The auto update of the build page with logs is not working properly, and even when it works, it has a major drawaback: the whole log is refreshed each time, which is not scalable at all.

The idea would be to tweak this behavior to send only new log lines. To keep time information as is today (displayed only when different from previous line) we will have to achieve some client side verification of the last line time to know if the time should be displayed on the client (because the cost on the server to know if the time must be displayed is too high compared to the benefit). Storing the last log line time in a hidden span seems to be a good approach to this problem.