Limit 1024 on Linux tells that entr is not using inotify

[abitrolly]

I try to set a build watcher for tflint and get hit by 1024 limit.

$ fd "\.go$" | entr go build -o ./flt
entr: Too many files listed; the hard limit for your login class is 1024. Please consult
http://eradman.com/entrproject/limits.html

But my limit is 8192.

$ cat /proc/sys/fs/inotify/max_user_watches  
8192

entr does not use inotify. Why?

[abitrolly]

The same error occurs when trying to watch directories with

$ fd "\.go$" | entr -d go build -o ./flt

But there are only 64 directories to watch.

$ fd -t d | wc -l

Using inotify with dir monitoring and custom filters could expand watching limits without changes to core system configuration.

[eradman]

The error you're seeing is caused by hitting the maximum number of file descriptors. inotify can monitor multiple files per file descriptor, but entr uses one file descriptor per file because this is the way kqueue on BSD and Mac works. This was a compromise to make entr portable.

To raised this limit, edit /etc/security/limits.conf

*       hard    nofile  16384
*       soft    nofile  16384

How many total files/directories are you monitoring?

[abitrolly]

Why entr can not use "multiple files per descriptor" interface setting limit of files to 1 if kqueue is used?

How many total files/directories are you monitoring?

About 1024.

$ fd "\.go$" | wc -l
1024

[eradman]

You are asking a good question--it would be better if users never needed to adjust the default resource limits. I will look into modifying entr to add the list of input files to a single inotify queue.

[abitrolly]

Thank you. entr is an awesome tool that I use constantly, and because it is available from major distros, it is easy to use. I'm looking forward to the new version. :D

On a side note, there is a new fanotify mechanism in Linux 5.1 which may or may not be more efficient.

• https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.1-Fanotify-Improvements
• https://github.com/torvalds/linux/commits/master/fs/notify/fanotify

[eradman]

Thanks for the kind words!

I uploaded a change for making better use of inotify in commit 9737442. This will respect limits set by /proc/sys/fs/inotify/max_user_watches

[eradman]

Updated the documentation limits on LInux at
file:///home/eradman/www/eradman.com/entrproject/limits.html

[abitrolly]

Looks good. Just two fixes for http://eradman.com/entrproject/limits.html#linux

s/permement/permanent/
s/was required //

[eradman]

Good catch! Text adjusted. Thanks @abitrolly