Re: notmuch dump: taking write-lock to protect from concurrent (cronned) notmuch...

diff --git a/cf/acf5003ceeafc03b095875b51c5d33742567f1 b/cf/acf5003ceeafc03b095875b51c5d33742567f1
new file mode 100644 (file)
index 0000000..8f5d13e
--- /dev/null
+++ b/cf/acf5003ceeafc03b095875b51c5d33742567f1
@@ -0,0 +1,122 @@
+Return-Path: <m.walters@qmul.ac.uk>\r
+X-Original-To: notmuch@notmuchmail.org\r
+Delivered-To: notmuch@notmuchmail.org\r
+Received: from localhost (localhost [127.0.0.1])\r
+       by olra.theworths.org (Postfix) with ESMTP id 20D34431FBC\r
+       for <notmuch@notmuchmail.org>; Thu, 12 Jun 2014 16:22:09 -0700 (PDT)\r
+X-Virus-Scanned: Debian amavisd-new at olra.theworths.org\r
+X-Spam-Flag: NO\r
+X-Spam-Score: 0.502\r
+X-Spam-Level: \r
+X-Spam-Status: No, score=0.502 tagged_above=-999 required=5\r
+       tests=[DKIM_ADSP_CUSTOM_MED=0.001, FREEMAIL_FROM=0.001,\r
+       NML_ADSP_CUSTOM_MED=1.2, RCVD_IN_DNSWL_LOW=-0.7] autolearn=disabled\r
+Received: from olra.theworths.org ([127.0.0.1])\r
+       by localhost (olra.theworths.org [127.0.0.1]) (amavisd-new, port 10024)\r
+       with ESMTP id 6ljCUhlWOIqo for <notmuch@notmuchmail.org>;\r
+       Thu, 12 Jun 2014 16:22:05 -0700 (PDT)\r
+Received: from mail2.qmul.ac.uk (mail2.qmul.ac.uk [138.37.6.6])\r
+       (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))\r
+       (No client certificate requested)\r
+       by olra.theworths.org (Postfix) with ESMTPS id DA6A7431FAF\r
+       for <notmuch@notmuchmail.org>; Thu, 12 Jun 2014 16:22:04 -0700 (PDT)\r
+Received: from smtp.qmul.ac.uk ([138.37.6.40])\r
+       by mail2.qmul.ac.uk with esmtp (Exim 4.71)\r
+       (envelope-from <m.walters@qmul.ac.uk>)\r
+       id 1WvEJe-0005o6-EA; Fri, 13 Jun 2014 00:21:56 +0100\r
+Received: from 5751dfa2.skybroadband.com ([87.81.223.162] helo=localhost)\r
+       by smtp.qmul.ac.uk with esmtpsa (TLSv1:AES128-SHA:128) (Exim 4.71)\r
+       (envelope-from <m.walters@qmul.ac.uk>)\r
+       id 1WvEJe-0003xt-0m; Fri, 13 Jun 2014 00:21:54 +0100\r
+From: Mark Walters <markwalters1009@gmail.com>\r
+To: David Bremner <david@tethera.net>, Maarten Aertsen <sagi-notmuch@rtsn.nl>,\r
+       notmuch@notmuchmail.org\r
+Subject: Re: notmuch dump: taking write-lock to protect from concurrent\r
+       (cronned) notmuch new?\r
+In-Reply-To: <87mwdhg2jh.fsf@zancas.localnet>\r
+References: <20140606080354.28047.77393@kardo.rtsn.nl>\r
+       <878upafegc.fsf@qmul.ac.uk> <87mwdhg2jh.fsf@zancas.localnet>\r
+User-Agent: Notmuch/0.15.2+615~g78e3a93 (http://notmuchmail.org) Emacs/23.4.1\r
+       (x86_64-pc-linux-gnu)\r
+Date: Fri, 13 Jun 2014 00:21:52 +0100\r
+Message-ID: <87zjhh67e7.fsf@qmul.ac.uk>\r
+MIME-Version: 1.0\r
+Content-Type: text/plain; charset=us-ascii\r
+X-Sender-Host-Address: 87.81.223.162\r
+X-QM-Geographic: According to ripencc,\r
+       this message was delivered by a machine in Britain (UK) (GB).\r
+X-QM-SPAM-Info: Sender has good ham record.  :)\r
+X-QM-Body-MD5: af87aa6497d32c89c7c7980043b12eff (of first 20000 bytes)\r
