange

This events get emitted if the chart if moved or zoomed.

g.on('changeStartRange',function(e){
    var start = e.start;
    var range = e.range;
    console.log('new start:' + start);
    console.log('new range:' + range);
});

rrdGraphCtrl.js

Is a control panel for explicitly choosing what information the charts should show. It works with two way data binding. As you manipulate the graph with your pointer, the control panel content will change accordingly.

Instantiation

var c = q(selector).rrdGraphCtrl(g,configMap);

The selector is expected to pick up a <div> tag. The control elements get added into the div tag. Note that g can also be an array of rrdGraphPng widgets.

<div class="ctrl"></div>

Configuration Properties

timeRanges

A map of pre configured time ranges. See the source for details.

initialTimeRange

Which time range to select at the start. Default: Today.

rangeMatchPrecision

How precisely should the range selector work as it is magically switching the range displayed as the graph is zoomed and scrolled. Default is 0.05.

showTimeBox

Display the time entry field. Default true

showDateBox

Display the date entry field. Default true

showTimeRanges

Show timeranges selector as a dropdown or as buttons. Use dropdown or buttons.

resetTimeOnDateChange

Reset the time to 0:00 when a new date is selected. Default: false

momentTz

If you have loaded the moment.js and moment-timezone-with-data.js libraries, you can now use the momentTz property to set the timezone the control should operate in.

If you want to change the timezone on an existing control, just run

ctrl.setConfig('momentTz','CET')

Methods

c.rebind(g)

Bind RrdGraphCtrl to a other instance of RrdGraphPng.

c.dispose()

Remove ourselves from the div.

rrdGraphSvg.js

rrdGraphSvg.js implements RRD graphs on the browser side. It leverages the wonderful d3.js library for low-level data manipulation. It requires the output of xport to get to the actual data. Since very few monitoring systems readily provide xport data access, this variant is more difficult to implement in an existing system.

Also the implementation does not yet cover all the drawing instructions available in rrd_graph. Especially for VDEF and GPRINT statements there is not even a plan yet on how to implement them.

NOTE rrdGraphSvg.js is taken from my extopus project ... it does not yet work in a generic way. It is just included as a place-holder at this point in time.

Example

<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <link href="rrdGraphCtrl.css" rel="stylesheet">
    <!-- the modules are implemented on top of the qxWeb library
         from www.qooxdoo.org. It provides excellent
         modularization and event normalization support out of
         the box and thus made implementation of these
         modules much simpler -->
    <script type="text/javascript" src="q-4.1.min.js"></script>
    <script type="text/javascript" src="rrdGraphPng.js"></script>
    <script type="text/javascript" src="rrdGraphCtrl.js"></script>
    <script type="text/javascript">
        q.ready(function(){

            // 'activate' the charts
            var graph = q('.graph').rrdGraphPng({
                canvasPadding: 120
            });

            // crate a control panel and attach it to the charts
            q('#ctrl').rrdGraphCtrl(graph,{
                initialTimeRange: 'Last 60 Minutes',
                resetTimeOnDateChange: true
            });

            // you can also remove all the magic again
            q('#button').on('click',function(){
                q('#ctrl').dispose();
                q('.graph').dispose();
            });
        });
    </script>
</head>
<body>
    <div id="ctrl"></div>

    <div><img
        style="width:695px;height:238px" class="graph"
        data-src-template="graphA?width={{width}}&amp;height={{height}}&amp;start={{start}}&amp;end={{end}}&amp;zoom={{zoom}}&amp;rand={{random}}"
    /></div>

    <div><img
        style="width:695px;height:238px" class="graph"
        data-src-template="graphB?width={{width}}&amp;height={{height}}&amp;start={{start}}&amp;end={{end}}&amp;zoom={{zoom}}&amp;rand={{random}}"
    /></div>

    <button id="remove">Remove it all!</button>
</body>
</html>