XLT 4.1.8 Update Release

XLT 4.1.8 has been released. It contains a couple of improvements and bug fixes. You can get the latest version here: https://lab.xceptance.de/releases/xlt/4.1.8/.

These are the two most important changes.

Optimized scanning CSS rules

XLT simulates the download behavior of a browser as close as possible. With com.xceptance.xlt.css.download.images set to onDemand, XLT carefully considers the download of image resources referred to in CSS files. It checks all CSS rules if they apply to all elements in the DOM tree and, if so, extracts the resource information for later download. This process was previously very expensive and ran for up to several seconds when a page was complex and a lot of CSS rules had to be matched. This has been optimized heavily.

Configurable retry behavior for keep-alive connections

If persistent connections (keep-alive) are enabled, test cases might failed sporadically with an exception such as:
java.lang.RuntimeException: org.apache.http.NoHttpResponseException: The target server failed to respond

This exception occurs only when the request was sent while the connection was about to be closed on the server side at the same time.

The underlying HttpClient retries requests if the connection was closed by the server. However, by default it retries only idempotent operations such as GET and HEAD, but not POST and PUT. In order to avoid these connection errors, the user can now configure whether non-idempotent operations are to be retried as well. Common browsers seem to use the same behavior and most certainly assume that the server did not start to process the request when it closes the connection immediately without responding with a proper HTTP status code.

A new boolean property com.xceptance.xlt.http.retry.nonIdempotentRequests in config/default.properties controls whether or not operations such as PUT and POST are retried in case of certain networking problems. Note that idempotent operations are always retried.

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