It doesn’t matter which RS, but that you have 1 thread for each region.
So for each thread, what’s happening.
Step by step, what is the code doing.
Now you’re comparing this against a single table scan, right?
What’s happening in the table scan…?
On Sep 12, 2014, at 2:04 PM, Guillermo Ortiz <konstt2...@gmail.com> wrote:
> Right, My table for example has keys between 0-9. in three regions
> 0-2,3-7,7-9
> I lauch three partial scans in parallel. The scans that I'm executing are:
> scan(0,2), scan(3,7), scan(7,9).
> Each region is if a different RS, so each thread goes to different RS. It's
> not exactly like that, but on the benchmark case it's like it's working.
>
> Really the code will execute a thread for each Region not for each
> RegionServer. But in the test I only have two regions for regionServer. I
> dont' think that's an important point, there're two threads for RS.
>
> 2014-09-12 14:48 GMT+02:00 Michael Segel <michael_se...@hotmail.com>:
>
>> Ok, lets again take a step back…
>>
>> So you are comparing your partial scan(s) against a full table scan?
>>
>> If I understood your question, you launch 3 partial scans where you set
>> the start row and then end row of each scan, right?
>>
>> On Sep 12, 2014, at 9:16 AM, Guillermo Ortiz <konstt2...@gmail.com> wrote:
>>
>>> Okay, then, the partial scan doesn't work as I think.
>>> How could it exceed the limit of a single region if I calculate the
>> limits?
>>>
>>>
>>> The only bad point that I see it's that If a region server has three
>>> regions of the same table, I'm executing three partial scans about this
>> RS
>>> and they could compete for resources (network, etc..) on this node. It'd
>> be
>>> better to have one thread for RS. But, that doesn't answer your
>> questions.
>>>
>>> I keep thinking...
>>>
>>> 2014-09-12 9:40 GMT+02:00 Michael Segel <michael_se...@hotmail.com>:
>>>
>>>> Hi,
>>>>
>>>> I wanted to take a step back from the actual code and to stop and think
>>>> about what you are doing and what HBase is doing under the covers.
>>>>
>>>> So in your code, you are asking HBase to do 3 separate scans and then
>> you
>>>> take the result set back and join it.
>>>>
>>>> What does HBase do when it does a range scan?
>>>> What happens when that range scan exceeds a single region?
>>>>
>>>> If you answer those questions… you’ll have your answer.
>>>>
>>>> HTH
>>>>
>>>> -Mike
>>>>
>>>> On Sep 12, 2014, at 8:34 AM, Guillermo Ortiz <konstt2...@gmail.com>
>> wrote:
>>>>
>>>>> It's not all the code, I set things like these as well:
>>>>> scan.setMaxVersions();
>>>>> scan.setCacheBlocks(false);
>>>>> ...
>>>>>
>>>>> 2014-09-12 9:33 GMT+02:00 Guillermo Ortiz <konstt2...@gmail.com>:
>>>>>
>>>>>> yes, that is. I have changed the HBase version to 0.98
>>>>>>
>>>>>> I got the start and stop keys with this method:
>>>>>> private List<RegionScanner> generatePartitions() {
>>>>>> List<RegionScanner> regionScanners = new
>>>>>> ArrayList<RegionScanner>();
>>>>>> byte[] startKey;
>>>>>> byte[] stopKey;
>>>>>> HConnection connection = null;
>>>>>> HBaseAdmin hbaseAdmin = null;
>>>>>> try {
>>>>>> connection = HConnectionManager.
>>>>>> createConnection(HBaseConfiguration.create());
>>>>>> hbaseAdmin = new HBaseAdmin(connection);
>>>>>> List<HRegionInfo> regions =
>>>>>> hbaseAdmin.getTableRegions(scanConfiguration.getTable());
>>>>>> RegionScanner regionScanner = null;
>>>>>> for (HRegionInfo region : regions) {
>>>>>>
>>>>>> startKey = region.getStartKey();
>>>>>> stopKey = region.getEndKey();
>>>>>>
>>>>>> regionScanner = new RegionScanner(startKey, stopKey,
>>>>>> scanConfiguration);
>>>>>> // regionScanner = createRegionScanner(startKey,
>>>> stopKey);
>>>>>> if (regionScanner != null) {
>>>>>> regionScanners.add(regionScanner);
>>>>>> }
>>>>>> }
>>>>>>
>>>>>> And I execute the RegionScanner with this:
>>>>>> public List<Result> call() throws Exception {
>>>>>> HConnection connection =
>>>>>> HConnectionManager.createConnection(HBaseConfiguration.create());
>>>>>> HTableInterface table =
>>>>>> connection.getTable(configuration.getTable());
>>>>>>
>>>>>> Scan scan = new Scan(startKey, stopKey);
>>>>>> scan.setBatch(configuration.getBatch());
>>>>>> scan.setCaching(configuration.getCaching());
>>>>>> ResultScanner resultScanner = table.getScanner(scan);
>>>>>>
>>>>>> List<Result> results = new ArrayList<Result>();
>>>>>> for (Result result : resultScanner) {
>>>>>> results.add(result);
>>>>>> }
>>>>>>
>>>>>> connection.close();
>>>>>> table.close();
>>>>>>
>>>>>> return results;
>>>>>> }
>>>>>>
>>>>>> They implement Callable.
