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Yi Liu commented on HDFS-8884: ------------------------------ This JIRA will also remove the duplicate code in {{BlockPlacementPolicyDefault#chooseLocalStorage}} and {{BlockPlacementPolicyWithNodeGroup#chooseLocalStorage}}. > Improve BlockPlacementPolicyDefault#chooseTarget to check candidate datanode > first > ----------------------------------------------------------------------------------- > > Key: HDFS-8884 > URL: https://issues.apache.org/jira/browse/HDFS-8884 > Project: Hadoop HDFS > Issue Type: Improvement > Reporter: Yi Liu > Assignee: Yi Liu > > In current BlockPlacementPolicyDefault, when choosing datanode storage to > place block, we have following logic: > {code} > final DatanodeStorageInfo[] storages = DFSUtil.shuffle( > chosenNode.getStorageInfos()); > int i = 0; > boolean search = true; > for (Iterator<Map.Entry<StorageType, Integer>> iter = storageTypes > .entrySet().iterator(); search && iter.hasNext(); ) { > Map.Entry<StorageType, Integer> entry = iter.next(); > for (i = 0; i < storages.length; i++) { > StorageType type = entry.getKey(); > final int newExcludedNodes = addIfIsGoodTarget(storages[i], > {code} > We will iterate (actually two {{for}}) all storages of the candidate datanode > even the datanode itself is not good (e.g. decommissioned, stale, too > busy..), since currently we do all the check in {{addIfIsGoodTarget}}. > We can fail-fast: check the datanode related conditions first, if the > datanode is not good, then no need to shuffle and iterate the storages. Then > it's more efficient. -- This message was sent by Atlassian JIRA (v6.3.4#6332)