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https://issues.apache.org/jira/browse/HDFS-9350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15191331#comment-15191331
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Chris Nauroth commented on HDFS-9350:
-------------------------------------
I think this patch should be reverted, because it broke the contract of the
static {{Block#toString}} method. Here is the code before the patch:
{code}
/**
* A helper method to output the string representation of the Block portion of
* a derived class' instance.
*
* @param b the target object
* @return the string representation of the block
*/
public static String toString(final Block b) {
return getBlockName() + "_" + getGenerationStamp();
}
{code}
Here is the code after the patch:
{code}
/**
* A helper method to output the string representation of the Block portion of
* a derived class' instance.
*
* @param b the target object
* @return the string representation of the block
*/
public static String toString(final Block b) {
StringBuilder sb = new StringBuilder();
b.appendStringTo(sb);
return sb.toString();
}
{code}
Notice that the JavaDocs say this method is supposed to provide just the basic
{{Block}} data, even in cases where the parameter is a subclass that may have
overridden {{appendStringTo}}. Having a widening cast to {{Block}} in the
method signature's argument does not influence the outcome of runtime dynamic
dispatch. One specific problem would be {{ReplicaUnderConstruction}}, which
overrides {{appendStringTo}}, so passing an instance of that will not in fact
give the caller the basic {{Block}} data.
Thoughts? Cc'ing [~jojochuang], who I think is the original author of the
static {{Block#toString}} method. He can help confirm the intent of the method.
> Avoid creating temprorary strings in Block.toString() and getBlockName()
> ------------------------------------------------------------------------
>
> Key: HDFS-9350
> URL: https://issues.apache.org/jira/browse/HDFS-9350
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: performance
> Affects Versions: 2.7.1
> Reporter: Staffan Friberg
> Assignee: Staffan Friberg
> Priority: Minor
> Fix For: 2.9.0
>
> Attachments: HDFS-9350.001.patch
>
>
> Minor change to use StringBuilders directly to avoid creating temporary
> strings of Long and Block name when doing toString on a Block.
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