[ https://issues.apache.org/jira/browse/HDFS-14378?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
star updated HDFS-14378: ------------------------ Attachment: HDFS-14378-trunk.004.patch > Simplify the design of multiple NN and both logic of edit log roll and > checkpoint > --------------------------------------------------------------------------------- > > Key: HDFS-14378 > URL: https://issues.apache.org/jira/browse/HDFS-14378 > Project: Hadoop HDFS > Issue Type: Improvement > Components: namenode > Affects Versions: 3.1.2 > Reporter: star > Assignee: star > Priority: Minor > Labels: patch > Attachments: HDFS-14378-trunk.001.patch, HDFS-14378-trunk.002.patch, > HDFS-14378-trunk.003.patch, HDFS-14378-trunk.004.patch > > > HDFS-6440 introduced a mechanism to support more than 2 NNs. It > implements a first-writer-win policy to avoid duplicated fsimage downloading. > Variable 'isPrimaryCheckPointer' is used to hold the first-writer state, with > which SNN will provide fsimage for ANN next time. Then we have three roles in > NN cluster: ANN, one primary SNN, one or more normal SNN. > Since HDFS-12248, there may be more than two primary SNN shortly after > a exception occurred. It takes care with a scenario that SNN will not upload > fsimage on IOE and Interrupted exceptions. Though it will not cause any > further functional issues, it is inconsistent. > Futher more, edit log may be rolled more frequently than necessary with > multiple Standby name nodes, HDFS-14349. (I'm not so sure about this, will > verify by unit tests or any one could point it out.) > Above all, I‘m wondering if we could make it simple with following > changes: > * There are only two roles:ANN, SNN > * ANN will roll its edit log every DFS_HA_LOGROLL_PERIOD_KEY period. > * ANN will select a SNN to download checkpoint. > SNN will just do logtail and checkpoint. Then provide a servlet for fsimage > downloading as normal. SNN will not try to roll edit log or send checkpoint > request to ANN. > In a word, ANN will be more active. Suggestions are welcomed. > -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org