From zookeeper-user-return-1498-apmail-hadoop-zookeeper-user-archive=hadoop.apache.org@hadoop.apache.org Sun Apr 11 22:53:39 2010 Return-Path: Delivered-To: apmail-hadoop-zookeeper-user-archive@minotaur.apache.org Received: (qmail 52632 invoked from network); 11 Apr 2010 22:53:39 -0000 Received: from unknown (HELO mail.apache.org) (140.211.11.3) by 140.211.11.9 with SMTP; 11 Apr 2010 22:53:39 -0000 Received: (qmail 84652 invoked by uid 500); 11 Apr 2010 22:53:39 -0000 Delivered-To: apmail-hadoop-zookeeper-user-archive@hadoop.apache.org Received: (qmail 84609 invoked by uid 500); 11 Apr 2010 22:53:38 -0000 Mailing-List: contact zookeeper-user-help@hadoop.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: zookeeper-user@hadoop.apache.org Delivered-To: mailing list zookeeper-user@hadoop.apache.org Received: (qmail 84601 invoked by uid 99); 11 Apr 2010 22:53:37 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Sun, 11 Apr 2010 22:53:37 +0000 X-ASF-Spam-Status: No, hits=-0.0 required=10.0 tests=SPF_HELO_PASS,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (nike.apache.org: local policy) Received: from [132.239.0.176] (HELO iport-c1-out.ucsd.edu) (132.239.0.176) by apache.org (qpsmtpd/0.29) with ESMTP; Sun, 11 Apr 2010 22:53:29 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Ai8FAKvvwUuE7zNQ/2dsb2JhbACPcoxErQOIXYUMBIMl X-IronPort-AV: E=Sophos;i="4.52,186,1270450800"; d="scan'208";a="221987687" X-Spam-Level: Received: from csesmtp2.ucsd.edu (HELO cse-smtp.ucsd.edu) ([132.239.51.80]) by iport-c1-out.ucsd.edu with ESMTP/TLS/ADH-AES256-SHA; 11 Apr 2010 15:53:07 -0700 Received: from numenor.lan (ip68-107-106-103.sd.sd.cox.net [68.107.106.103]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by cse-smtp.ucsd.edu (Postfix) with ESMTP id 290375005C for ; Sun, 11 Apr 2010 15:53:07 -0700 (PDT) Message-Id: From: Kevin Webb To: zookeeper-user@hadoop.apache.org Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (Apple Message framework v936) Subject: znode cversion decreasing? Date: Sun, 11 Apr 2010 15:53:01 -0700 X-Mailer: Apple Mail (2.936) X-Virus-Checked: Checked by ClamAV on apache.org X-Old-Spam-Status: No I'm using Zookeeper (3.2.2) for a simple group membership service in the manner that is typically described[1,2]: I create a znode for the group, and each present group member adds an ephemeral node under the group node. I'm using the cversion of the group node as a "group number". I expected this value to be monotonically increasing, but I'm seeing instances where this isn't the case. According to the programmer's guide, changes to a node will cause the appropriate version number to increase, but it says nothing about decreasing. Am I misunderstanding something about the way node version numbers work? Is there a better/recommended way to implement a monotonically increasing group number? Thanks! Kevin [1] http://hadoop.apache.org/zookeeper/docs/r3.2.2/recipes.html [2] http://eng.kaching.com/2010/01/actually-implementing-group-management.html