From c31965449f18a2906663550d5eaccef5d9d32400 Mon Sep 17 00:00:00 2001 From: Mark Walters Date: Wed, 16 Jul 2014 07:50:41 +0100 Subject: [PATCH] Re: [PATCH] dump: make dump take Xapian write lock --- 00/be692acddb50ea603467afd34fa628aa9278f5 | 116 ++++++++++++++++++++++ 1 file changed, 116 insertions(+) create mode 100644 00/be692acddb50ea603467afd34fa628aa9278f5 diff --git a/00/be692acddb50ea603467afd34fa628aa9278f5 b/00/be692acddb50ea603467afd34fa628aa9278f5 new file mode 100644 index 000000000..0e7d81541 --- /dev/null +++ b/00/be692acddb50ea603467afd34fa628aa9278f5 @@ -0,0 +1,116 @@ +Return-Path: +X-Original-To: notmuch@notmuchmail.org +Delivered-To: notmuch@notmuchmail.org +Received: from localhost (localhost [127.0.0.1]) + by olra.theworths.org (Postfix) with ESMTP id 1F79F431FC0 + for ; Tue, 15 Jul 2014 23:51:15 -0700 (PDT) +X-Virus-Scanned: Debian amavisd-new at olra.theworths.org +X-Spam-Flag: NO +X-Spam-Score: 0.502 +X-Spam-Level: +X-Spam-Status: No, score=0.502 tagged_above=-999 required=5 + tests=[DKIM_ADSP_CUSTOM_MED=0.001, FREEMAIL_FROM=0.001, + NML_ADSP_CUSTOM_MED=1.2, RCVD_IN_DNSWL_LOW=-0.7] autolearn=disabled +Received: from olra.theworths.org ([127.0.0.1]) + by localhost (olra.theworths.org [127.0.0.1]) (amavisd-new, port 10024) + with ESMTP id hI9ybJZr3EGN for ; + Tue, 15 Jul 2014 23:51:07 -0700 (PDT) +Received: from mail1.qmul.ac.uk (mail1.qmul.ac.uk [138.37.6.7]) + (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) + (No client certificate requested) + by olra.theworths.org (Postfix) with ESMTPS id DBFCD431FBD + for ; Tue, 15 Jul 2014 23:51:06 -0700 (PDT) +Received: from smtp.qmul.ac.uk ([138.37.6.40]) + by mail1.qmul.ac.uk with esmtp (Exim 4.71) + (envelope-from ) + id 1X7J3N-0005fj-Ba; Wed, 16 Jul 2014 07:51:01 +0100 +Received: from [194.42.225.51] (helo=localhost) + by smtp.qmul.ac.uk with esmtpsa (TLSv1:AES128-SHA:128) (Exim 4.71) + (envelope-from ) + id 1X7J3N-0004w5-5d; Wed, 16 Jul 2014 07:51:01 +0100 +From: Mark Walters +To: David Bremner , notmuch@notmuchmail.org +Subject: Re: [PATCH] dump: make dump take Xapian write lock +In-Reply-To: <87y4vuaf10.fsf@maritornes.cs.unb.ca> +References: <87zjhh67e7.fsf@qmul.ac.uk> + <1403554349-8888-1-git-send-email-markwalters1009@gmail.com> + <87y4vuaf10.fsf@maritornes.cs.unb.ca> +User-Agent: Notmuch/0.15.2+615~g78e3a93 (http://notmuchmail.org) Emacs/23.4.1 + (x86_64-pc-linux-gnu) +Date: Wed, 16 Jul 2014 07:50:41 +0100 +Message-ID: <871ttlztj2.fsf@qmul.ac.uk> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-QM-SPAM-Info: 194.42.225.51 is in Janet mirror of Spamhaus XBL; + see http://www.spamhaus.org/xbl/ +X-Sender-Host-Address: 194.42.225.51 +X-QM-Geographic: According to ripencc, + this message was delivered by a machine in Britain (UK) (GB). +X-QM-SPAM-Info: Sender has good ham record. :) +X-QM-Body-MD5: 402ab17fd2c5d35e4d7b1c38f424c9e1 (of first 20000 bytes) +X-SpamAssassin-Score: -0.1 +X-SpamAssassin-SpamBar: / +X-SpamAssassin-Report: The QM spam filters have analysed this message to + determine if it is + spam. We require at least 5.0 points to mark a message as spam. + This message scored -0.1 points. + Summary of the scoring: + * 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail + provider * (markwalters1009[at]gmail.com) + * -0.1 AWL AWL: From: address is in the auto white-list +X-QM-Scan-Virus: ClamAV says the message is clean +X-BeenThere: notmuch@notmuchmail.org +X-Mailman-Version: 2.1.13 +Precedence: list +List-Id: "Use and development of the notmuch mail system." + +List-Unsubscribe: , + +List-Archive: +List-Post: +List-Help: +List-Subscribe: , + +X-List-Received-Date: Wed, 16 Jul 2014 06:51:15 -0000 + + +On Tue, 15 Jul 2014, David Bremner wrote: +> Mark Walters writes: +> +>> +>> Discussion with Olly on irc indicates that this is currently the best +>> solution: in xapian trunk there may be better possibilities using +>> snapshots but they need to make it to a release and propogate out to +>> users before we can switch approach. +> +> I agree that this seems to be the only feasible approach to make dump +> atomic. I'm a little unsure about the benefits to the end user though. +> Currently, the user has to check the return code of dump to ensure it +> completed correctly. With this change, the user will still have to +> check that dump did not error out when trying to acquire a write lock. +> The following ticket +> +> http://trac.xapian.org/ticket/275 +> +> suggests that if we wanted to a blocking open, we'd be on our own. +> +> Did I miss something here about the benefits? I agree that failing +> earlier is nicer, but is that it? + +You are correct that we may still fail. I think there are two +advantages in addition to failing earlier. + +First, I think that if the dump fails there will not be any output file: +I think the old version would leave a partial dump (note I haven't +checked that carefully). This makes it more likely the failing dump is +noticed. + +Secondly, this version will only fail if the database is being written +to when it starts: the old version would fail if something attempted to +write to it at any point during the dump, which can be relatively +lengthy. This should at least reduce the frequency of problems. + +Best wishes + +Mark + -- 2.26.2