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From "Konstantin Shvachko (Jira)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-14305) Serial number in BlockTokenSecretManager could overlap between different namenodes
Date Thu, 26 Sep 2019 18:55:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-14305?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16938878#comment-16938878
] 

Konstantin Shvachko commented on HDFS-14305:
--------------------------------------------

Hey Arpit, let's first agree this is an incompatible change between minor releases.
Suppose you do a rolling upgrade from HDFS 3.2.0, which doesn't have this patch, to HDFS 3.2.1,
which does, with two standard NameNodes - active and standby. If you start the NNs in arbitrary
order, you can get block token collisions because the ranges will change in 3.2.1 compared
to 3.2.0.

> 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: Xiaoqiao He
>            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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