>>>>>>
>>>>>>
>>>>>> 2014-09-12 9:26 GMT+02:00 Michael Segel <michael_se...@hotmail.com>:
>>>>>>
>>>>>>> Lets take a step back….
>>>>>>>
>>>>>>> Your parallel scan is having the client create N threads where in
>> each
>>>>>>> thread, you’re doing a partial scan of the table where each partial
>>>> scan
>>>>>>> takes the first and last row of each region?
>>>>>>>
>>>>>>> Is that correct?
>>>>>>>
>>>>>>> On Sep 12, 2014, at 7:36 AM, Guillermo Ortiz <konstt2...@gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> I was checking a little bit more about,, I checked the cluster and
>>>> data
>>>>>>> is
>>>>>>>> store in three different regions servers, each one in a differente
>>>> node.
>>>>>>>> So, I guess the threads go to different hard-disks.
>>>>>>>>
>>>>>>>> If someone has an idea or suggestion.. why it's faster a single scan
>>>>>>> than
>>>>>>>> this implementation. I based on this implementation
>>>>>>>> https://github.com/zygm0nt/hbase-distributed-search
>>>>>>>>
>>>>>>>> 2014-09-11 12:05 GMT+02:00 Guillermo Ortiz <konstt2...@gmail.com>:
>>>>>>>>
>>>>>>>>> I'm working with HBase 0.94 for this case,, I'll try with 0.98,
>>>>>>> although
>>>>>>>>> there is not difference.
>>>>>>>>> I disabled the table and disabled the blockcache for that family
>> and
>>>> I
>>>>>>> put
>>>>>>>>> scan.setBlockcache(false) as well for both cases.
>>>>>>>>>
>>>>>>>>> I think that it's not possible that I executing an complete scan
>> for
>>>>>>> each
>>>>>>>>> thread since my data are the type:
>>>>>>>>> 000001 f:q value=1
>>>>>>>>> 000002 f:q value=2
>>>>>>>>> 000003 f:q value=3
>>>>>>>>> ...
>>>>>>>>>
>>>>>>>>> I add all the values and get the same result on a single scan than
>> a
>>>>>>>>> distributed, so, I guess that DistributedScan did well.
>>>>>>>>> The count from the hbase shell takes about 10-15seconds, I don't
>>>>>>> remember,
>>>>>>>>> but like 4x of the scan time.
>>>>>>>>> I'm not using any filter for the scans.
>>>>>>>>>
>>>>>>>>> This is the way I calculate number of regions/scans
>>>>>>>>> private List<RegionScanner> generatePartitions() {
>>>>>>>>> List<RegionScanner> regionScanners = new
>>>>>>>>> ArrayList<RegionScanner>();
>>>>>>>>> byte[] startKey;
>>>>>>>>> byte[] stopKey;
>>>>>>>>> HConnection connection = null;
>>>>>>>>> HBaseAdmin hbaseAdmin = null;
>>>>>>>>> try {
>>>>>>>>> connection =
>>>>>>>>> HConnectionManager.createConnection(HBaseConfiguration.create());
>>>>>>>>> hbaseAdmin = new HBaseAdmin(connection);
>>>>>>>>> List<HRegionInfo> regions =
>>>>>>>>> hbaseAdmin.getTableRegions(scanConfiguration.getTable());
>>>>>>>>> RegionScanner regionScanner = null;
>>>>>>>>> for (HRegionInfo region : regions) {
>>>>>>>>>
>>>>>>>>> startKey = region.getStartKey();
>>>>>>>>> stopKey = region.getEndKey();
>>>>>>>>>
>>>>>>>>> regionScanner = new RegionScanner(startKey, stopKey,
>>>>>>>>> scanConfiguration);
>>>>>>>>> // regionScanner = createRegionScanner(startKey,
>>>>>>> stopKey);
>>>>>>>>> if (regionScanner != null) {
>>>>>>>>> regionScanners.add(regionScanner);
>>>>>>>>> }
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> I did some test for a tiny table and I think that the range for
>> each
>>>>>>> scan
>>>>>>>>> works fine. Although, I though that it was interesting that the
>> time
>>>>>>> when I
>>>>>>>>> execute distributed scan is about 6x.
