kudu-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Todd Lipcon <t...@cloudera.com>
Subject Re: strange behavior of getPendingErrors
Date Sat, 17 Nov 2018 08:01:32 GMT
Hey Alexey,

I think your explanation makes sense from an implementation perspective.
But, I think we should treat this behavior as a bug. From the user
perspective, such an error is a per-row data issue and should only affect
the row with the problem, not some arbitrary subset of rows in the batch
which happened to share a partition.

Does anyone disagree?

Todd

On Fri, Nov 16, 2018, 9:28 PM Alexey Serbin <aserbin@cloudera.com wrote:

> Hi Boris,
>
> Kudu clients (both Java and C++ ones) send write operations to
> corresponding tablet servers in batches when using the AUTO_FLUSH_BACKGROUND
> and MANUAL_FLUSH modes.  When a tablet server receives a Write RPC
> (WriteRequestPB is the corresponding type of the parameter), it decodes the
> operations from the batch:
> https://github.com/apache/kudu/blob/master/src/kudu/tablet/local_tablet_writer.h#L97
>
> While decoding operations from a batch, various constraints are being
> checked.  One of those is checking for nulls in non-nullable columns.  If
> there is a row in the batch that violates the non-nullable constraint, the
> whole batch is rejected.
>
> That's exactly what happened in your example: a batch to one tablet
> consisted of 3 rows one of which had a row with violation of the
> non-nullable constraint for the dt_tm column, so the whole batch of 3
> operations was rejected.  You can play with different partition schemes:
> e.g., in case of 10 hashed partitions it might happen that only 2
> operations would be rejected, in case of 30 partitions -- just the single
> key==2 row could be rejected.
>
> BTW, that might also happen if using the MANUAL_FLUSH mode.  However, with
> the AUTO_FLUSH_SYNC mode, the client sends operations in batches of size 1.
>
>
> Kind regards,
>
> Alexey
>
> On Fri, Nov 16, 2018 at 7:24 PM Boris Tyukin <boris@boristyukin.com>
> wrote:
>
>> Hi Todd,
>>
>> We are on Kudu 1.5 still and I used Kudu client 1.7
>>
>> Thanks,
>> Boris
>>
>> On Fri, Nov 16, 2018, 17:07 Todd Lipcon <todd@cloudera.com wrote:
>>
>>> Hi Boris,
>>>
>>> This is interesting. Just so we're looking at the same code, what
>>> version of the kudu-client dependency have you specified, and what version
>>> of the server?
>>>
>>> -Todd
>>>
>>> On Fri, Nov 16, 2018 at 1:12 PM Boris Tyukin <boris@boristyukin.com>
>>> wrote:
>>>
>>>> Hey guys,
>>>>
>>>> I am playing with Kudu Java client (wow it is fast), using mostly code
>>>> from Kudu Java example.
>>>>
>>>> While learning about exceptions during rows inserts, I stumbled upon
>>>> something I could not explain.
>>>>
>>>> If I insert 10 rows into a brand new Kudu table (AUTO_FLUSH_BACKGROUND
>>>> mode) and I make one row to be "bad" intentionally (one column cannot be
>>>> NULL), I actually get 3 rows that cannot be inserted into Kudu, not 1 as
I
>>>> was expected.
>>>>
>>>> But if I do session.flush() after every single insert, I get only one
>>>> error row (but this ruins the purpose of AUTO_FLUSH_BACKGROUND mode).
>>>>
>>>> Any ideas one? We cannot afford losing data and need to track all rows
