From user-return-24577-apmail-cassandra-user-archive=cassandra.apache.org@cassandra.apache.org Tue Mar 6 10:14:29 2012 Return-Path: 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 C4040961C for ; Tue, 6 Mar 2012 10:14:29 +0000 (UTC) Received: (qmail 80705 invoked by uid 500); 6 Mar 2012 10:14:27 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 80682 invoked by uid 500); 6 Mar 2012 10:14:27 -0000 Mailing-List: contact user-help@cassandra.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@cassandra.apache.org Delivered-To: mailing list user@cassandra.apache.org Received: (qmail 80670 invoked by uid 99); 6 Mar 2012 10:14:27 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 06 Mar 2012 10:14:27 +0000 X-ASF-Spam-Status: No, hits=2.2 required=5.0 tests=HTML_MESSAGE,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (nike.apache.org: local policy) Received: from [94.75.197.170] (HELO mail.unitedgames.com) (94.75.197.170) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 06 Mar 2012 10:14:20 +0000 Received: from localhost (localhost [127.0.0.1]) by mail.unitedgames.com (Postfix) with ESMTP id A26B32D7D9 for ; Tue, 6 Mar 2012 11:13:59 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=unitedgames.com; h=content-type:content-type:in-reply-to:references:subject :subject:to:mime-version:user-agent:from:from:date:date :message-id; s=dkim; t=1331028838; x=1331892838; bh=0cHTqTvIxgFi l1UEA+oRX+3bGhSZtch96Mx7SgzUp50=; b=qhdBWdTasHNDGO44kqI9k+zBNzpK M2PsXUUQpzDNBv9Zv5RN0gSEguSd0Cvz6g2MznHGZfbh6Lx3ZCHXa2IUP9Uat3CF rphzYMqsNjsWxExdcTS+v2HFo7xwbUbp+QA385w6McNcy/qfF6D68VOaqr8s9zrE 8xR5bU+us/YwrZA= X-Virus-Scanned: Debian amavisd-new at mail.unitedgames.com Received: from mail.unitedgames.com ([127.0.0.1]) by localhost (mail.unitedgames.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id jNWqS06zVaN8 for ; Tue, 6 Mar 2012 11:13:58 +0100 (CET) Received: from [192.168.1.92] (unknown [188.204.191.147]) by mail.unitedgames.com (Postfix) with ESMTPA id BB55A2D7C7 for ; Tue, 6 Mar 2012 11:13:58 +0100 (CET) Message-ID: <4F55E362.3080307@unitedgames.com> Date: Tue, 06 Mar 2012 11:13:54 +0100 From: Stefan Reek User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.16) Gecko/20110307 Iceowl/1.0b1 Icedove/3.0.11 MIME-Version: 1.0 To: user@cassandra.apache.org Subject: Re: Old data coming alive after adding node References: <4F55D522.7080807@unitedgames.com> <745045D3-5C52-4B71-BFF4-2B14EEBC6EFA@thelastpickle.com> In-Reply-To: <745045D3-5C52-4B71-BFF4-2B14EEBC6EFA@thelastpickle.com> Content-Type: multipart/alternative; boundary="------------010605000903010301090006" X-Virus-Checked: Checked by ClamAV on apache.org This is a multi-part message in MIME format. --------------010605000903010301090006 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Hi Aaron, Thanks for the quick reply. All our writes/deletes are done with CL.QUORUM. Our reads are done with CL.ONE. Although the reads that confirmed the old data were done with CL.QUORUM. According to https://svn.apache.org/viewvc/cassandra/branches/cassandra-0.6/CHANGES.txt 0.6.6 has the same patch for (CASSANDRA-1074) as 0.7 and so I assumed that minor compactions in 0.6.6 and up also purged tombstones. The only suspicious thing I noticed was that after adding the fourth node repairs became extremely slow and heavy. Running it degraded the performance of the whole cluster and the new node even went OOM when running it. Cheers, Stefan On 03/06/2012 10:51 AM, aaron morton wrote: >> After we added a fourth node, keeping RF=3, some old data appeared in >> the database. > What CL are you working at ? (Should not matter too much with repair > working, just asking) > > >> We don't run compact on the nodes explicitly as I understand that >> running repair will trigger a >> major compaction. I'm not entirely sure if it does so, but in any >> case the tombstones will be removed by a minor >> compaction. > In 0.6.x tombstones were only purged during a major / manual > compaction. Purging during minor compaction came in during 0.7 > https://github.com/apache/cassandra/blob/trunk/CHANGES.txt#L1467 > >> Can anyone think of any reason why the old data reappeared? > It sounds like you are doing things correctly. The complicating factor > is 0.6 is so very old. > > > If I wanted to poke around some more I would conduct reads as CL one > against nodes and see if they return the "deleted" data or not. This > would help me understand if the tombstone is still out there. > > I would also poke around a lot in the logs to make sure repair was > running as expected and completing. If you find anything suspicious > post examples. > > Finally I would ensure CL QUROUM was been used. > > Hope that helps. > > > ----------------- > Aaron Morton > Freelance Developer > @aaronmorton > http://www.thelastpickle.com > > On 6/03/2012, at 10:13 PM, Stefan Reek wrote: > >> Hi, >> >> We were running a 3-node cluster of cassandra 0.6.13 with RF=3. >> After we added a fourth node, keeping RF=3, some old data appeared in >> the database. >> As far as I understand this can only happen if nodetool repair wasn't >> run for more than GCGraceSeconds. >> Our GCGraceSeconds is set to the default of 10 days (864000 seconds). >> We have a scheduled cronjob to run repair once each week on every >> node, each on another day. >> I'm sure that none of the nodes ever skipped running a repair. >> We don't run compact on the nodes explicitly as I understand that >> running repair will trigger a >> major compaction. I'm not entirely sure if it does so, but in any >> case the tombstones will be removed by a minor >> compaction. So I expected that the reappearing data, which is a >> couple of months old in some cases, was long gone >> by the time we added the node. >> >> Can anyone think of any reason why the old data reappeared? >> >> Stefan > --------------010605000903010301090006 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Hi Aaron,

