You are viewing a plain text version of this content. The canonical link for it is here.
Posted to hdfs-user@hadoop.apache.org by stack <st...@duboce.net> on 2009/10/09 22:13:37 UTC
hflush not working for me?
I'm putting together some unit tests up in our application that exercise
hflush. I'm using minidfscluster and a jar made by building head of the
0.21 branch of hdfs (from about a minute ago).
Code opens a file, writes a bunch of edits, invokes hflush (by calling sync
on DFSDataOutputStream instance) and then, without closing the Writer, opens
a Reader on same file. This Reader does not see any edits not to mind edits
up to the sync invocation.
I can trace the code and see how on hflush it sends the queued packets of
edits.
I studied TestReadWhileWriting. I've set setBoolean("dfs.support.append",
true) before minidfscluster spins up. I can't set soft lease to 1 second
because not in same package so I just wait out the default minute. It
doesn't seem to make a difference.
Do I have to do open as another user?
Thanks for any pointers,
St.Ack
Re: hflush not working for me?
Posted by stack <st...@duboce.net>.
I just tried opening Reader as another user but that made no difference.
St.Ack
On Fri, Oct 9, 2009 at 1:13 PM, stack <st...@duboce.net> wrote:
> I'm putting together some unit tests up in our application that exercise
> hflush. I'm using minidfscluster and a jar made by building head of the
> 0.21 branch of hdfs (from about a minute ago).
>
> Code opens a file, writes a bunch of edits, invokes hflush (by calling sync
> on DFSDataOutputStream instance) and then, without closing the Writer, opens
> a Reader on same file. This Reader does not see any edits not to mind edits
> up to the sync invocation.
>
> I can trace the code and see how on hflush it sends the queued packets of
> edits.
>
> I studied TestReadWhileWriting. I've set setBoolean("dfs.support.append",
> true) before minidfscluster spins up. I can't set soft lease to 1 second
> because not in same package so I just wait out the default minute. It
> doesn't seem to make a difference.
>
> Do I have to do open as another user?
>
> Thanks for any pointers,
> St.Ack
>
Re: hflush not working for me?
Posted by stack <st...@duboce.net>.
Thank you for figuring it Nicholas.
St.Ack
On Fri, Oct 9, 2009 at 3:27 PM, Tsz Wo (Nicholas), Sze <
s29752-hadoopuser@yahoo.com> wrote:
> Hi St.Ack,
>
> HLog uses SequenceFile.Reader. When a SequenceFile.Reader is constructed,
> it calls fs.getFileStatus(file).getLen(). However,
> fs.getFileStatus(file).getLen() does not return the hflushed length for
> un-closed file since the Namenode does not know the hflushed length.
> DFSClient have to ask a datanode for the length last block which is being
> written; see also HDFS-570. That's why "hflush not working for you". Sorry
> ...
>
> We have to change SequenceFile.Reader in order to support reading on
> unclosed SequenceFile.
>
> Nicholas
>
>
> *From:* "Tsz Wo (Nicholas), Sze" <s2...@yahoo.com>
> *To:* hdfs-user@hadoop.apache.org
> *Sent:* Fri, October 9, 2009 2:40:34 PM
>
> *Subject:* Re: hflush not working for me?
>
> Soft lease is for another writer to obtain the file lease if the original
> writer appears to abandon the file. In the current TestReadWhileWriting
> (not counting part (c) and (d)), there is only one writer. So soft lease is
> not related.
>
> Will check your test.
>
> Nicholas
>
>
> *From:* stack <st...@duboce.net>
> *To:* hdfs-user@hadoop.apache.org
> *Sent:* Fri, October 9, 2009 2:32:02 PM
> *Subject:* Re: hflush not working for me?
>
> On Fri, Oct 9, 2009 at 1:27 PM, Tsz Wo (Nicholas), Sze <
> s29752-hadoopuser@yahoo.com> wrote:
>
>> Hi St.Ack,
>>
>> > ... soft lease to 1 second ...