+X-SpamAssassin-Score: -0.1\r
+X-SpamAssassin-SpamBar: /\r
+X-SpamAssassin-Report: The QM spam filters have analysed this message to\r
+       determine if it is\r
+       spam. We require at least 5.0 points to mark a message as spam.\r
+       This message scored -0.1 points.\r
+       Summary of the scoring: \r
+       * 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail\r
+       provider *      (markwalters1009[at]gmail.com)\r
+       * -0.1 AWL AWL: From: address is in the auto white-list\r
+X-QM-Scan-Virus: ClamAV says the message is clean\r
+X-BeenThere: notmuch@notmuchmail.org\r
+X-Mailman-Version: 2.1.13\r
+Precedence: list\r
+List-Id: "Use and development of the notmuch mail system."\r
+       <notmuch.notmuchmail.org>\r
+List-Unsubscribe: <http://notmuchmail.org/mailman/options/notmuch>,\r
+       <mailto:notmuch-request@notmuchmail.org?subject=unsubscribe>\r
+List-Archive: <http://notmuchmail.org/pipermail/notmuch>\r
+List-Post: <mailto:notmuch@notmuchmail.org>\r
+List-Help: <mailto:notmuch-request@notmuchmail.org?subject=help>\r
+List-Subscribe: <http://notmuchmail.org/mailman/listinfo/notmuch>,\r
+       <mailto:notmuch-request@notmuchmail.org?subject=subscribe>\r
+X-List-Received-Date: Thu, 12 Jun 2014 23:22:09 -0000\r
+\r
+\r
+Hi\r
+\r
+On Thu, 12 Jun 2014, David Bremner <david@tethera.net> wrote:\r
+> Mark Walters <markwalters1009@gmail.com> writes:\r
+>\r
+>\r
+>>> mjw1009 suggested to change NOTMUCH_DATABASE_MODE_READ_ONLY on line\r
+>>> 215 of notmuch-dump.c to NOTMUCH_DATABASE_MODE_READ_WRITE\r
+>>>\r
+>>> I'm wondering if this hits enough people to motivate the addition of a\r
+>>> command line switch (or perhaps even a change in default behaviour?)\r
+>>\r
+>> I think this is a clear bug but the fix is a little unclear. The above\r
+>> fix works but it breaks one of the tests: "unicode message-ids" in\r
+>> T150-tagging.sh.\r
+>>\r
+>> I think the problem is that it does \r
+>> notmuch dump | sed... | notmuch restore\r
+>>\r
+>\r
+> My first reaction was "argh, we should be locking things less, not\r
+> more".  But then I read \r
+>\r
+>         http://getting-started-with-xapian.readthedocs.org/en/latest/xapian-core-rst/admin_notes.html?highlight=backup#id10\r
+>\r
+> and now I'm not so sure, maybe write lock for dump is the right answer.\r
+\r
+On irc Olly said\r
+\r
+"I'd suggest locking the db by opening it R/W for the dump at least\r
+until you can use reader locking to keep the read revision valid, but\r
+it'll be a while before that's in a stable release"\r
+\r
+and he also said that pipes of the form notmuch dump | ... notmuch\r
+restore will probably fail if they change many tags.\r
+\r
+So it is probably the way to go. But it does run the risk of breaking\r
+some peoples (already fragile) scripts.\r
+\r
+> It seems hard to do anything sensible with "Database.reopen" in the\r
+> context of a backup.\r
+\r
+Yes I agree.\r
+\r
+Best wishes\r
+\r
+Mark\r