Return-Path: X-Original-To: apmail-hbase-user-archive@www.apache.org Delivered-To: apmail-hbase-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 35ED4107E4 for ; Thu, 24 Oct 2013 15:50:31 +0000 (UTC) Received: (qmail 89748 invoked by uid 500); 24 Oct 2013 15:50:26 -0000 Delivered-To: apmail-hbase-user-archive@hbase.apache.org Received: (qmail 89682 invoked by uid 500); 24 Oct 2013 15:50:26 -0000 Mailing-List: contact user-help@hbase.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@hbase.apache.org Delivered-To: mailing list user@hbase.apache.org Received: (qmail 89413 invoked by uid 99); 24 Oct 2013 15:50:25 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 24 Oct 2013 15:50:25 +0000 X-ASF-Spam-Status: No, hits=1.7 required=5.0 tests=FREEMAIL_ENVFROM_END_DIGIT,HTML_MESSAGE,RCVD_IN_DNSWL_LOW,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (nike.apache.org: domain of vboylin1987@gmail.com designates 209.85.160.42 as permitted sender) Received: from [209.85.160.42] (HELO mail-pb0-f42.google.com) (209.85.160.42) by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 24 Oct 2013 15:50:19 +0000 Received: by mail-pb0-f42.google.com with SMTP id jt11so2289645pbb.29 for ; Thu, 24 Oct 2013 08:49:57 -0700 (PDT) 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=ugLyG43PV904VdRmNMSFwZ9Jeq+yT2F9C9ZxBUeaxHc=; b=it64ArrKNiiY7leI/2nf0kImSq2mQOwejXmQKlAo2kWq/3BaYQr7JC2heFSbY4SSuY M5wYw4MmT/EJm2+skL5GnuoE+pybVEK4ZHd4lmM2m8G8OpXa7D5cb0Eg5m0xlMWbqr04 G3nf2oxEGJv6JFFnYv7vldgTY4iKmAOs5hyd/Y6+yTnPk8HgKLDqyQAx+PkKvTRCUFab k0O1TjkGIJBImjNsHKuZeMqw065djwX62aqDMNJYs3v4p8hJfkP5mSwPw+R3GaHmW302 ewTHL+eiScjlNFalVsAL/WoKxQnO1ZTiSHdWCsOw8uNqwLvnUOMU6h2HPH8KANA8DVw5 i+Wg== MIME-Version: 1.0 X-Received: by 10.66.197.135 with SMTP id iu7mr3890626pac.149.1382629797824; Thu, 24 Oct 2013 08:49:57 -0700 (PDT) Received: by 10.70.41.70 with HTTP; Thu, 24 Oct 2013 08:49:57 -0700 (PDT) Date: Thu, 24 Oct 2013 23:49:57 +0800 Message-ID: Subject: Some questions on HLog From: Wukang Lin To: user@hbase.apache.org Content-Type: multipart/alternative; boundary=047d7bd8fc22f48e5d04e97e95b0 X-Virus-Checked: Checked by ClamAV on apache.org --047d7bd8fc22f48e5d04e97e95b0 Content-Type: text/plain; charset=ISO-8859-1 Hi all, Recently, i read the source of HBase's HLog, and i got some questions that puzzled me a lot. here there are: 1 why use reflection to init a SequenceFile.Writer in SequenceFileLogWriter? i read HBASE-2312 but still can't catch the point. 2 It seems that hlog use SequenceFile.Writer's append method to sync the WAL logs to DataNode, not FSDataOutputStream.hflush(), for each mutation(or batch mutations), so may it lose data when HDFS crash while WAL logs were 'sync' to DataNode but not flush to disk? or are there something i misunderstanded? Thank you. --047d7bd8fc22f48e5d04e97e95b0--