>> You are right that you don't have to change soft lease. It is for append
>> but not related to hflash.
>>
>
> I should not have to set it then? I can remove this 70 second pause in
> middle of my test?
>
>
>
>>
>> > Do I have to do open as another user?
>> This should not be necessary.
>>
>> Could you send me/post your test?
>>
>>
> Sure, as long as you don't hold this ugly code against me ever after.
>
> I checked in the code so you could try it:
> http://svn.apache.org/repos/asf/hadoop/hbase/trunk/src/test/org/apache/hadoop/hbase/regionserver/TestHLog.java
>
> Its the first test, testSync.
>
> It starts out by copying whats down in the hdfs testReadWhileWriting. That
> bit works fine.
>
> Then comes the ugly stuff.
>
> HLog is our write-ahead log wrapper. Internally it writes out to a
> SequenceFile.Writer. The SequenceFile.Writer has been doctored using
> reflection so the out datamember is non-private. A call to HLog.sync runs
> the SequenceFile.Writer.sync -- which DOES NOT call sync on the backing
> output stream -- and then it calls sync on the now accessible out stream
> (Sorry its so ugly -- I'm trying to hack stuff up fast so all of hbase gets
> access to this new facility). If I trace in the debugger, I can see that
> the sync on the out data member goes down into hflush. Queued up edits are
> flushed. It seems like it should be working.
>
> Do I have to do some doctoring of the reader? (It doesn't seem so given
> that the code at the head of this test works).
>
> Thanks for taking a look Nicholas.
>
> To run the test, you can do "ant clean jar test -Dtestcase=TestHLog".
>
> (Let me know if you want an eclipse .project + .classpath so you can get it
> up in an ide to run debugger).
>
> St.Ack
>
>
>
>
>
>> Nicholas Sze
>>
>>
>> *From:* stack <st...@duboce.net>
>> *To:* hdfs-user@hadoop.apache.org
>> *Sent:* Fri, October 9, 2009 1:13:37 PM
>> *Subject:* hflush not working for me?
>>
>> I'm putting together some unit tests up in our application that exercise
>> hflush. I'm using minidfscluster and a jar made by building head of the
>> 0.21 branch of hdfs (from about a minute ago).
>>
>> Code opens a file, writes a bunch of edits, invokes hflush (by calling
>> sync on DFSDataOutputStream instance) and then, without closing the Writer,
>> opens a Reader on same file. This Reader does not see any edits not to mind
>> edits up to the sync invocation.
>>
>> I can trace the code and see how on hflush it sends the queued packets of
>> edits.
>>
>> I studied TestReadWhileWriting. I've set setBoolean("dfs.support.append",
>> true) before minidfscluster spins up. I can't set soft lease to 1 second
>> because not in same package so I just wait out the default minute. It
>> doesn't seem to make a difference.
>>
>> Do I have to do open as another user?
>>
>> Thanks for any pointers,
>> St.Ack
>>
>>
>
Re: hflush not working for me?
Posted by "Tsz Wo (Nicholas), Sze" <s2...@yahoo.com>.
Hi St.Ack,
HLog uses SequenceFile.Reader. When a SequenceFile.Reader is constructed, it calls fs.getFileStatus(file).getLen(). However, fs.getFileStatus(file).getLen() does not return the hflushed length for un-closed file since the Namenode does not know the hflushed length. DFSClient have to ask a datanode for the length last block which is being written; see also HDFS-570. That's why "hflush not working for you". Sorry ...
We have to change SequenceFile.Reader in order to support reading on unclosed SequenceFile.
Nicholas
From: "Tsz Wo (Nicholas), Sze" <s2...@yahoo.com>
>To: hdfs-user@hadoop.apache.org
>Sent: Fri, October 9, 2009 2:40:34 PM
>Subject: Re: hflush not working for me?
