[ https://issues.apache.org/jira/browse/HDFS-10206?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Ming Ma updated HDFS-10206: --------------------------- Issue Type: Improvement (was: Bug) > getBlockLocations might not sort datanodes properly by distance > --------------------------------------------------------------- > > Key: HDFS-10206 > URL: https://issues.apache.org/jira/browse/HDFS-10206 > Project: Hadoop HDFS > Issue Type: Improvement > Reporter: Ming Ma > > If the DFSClient machine is not a datanode, but it shares its rack with some > datanodes of the HDFS block requested, {{DatanodeManager#sortLocatedBlocks}} > might not put the local-rack datanodes at the beginning of the sorted list. > That is because the function didn't call {{networktopology.add(client);}} to > properly set the node's parent node; something required by > {{networktopology.sortByDistance}} to compute distance between two nodes in > the same topology tree. > Another issue with {{networktopology.sortByDistance}} is it only > distinguishes local rack from remote rack, but it doesn't support general > distance calculation to tell how remote the rack is. > {noformat} > NetworkTopology.java > protected int getWeight(Node reader, Node node) { > // 0 is local, 1 is same rack, 2 is off rack > // Start off by initializing to off rack > int weight = 2; > if (reader != null) { > if (reader.equals(node)) { > weight = 0; > } else if (isOnSameRack(reader, node)) { > weight = 1; > } > } > return weight; > } > {noformat} > HDFS-10203 has suggested moving the sorting from namenode to DFSClient to > address another issue. Regardless of where we do the sorting, we still fix > the issues outline here. -- This message was sent by Atlassian JIRA (v6.3.4#6332)