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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: repeated timeouts on quorum reads
Date Thu, 22 Oct 2009 17:05:31 GMT
What is the CF definition for movie? the part from your config file like
      <ColumnFamily CompareWith="BytesType" Name="Movie"/>

On Thu, Oct 22, 2009 at 12:04 PM, Jonathan Ellis <jbellis@gmail.com> wrote:
> On Thu, Oct 22, 2009 at 10:59 AM, Edmond Lau <edmond@ooyala.com> wrote:
>> Try:
>>
>> keyspace: "Analytics"
>> key: "o:movie"
>> column family: "movie"
>> super column: "all"
>>
>> I was able to get timeouts with a few concurrent get_slice() calls
>> (3-4 with debug logging, 6 without) on the super column, with start =
>> "", finish = "", and count = 1.
>>
>> Edmond
>>
>> On Thu, Oct 22, 2009 at 7:42 AM, Jonathan Ellis <jbellis@gmail.com> wrote:
>>> What is your columnfamily definition?  What query should I test with?
>>>
>>> On Wed, Oct 21, 2009 at 7:33 PM, Edmond Lau <edmond@ooyala.com> wrote:
>>>> On Tue, Oct 20, 2009 at 2:03 PM, Jonathan Ellis <jbellis@gmail.com>
wrote:
>>>>> Okay, so we have 2 problems:
>>>>>
>>>>>  - the read is simply too slow
>>>>>  - we're doing unnecessary(?) read repairs
>>>>>
>>>>> For the first I think it's going to be easiest if you can export the
>>>>> row in question so we can do some profiling.  (Eric will have a tool
>>>>> to do this soon.)
>>>>
>>>> Ok - I've created a cassandra setup with just the row in question and
>>>> tarred up the data + storage-conf.xml for the three nodes:
>>>>
>>>> http://demo.ooyala.com/cassandra/cassandra-1.tgz
>>>> http://demo.ooyala.com/cassandra/cassandra-2.tgz
>>>> http://demo.ooyala.com/cassandra/cassandra-3.tgz
>>>>
>>>>>
>>>>> For the second, how sure are you that the repair is unnecessary?  Does
>>>>> it repeat the repair when you do the query again after letting the
>>>>> callbacks complete?
>>>>
>>>> I didn't do any writes as I was debugging the issue whereas I was
>>>> reading the same data a whole bunch of times, so the repair should've
>>>> been unnecessary.
>>>>
>>>> Thanks for your help,
>>>> Edmond
>>>>
>>>>>
>>>>> -Jonathan
>>>>>
>>>>> On Mon, Oct 19, 2009 at 11:38 PM, Edmond Lau <edmond@ooyala.com>
wrote:
>>>>>> A single local read with debug logging takes 3-4 secs on the node
with
>>>>>> 3 data files.  It actually takes roughly as long on the other nodes
as
>>>>>> well (I was incorrect in saying that they were fast).
>>>>>>
>>>>>> DEBUG [pool-1-thread-22] 2009-10-20 04:26:06,953 CassandraServer.java
>>>>>> (line 219) get_slice
>>>>>> DEBUG [pool-1-thread-22] 2009-10-20 04:26:06,955 StorageProxy.java
>>>>>> (line 468) weakreadlocal reading
>>>>>> SliceFromReadCommand(table='Analytics', key='o:movie',
>>>>>> column_parent='QueryPath(columnFamilyName='movie',
>>>>>> superColumnName='[B@26e00675', columnName='null')', start='',
>>>>>> finish='', reversed=false, count=1)
>>>>>> DEBUG [pool-1-thread-22] 2009-10-20 04:26:10,382 SliceQueryFilter.java
>>>>>> (line 115) collecting 1000036:false:515@1255978226411394
>>>>>> DEBUG [CONSISTENCY-MANAGER:2] 2009-10-20 04:26:10,383
>>>>>> ConsistencyManager.java (line 168) Reading consistency digest for
>>>>>> o:movie from 2926@[172.16.129.71:7000, 172.16.129.72:7000]
>>>>>> DEBUG [RESPONSE-STAGE:1] 2009-10-20 04:26:13,332
>>>>>> ResponseVerbHandler.java (line 34) Processing response on a callback
>>>>>> from 2926@172.16.129.71:7000
>>>>>> DEBUG [RESPONSE-STAGE:3] 2009-10-20 04:26:13,675
>>>>>> ResponseVerbHandler.java (line 34) Processing response on a callback
>>>>>> from 2926@172.16.129.72:7000
>>>>>> DEBUG [RESPONSE-STAGE:3] 2009-10-20 04:26:13,677
>>>>>> ConsistencyManager.java (line 96) Performing read repair for o:movie
>>>>>> to 2937@[172.16.129.71:7000, 172.16.129.72:7000, 172.16.129.75:7000]
>>>>>>
>>>>>> Also, it's unclear why there's a read repair going on above, since
I
>>>>>> haven't made any updates.
