记一次hadoop高可用(HA)namenode格式化异常:Unable to check if JNs are ready...

错误日志：19/11/07 19:20:42 INFO ipc.Client: Retrying connect to server: hadoop05/192.168.0.111:8485. Already tried 9 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
19/11/07 19:20:42 WARN namenode.NameNode: Encountered exception during format:
org.apache.hadoop.hdfs.qjournal.client.QuorumException: Unable to check if JNs are ready for formatting. 1 exceptions thrown:
192.168.0.107:8485: Call From hadoop01/192.168.0.105 to hadoop03:8485 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused
        at org.apache.hadoop.hdfs.qjournal.client.QuorumException.create(QuorumException.java:81)
        at org.apache.hadoop.hdfs.qjournal.client.QuorumCall.rethrowException(QuorumCall.java:286)
        at org.apache.hadoop.hdfs.qjournal.client.QuorumJournalManager.hasSomeData(QuorumJournalManager.java:230)
        at org.apache.hadoop.hdfs.server.common.Storage.confirmFormat(Storage.java:981)
        at org.apache.hadoop.hdfs.server.namenode.FSImage.confirmFormat(FSImage.java:195)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.format(NameNode.java:1168)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1614)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1741)
19/11/07 19:20:42 ERROR namenode.NameNode: Failed to start namenode.
org.apache.hadoop.hdfs.qjournal.client.QuorumException: Unable to check if JNs are ready for formatting. 1 exceptions thrown:
192.168.0.107:8485: Call From hadoop01/192.168.0.105 to hadoop03:8485 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused
        at org.apache.hadoop.hdfs.qjournal.client.QuorumException.create(QuorumException.java:81)
        at org.apache.hadoop.hdfs.qjournal.client.QuorumCall.rethrowException(QuorumCall.java:286)
        at org.apache.hadoop.hdfs.qjournal.client.QuorumJournalManager.hasSomeData(QuorumJournalManager.java:230)
        at org.apache.hadoop.hdfs.server.common.Storage.confirmFormat(Storage.java:981)
        at org.apache.hadoop.hdfs.server.namenode.FSImage.confirmFormat(FSImage.java:195)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.format(NameNode.java:1168)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1614)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1741)
19/11/07 19:20:42 INFO util.ExitUtil: Exiting with status 1: org.apache.hadoop.hdfs.qjournal.client.QuorumException: Unable to check if JNs are ready for formatting. 1 exceptions thrown:
192.168.0.107:8485: Call From hadoop01/192.168.0.105 to hadoop03:8485 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused
19/11/07 19:20:42 INFO namenode.NameNode: SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at hadoop01/192.168.0.105

问题原因：
以前只是按着文档顺序搭建hadoop集群，在格式化namenode的时候，忘记启动journalnode 了，导致格式化namenode报错。
解决办法：先启动journalnode，在格式化 namenode.

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