>>>> which cannot be inserted.
>>>>
>>>> AUTO_FLUSH mode works much better and I do not have an issue like
>>>> above, but then it is way slower than AUTO_FLUSH_BACKGROUND.
>>>>
>>>> My code is below. It is in Groovy, but I think you will get an idea :)
>>>> https://gist.github.com/boristyukin/8703d2c6ec55d6787843aa133920bf01
>>>>
>>>> Here is output from my test code that hopefully illustrates my
>>>> confusion - out of 10 rows inserted, 9 should be good and 1 bad, but it
>>>> turns out Kudu flagged 3 as bad:
>>>>
>>>> Created table kudu_groovy_example
>>>> Inserting 10 rows in AUTO_FLUSH_BACKGROUND flush mode ...
>>>> (int32 key=1, string value="value 1", unixtime_micros
>>>> dt_tm=2018-11-16T20:57:03.469000Z)
>>>> (int32 key=2, string value=NULL)  BAD ROW
>>>> (int32 key=3, string value="value 3", unixtime_micros
>>>> dt_tm=2018-11-16T20:57:03.595000Z)
>>>> (int32 key=4, string value=NULL, unixtime_micros
>>>> dt_tm=2018-11-16T20:57:03.596000Z)
>>>> (int32 key=5, string value="value 5", unixtime_micros
>>>> dt_tm=2018-11-16T20:57:03.597000Z)
>>>> (int32 key=6, string value=NULL, unixtime_micros
>>>> dt_tm=2018-11-16T20:57:03.597000Z)
>>>> (int32 key=7, string value="value 7", unixtime_micros
>>>> dt_tm=2018-11-16T20:57:03.598000Z)
>>>> (int32 key=8, string value=NULL, unixtime_micros
>>>> dt_tm=2018-11-16T20:57:03.602000Z)
>>>> (int32 key=9, string value="value 9", unixtime_micros
>>>> dt_tm=2018-11-16T20:57:03.603000Z)
>>>> (int32 key=10, string value=NULL, unixtime_micros
>>>> dt_tm=2018-11-16T20:57:03.603000Z)
>>>> 3 errors inserting rows - why 3???? only 1 expected to be bad...
>>>> there were errors inserting rows to Kudu
>>>> the first few errors follow:
>>>> ??? key 1 and 6 supposed to be fine!
>>>> Row error for primary key=[-128, 0, 0, 1], tablet=null, server=null,
>>>> status=Invalid argument: No value provided for required column:
>>>> dt_tm[unixtime_micros NOT NULL] (error 0)
>>>> Row error for primary key=[-128, 0, 0, 2], tablet=null, server=null,
>>>> status=Invalid argument: No value provided for required column:
>>>> dt_tm[unixtime_micros NOT NULL] (error 0)
>>>> Row error for primary key=[-128, 0, 0, 6], tablet=null, server=null,
>>>> status=Invalid argument: No value provided for required column:
>>>> dt_tm[unixtime_micros NOT NULL] (error 0)
>>>> Rows counted in 485 ms
>>>> Table has 7 rows - ??? supposed to be 9!
>>>> INT32 key=4, STRING value=NULL, UNIXTIME_MICROS
>>>> dt_tm=2018-11-16T20:57:03.596000Z
>>>> INT32 key=8, STRING value=NULL, UNIXTIME_MICROS
>>>> dt_tm=2018-11-16T20:57:03.602000Z
>>>> INT32 key=9, STRING value=value 9, UNIXTIME_MICROS
>>>> dt_tm=2018-11-16T20:57:03.603000Z
>>>> INT32 key=3, STRING value=value 3, UNIXTIME_MICROS
>>>> dt_tm=2018-11-16T20:57:03.595000Z
>>>> INT32 key=10, STRING value=NULL, UNIXTIME_MICROS
>>>> dt_tm=2018-11-16T20:57:03.603000Z
>>>> INT32 key=5, STRING value=value 5, UNIXTIME_MICROS
>>>> dt_tm=2018-11-16T20:57:03.597000Z
>>>> INT32 key=7, STRING value=value 7, UNIXTIME_MICROS
>>>> dt_tm=2018-11-16T20:57:03.598000Z
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>> --
>>> Todd Lipcon
>>> Software Engineer, Cloudera
>>>
>>

Mime
View raw message