>>>>>>>>>
>>>>>>>>> I'm going to check about the hard disks, but I think that ti's
>> right.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> 2014-09-11 7:50 GMT+02:00 lars hofhansl <la...@apache.org>:
>>>>>>>>>
>>>>>>>>>> Which version of HBase?
>>>>>>>>>> Can you show us the code?
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Your parallel scan with caching 100 takes about 6x as long as the
>>>>>>> single
>>>>>>>>>> scan, which is suspicious because you say you have 6 regions.
>>>>>>>>>> Are you sure you're not accidentally scanning all the data in each
>>>> of
>>>>>>>>>> your parallel scans?
>>>>>>>>>>
>>>>>>>>>> -- Lars
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> ________________________________
>>>>>>>>>> From: Guillermo Ortiz <konstt2...@gmail.com>
>>>>>>>>>> To: "user@hbase.apache.org" <user@hbase.apache.org>
>>>>>>>>>> Sent: Wednesday, September 10, 2014 1:40 AM
>>>>>>>>>> Subject: Scan vs Parallel scan.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Hi,
>>>>>>>>>>
>>>>>>>>>> I developed an distributed scan, I create an thread for each
>> region.
>>>>>>> After
>>>>>>>>>> that, I've tried to get some times Scan vs DistributedScan.
>>>>>>>>>> I have disabled blockcache in my table. My cluster has 3 region
>>>>>>> servers
>>>>>>>>>> with 2 regions each one, in total there are 100.000 rows and
>>>> execute a
>>>>>>>>>> complete scan.
>>>>>>>>>>
>>>>>>>>>> My partitions are
>>>>>>>>>> -01666 -> request 16665
>>>>>>>>>> 016666-033332 -> request 16666
>>>>>>>>>> 033332-049998 -> request 16666
>>>>>>>>>> 049998-066664 -> request 16666
>>>>>>>>>> 066664-083330 -> request 16666
>>>>>>>>>> 083330- -> request 16671
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> 14/09/10 09:15:47 INFO hbase.HbaseScanTest: NUM ROWS 100000
>>>>>>>>>> 14/09/10 09:15:47 INFO util.TimerUtil: SCAN
>>>>>>> PARALLEL:22089ms,Counter:2 ->
>>>>>>>>>> Caching 10
>>>>>>>>>>
>>>>>>>>>> 14/09/10 09:16:04 INFO hbase.HbaseScanTest: NUM ROWS 100000
>>>>>>>>>> 14/09/10 09:16:04 INFO util.TimerUtil: SCAN
>>>>>>> PARALJEL:16598ms,Counter:2 ->
>>>>>>>>>> Caching 100
>>>>>>>>>>
>>>>>>>>>> 14/09/10 09:16:22 INFO hbase.HbaseScanTest: NUM ROWS 100000
>>>>>>>>>> 14/09/10 09:16:22 INFO util.TimerUtil: SCAN
>>>>>>> PARALLEL:16497ms,Counter:2 ->
>>>>>>>>>> Caching 1000
>>>>>>>>>>
>>>>>>>>>> 14/09/10 09:17:41 INFO hbase.HbaseScanTest: NUM ROWS 100000
>>>>>>>>>> 14/09/10 09:17:41 INFO util.TimerUtil: SCAN
>> NORMAL:68288ms,Counter:2
>>>>>>> ->
>>>>>>>>>> Caching 1
>>>>>>>>>>
>>>>>>>>>> 14/09/10 09:17:48 INFO hbase.HbaseScanTest: NUM ROWS 100000
>>>>>>>>>> 14/09/10 09:17:48 INFO util.TimerUtil: SCAN
>> NORMAL:2646ms,Counter:2
>>>> ->
>>>>>>>>>> Caching 100
>>>>>>>>>>
>>>>>>>>>> 14/09/10 09:17:58 INFO hbase.HbaseScanTest: NUM ROWS 100000
>>>>>>>>>> 14/09/10 09:17:58 INFO util.TimerUtil: SCAN
>> NORMAL:3903ms,Counter:2
>>>> ->
>>>>>>>>>> Caching 1000
>>>>>>>>>>
>>>>>>>>>> Parallel scan works much worse than simple scan,, and I don't know
>>>> why
>>>>>>>>>> it's
>>>>>>>>>> so fast,, it's really much faster than execute an "count" from
>> hbase
>>>>>>>>>> shell,
>>>>>>>>>> what it doesn't look pretty notmal. The only time that it works
>>>> better
>>>>>>>>>> parallel is when I execute a normal scan with caching 1.
>>>>>>>>>>
>>>>>>>>>> Any clue about it?
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>
>>>>
>>
>>
