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https://issues.apache.org/jira/browse/HDFS-15443?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17149379#comment-17149379
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jianghua zhu commented on HDFS-15443:
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The value of the parameter (dfs.datanode.max.transfer.threads) should be
greater than 1.
We should add the verification code in the constructor of the DataXceiverServer
class.
When the value is less than 1, the DataXceiverServer fails to initialize.
[~elgoiri] , do you have any other suggestions?
> Setting dfs.datanode.max.transfer.threads to a very small value can cause
> strange failure.
> ------------------------------------------------------------------------------------------
>
> Key: HDFS-15443
> URL: https://issues.apache.org/jira/browse/HDFS-15443
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Reporter: AMC-team
> Priority: Major
>
> Configuration parameter dfs.datanode.max.transfer.threads is to specify the
> maximum number of threads to use for transferring data in and out of the DN.
> This is a vital param that need to tune carefully.
> {code:java}
> // DataXceiverServer.java
> // Make sure the xceiver count is not exceeded
> intcurXceiverCount = datanode.getXceiverCount();
> if (curXceiverCount > maxXceiverCount) {
> thrownewIOException("Xceiver count " + curXceiverCount
> + " exceeds the limit of concurrent xceivers: "
> + maxXceiverCount);
> }
> {code}
> There are many issues that caused by not setting this param to an appropriate
> value. However, there is no any check code to restrict the parameter.
> Although having a hard-and-fast rule is difficult because we need to consider
> number of cores, main memory etc, *we can prevent users from setting this
> value to an absolute wrong value by accident.* (e.g. a negative value that
> totally break the availability of datanode.)
> *How to fix:*
> Add proper check code for the parameter.
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