From hdfs-issues-return-238261-archive-asf-public=cust-asf.ponee.io@hadoop.apache.org Mon Oct 15 16:14:04 2018 Return-Path: X-Original-To: archive-asf-public@cust-asf.ponee.io Delivered-To: archive-asf-public@cust-asf.ponee.io Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by mx-eu-01.ponee.io (Postfix) with SMTP id 1EEDA180647 for ; Mon, 15 Oct 2018 16:14:03 +0200 (CEST) Received: (qmail 7662 invoked by uid 500); 15 Oct 2018 14:14:03 -0000 Mailing-List: contact hdfs-issues-help@hadoop.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Delivered-To: mailing list hdfs-issues@hadoop.apache.org Received: (qmail 7651 invoked by uid 99); 15 Oct 2018 14:14:03 -0000 Received: from pnap-us-west-generic-nat.apache.org (HELO spamd4-us-west.apache.org) (209.188.14.142) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 15 Oct 2018 14:14:03 +0000 Received: from localhost (localhost [127.0.0.1]) by spamd4-us-west.apache.org (ASF Mail Server at spamd4-us-west.apache.org) with ESMTP id A5880C0656 for ; Mon, 15 Oct 2018 14:14:02 +0000 (UTC) X-Virus-Scanned: Debian amavisd-new at spamd4-us-west.apache.org X-Spam-Flag: NO X-Spam-Score: -110.301 X-Spam-Level: X-Spam-Status: No, score=-110.301 tagged_above=-999 required=6.31 tests=[ENV_AND_HDR_SPF_MATCH=-0.5, RCVD_IN_DNSWL_MED=-2.3, SPF_PASS=-0.001, USER_IN_DEF_SPF_WL=-7.5, USER_IN_WHITELIST=-100] autolearn=disabled Received: from mx1-lw-eu.apache.org ([10.40.0.8]) by localhost (spamd4-us-west.apache.org [10.40.0.11]) (amavisd-new, port 10024) with ESMTP id v0ablq4S_OYl for ; Mon, 15 Oct 2018 14:14:01 +0000 (UTC) Received: from mailrelay1-us-west.apache.org (mailrelay1-us-west.apache.org [209.188.14.139]) by mx1-lw-eu.apache.org (ASF Mail Server at mx1-lw-eu.apache.org) with ESMTP id 25BDF5F21F for ; Mon, 15 Oct 2018 14:14:01 +0000 (UTC) Received: from jira-lw-us.apache.org (unknown [207.244.88.139]) by mailrelay1-us-west.apache.org (ASF Mail Server at mailrelay1-us-west.apache.org) with ESMTP id 61B5EE1328 for ; Mon, 15 Oct 2018 14:14:00 +0000 (UTC) Received: from jira-lw-us.apache.org (localhost [127.0.0.1]) by jira-lw-us.apache.org (ASF Mail Server at jira-lw-us.apache.org) with ESMTP id 2CBAE24DDC for ; Mon, 15 Oct 2018 14:14:00 +0000 (UTC) Date: Mon, 15 Oct 2018 14:14:00 +0000 (UTC) From: "BELUGA BEHR (JIRA)" To: hdfs-issues@hadoop.apache.org Message-ID: In-Reply-To: References: Subject: [jira] [Commented] (HDFS-13990) Synchronization Issue With HashResolver.java MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-JIRA-FingerPrint: 30527f35849b9dde25b450d4833f0394 [ https://issues.apache.org/jira/browse/HDFS-13990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16650271#comment-16650271 ] BELUGA BEHR commented on HDFS-13990: ------------------------------------ The {{get(hash)}} code is synchronized internally, so in both scenarios (current code / my patch), the code enters a synchronized block once. My proposed patch has a 'null' check and the call to {{get(hash)}} function inside it's synchronized block. I don't think you'll see any measurable difference in performance for those two operations. If a new {{HashResolver}} is required, the current code must enter a synchronized section two times. > Synchronization Issue With HashResolver.java > -------------------------------------------- > > Key: HDFS-13990 > URL: https://issues.apache.org/jira/browse/HDFS-13990 > Project: Hadoop HDFS > Issue Type: Bug > Components: federation > Affects Versions: 3.2.0 > Reporter: BELUGA BEHR > Assignee: BELUGA BEHR > Priority: Minor > Attachments: HDFS-13990.1.patch > > > {code:java|title=HashResolver.java} > private ConsistentHashRing getHashResolver(final Set namespaces) { > int hash = namespaces.hashCode(); > ConsistentHashRing resolver = this.hashResolverMap.get(hash); > if (resolver == null) { > resolver = new ConsistentHashRing(namespaces); > this.hashResolverMap.put(hash, resolver); > } > return resolver; > } > {code} > The {{hashResolverMap}} is a {{ConcurrentHashMap}} so presumably there is concern here for concurrency issues. However, there is no synchronization around this method, so two threads could call {{get(hash)}} both see a 'null' value and then both add two entries into the {{Map}}. Add synchronization here. -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-issues-unsubscribe@hadoop.apache.org For additional commands, e-mail: hdfs-issues-help@hadoop.apache.org