>
>
>Soft lease is for another writer to obtain the file lease if the original writer appears to abandon the file. In the current TestReadWhileWriting (not counting part (c) and (d)), there is only one writer. So soft lease is not related.
>
>Will check your test.
>
>Nicholas
>
>
>
>From: stack <st...@duboce.net>
>>To: hdfs-user@hadoop.apache.org
>>Sent: Fri, October 9, 2009 2:32:02 PM
>>Subject: Re: hflush not working for me?
>>
>>>>On Fri, Oct 9, 2009 at 1:27 PM, Tsz Wo (Nicholas), Sze <s2...@yahoo.com> wrote:
>>
>>Hi St.Ack,
>>>
>>>> ... soft lease to 1 second ...
>>>You are right that you don't have to change soft lease. It is for append but not related to hflash.
>>>
>>>
>>
>>I should not have to set it then? I can remove this 70 second pause in middle of my test?
>>
>>
>>
>>>> Do I have to do open as another user?
>>>This should not be necessary.
>>>
>>>Could you send me/post your test?
>>>
>>>
>>
>>Sure, as long as you don't hold this ugly code against me ever after.
>>
>>I checked in the code so you could try it: http://svn.apache.org/repos/asf/hadoop/hbase/trunk/src/test/org/apache/hadoop/hbase/regionserver/TestHLog.java
>>
>>Its the first test, testSync.
>>
>>It starts out by copying whats down in the hdfs testReadWhileWriting. That bit works fine.
>>
>>Then comes the ugly stuff.
>>
>>HLog is our write-ahead log wrapper. Internally it writes out to a SequenceFile.Writer. The SequenceFile.Writer has been doctored using reflection so the out datamember is non-private. A call to HLog.sync runs the SequenceFile.Writer.sync -- which DOES NOT call sync on the backing output stream -- and then it calls sync on the now accessible out stream (Sorry its so ugly -- I'm trying to hack stuff up fast so all of hbase gets access to this new facility). If I trace in the debugger, I can see that the sync on the out data member goes down into hflush. Queued up edits are flushed. It seems like it should be working.
>>
>>Do I have to do some doctoring of the reader? (It doesn't seem so given that the code at the head of this test works).
>>
>>Thanks for taking a look Nicholas.
>>
>>To run the test, you can do "ant clean jar test -Dtestcase=TestHLog".
>>
>>(Let me know if you want an eclipse .project + .classpath so you can get it up in an ide to run debugger).
>>
>>St.Ack
>>
>>
>>
>>
>>Nicholas Sze
>>>
>>>
>>>
>>>From: stack <st...@duboce.net>
>>>>To: hdfs-user@hadoop.apache.org
>>>>Sent: Fri, October 9, 2009 1:13:37 PM
>>>>Subject: hflush not working for me?
>>>>
>>>>
>>>>>>>>I'm putting together some unit tests up in our application that exercise hflush. I'm using minidfscluster and a jar made by building head of the 0.21 branch of hdfs (from about a minute ago).
>>>>
>>>>Code opens a file, writes a bunch of edits, invokes hflush (by calling sync on DFSDataOutputStream instance) and then, without closing the Writer, opens a Reader on same file. This Reader does not see any edits not to mind edits up to the sync invocation.
>>>>
>>>>I can trace the code and see how on hflush it sends the queued packets of edits.
>>>>
>>>>I studied TestReadWhileWriting. I've set setBoolean("dfs.support.append", true) before minidfscluster spins up. I can't set soft lease to 1 second because not in same package so I just wait out the default minute. It doesn't seem to make a difference.
>>>>
>>>>Do I have to do open as another user?
>>>>
>>>>Thanks for any pointers,
>>>>St.Ack
>>>>
>>
Re: hflush not working for me?
Posted by "Tsz Wo (Nicholas), Sze" <s2...@yahoo.com>.
