our rails web app has to download/unpack archives with html pages from ftp on request for user’s viewing through the browser.
the archive can be quite big, so user has to wait until it downloads/unpacks on the server.
i implemented progress bar the way that i call fork/Process.detach in user’s request, so that his request is done but downloading/unpacking process continues running in the background. and javascript rendered in his browser pings our server for status until all is ready and then it redirects him to unpacked html pages.
as long as user requests one archive, everything goes smoothly, but if he tries to run 2 or more requests at the same time(so that more forks are started), it seems that only one of them completes, and the rest expires/times outs/gets killed by passenger(?). i suppose its the issue with Passenger/forking.
i am not sure if its possible to fix it somehow so i guess i need to switch to another solution. the solution needs to permit immediate and parallel processing of downloads. so that if user requests multiple archives, he has to see download/decompression progress in all of them at the same time.
i was thinking about running background rake job immediately but it seems very slow to startup(also there’s a lot of cron rake tasks happening every minute on our server). reason i liked fork was that it was very fast to start. i know there is delayed job, we also use it heavily for other tasks. but can it start multiple processes at the same time immediately without queues?
solved by keeping the fork and using single dj worker. this way i can have as many processes starting at the same time as needed without trouble with passenger/modifying our product’s gemset (which we are trying to avoid since it resulted in bugs in the past)
not sure if forking inside dj worker can cause any troubles, so asked at
running fork in delayed job
if id be free to modify gemset, id probably use resque as wrdevos suggested, or sidekiq, or girl_friday(but thats less probable because it depends on the server running).