From: Eric Wong <e@80x24.org>
To: Cedric Maion <cedric@maion.com>
Cc: unicorn-public@bogomips.org
Subject: Re: Log reopening broken on Rails 4 with config.autoflush_log = false?
Date: Thu, 3 Jul 2014 17:24:10 +0000 [thread overview]
Message-ID: <20140703172410.GA17685@dcvr.yhbt.net> (raw)
In-Reply-To: <20140703144048.GA6674@cedric-maion.com>
Cedric Maion <cedric@maion.com> wrote:
> On a Rails 4.0 app with 'config.autoflush_log = false', it seems to me
> that telling unicorn to reopen log files fails (e.g., after a log
> rotation and USR1 signal, Rails/unicorn still writes to the old rotated
> file instead of reopening a new one).
>
> Without this config option, logs does properly get reopened.
>
> Is this something known?
Yes, log buffering via File#sync=true is incompatible with reopening in
multiprocess servers. File#sync=true does not guarantee writes are
atomic on line boundaries, so it's dangerous to assume they're logs.
Even without reopening, enabling this option on a multiprocess server
might corrupt logs (depending on the buffering implementation)
because the synchronization is within each process rather for the
entire OS.
Looking at the rails source:
==> railties/lib/rails/application/bootstrap.rb <==
f = File.open path, 'a'
f.binmode
f.sync = config.autoflush_log # if true make sure every write flushes
You're not likely to notice any performance difference unless you're
logging excessively. Keep in mind the Linux kernel also does buffering
and you can tune that via the sys.vm.dirty_* sysctls.
next prev parent reply other threads:[~2014-07-03 17:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-03 14:40 Log reopening broken on Rails 4 with config.autoflush_log = false? Cedric Maion
2014-07-03 17:24 ` Eric Wong [this message]
2014-07-03 19:28 ` [PATCH] FAQ: add entry for Rails autoflush_log Eric Wong
2014-07-04 9:13 ` Log reopening broken on Rails 4 with config.autoflush_log = false? Cedric Maion
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://yhbt.net/unicorn/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20140703172410.GA17685@dcvr.yhbt.net \
--to=e@80x24.org \
--cc=cedric@maion.com \
--cc=unicorn-public@bogomips.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://yhbt.net/unicorn.git/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).