Thanks for the quick reply.
All our writes/deletes are done with CL.QUORUM.
Our reads are done with CL.ONE. Although the reads that confirmed the old data were done with CL.QUORUM.
According to https://svn.apache.org/viewvc/cassandra/branches/cassandra-0.6/CHANGES.txt 0.6.6 has the same patch
for (CASSANDRA-1074) as 0.7 and so I assumed that minor compactions in 0.6.6 and up also purged tombstones.
The only suspicious thing I noticed was that after adding the fourth node repairs became extremely slow and heavy.
Running it degraded the performance of the whole cluster and the new node even went OOM when running it.

Cheers,

Stefan

On 03/06/2012 10:51 AM, aaron morton wrote:
After we added a fourth node, keeping RF=3, some old data appeared in the database.
What CL are you working at ? (Should not matter too much with repair working, just asking)


We don't run compact on the nodes explicitly as I understand that running repair will trigger a
major compaction. I'm not entirely sure if it does so, but in any case the tombstones will be removed by a minor
compaction.
In 0.6.x tombstones were only purged during a major / manual compaction. Purging during minor compaction came in during 0.7
https://github.com/apache/cassandra/blob/trunk/CHANGES.txt#L1467

Can anyone think of any reason why the old data reappeared?
It sounds like you are doing things correctly. The complicating factor is 0.6 is so very old. 


If I wanted to poke around some more I would conduct reads as CL one against nodes and see if they return the "deleted" data or not. This would help me understand if the tombstone is still out there. 

I would also poke around a lot in the logs to make sure repair was running as expected and completing. If you find anything suspicious post examples. 

Finally I would ensure CL QUROUM was been used. 

Hope that helps.


-----------------
Aaron Morton
Freelance Developer
@aaronmorton

On 6/03/2012, at 10:13 PM, Stefan Reek wrote:

Hi,

We were running a 3-node cluster of cassandra 0.6.13 with RF=3.
After we added a fourth node, keeping RF=3, some old data appeared in the database.
As far as I understand this can only happen if nodetool repair wasn't run for more than GCGraceSeconds.
Our GCGraceSeconds is set to the default of 10 days (864000 seconds).
We have  a scheduled cronjob to run repair once each week on every node, each on another day.
I'm sure that none of the nodes ever skipped running a repair.
We don't run compact on the nodes explicitly as I understand that running repair will trigger a
major compaction. I'm not entirely sure if it does so, but in any case the tombstones will be removed by a minor
compaction. So I expected that the reappearing data, which is a couple of months old in some cases, was long gone
by the time we added the node.

Can anyone think of any reason why the old data reappeared?

Stefan


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