>>>>>>
>>>>>> Doing a quorum read on the node with 3 data files takes 7 seconds
w/
>>>>>> debug logging and leads to a DigestMismatchException, again even
>>>>>> though I haven't made any updates.
>>>>>>
>>>>>> DEBUG [pool-1-thread-25] 2009-10-20 04:30:00,892 CassandraServer.java
>>>>>> (line 219) get_slice
>>>>>> DEBUG [pool-1-thread-25] 2009-10-20 04:30:00,894 StorageProxy.java
>>>>>> (line 374) strongread reading data for
>>>>>> SliceFromReadCommand(table='Analytics', key='o:movie',
>>>>>> column_parent='QueryPath(columnFamilyName='movie',
>>>>>> superColumnName='[B@2cf50c5f', columnName='null')', start='',
>>>>>> finish='', reversed=false, count=1) from 3675@172.16.129.75:7000
>>>>>> DEBUG [pool-1-thread-25] 2009-10-20 04:30:00,894 StorageProxy.java
>>>>>> (line 381) strongread reading digest for
>>>>>> SliceFromReadCommand(table='Analytics', key='o:movie',
>>>>>> column_parent='QueryPath(columnFamilyName='movie',
>>>>>> superColumnName='[B@2cf50c5f', columnName='null')', start='',
>>>>>> finish='', reversed=false, count=1) from 3676@172.16.129.71:7000
>>>>>> DEBUG [pool-1-thread-25] 2009-10-20 04:30:00,895 StorageProxy.java
>>>>>> (line 381) strongread reading digest for
>>>>>> SliceFromReadCommand(table='Analytics', key='o:movie',
>>>>>> column_parent='QueryPath(columnFamilyName='movie',
>>>>>> superColumnName='[B@2cf50c5f', columnName='null')', start='',
>>>>>> finish='', reversed=false, count=1) from 3676@172.16.129.72:7000
>>>>>> DEBUG [RESPONSE-STAGE:3] 2009-10-20 04:30:03,994
>>>>>> ResponseVerbHandler.java (line 34) Processing response on a callback
>>>>>> from 15445226-F6EF-C97B-F239-FC0316748C5E@172.16.129.71:7000
>>>>>> DEBUG [RESPONSE-STAGE:2] 2009-10-20 04:30:04,107
>>>>>> ResponseVerbHandler.java (line 34) Processing response on a callback
>>>>>> from 15445226-F6EF-C97B-F239-FC0316748C5E@172.16.129.72:7000
>>>>>> DEBUG [ROW-READ-STAGE:9] 2009-10-20 04:30:04,787 SliceQueryFilter.java
>>>>>> (line 115) collecting 1000036:false:515@1255978226411394
>>>>>> DEBUG [ROW-READ-STAGE:9] 2009-10-20 04:30:04,788 ReadVerbHandler.java
>>>>>> (line 100) Read key o:movie; sending response to
>>>>>> 15445226-F6EF-C97B-F239-FC0316748C5E@172.16.129.75:7000
>>>>>> DEBUG [RESPONSE-STAGE:4] 2009-10-20 04:30:04,788
>>>>>> ResponseVerbHandler.java (line 34) Processing response on a callback
>>>>>> from 15445226-F6EF-C97B-F239-FC0316748C5E@172.16.129.75:7000
>>>>>> DEBUG [pool-1-thread-25] 2009-10-20 04:30:04,789
>>>>>> ReadResponseResolver.java (line 84) Response deserialization time
: 0
>>>>>> ms.
