Category: Rant

Nearly lost my drone today

So I went skiing at Bristol today. I brought my drone alone just in case it wasn’t too crowded. However I made several mistakes:

  • I didn’t bring my reading glasses, which makes it hard to see what’s on the controller screen
  • I didn’t preload a map of the place on the controller
  • I didn’t recharge the batteries even though it’s been long enough that (I now know) the batteries purposely discharge to 60% or so
  • I didn’t realize that the wind was very strong above the treetops, and do something about the battery low or loss of signal RTH (Return to Home) function to do something other than rise up to 300 feet and get blown away
  • I didn’t set the home point somewhere where there were no trees overhead

So anyway, it was doing a fantastic job following me. I kept glancing back because the Mini 3 Pro is so quiet you can’t hear it unless there’s no other sound around. Even people who skied past me didn’t seem to realize there was a drone behind me. (Obviously I had it flying high enough that it wouldn’t hit anybody) But with about 300 meters left on the course I suddenly realized it wasn’t following me. I couldn’t read the messages on the screen, but I suspected it had done an RTH.

I quickly continued on to the home point, and it wasn’t there. I was looking up and I couldn’t see it or hear it, although if it was still up at 300 feet I probably couldn’t do either. Eventually I realized that the video was just pure white and it had a message about the motor stopping, so I realized it was probably crashed in the snow, but it might have been in a tree top.

I took off my skis and hiked a direct line through the woods between the home point and where I’d last seen it, scanning the snow and tree tops all the way. Then I hiked back to the home point along the trail, still examining the tree tops and snow to either side of the trail.

Around this time I remembered that the controller had a “Find My Drone” function, which I quickly activated while the controller continued to tell me how close the drone’s battery was to dying. Unfortunately, I hadn’t looked at the manual for this, and I wasn’t sure what I was seeing on the map. Again, I forgot to preload the map so all I had was a triangle and a dot with a line between them. I started to ski backwards around the trail, and the line seemed to be getting shorter, so I thought the dot was me. Eventually, however, I realized there was a third dot, and the reason the line was getting shorter was the third dot represented me (or rather the controller) and the map was zooming out to show that third dot as it moved further away from the other two dots.

Applying my masterful powers of deduction, realized the triangle and dot with a line between them probably represented the drone and the home point. I quickly returned to the home point, and that told me that the dot was the home point. Using my amazing orienteering skills, I headed in the direction of the triangle, and found my drone sitting in the snow beside one of the downhill trails. Phew. Can’t wait to see if the video looks any good. I’d love to do this at Cummings Nature Center if they ever get any snow.

Update: It turns out that because I didn’t have my reading glasses and couldn’t see the screen, I didn’t actually record any video during the important part. I got some video of my trying to get my drone set up to follow me, some still pics, and then nothing until a weird little bit of video evidently recorded during the RTH where I have about a second of a view over the valley taken from very high up, and then everything gets very over exposed and you can’t make out anything.

Can’t see a difference

My Garmin VIRB360 camera has two modes when shooting 360 degree video. In the first, it records 4K video and stitches the front and back lens videos in the camera, so it uploads into VIRB Edit nice and fast. In the second mode, it records the front and back lens videos separately, and VIRB Edit stitches as it uploads the pictures. This results in a supposed 5K video, but the stitching process takes literally hours at a time. I’ve done a few tests and honestly I don’t see the point – the 5K doesn’t look much better.

Here are some screen shots from two days shooting, one at 5K and one at 4K. Can you tell me which is which?

Picture 1
Picture 2

A weird thought

I had a weird thought the other night. There are a couple of programming tasks on my massive “to do” list that I figured I’d power through in the first few months of retirement before I started spending hours and hours alternating between training in my kayak and touring on bikes with my wife.

Well, life doesn’t always work out the way you intended and none of my todo items has been checked off because the pain that last year made it uncomfortable to sit for too long, and which was just on the “barely tolerable” end of things by the end of a normal length kayak race has now progressed to absolutely intolerable for even short stints at a desk chair or kayak. I’ve spent about 15 minutes total all winter in my erg, and haven’t even put my kayaks in the water. Normally by this time of the year I’d have 30 or 40 hours on the erg and about the same on the water. And I limit my sitting at my desk chair to short periods to deal with bills and paying taxes and the like. Even the library easy chairs are uncomfortable verging on painful these days.

But back to my weird thought. I have a new iPad. I can’t afford a new laptop. So I was thinking that for those programming tasks, what I might try is to install “code-server”, which is a hosted version of Visual Studio Code, on my linux server. This gives you the full power of a pretty extensive IDE available through an iPads web browser. I could try coding up one of those projects using that, maybe using the git integration to push the app to a free heroku instance for testing and debugging. I wonder if that’s doable?

