How to detect an event as soon as it happens on an external component. Don't want to poll, any alternatives?

Question

I don't want to use polling technique or any library which underneath uses polling, things like Thread.sleep etc. Any suggestions? This is an open ended question I am just interested in approach.

Examples : Pulling up a file from FTP as soon as it lands up there, etc.

If we take example of FTP, FTP can't push the events, in that case, is polling only available option? — Gaurav Khare, Feb 09 '19 at 09:45
FTP doesn't have push events, but that doesn't mean that you cannot run a small non-FTP server w/ push capabilities alongside your FTP if you don't want to rely on polling... — zwer, Feb 09 '19 at 10:01
https://stackoverflow.com/questions/4060212/how-to-run-a-shell-script-when-a-file-or-directory-changes — stark, Feb 09 '19 at 14:49
I voted to close this question as too ... openended :) In general, everything, that starts with "I don't want to use ..." is a clear indicatiion of an XY-problem — Dima, Feb 09 '19 at 20:45

score 1 · Answer 1 · answered Feb 09 '19 at 10:07

In principle, there's no way around

either you poll (proactive)
or "server" pushes event to you (reactive)

Obviously, there's ways to wrap polling into reactive-like interfaces.

Regarding ftp – the alternatives is making service-in-the-middle that does pushing, or using inotify (which may wrap it for you effectively)

How to detect an event as soon as it happens on an external component. Don't want to poll, any alternatives?

1 Answers1