Soft lease is for another writer to obtain the file lease if the original writer appears to abandon the file. In the current TestReadWhileWriting (not counting part (c) and (d)), there is only one writer. So soft lease is not related.
Will check your test.
Nicholas
From: stack <st...@duboce.net>
>To: hdfs-user@hadoop.apache.org
>Sent: Fri, October 9, 2009 2:32:02 PM
>Subject: Re: hflush not working for me?
>
>>On Fri, Oct 9, 2009 at 1:27 PM, Tsz Wo (Nicholas), Sze <s2...@yahoo.com> wrote:
>
>Hi St.Ack,
>>
>>> ... soft lease to 1 second ...
>>You are right that you don't have to change soft lease. It is for append but not related to hflash.
>>
>>
>
>I should not have to set it then? I can remove this 70 second pause in middle of my test?
>
>
>
>>> Do I have to do open as another user?
>>This should not be necessary.
>>
>>Could you send me/post your test?
>>
>>
>
>Sure, as long as you don't hold this ugly code against me ever after.
>
>I checked in the code so you could try it: http://svn.apache.org/repos/asf/hadoop/hbase/trunk/src/test/org/apache/hadoop/hbase/regionserver/TestHLog.java
>
>Its the first test, testSync.
>
>It starts out by copying whats down in the hdfs testReadWhileWriting. That bit works fine.
>
>Then comes the ugly stuff.
>
>HLog is our write-ahead log wrapper. Internally it writes out to a SequenceFile.Writer. The SequenceFile.Writer has been doctored using reflection so the out datamember is non-private. A call to HLog.sync runs the SequenceFile.Writer.sync -- which DOES NOT call sync on the backing output stream -- and then it calls sync on the now accessible out stream (Sorry its so ugly -- I'm trying to hack stuff up fast so all of hbase gets access to this new facility). If I trace in the debugger, I can see that the sync on the out data member goes down into hflush. Queued up edits are flushed. It seems like it should be working.
>
>Do I have to do some doctoring of the reader? (It doesn't seem so given that the code at the head of this test works).
>
>Thanks for taking a look Nicholas.
>
>To run the test, you can do "ant clean jar test -Dtestcase=TestHLog".
>
>(Let me know if you want an eclipse .project + .classpath so you can get it up in an ide to run debugger).
>
>St.Ack
>
>
>
>
>Nicholas Sze
>>
>>
>>
>>From: stack <st...@duboce.net>
>>>To: hdfs-user@hadoop.apache.org
>>>Sent: Fri, October 9, 2009 1:13:37 PM
>>>Subject: hflush not working for me?
>>>
>>>
>>>>>>I'm putting together some unit tests up in our application that exercise hflush. I'm using minidfscluster and a jar made by building head of the 0.21 branch of hdfs (from about a minute ago).
>>>
>>>Code opens a file, writes a bunch of edits, invokes hflush (by calling sync on DFSDataOutputStream instance) and then, without closing the Writer, opens a Reader on same file. This Reader does not see any edits not to mind edits up to the sync invocation.
>>>
>>>I can trace the code and see how on hflush it sends the queued packets of edits.
>>>
>>>I studied TestReadWhileWriting. I've set setBoolean("dfs.support.append", true) before minidfscluster spins up. I can't set soft lease to 1 second because not in same package so I just wait out the default minute. It doesn't seem to make a difference.
>>>
>>>Do I have to do open as another user?
>>>
>>>Thanks for any pointers,
>>>St.Ack
>>>
>
Re: hflush not working for me?
Posted by stack <st...@duboce.net>.
On Fri, Oct 9, 2009 at 1:27 PM, Tsz Wo (Nicholas), Sze <
s29752-hadoopuser@yahoo.com> wrote:
> Hi St.Ack,
>
> > ... soft lease to 1 second ...
> You are right that you don't have to change soft lease. It is for append
> but not related to hflash.
>
I should not have to set it then? I can remove this 70 second pause in
middle of my test?
