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https://issues.apache.org/jira/browse/HADOOP-14872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16184098#comment-16184098
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Steve Loughran commented on HADOOP-14872:
-----------------------------------------
LGTM +1,
can you cut the extra blank line added to {{TestUnbuffer.java}} when you commit
it?
Related to this JIRA, I've been instrumenting an s3a stream (and the FS
itself), using a switch statement.
I can't use the enums, as to get the string value I have to go
StreamCapability.HSYNC.getValue(), and you can only use string constants in
enums. Nor can i use the enums in a switch as I'm adding my own values. I've
ended up just using "hsync" and "hflush" as string constants.
{code}
public boolean hasCapability(String capability) {
switch (capability.toLowerCase(Locale.ENGLISH)) {
// does the output stream have delayed visibility
case CommitConstants.STREAM_CAPABILITY_MAGIC_OUTPUT:
return putTracker.isDelayedVisibility();
// The flush/sync options are absolutely not supported
case "hflush":
case "hsync":
return false;
default:
return false;
}
}
{code}
I think we will need to supplement the {{StreamCapability}} enums with a string
constant for every value
> CryptoInputStream should implement unbuffer
> -------------------------------------------
>
> Key: HADOOP-14872
> URL: https://issues.apache.org/jira/browse/HADOOP-14872
> Project: Hadoop Common
> Issue Type: Improvement
> Components: fs
> Affects Versions: 2.6.4
> Reporter: John Zhuge
> Assignee: John Zhuge
> Attachments: HADOOP-14872.001.patch, HADOOP-14872.002.patch,
> HADOOP-14872.003.patch, HADOOP-14872.004.patch, HADOOP-14872.005.patch,
> HADOOP-14872.006.patch
>
>
> Discovered in IMPALA-5909.
> Opening an encrypted HDFS file returns a chain of wrapped input streams:
> {noformat}
> HdfsDataInputStream
> CryptoInputStream
> DFSInputStream
> {noformat}
> If an application such as Impala or HBase calls HdfsDataInputStream#unbuffer,
> FSDataInputStream#unbuffer will be called:
> {code:java}
> try {
> ((CanUnbuffer)in).unbuffer();
> } catch (ClassCastException e) {
> throw new UnsupportedOperationException("this stream does not " +
> "support unbuffering.");
> }
> {code}
> If the {{in}} class does not implement CanUnbuffer, UOE will be thrown. If
> the application is not careful, tons of UOEs will show up in logs.
> In comparison, opening an non-encrypted HDFS file returns this chain:
> {noformat}
> HdfsDataInputStream
> DFSInputStream
> {noformat}
> DFSInputStream implements CanUnbuffer.
> It is good for CryptoInputStream to implement CanUnbuffer for 2 reasons:
> * Release buffer, cache, or any other resource when instructed
> * Able to call its wrapped DFSInputStream unbuffer
> * Avoid the UOE described above. Applications may not handle the UOE very
> well.
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