[Bug 1434758] Re: mysqld: errno: 24 - Too many open files

[Robie Basak]

I'm reluctant to raise the default limit to infinity because this may
introduce a security vulnerability due to select() macro overflow. See
https://lists.ubuntu.com/archives/ubuntu-
devel/2010-September/031446.html for details. If someone from upstream
can confirm definitely that MySQL definitely does handle higher number
file descriptors correctly though, then I have no objection.

I understand though that users do want to be able to tune the value. So,
what else can we do? It seems to me that now that we're using systemd
there are two different places where the setting can be made - from
my.cnf, or from the systemd service definition - whereas previously
users tended to do it in just my.cnf. Having it set in two places is
confusing. my.cnf cannot raise beyond the systemd setting, but we cannot
make the systemd setting "infinity" because of the security concern
above.

So given that I don't want to change systemd's default to "infinity", I
think it makes sense to expect users to change the systemd service
definition (copy /lib/systemd/system/mysql.service to
/etc/systemd/system/ and set LimitNOFILE etc there) if they want to
change the default value, and to not set open_files_limit in my.cnf at
all.

If this is reasonable, then this bug is Invalid. Is it reasonable?
Comments appreciated.

** Changed in: mysql-5.6 (Ubuntu)
   Importance: Undecided => Medium

** Changed in: mysql-5.6 (Ubuntu)
       Status: New => Triaged

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Title:
  mysqld: errno: 24 - Too many open files

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