From user-return-7003-apmail-zookeeper-user-archive=zookeeper.apache.org@zookeeper.apache.org Tue Nov 19 20:51:41 2013 Return-Path: X-Original-To: apmail-zookeeper-user-archive@www.apache.org Delivered-To: apmail-zookeeper-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 4389310CB3 for ; Tue, 19 Nov 2013 20:51:41 +0000 (UTC) Received: (qmail 52606 invoked by uid 500); 19 Nov 2013 20:51:40 -0000 Delivered-To: apmail-zookeeper-user-archive@zookeeper.apache.org Received: (qmail 52554 invoked by uid 500); 19 Nov 2013 20:51:40 -0000 Mailing-List: contact user-help@zookeeper.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@zookeeper.apache.org Delivered-To: mailing list user@zookeeper.apache.org Received: (qmail 52546 invoked by uid 99); 19 Nov 2013 20:51:40 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 19 Nov 2013 20:51:40 +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 (nike.apache.org: domain of mohammadshamma@gmail.com designates 209.85.128.50 as permitted sender) Received: from [209.85.128.50] (HELO mail-qe0-f50.google.com) (209.85.128.50) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 19 Nov 2013 20:51:33 +0000 Received: by mail-qe0-f50.google.com with SMTP id 1so5528754qee.37 for ; Tue, 19 Nov 2013 12:51:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:date:message-id:subject:from:to:content-type; bh=UTluE5TJ8hS/gBqo0od9xieP20Cl8sUTsvvDXTP4arI=; b=p1nSfsFG13TQ9JT7HfiXsK2C0kJ6tdfpl8lNTKiNPKNkR/08TUzMb/8hcPqEHVWm/o qYOfKvWAR8vhs3sLJfP0alGyJb8fQhTchxptyZ3J8RkmFOwMOrJY2mVOpQqg60RbsMHr PoUZXxpxrGSt64A2r9Q+J8nEsvv3ZZo4Fd6o15mAAFKGWww2TA6dbJhO3qhDovT6dR5x EbUag2yO3XXPtNRRKZAoSr/vGo1KzZxezFysi1XnOKe9xePDt0LPQdUQLiH11vzumirL 7/nqJwmJRrRudstHyYEp6MVLpEkvINLGbo6CkSf3VKqzCElLdE90ofmrVeSCmfWTv3RT 029w== MIME-Version: 1.0 X-Received: by 10.49.41.3 with SMTP id b3mr41200558qel.44.1384894273197; Tue, 19 Nov 2013 12:51:13 -0800 (PST) Received: by 10.224.38.137 with HTTP; Tue, 19 Nov 2013 12:51:13 -0800 (PST) Date: Tue, 19 Nov 2013 12:51:13 -0800 Message-ID: Subject: zookeeper client session write-read consistency From: Mohammad Shamma To: user@zookeeper.apache.org Content-Type: multipart/alternative; boundary=047d7bea33d634a04304eb8dd323 X-Virus-Checked: Checked by ClamAV on apache.org --047d7bea33d634a04304eb8dd323 Content-Type: text/plain; charset=ISO-8859-1 I have a question about the consistency guarantees of zookeeper. As far as I understand, zookeeper provides eventual consistency guarantees. Updates are not guaranteed to be seen by read operations following an update (reads are not necessarily consistent). The reason behind this is that reads might be served by a server that was not part of the quorum that approved of an update (and the server serving the read has not yet received the update). I have observed such write/read inconsistencies on operations within the same client session. Is this behavior expected? This write/read inconsistency is expected when the read and write are dispatched to different servers, however it seems a bit odd that writes and reads that are dispatched against the same server would be inconsistent. -- Mohammad Shamma --047d7bea33d634a04304eb8dd323--