>>>>>> DEBUG [pool-1-thread-25] 2009-10-20 04:30:04,790
>>>>>> ReadResponseResolver.java (line 84) Response deserialization time
: 0
>>>>>> ms.
>>>>>> DEBUG [pool-1-thread-25] 2009-10-20 04:30:04,791
>>>>>> ReadResponseResolver.java (line 84) Response deserialization time
: 1
>>>>>> ms.
>>>>>>  INFO [pool-1-thread-25] 2009-10-20 04:30:04,792 StorageProxy.java
>>>>>> (line 410) DigestMismatchException: o:movie
>>>>>> DEBUG [RESPONSE-STAGE:1] 2009-10-20 04:30:07,953
>>>>>> ResponseVerbHandler.java (line 34) Processing response on a callback
>>>>>> from 3690@172.16.129.71:7000
>>>>>> DEBUG [RESPONSE-STAGE:3] 2009-10-20 04:30:08,130
>>>>>> ResponseVerbHandler.java (line 34) Processing response on a callback
>>>>>> from 3690@172.16.129.72:7000
>>>>>> DEBUG [pool-1-thread-25] 2009-10-20 04:30:08,132
>>>>>> ReadResponseResolver.java (line 84) Response deserialization time
: 1
>>>>>> ms.
>>>>>> DEBUG [pool-1-thread-25] 2009-10-20 04:30:08,132
>>>>>> ReadResponseResolver.java (line 84) Response deserialization time
: 0
>>>>>> ms.
>>>>>> DEBUG [pool-1-thread-25] 2009-10-20 04:30:08,132
>>>>>> ReadResponseResolver.java (line 149) resolve: 1 ms.
>>>>>> DEBUG [ROW-READ-STAGE:10] 2009-10-20 04:30:08,235
>>>>>> SliceQueryFilter.java (line 115) collecting
>>>>>> 1000036:false:515@1255978226411394
>>>>>> DEBUG [ROW-READ-STAGE:10] 2009-10-20 04:30:08,235 ReadVerbHandler.java
>>>>>> (line 100) Read key o:movie; sending response to
>>>>>> 3690@172.16.129.75:7000
>>>>>>
>>>>>> Edmond
>>>>>>
>>>>>> On Mon, Oct 19, 2009 at 8:04 PM, Jonathan Ellis <jbellis@gmail.com>
wrote:
>>>>>>> On Mon, Oct 19, 2009 at 9:48 PM, Edmond Lau <edmond@ooyala.com>
wrote:
>>>>>>>> 8 data files total.  3 nodes have 1, 1 has 2, the 3rd has
3.
>>>>>>>>
>>>>>>>>> Does it still take ~8s if you direct a CL.ONE query at
one of the
>>>>>>>>> nodes you know has the data (i.e., a local read)?
>>>>>>>>
>>>>>>>> Local reads return quickly, but if you look at the logs below,
there's
>>>>>>>> 6 secs from when cassandra prints that it's reading a consistency
>>>>>>>> digest to when it processes a callback.
>>>>>>>
>>>>>>> That's from when it sends the digest command, to when it gets
a callback.
>>>>>>>
>>>>>>> Something doesn't add up.  If computing &sending a digest
response
>>>>>>> takes 6s, either reading the row or computing the digest must
be
>>>>>>> taking substantial time.  But if local reads are fast, it's
not
>>>>>>> reading the row that is slow, and if resolve is fast (from your
logs,
>>>>>>> it is 2ms) then it's not computing the digest that is slow.
>>>>>>>
>>>>>>> Try doing a local read from the node with 3 data files, see if
that is slower.
>>>>>>>
>>>>>>> If you still see a fast read there, add some more debug logging
in
>>>>>>> ReadVerbHandler.java, where it says something like (I'm going
from
>>>>>>> trunk here but 0.4.1 is similar)
>>>>>>>
>>>>>>>            Row row = readCommand.getRow(table);
>>>>>>>            ReadResponse readResponse;
>>>>>>>            if (readCommand.isDigestQuery())
>>>>>>>            {
>>>>>>>                readResponse = new ReadResponse(row.digest());
>>>>>>>
>>>>>>> time the getRow and the row.digest() calls and log how long those
take
>>>>>>> in the quorum scenario.
>>>>>>>
>>>>>>> -Jonathan
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>

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