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https://issues.apache.org/jira/browse/HDFS-16697?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17721773#comment-17721773
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ASF GitHub Bot commented on HDFS-16697:
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Likkey opened a new pull request, #5569:
URL: https://github.com/apache/hadoop/pull/5569
### Description of PR
It is found that “dfs.namenode.resource.checked.volumes.minimum” lacks a
condition check and an associated exception handling mechanism, which makes it
impossible to find the root cause of the impact when a misconfiguration occurs.
Add a mechanism to check the value of minimumRedundantVolumes to ensure that
the value is greater than the number of NameNode storage volumes to avoid never
being able to turn off safe mode afterwards.
JIRA:(https://issues.apache.org/jira/browse/HDFS-16697))]
### How was this patch tested?
This patch provides a check of the configuration items，it will throw an
IllegalArgumentException and a detailed error message when the value is greater
than the number of NameNode storage volumes, and printing a warning message in
the log in order to solve the problem in time and avoid the misconfiguration
from affecting the subsequent operations of the program.
> Randomly setting “dfs.namenode.resource.checked.volumes.minimum” will always
> prevent safe mode from being turned off
> --------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-16697
> URL: https://issues.apache.org/jira/browse/HDFS-16697
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 3.1.3
> Environment: Linux version 4.15.0-142-generic
> (buildd@lgw01-amd64-039) (gcc version 5.4.0 20160609 (Ubuntu
> 5.4.0-6ubuntu1~16.04.12))
> java version "1.8.0_162"
> Java(TM) SE Runtime Environment (build 1.8.0_162-b12)
> Java HotSpot(TM) 64-Bit Server VM (build 25.162-b12, mixed mode)
> Reporter: ECFuzz
> Assignee: ECFuzz
> Priority: Major
> Labels: pull-request-available
> Time Spent: 1h 50m
> Remaining Estimate: 0h
>
> {code:java}
> <property>
> <name>dfs.namenode.resource.checked.volumes.minimum</name>
> <value>1</value>
> <description>
> The minimum number of redundant NameNode storage volumes required.
> </description>
> </property>{code}
> I found that when setting the value of
> “dfs.namenode.resource.checked.volumes.minimum” is greater than the total
> number of storage volumes in the NameNode, it is always impossible to turn
> off the safe mode, and when in safe mode, the file system only accepts read
> data requests, but not delete, modify and other change requests, which is
> greatly limited by the function.
> The default value of the configuration item is 1, we set to 2 as an example
> for illustration, after starting hdfs logs and the client will throw the
> relevant reminders.
> {code:java}
> 2022-07-27 17:37:31,772 WARN
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem: NameNode low on
> available disk space. Already in safe mode.
> 2022-07-27 17:37:31,772 INFO org.apache.hadoop.hdfs.StateChange: STATE* Safe
> mode is ON.
> Resources are low on NN. Please add or free up more resourcesthen turn off
> safe mode manually. NOTE: If you turn off safe mode before adding resources,
> the NN will immediately return to safe mode. Use "hdfs dfsadmin -safemode
> leave" to turn safe mode off.
> {code}
> {code:java}
> org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot create
> directory /hdfsapi/test. Name node is in safe mode.
> Resources are low on NN. Please add or free up more resourcesthen turn off
> safe mode manually. NOTE: If you turn off safe mode before adding resources,
> the NN will immediately return to safe mode. Use "hdfs dfsadmin -safemode
> leave" to turn safe mode off. NamenodeHostName:192.168.1.167
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.newSafemodeException(FSNamesystem.java:1468)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkNameNodeSafeMode(FSNamesystem.java:1455)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirs(FSNamesystem.java:3174)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.mkdirs(NameNodeRpcServer.java:1145)
> at
> org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.mkdirs(ClientNamenodeProtocolServerSideTranslatorPB.java:714)
> at
> org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
> at
> org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:527)
> at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1036)
> at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:1000)
> at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:928)
> at java.base/java.security.AccessController.doPrivileged(Native
> Method)
> at java.base/javax.security.auth.Subject.doAs(Subject.java:423)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1729)
> at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2916){code}
> According to the prompt, it is believed that there is not enough resource
> space to meet the corresponding conditions to close safe mode, but after
> adding or releasing more resources and lowering the resource condition
> threshold "dfs.namenode.resource.du.reserved", it still fails to close safe
> mode and throws the same prompt .
> According to the source code, we know that if the NameNode has redundant
> storage volumes less than the "dfs.namenode.resource.checked.volumes.minimum"
> set the minimum number of redundant storage volumes will enter safe mode.
> After debugging, *we found that the current NameNode storage volumes are
> abundant resource space, but because the total number of NameNode storage
> volumes is less than the set value, so the number of NameNode storage volumes
> with redundancy space must also be less than the set value, resulting in
> always entering safe mode.*
> In summary, it is found that the configuration item lacks a condition check
> and an associated exception handling mechanism, which makes it impossible to
> find the root cause of the impact when a misconfiguration occurs.
> The solution I propose is to add a mechanism to check the value of this
> configuration item, throwing an IllegalArgumentException and a detailed error
> message when the value is greater than the number of NameNode storage
> volumes, and printing a warning message in the log to avoid the
> misconfiguration from affecting the subsequent operations of the program.
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