Tim,
Even without his code, this should be pretty straightforward on how to duplicate. Create the table with a sequence as a column in a column family. Then write a non-m/r job that has multiple threads that connect to HBase and see what they get when they hit the small table in a single region. If you can duplicate the problem, that would be the test code for the jira. -Mike > Date: Thu, 22 Apr 2010 16:13:31 +0200 > Subject: Re: multiple scanners on same table will cause problem? Scan results > change among different tries. > From: timrobertson...@gmail.com > To: hbase-user@hadoop.apache.org > > Could you please post your code that is doing the scanning Steven? > > > > On Thu, Apr 22, 2010 at 3:50 PM, Michael Segel > <michael_se...@hotmail.com> wrote: > > > > Ok... > > > > This is something that I think we'll need input from a major contributor... > > > > It looks like there may be an issue with respect to row locking... > > > > I guess the questions to ask are: > > > > - How does HBase handle row level locking? > > -Concurrent reads/fetches of the same row? > > > > To be honest and fair, HBase is still an immature product when compared to > > databases and there going to be some issues that need to be fleshed out. > > (Lets see where we are in 20+ years ;-) > > > > I wish I knew more about the internals of HBase, but there are only so many > > hours in the day and my wife forces me to work so I can keep up with her > > spending. ;-) (And if any of you happen to ever meet her, please don't > > bring this up, she'll kill me. :-D ) > > > > Lets see what St.Ack or Andrew have to say. This might be a JIRA issue. > > > > Thx > > > > -Mike > > > > > > > >> Date: Thu, 22 Apr 2010 20:17:12 +0800 > >> Subject: Re: multiple scanners on same table will cause problem? Scan > >> results change among different tries. > >> From: steven.zhuang.1...@gmail.com > >> To: hbase-user@hadoop.apache.org > >> > >> hi, Michael, > >> > >> Sorry for not making the question clear, there are multiple > >> scanners scanning a single table, there might be the case multiple scanners > >> reading from a single region. > >> please see answers inline. > >> > >> On Thu, Apr 22, 2010 at 8:08 PM, Michael Segel > >> <michael_se...@hotmail.com>wrote: > >> > >> > > >> > I'm sorry, but are you trying to say that you have multiple scanners > >> > trying > >> > to read from a single region and the result sets do not match? > >> > > >> > Yes, the result sets do not match. > >> > >> > I guess it would be an easy test, enter a bunch of rows in to a region > >> > and > >> > have a unique integer for each row. (1,2,3,...) > >> > Then run a bunch of unfiltered scans in parallel, and generate a sum from > >> > the scan. If any of the sums do not match, then you have a potential > >> > issue > >> > on concurency/row locking, and row isolation level. How does HBase > >> > handle > >> > row level locking and isolation levels? > >> > > >> > I have iterate on the rows/columnfamilies/cells, and printed the content > >> > of > >> each cell, found that there are some cells missing in some scan result set. > >> > >> > -Mike > >> > > >> > > Date: Thu, 22 Apr 2010 17:07:47 +0800 > >> > > Subject: multiple scanners on same table will cause problem? Scan > >> > > results > >> > change among different tries. > >> > > From: steven.zhuang.1...@gmail.com > >> > > To: hbase-user@hadoop.apache.org > >> > > > >> > > hi, All, > >> > > Has anybody do scan on one table using multiple scanners at > >> > > the > >> > > same time and found some inconsistent problem? > >> > > I am doing query on a table using dozens(20-120) of scanners > >> > > in > >> > > parallel(multiple threads), trying to take advantage of the multiple > >> > cores. > >> > > But I found the scan results doesn't consist among several goes. I have > >> > > checked my code, seems there is no bug in it. So I guess the problem > >> > > may > >> > > come from the HBase itself. > >> > > My HBase version is 0.20.3. > >> > > >> > _________________________________________________________________ > >> > The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with > >> > Hotmail. > >> > > >> > http://www.windowslive.com/campaign/thenewbusy?tile=multicalendar&ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_5 > >> > > > > > _________________________________________________________________ > > Hotmail is redefining busy with tools for the New Busy. Get more from your > > inbox. > > http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_2 _________________________________________________________________ The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with Hotmail. http://www.windowslive.com/campaign/thenewbusy?tile=multicalendar&ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_5
