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https://issues.apache.org/jira/browse/HDFS-14305?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16918256#comment-16918256
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He Xiaoqiao commented on HDFS-14305:
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[~shv], Thanks very much for picking up this JIRA and revisiting it.
IMO, in order to avoid overlap between different NameNode, we have to split and
distribute serial number to different NNs, however, we could not make sure
total number NNs per namespace only relay on configuration especially for
multi-nns setups(HDFS-6440), Please correct me if I am wrong. So bring the
restrict that less possible chance to setup more than 64 NNs in one NS. I would
like to follow up and update this logic if any other thought? Thanks [~shv].
> Serial number in BlockTokenSecretManager could overlap between different
> namenodes
> ----------------------------------------------------------------------------------
>
> Key: HDFS-14305
> URL: https://issues.apache.org/jira/browse/HDFS-14305
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode, security
> Reporter: Chao Sun
> Assignee: He Xiaoqiao
> Priority: Major
> Fix For: 3.0.4, 3.3.0, 3.2.1, 3.1.3
>
> Attachments: HDFS-14305.001.patch, HDFS-14305.002.patch,
> HDFS-14305.003.patch, HDFS-14305.004.patch, HDFS-14305.005.patch,
> HDFS-14305.006.patch
>
>
> Currently, a {{BlockTokenSecretManager}} starts with a random integer as the
> initial serial number, and then use this formula to rotate it:
> {code:java}
> this.intRange = Integer.MAX_VALUE / numNNs;
> this.nnRangeStart = intRange * nnIndex;
> this.serialNo = (this.serialNo % intRange) + (nnRangeStart);
> {code}
> while {{numNNs}} is the total number of NameNodes in the cluster, and
> {{nnIndex}} is the index of the current NameNode specified in the
> configuration {{dfs.ha.namenodes.<nameservice>}}.
> However, with this approach, different NameNode could have overlapping ranges
> for serial number. For simplicity, let's assume {{Integer.MAX_VALUE}} is 100,
> and we have 2 NameNodes {{nn1}} and {{nn2}} in configuration. Then the ranges
> for these two are:
> {code}
> nn1 -> [-49, 49]
> nn2 -> [1, 99]
> {code}
> This is because the initial serial number could be any negative integer.
> Moreover, when the keys are updated, the serial number will again be updated
> with the formula:
> {code}
> this.serialNo = (this.serialNo % intRange) + (nnRangeStart);
> {code}
> which means the new serial number could be updated to a range that belongs to
> a different NameNode, thus increasing the chance of collision again.
> When the collision happens, DataNodes could overwrite an existing key which
> will cause clients to fail because of {{InvalidToken}} error.
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