Return-Path: 
 <user-return-29610-apmail-cassandra-user-archive=cassandra.apache.org@cassandra.apache.org>
X-Original-To: apmail-cassandra-user-archive@www.apache.org
Delivered-To: apmail-cassandra-user-archive@www.apache.org
Received: from mail.apache.org (hermes.apache.org [140.211.11.3])
	by minotaur.apache.org (Postfix) with SMTP id 047D9D123
	for <apmail-cassandra-user-archive@www.apache.org>;
 Thu, 18 Oct 2012 17:34:52 +0000 (UTC)
Received: (qmail 75710 invoked by uid 500); 18 Oct 2012 17:34:49 -0000
Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org
Received: (qmail 75374 invoked by uid 500); 18 Oct 2012 17:34:45 -0000
Mailing-List: contact user-help@cassandra.apache.org; run by ezmlm
Precedence: bulk
List-Help: <mailto:user-help@cassandra.apache.org>
List-Unsubscribe: <mailto:user-unsubscribe@cassandra.apache.org>
List-Post: <mailto:user@cassandra.apache.org>
List-Id: <user.cassandra.apache.org>
Reply-To: user@cassandra.apache.org
Delivered-To: mailing list user@cassandra.apache.org
Received: (qmail 75345 invoked by uid 99); 18 Oct 2012 17:34:44 -0000
Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136)
    by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 18 Oct 2012 17:34:44 +0000
X-ASF-Spam-Status: No, hits=1.5 required=5.0
	tests=HTML_MESSAGE,RCVD_IN_DNSWL_LOW,SPF_PASS
X-Spam-Check-By: apache.org
Received-SPF: pass (athena.apache.org: domain of markusklems@gmail.com
 designates 209.85.220.172 as permitted sender)
Received: from [209.85.220.172] (HELO mail-vc0-f172.google.com)
 (209.85.220.172)
    by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 18 Oct 2012 17:34:37 +0000
Received: by mail-vc0-f172.google.com with SMTP id fl11so10810538vcb.31
        for <user@cassandra.apache.org>; Thu, 18 Oct 2012 10:34:16 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=20120113;
        h=mime-version:from:date:message-id:subject:to:content-type;
        bh=ZdA6U1GZeSk3qfpGaMpQw4kRPfw/2D0bSFs+f2oml4I=;
        b=LzUl/lCl3pRcqg9kgG+lGGVJWXJXRpYoOcIQ3SlYrdjs1erMY9h573xC8UnrHLq98Z
         5nn4LNT72MrT0Rm1DRvkx53vfRZlN0KiVFwumcNzHAIbuK/q77UTzJBpa/60Hnzsp8NA
         Retq+rDVs69xD4wPnn/JHREBxtYW6KIyfGho1MtIJqYBb9MJM02X/CRfKypgLonjeRPV
         oZAcoxYOKL5fkFOS5HI+hrpp6U27UUglJy9LEQ2zZajciK60asMJk9cCHx7CEMSKtig2
         Yx2PJJq/Jqhl0IivJuDDChcmXj8GIDO+AKclfn7KIdl2zmkMLEcjSL7wWLYRds7aBWeG
         B5FA==
Received: by 10.52.90.147 with SMTP id bw19mr13483822vdb.17.1350581656609;
 Thu, 18 Oct 2012 10:34:16 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.58.15.4 with HTTP; Thu, 18 Oct 2012 10:33:56 -0700 (PDT)
From: Markus Klems <markusklems@gmail.com>
Date: Thu, 18 Oct 2012 19:33:56 +0200
Message-ID: 
 <CAPXRZfv1mcaaRNppMEfA57gedbdhrOjK66NX3msUfxXsaDXfRg@mail.gmail.com>
Subject: What does ReadRepair exactly do?
To: user@cassandra.apache.org
Content-Type: multipart/alternative; boundary=20cf307f3bd8e1e3c404cc58cbcc
X-Virus-Checked: Checked by ClamAV on apache.org

--20cf307f3bd8e1e3c404cc58cbcc
Content-Type: text/plain; charset=UTF-8

Hi guys,

I am looking through the Cassandra source code in the github trunk to
better understand how Cassandra's fault-tolerance mechanisms work. Most
things make sense. I am also aware of the wiki and DataStax documentation.
However, I do not understand what read repair does in detail. The method
RowRepairResolver.resolveSuperset(Iterable<ColumnFamily> versions) seems to
do the trick of merging conflicting versions of column family replicas and
builds the set of columns that need to be "repaired". From looking at the
source code, I do not understand how this set is built and I do not
understand how the reconciliation is executed. ReadRepair does not seem to
trigger a Column.reconcile() to reconcile conflicting column versions on
different servers. Does it?

If this is not what read repair does, then: What kind of inconsistencies
are resolved by read repair? And: How are the inconsistencies resolved?

Could someone give me a hint?

Thanks so much,

-Markus

--20cf307f3bd8e1e3c404cc58cbcc
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

Hi guys,<div><br></div><div>I am looking through the Cassandra source code =
in the github trunk to better understand how Cassandra&#39;s fault-toleranc=
e mechanisms work. Most things make sense. I am also aware of the wiki and =
DataStax documentation. However, I do not understand what read repair does =
in detail.=C2=A0The method RowRepairResolver.resolveSuperset(Iterable&lt;Co=
lumnFamily&gt; versions) seems to do the trick of merging conflicting versi=
ons of column family replicas and builds the set of columns that need to be=
 &quot;repaired&quot;. From looking at the source code, I do not understand=
 how this set is built and I do not understand how the reconciliation is ex=
ecuted.=C2=A0ReadRepair does not seem to trigger a Column.reconcile() to re=
concile conflicting column versions on different servers. Does it?</div>

<div><br></div><div>If this is not what read repair does, then: What kind o=
f inconsistencies are resolved by read repair?=C2=A0And: How are the incons=
istencies resolved?</div><div><br></div><div>Could someone give me a hint?<=
/div>

<div><br></div><div>Thanks so much,</div><div><br></div><div>-Markus</div>








--20cf307f3bd8e1e3c404cc58cbcc--