Showing posts from February, 2014

SSH with Personal Environment

A colleague, Eric Grehm, raised an interesting challenge: How to maintain his personal work environment (VIM settings, .bashrc ...) on all servers? The first thought was putting this somehow into our software distribution, but we quickly realized that this would trigger needless updates on hundreds of servers. The benefit would be that the personal work environment is already on every server upon first access. The next idea is to switch from a pre-installed personal environment to an on-demand solution where the personal environment is transferred each time a remote connection (over SSH) is established. A simple implementation would just to a scp before the ssh, but that entails two connections which takes more time and might also bother the user with a double password request. Side-channel data transfer An alternative is to piggyback the file transfer onto the regular SSH connection so that the personal environment is transferred in a side channel: On the client creat

Rough Measurement for HTTP Client Download Speed

Henrik G. Vogel  / Ever wonder if your website is slow because of the server or because of the clients? Do you want to know how fast is your clients' connection to the Internet? Don't want to use external tracking services, injecting JavaScript etc.? Why not simply measure how long it takes to deliver the content from your webserver to your users? Apache and nginx both support logging the total processing time of a request with a suitably high precision. That gives the time from starting with first byte received from the client and ending after the last byte sent to the client. To try out this idea I added %D to the log format for access.log of my Apache server and wrote a little Python script to calculate the transfer speeds. With the help of the apachelog Python module parsing the Apache access.log is really simple. This module takes a log format definition as configuration and automatically breaks down a log line into the corresponding values.
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