>
> > Do I have to do open as another user?
> This should not be necessary.
>
> Could you send me/post your test?
>
>
Sure, as long as you don't hold this ugly code against me ever after.
I checked in the code so you could try it:
http://svn.apache.org/repos/asf/hadoop/hbase/trunk/src/test/org/apache/hadoop/hbase/regionserver/TestHLog.java
Its the first test, testSync.
It starts out by copying whats down in the hdfs testReadWhileWriting. That
bit works fine.
Then comes the ugly stuff.
HLog is our write-ahead log wrapper. Internally it writes out to a
SequenceFile.Writer. The SequenceFile.Writer has been doctored using
reflection so the out datamember is non-private. A call to HLog.sync runs
the SequenceFile.Writer.sync -- which DOES NOT call sync on the backing
output stream -- and then it calls sync on the now accessible out stream
(Sorry its so ugly -- I'm trying to hack stuff up fast so all of hbase gets
access to this new facility). If I trace in the debugger, I can see that
the sync on the out data member goes down into hflush. Queued up edits are
flushed. It seems like it should be working.
Do I have to do some doctoring of the reader? (It doesn't seem so given that
the code at the head of this test works).
Thanks for taking a look Nicholas.
To run the test, you can do "ant clean jar test -Dtestcase=TestHLog".
(Let me know if you want an eclipse .project + .classpath so you can get it
up in an ide to run debugger).
St.Ack
> Nicholas Sze
>
>
> *From:* stack <st...@duboce.net>
> *To:* hdfs-user@hadoop.apache.org
> *Sent:* Fri, October 9, 2009 1:13:37 PM
> *Subject:* hflush not working for me?
>
> I'm putting together some unit tests up in our application that exercise
> hflush. I'm using minidfscluster and a jar made by building head of the
> 0.21 branch of hdfs (from about a minute ago).
>
> Code opens a file, writes a bunch of edits, invokes hflush (by calling sync
> on DFSDataOutputStream instance) and then, without closing the Writer, opens
> a Reader on same file. This Reader does not see any edits not to mind edits
> up to the sync invocation.
>
> I can trace the code and see how on hflush it sends the queued packets of
> edits.
>
> I studied TestReadWhileWriting. I've set setBoolean("dfs.support.append",
> true) before minidfscluster spins up. I can't set soft lease to 1 second
> because not in same package so I just wait out the default minute. It
> doesn't seem to make a difference.
>
> Do I have to do open as another user?
>
> Thanks for any pointers,
> St.Ack
>
>
Re: hflush not working for me?
Posted by "Tsz Wo (Nicholas), Sze" <s2...@yahoo.com>.
Hi St.Ack,
> ... soft lease to 1 second ...
You are right that you don't have to change soft lease. It is for append but not related to hflash.
> Do I have to do open as another user?
This should not be necessary.
Could you send me/post your test?
Nicholas Sze
From: stack <st...@duboce.net>
>To: hdfs-user@hadoop.apache.org
>Sent: Fri, October 9, 2009 1:13:37 PM
>Subject: hflush not working for me?
>
>>I'm putting together some unit tests up in our application that exercise hflush. I'm using minidfscluster and a jar made by building head of the 0.21 branch of hdfs (from about a minute ago).
>
>Code opens a file, writes a bunch of edits, invokes hflush (by calling sync on DFSDataOutputStream instance) and then, without closing the Writer, opens a Reader on same file. This Reader does not see any edits not to mind edits up to the sync invocation.
>
>I can trace the code and see how on hflush it sends the queued packets of edits.
>
>I studied TestReadWhileWriting. I've set setBoolean("dfs.support.append", true) before minidfscluster spins up. I can't set soft lease to 1 second because not in same package so I just wait out the default minute. It doesn't seem to make a difference.
>
>Do I have to do open as another user?
>
>Thanks for any pointers,
>St.Ack
>