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contrib/plugins/disk/du-2 does not work first time until du.cache file is created manually #914

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Talkless opened this issue Mar 28, 2018 · 4 comments
Open

contrib/plugins/disk/du-2 does not work first time until du.cache file is created manually #914

Talkless opened this issue Mar 28, 2018 · 4 comments
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@Talkless
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It seems that I have to create /var/lib/munin-node/plugin-state/root/du.cache file manually, or else plugin does not return anything.

strace show that it fails to open that file and exits:

open("/var/lib/munin-node/plugin-state/root/du.cache", O_RDONLY) = -1 ENOENT (No such file or directory)
rt_sigaction(SIGHUP, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGINT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGQUIT, NULL, {SIG_DFL, [], 0}, 8) = 0
...
exit_group(1)                           = ?
+++ exited with 1 +++

I'm guessing it's because of

contrib/plugins/disk/du-2

Line 90 in 3f253eb

open (FILE, "<", $CACHEFILE) or munin_exit_fail();
and/or

contrib/plugins/disk/du-2

Line 109 in 3f253eb

open (FILE, "<", $CACHEFILE) or munin_exit_fail();
statements.
@Talkless
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Talkless commented Mar 28, 2018 •
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Seems that it has another problems, like "No .label provided":
munin-du-2

For this config:

[du]
user root
env.dirs /var/lib/postgresql/10/main/pg_wal/ /var/lib/postgresql/9.6/main/pg_xlog/ /var/lib/postgresql/9.6/secondary/pg_xlog/ 
env.interval 5
timeout 300

Any ides how to quick-fix it?

It's munin-node 2.0.33-1~bpo8+1 on Debian 8 (jessie).

@Talkless
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I've provided fix for that "No .label provied":
#915

@sumpfralle
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Thank you for fixing the first half!

The second half looks reasonable, too:

  • fetch: the "daemonize" function should be called before exiting in case of a missing cache file
    • we probably cannot simply call it before the "fetch" section, since this would cause a race condition between writing the new data and reading the old data
  • config: the "config" section should not use the cache, but just go through the list of environment items instead
    • otherwise the master would receive an empty config and would not bother to ask for the values (which is necessary for triggering the "daemonize" function)

It is a bit mysterious, that all previous users of that plugin seem to have "solved" the problem manually without talking about it :(

mikini added a commit to mikini/contrib that referenced this issue Oct 4, 2018
@mikini
Generate cache file if missing
21c2863 
Don't exit with error if cache file is missing, instead refrain from sending values and daemonize() in an attempt to generate one.
Invocation using 'config' before generation is successful will fail, as mentioned in munin-monitoring#914, but configuration will get picked up as soon as it is present.
@mikini mikini mentioned this issue Oct 4, 2018
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Stale issue message

@steveschnepp steveschnepp reopened this Apr 27, 2021
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@Talkless @steveschnepp @sumpfralle