Chen Liang created HDFS-11507: --------------------------------- Summary: NetworkTopology#chooseRandom may run into a dead loop due to race condition Key: HDFS-11507 URL: https://issues.apache.org/jira/browse/HDFS-11507 Project: Hadoop HDFS Issue Type: Bug Components: namenode Reporter: Chen Liang Assignee: Chen Liang
{{NetworkTopology#chooseRandom()}} works as: 1. counts the number of available nodes as {{availableNodes}}, 2. checks how many nodes are excluded, deduct from {{availableNodes}} 3. if {{availableNodes}} still > 0, then there are nodes available. 4. keep looping to find that node But now imagine, in the meantime, the actually available nodes got removed in step 3 or step 4, and all remaining nodes are excluded nodes. Then, although there are no more nodes actually available, the code would still run as {{availableNodes}} > 0, and then it would keep getting excluded node and loop forever, as {{if (excludedNodes == null || !excludedNodes.contains(ret))}} will always be false. We may fix this by expanding the while loop to also include the {{availableNodes}} calculation. Such that we re-calculate {{availableNodes}} every time it fails to find an available node. -- This message was sent by Atlassian JIRA (v6.3.15#6346) --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-dev-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-dev-h...@hadoop.apache.org