Well, in order to find out, first I’d have to install code-server and make it available through my web server. Oh, what’s this, it appears you need to use nginx as your web server rather than Apache to do that. Well, no problem, I’ve been intending to make that switch to make it easier to use LetsEncrypt to put everything behind https like I should have years ago. Oh wait, one of my sites uses Perl fastcgi. Looks like there’s some extra hoops you have to jump through to configure that. And also convert all my .htacess files into clauses in the nginx configuration files.

Sigh, this is going to be a full in yak shaving exercise, isn’t it? I just wish the pain killers I take to be able to sleep at night didn’t leave me dizzy and disoriented all day, or that they actually killed the pain instead of just knocking me out.

Well that aint good

Further to Scraping a third party site:

Woke up this morning to an email from Linode saying my linode server has been running at 200% CPU. Logged in, and sure enough CPU is high, and there are a bazillion “firefox-esr” processes running. Did a kill-all on them, and the CPU immediately dropped to reasonable numbers. There was still a “geckodriver” process running, and when I killed that it went into zombie state instead of going away. I had to do an /etc/init.d/apache2 reload to make that one go away.

Did some tests, both from the nightly “scrape the whole damn site” cron job and the web site’s “scrape one flight plan when the user clicks on that flight plan” and I’m not currently seeing any orphaned firefox-esr or geckodriver processes. So it appears that when I scrape, I correctly close the Webdriver connection which correctly stops the firefox and geckodriver processes.

So I guess I need to keep an eye on this and see if I can figure out what the client is doing to make the website fail to close the Webdriver connection. Or maybe I left some turdlets around on the system when I was doing testing? I don’t know.

Scraping a third party site

For my sins, I wrote a website for a friend’s company that relies on scraping information off another company’s website. The company I’m doing this for does have a paid account on the third party’s website so there’s nothing ethically dubious going on here – I’m basically taking off information my clients had put into the third party site.

I couldn’t figure out the third party site’s authentication system, so instead of pulling in a page and parsing it using BeautifulSoup, I use Selenium to attach to it like a web browser.

The third party site, however, is utterly terribly written. It’s full of tables nested within tables, and missing closing tags and everything else that reminds you of the old “FrontPage” designed sites that only worked on IE. They don’t consistently use ids or names or anything else to help me find the right bits of data, so I’ve had to wing it and parse things out using regular expressions all over the place. But worse is that every now and then they change things around a bit in a way that breaks my scraping.

The way I’ve been scraping in the past was I used the Selenium “standalone” jar, attaching to this java process that pretends to be a web browser without actually being a browser. Which is important, because I run the scraping process on my web server, which is a headless linode, and like most web servers doesn’t even have X11 running on it. (Some components of X11 got installed on it a while back because something needed something that needed something that needed fonts, and voila, suddenly I’ve got bits of X11 installed.)

This method has worked great for several years – when I’m debugging at home I use the version of the Selenium webdriver that fires up a Chrome or a Firefox instance and scrapes, but then when it’s working fine I switch over to the version that connects to a java -jar selenium-standalone.jar process. I don’t know what the official term is, so I’m just going to call it “the selenium process”.

A couple of years ago they (the third party) made a change to their website that caused the selenium process to die with JavaScript errors. Like I said, their website is crap, and I shouldn’t be surprised it has crappy JavaScript. Fortunately at the same time they introduced these JavaScript errors, they put a big “submit” button on the page that would go to the selected page even if you disabled JavaScript, and so that’s what I did with my scraper back then.

Flash forward to now, and they’ve changed the site again. They still have the broken JavaScript that freaks out the selenium process, but now you can’t navigate the site if you turn off JavaScript. So I tried turning on JavaScript in my scraper and the selenium process, and as expected from 2 years ago it failed spectacularly. So I tried updating the selenium process jar, and it doesn’t even connect at all – even though my Python selenium API version number and selenium process jar version number are the same (3.141.59, I had been using selenium jar version 3.12.0 before). I did some googling and found the names of the arguments had changed a bit, so I changed that and I still couldn’t get anything working.

I tried a bunch of different ideas, and followed a bazillion web links and tried a bunch of things from those places. Nothing worked. Eventually I had to give up and install Firefox on my web server, and an optional piece of the selenium api called “geckodriver” that launches Firefox. Fortunately selenium knows how to launch Firefox in a headless manner (although installing it did drag in even more bits of X11 that I don’t actually want or need). That actually worked on the site, after I figured out how to put the geckodriver file somewhere on the path and get the geckodriver.log file put somewhere useful. But I’ve got it done for now. Until the next gratuitous change.