Sunday, 29 March 2015

Series Torrent Downloader to Dropbox

Blog post after a lonnng time. So I like to watch movies and series a lot. I started following so many series that it became difficult to keep track of what series is aired when and what episode am I on. It was almost like monday one, tuesday another, wednesday third one. And after that search and download it from somewhere( ;) torrents). So for a long time I had this idea that there should be some application that automatically takes care of everything from keeping track of all my series (which episode is aired when and download the next aired episode from torrents to my dropbox and notify me after that). But didn't find time to build one. But finally I was able to put something together. 

So it all started when I came across the popcorn app, which is used for streaming movies and series from torrents. So I just got curious about how it works, and I came the torrent stream library, that the popcorn app used. It basically takes a torrent and generates a stream out of it, and you can write it to a file, stream it on a video player. So I thought if I could upload the stream to some cloud storage. Now dropbox provides a chunked upload feature that can take chunks of file, so essentially you could break down a very large file into chunks and upload it, or resume a partial download using this feature. So I took the chunks in stream provided by library and uploaded chunks to dropbox. It seems even google drive provides an api for it. But for now I have it only for dropbox. As I am open sourcing it, someone might be interested in extending it to other cloud storage services. So now I had the portion that uploaded a torrent to dropbox. Now as this library is in nodejs. But I am not so proficient in JS. So for the other part I used ruby. So I wrote a service that essentially monitors all series that you specify in configs and download them to dropbox using the nodejs script. It uses the tv maze api, to get the next episode for each series that it needs to download. So it essentially runs like a cron, every 2 hours it gets an episode of a series from api checks if that episode is out for download, if not it records it in a DbStore. (I used redis as my db store.) and sleeps. Next time when it runs it checks if the next episode in my db store is available. Now if it is then it downloads the file to dropbox, and then updates the next episode to download in db store. 

Once both scripts were done, I thought of deploying it to my (free) heroku instance. However the challenge with that is how do I trigger it at specific times in a day. It does provide something called a worker dyno, but I don't have much idea if heroku provides a free plugin for scheduling scripts. So I came up with this. I run a web server (I used sinatra), and have a continuous background thread that actually runs the above task, then sleeps for x hours and then comes back, so essentially behaving like a scheduled task. And using this technique I could also add a route that simple dumps the logs of the task to monitor if everything went well. Now there was one more small issue with heroku. Heroku shuts down your app if there is inactivity for some time( I think 15 minutes.) But now I cannot afford my task shutting down as I don't have any way to track if it shutdown in between a download. So to keep it up all the time, I used a service (pingdom) that sends a ping to the app every 5 minutes. It is essentially used to track the uptime of a service. Ironically, I used it to keep my app up all the time.

I have open sourced it on github. You could check it out, and help me improve it. And use it at your own risk. It can be deployed in both modes as a webserver on heroku or a cron on some other cloud instance. Although to use it you need to create a app on your dropbox, authorize it and get a access token. And add the access token to dnode.js. It is the nodejs script that is actually used for downloading the torrent to dropbox. If you want yourself to be notified you could also create a mailgun account and create a key and add it to constants.yml that is used to send emails to your specified email. Otherwise you could comment the mail sending line. You also need a redis node on cloud, which is used as a db store. I used redislabs service which provides a 25 MB node for free. And to add the series you want to monitor you could add it to the list in constants.yml.




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