From: Sape Mullender <sape@plan9.bell-labs.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] QTCTL?
Date: Thu, 1 Nov 2007 13:12:02 -0400 [thread overview]
Message-ID: <66617ff87621f7f51e91bc31dad097c4@plan9.bell-labs.com> (raw)
In-Reply-To: <20071101170234.13E9E1E8C55@holo.morphisms.net>
> It's also why this doesn't work:
>
>> Tcache asks whether the server is prepared to cache
>> Rcache makes lease available with parameters, Rerror says no.
>>
>> Tlease says, ok start my lease now (almost immediately follows Rache)
>> Rlease lease expired or lease needs to be given back early
>>
>> Tcache done with old lease (may immediately ask for a new lease)
>> etc.
>
> because the Rlease/Tcache sequence is a s->c->s
> message. If a client doesn't respond with the Tcache
> to formally give up the lease, the server has no choice
> but to wait.
Correct. And if the server *does* wait in that case, single-copy
semantics are maintained. My assumption is that clients will, in
general, be well-behaved and use Tcache to allow the server to reuse
the file earlier than indicated in the lease.
Any maliciousness on the part of clients in this scheme would result
in (possibly one-time only) temporary denial of service to users
sharing a file; such users are not usually maliciously inclined.
Indeed, the Rlease/Tcache sequence forms a s->c->s interaction
and the second half (c->s) is a necessary one for synchronizing
the client's release of the file to the next client's access to
that file.
This discussion reminds me of the distributed file system discussion
raging in the eighties. I'm showing my age (and nothing has changed,
but much has been forgotten).
Sape
next prev parent reply other threads:[~2007-11-01 17:12 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-31 18:40 Francisco J Ballesteros
2007-10-31 18:56 ` Eric Van Hensbergen
2007-10-31 19:13 ` Charles Forsyth
2007-10-31 19:33 ` Eric Van Hensbergen
2007-10-31 19:39 ` erik quanstrom
2007-10-31 20:43 ` geoff
2007-10-31 21:32 ` Charles Forsyth
2007-10-31 22:48 ` roger peppe
2007-10-31 23:35 ` erik quanstrom
2007-11-01 9:29 ` roger peppe
2007-11-01 11:03 ` Eric Van Hensbergen
2007-11-01 11:19 ` Charles Forsyth
2007-11-01 12:11 ` erik quanstrom
2007-10-31 19:42 ` erik quanstrom
2007-10-31 19:49 ` Eric Van Hensbergen
2007-10-31 20:03 ` erik quanstrom
2007-10-31 20:10 ` Latchesar Ionkov
2007-10-31 20:12 ` Eric Van Hensbergen
2007-10-31 20:17 ` Russ Cox
2007-10-31 20:29 ` Francisco J Ballesteros
2007-10-31 20:48 ` Charles Forsyth
2007-10-31 21:23 ` Francisco J Ballesteros
2007-10-31 21:40 ` Russ Cox
2007-10-31 22:11 ` Charles Forsyth
2007-10-31 22:26 ` Francisco J Ballesteros
2007-10-31 22:37 ` Charles Forsyth
2007-10-31 22:43 ` Francisco J Ballesteros
2007-10-31 23:32 ` Eric Van Hensbergen
2007-10-31 23:41 ` [V9fs-developer] " Charles Forsyth
[not found] ` <606b6f003ae9f0ed3e8c3c5f90ddc720@terzarima.net>
2007-11-01 1:13 ` Eric Van Hensbergen
2007-10-31 23:54 ` erik quanstrom
2007-11-01 0:03 ` Charles Forsyth
2007-11-01 1:25 ` Eric Van Hensbergen
2007-11-01 1:44 ` erik quanstrom
2007-11-01 2:15 ` Eric Van Hensbergen
2007-11-01 7:34 ` Skip Tavakkolian
2007-11-01 6:21 ` Bakul Shah
2007-11-01 14:28 ` Russ Cox
2007-11-01 14:38 ` erik quanstrom
2007-11-01 14:41 ` Charles Forsyth
2007-11-01 15:26 ` Sape Mullender
2007-11-01 15:51 ` Latchesar Ionkov
2007-11-01 16:04 ` ron minnich
2007-11-01 16:16 ` Latchesar Ionkov
2007-11-01 16:21 ` Sape Mullender
2007-11-01 16:58 ` Francisco J Ballesteros
2007-11-01 17:11 ` Charles Forsyth
2007-11-01 17:11 ` Francisco J Ballesteros
2007-11-01 17:13 ` Sape Mullender
2007-11-01 17:38 ` ron minnich
2007-11-01 17:56 ` Francisco J Ballesteros
2007-11-01 18:01 ` Francisco J Ballesteros
2007-11-01 18:52 ` Eric Van Hensbergen
2007-11-01 19:29 ` Francisco J Ballesteros
2007-11-01 23:24 ` ron minnich
2007-11-01 17:03 ` Russ Cox
2007-11-01 17:12 ` Sape Mullender [this message]
2007-11-01 17:35 ` erik quanstrom
2007-11-01 18:36 ` erik quanstrom
2007-11-01 17:13 ` Charles Forsyth
2007-11-01 17:16 ` Charles Forsyth
2007-11-01 17:20 ` Charles Forsyth
2007-11-01 17:52 ` Eric Van Hensbergen
2007-11-01 18:00 ` Latchesar Ionkov
2007-11-01 18:03 ` Francisco J Ballesteros
2007-11-01 18:08 ` Latchesar Ionkov
2007-11-01 18:16 ` erik quanstrom
2007-11-01 18:19 ` Francisco J Ballesteros
2007-11-01 18:35 ` Sape Mullender
2007-11-01 19:09 ` Charles Forsyth
2007-11-01 19:07 ` erik quanstrom
2007-11-01 17:14 ` Bakul Shah
2007-11-01 16:17 ` Sape Mullender
2007-11-01 16:27 ` Sape Mullender
2007-11-01 16:58 ` Sape Mullender
2007-11-01 16:59 ` Bakul Shah
2007-11-01 4:21 Brian L. Stuart
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
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=66617ff87621f7f51e91bc31dad097c4@plan9.bell-labs.com \
--to=sape@plan9.bell-labs.com \
--cc=9fans@cse.psu.edu \
/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.
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 NNTP newsgroup(s).