BELUGA BEHR created HDFS-14102: ---------------------------------- Summary: verifyBlockPlacement Key: HDFS-14102 URL: https://issues.apache.org/jira/browse/HDFS-14102 Project: Hadoop HDFS Issue Type: Improvement Reporter: BELUGA BEHR
{code:java|title=BlockPlacementPolicyDefault.java} // 1. Check that all locations are different. // 2. Count locations on different racks. Set<String> racks = new TreeSet<>(); for (DatanodeInfo dn : locs) racks.add(dn.getNetworkLocation()); ... racks.size(){code} Here, the code is counting the number of distinct Network Locations. However, it is using a TreeSet which has overhead to maintain item order and uses a linked structure internally. This overhead is unneeded since all that is required here is a count. {quote}A NavigableSet implementation based on a TreeMap. The elements are ordered using their natural ordering, or by a Comparator provided at set creation time, depending on which constructor is used. This implementation provides guaranteed log(n) time cost for the basic operations (add, remove and contains). [https://docs.oracle.com/javase/7/docs/api/java/util/TreeSet.html] {quote} Use Java streams for readability and because it uses a {{HashSet}} under the covers to perform the distinct action. {{HashSet}} uses an array internally and has constant time performance for the {{add}} method. [https://github.com/apache/hadoop/blob/27978bcb66a9130cbf26d37ec454c0b7fcdc2530/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockPlacementPolicyDefault.java#L1042] -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-dev-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-dev-h...@hadoop.apache.org