Monitoring instrumented web pages
When a customer implements a Content Delivery Network (CDN), such as Akamai, Foglight Experience Monitor cannot automatically measure how long the CDN servers take to respond to a request for content. Therefore, the reported page load time becomes the time the in-house web server spends on the initial request for main.html before passing it on to a CDN server. This results in a partial page response. To get a more accurate page load time, customers can instrument their web pages so that Foglight Experience Monitor can track the time spent on CDN servers.
This section describes how to instrument web pages and how to configure Foglight Experience Monitor to monitor the collected data. For more information on how the page load time is calculated in a CDN environment, see “Instrumentation metrics” in the Foglight Experience Monitor Metric Reference Guide.
For more information, see these topics:
Instrumenting web pages
To get started with instrumentation, use the quest-fxm.js JavaScript file provided on the FxM web console—see the Instrumentation Script (quest-fxm.js) link at the bottom of the Instrumentation page, to track page load and other event times.
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NOTE: By default, 404 Page not Found errors are transmitted as the response for these HTTP requests. It is recommended that customers set up their web servers to specifically return a 200 OK response, to avoid distorting other Foglight Experience Monitor metrics with false 404 errors. |
The following table describes the HTTP request fields.
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Optional. Unique session ID for the page, either automatically created or overridden. | |
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Required. The page name. This field dictates the name that appears in the resource list for the Instrumented Page category. It can be either window.location() or any custom value. | |
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Required. Elapsed times serialized. Each element in this object is the name of the measure and its elapsed time; for example, slowJS(measure name):12(elapsed time). By default, ets is set to record load and unload times, but it can be set to different JavaScript events. For more information about these events, see http://www.w3schools.com/jsref/jsref_events.asp. |
The administrator needs to configure the Foglight Experience Monitor to recognize these HTTP requests as “instrumentation hits” containing metrics that are then funneled into the Instrumented Page category of metrics in the Foglight Experience Monitor metric database. For more information, see Configuring instrumentation options and metrics.
If you need to define metrics other than the default metrics provided with the instrumentation script, your pages must include the appropriate instrumentation calls to record these metric values. For example, if your pages need to do some calculations at a certain point using JavaScript, you can place some instrumentation calls before and after the calculations, using quest-fxm.js, as presented in the following example.
The window.fxm.start() call starts the timer and the window.fxm.stop() call stops it. With the code presented in this example, you can see hits like these coming into the site:
Configuring instrumentation options and metrics
The Instrumentation page, accessed by clicking Configure > Monitoring > Instrumentation, allows you to configure your system to monitor pages that are instrumented for performance metrics.
You can set the following options:
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Transmit instrumentation hits to FxV — While this option is enabled, information about hits is sent to Foglight Experience Viewer. |
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Exclude instrumentation hits from other category metrics — While this option is enabled, HTTP traffic generated by the JavaScript instrumentation module is excluded from all metric categories except the Instrumented Page category. Generally, this is the preferred behavior because it ensures that instrumentation traffic does not inflate the metrics for other categories. |
An instrumentation URL is a URL on the customer’s web site that receives the instrumentation hits from the instrumentation code. By default, the quest-fxm.js script uses the /rx URL. You should add this URL to this list. If you modified the script to point to a different URL, include the modified URL in this list.
You can perform the following tasks:
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To view a real-time display of incoming hits from the instrumented pages deployed on the customer web site, click the Display Instrumentation Hits link. |
This auto-discovery mechanism checks the specified instrumentation URLs and displays incoming hits.
To stop the auto-discovery operation, click Stop. The URL list is updated to display a details link for each instrumentation hit found in the monitored traffic. Click details to display additional details about an instrumentation hit.
To review the quest-fxm.js JavaScript file provided with the FxM appliance, click the Instrumentation Script (quest-fxm.js) link at the bottom of the Instrumentation page. You have the option to open or to save the script file.
The Instrumentation Metrics section of the Instrumentation page allows you to manage the metrics that are tracked using the instrumentation. The Foglight Experience Monitor script collects some metrics by default, including Load Time and Unload Time. To review the default instrumentation metrics, see Viewing a complete list of instrumentation metrics.
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Click Add Instrumentation Metric. |
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Type the metric name in the Name box. This is the metric name to be displayed in the web console (for example, Load Time). |
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In the Tag box, type in the tag used in the ets (elapsed times serialized) field of the instrumentation hits (for example, load). For details about this field, see Instrumenting web pages. |
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Choose the metric type by selecting one of the available option buttons: Standard metric or Count metric. |
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Click OK to save the metric. |
After you finish defining metrics, you can review the metrics in the Metrics Analysis page.
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Navigate to Analysis > Metric Analysis. |
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Find the Content section and expand Instrumented Page. |
Transforming monitored URLs
This section describes how to configure URLs found in the monitored traffic.