I worked at a company once that had a really decent HTTP server library… That they put in every program.
You’d launch an app, and to debug it, you’d access http://localhost:9001. From there, you could go to URLs for different libraries in the app. Like, if you had a compression library, you could go http://localhost:9001/compression. It would show stats about the recent work it had done, how long it took, how much CPU, RAM, disk it used. The state of variables now, etc. You could click a button to get it to dump its cache, etc.
If you were running a service on a remote machine, accessing it over HTTP to control it was just awesome. http://r2d2:9001/restart. http://r2d2:9001/quit. http://r2d2:9001/logfile.
Oh, and the services running on that remote machine would register with a system-level monitor. So, if you went to http://r2d2/services, you could see a list of links to connect to all of the running services.
…and every service registered with a global monitor for that service. So, if you knew a Potato process was running somewhere, but you weren’t sure which machine it was on, you could find it by going to http://globalmonitor/Potato, and you’d see a list of machines it was running on.
Just all kinds of awesomeness were possible. Can not recommend enough.
And, I mean like, programs with a GUI. Like, picture a game. Except on my second monitor, I had Chrome open, talking to the game’s engine. I could use things like WebSockets to stream data to the browser. Like, every time the game engine rendered a shot, I could update it (VNC-style) in the browser window. Except annotated with stats, etc. It was just the most useful way to organize different debug information.
And what was great was that writing a library, and wanting to output information, you wouldn’t write it to std out… You’d make HTML content, and write to it. Want to update it? Clear the buffer and write to it again. As a user, if you ever want to read the buffer, you just browse it. Want to update it? Refresh the window. Or better yet, stream it over a websocket. Like Std Out on steroids. If you need to combine the output from a few libraries in a new window, you just write a bit more HTML in your code, and you’re doin’ it.
It’s just another example, in my mind, of the power of libraries. We all get used to thinking of frameworks (IIS, Apache) as the only way to solve a problem, that we forget to even think about putting things together in new and unexpected ways. HTTP as a library – HELL YES.
Using HTML to debug programs, live, is highly under-utilized.