File not closed on timeout or SIGINT

[kdee-korreyd]

Issue

filelock-unix.c; file descriptor "filedes" is not closed if no lock is received (due to timeout or SIGINT). This can cause a bunch of files to be left open if using filelock through an interactive shell (R, rstudio, etc..)

Reproduce

session 1:

$ R --vanilla
> library(filelock)
> lock("/tmp/test.lck")
Lock on ‘/tmp/test.lck’

lsof:

$ lsof | grep "test.lck"
R          2504               jacobs    3u      REG   0,53        0    2393006 /tmp/test.lck

session 2:

$ R --vanilla
> library(filelock)
> lock("/tmp/test.lck",timeout=1)
NULL #<-- timeout, as expected

lsof:

# at this point I'd expect there to still only be 1 open file but...:
$ lsof | grep "test.lck"
R         11476               jacobs    3u      REG   0,53        0    2393006 /tmp/test.lck
R         17162               jacobs    3u      REG   0,53        0    2393006 /tmp/test.lck

Workaround

The workaround I am currently using for this can be found here:
#master...kdee-korreyd:closefile

[gaborcsardi]

We could use r-lib/cleancall to close the FD.

[gaborcsardi]

Reprex:

tmp <- tempfile()

l <- filelock::lock(tmp)

rs <- callr::r_session$new()
rs$call(function(path) .GlobalEnv$lock <- filelock::lock(path, timeout = 1), list(tmp))
rs$poll_io(3000)
#>   output    error  process 
#> "silent" "silent"  "ready"
rs$read()
#> $code
#> [1] 200
#> 
#> $message
#> [1] "done callr-rs-result-5bde6b93fe4a"
#> 
#> $result
#> NULL
#> 
#> $stdout
#> [1] ""
#> 
#> $stderr
#> [1] ""
#> 
#> $error
#> NULL
#> 
#> attr(,"class")
#> [1] "callr_session_result"

ps::ps_open_files(ps::ps_handle(rs$get_pid()))
#> # A tibble: 1 x 2
#>      fd path                                                                    
#>   <int> <chr>                                                                   
#> 1     4 /private/var/folders/59/0gkmw1yj2w7bf2dfc3jznv5w0000gn/T/RtmpnQ6TKj/fil…

^{Created on 2020-09-14 by the reprex package (v0.3.0)}

[kdee-korreyd]

yes that's a better solution, and clears up the issue.

[kdee-korreyd]

is the change you used for the example above something that can be committed to master?

these are the changes i used to implement the cleancall solution:
kdee-korreyd@182fd88

[krivit]

Seconding this, I have an application that makes a large number of calls to filelock::lock(filename.lock, timeout = 0) that tests if a lock is stale, so I often hit a limit on the number of open files due to this file descriptor leak.