incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Dop Sun" <su...@dopsun.com>
Subject RE: read operation is slow
Date Tue, 15 Jun 2010 23:14:25 GMT
Thanks for your updates, good to know that your performance is better now.

 

Actually, if the user asks one record a time, usually it will be done in
multi-threading, since most likely the requests coming from different users.

 

If a single users want 200k, and there are no difference to get 1 at a time,
or get 100 at a time.  Since the result set is exactly same.

 

By the way: the Jassandra you are using is updated for the issue you raised.
Now, the result set from select is sorted.

 

Thanks,

Regards,

dop

 

From: Caribbean410 [mailto:caribbean410@gmail.com] 
Sent: Tuesday, June 15, 2010 9:16 AM
To: user@cassandra.apache.org
Subject: Re: read operation is slow

 

Now I read 100 records each time, and the total time to read 200k records
(1M each) reduce to 10s. Looks good. But I am still curious how to handle
the case that users read one record each time,

On Fri, Jun 11, 2010 at 6:05 PM, Dop Sun <sunht@dopsun.com> wrote:

And also, you are only select 1 key and 10 columns?

 

criteria.keyList(Lists.newArrayList(userName)).columnRange(nameFirst,
nameFirst, 10);

 

Then, if you have 200k keys, you have 200k Thrift calls.  If this is the
case, you may need to optimize the way you do the query (to combine multiple
keys into a single query), and to reduce the number of calls.

 

From: Dop Sun [mailto:sunht@dopsun.com] 
Sent: Saturday, June 12, 2010 8:57 AM


To: user@cassandra.apache.org

Subject: RE: read operation is slow

 

You mean after you "I remove some unnecessary column family and change the
size of rowcache and keycache, now the latency changes from 0.25ms to
0.09ms. In essence 0.09ms*200k=18s.", it still takes 400 seconds to
returning?

 

From: Caribbean410 [mailto:caribbean410@gmail.com] 
Sent: Saturday, June 12, 2010 8:48 AM
To: user@cassandra.apache.org
Subject: Re: read operation is slow

 

Hi, do you mean this one should not introduce much extra delay? To read a
record, I need select here, not sure where the extra delay comes from.

On Fri, Jun 11, 2010 at 5:29 PM, Dop Sun <sunht@dopsun.com> wrote:

Jassandra is used here:

 

Map<String, List<IColumn>> map = criteria.select();

 

The select here basically is a call to Thrift API: get_range_slices

 

 

From: Caribbean410 [mailto:caribbean410@gmail.com] 
Sent: Saturday, June 12, 2010 8:00 AM


To: user@cassandra.apache.org
Subject: Re: read operation is slow

 

I remove some unnecessary column family and change the size of rowcache and
keycache, now the latency changes from 0.25ms to 0.09ms. In essence
0.09ms*200k=18s. I don't know why it takes more than 400s total. Here is the
client code and cfstats. There are not many operations here, why is the
extra time so large?



              long start = System.currentTimeMillis();
              for (int j = 0; j < 1; j++) {
                  for (int i = 0; i < numOfRecords; i++) {
                      int n = random.nextInt(numOfRecords);
                      ICriteria criteria = cf.createCriteria();
                      userName = keySet[n];
 
criteria.keyList(Lists.newArrayList(userName)).columnRange(nameFirst,
nameFirst, 10);                                             
                      Map<String, List<IColumn>> map = criteria.select(); 
                      List<IColumn> list = map.get(userName); 
//                      ByteArray bloc = list.get(0).getValue();
//                      byte[] byteArrayloc = bloc.toByteArray();
//                      loc = new String(byteArrayloc);

//                      readBytes = readBytes + loc.length();
                      readBytes = readBytes + blobSize;
                  }
              }
                            
            long finish=System.currentTimeMillis();
            
            float totalTime=(finish-start)/1000;


Keyspace: Keyspace1
    Read Count: 600000
    Read Latency: 0.09053006666666667 ms.
    Write Count: 200000
    Write Latency: 0.01504989 ms.
    Pending Tasks: 0
        Column Family: Standard2
        SSTable count: 3
        Space used (live): 265990358
        Space used (total): 265990358
        Memtable Columns Count: 2615
        Memtable Data Size: 2667300
        Memtable Switch Count: 3
        Read Count: 600000
        Read Latency: 0.091 ms.
        Write Count: 200000
        Write Latency: 0.015 ms.
        Pending Tasks: 0
        Key cache capacity: 10000000
        Key cache size: 187465
        Key cache hit rate: 0.0
        Row cache capacity: 10000000
        Row cache size: 189990
        Row cache hit rate: 0.68335
        Compacted row minimum size: 0
        Compacted row maximum size: 0
        Compacted row mean size: 0

----------------
Keyspace: system
    Read Count: 1
    Read Latency: 10.954 ms.
    Write Count: 4
    Write Latency: 0.28075 ms.
    Pending Tasks: 0
        Column Family: HintsColumnFamily
        SSTable count: 0
        Space used (live): 0
        Space used (total): 0
        Memtable Columns Count: 0
        Memtable Data Size: 0
        Memtable Switch Count: 0
        Read Count: 0
        Read Latency: NaN ms.
        Write Count: 0
        Write Latency: NaN ms.
        Pending Tasks: 0
        Key cache capacity: 1
        Key cache size: 0
        Key cache hit rate: NaN
        Row cache: disabled
        Compacted row minimum size: 0
        Compacted row maximum size: 0
        Compacted row mean size: 0

        Column Family: LocationInfo
        SSTable count: 2
        Space used (live): 3232
        Space used (total): 3232
        Memtable Columns Count: 2
        Memtable Data Size: 46
        Memtable Switch Count: 1
        Read Count: 1
        Read Latency: 10.954 ms.
        Write Count: 4
        Write Latency: 0.281 ms.
        Pending Tasks: 0
        Key cache capacity: 1
        Key cache size: 1
        Key cache hit rate: 0.0
        Row cache: disabled
        Compacted row minimum size: 0
        Compacted row maximum size: 0
        Compacted row mean size: 0

----------------

On Fri, Jun 11, 2010 at 1:50 PM, Jonathan Ellis <jbellis@gmail.com> wrote:

you need to look at cfstats to see what the latency is internal to
cassandra, vs what your client is introducing

then you should probably read the comments in the configuration file
about caching


On Fri, Jun 11, 2010 at 9:38 AM, Caribbean410 <caribbean410@gmail.com>
wrote:
>
> Thanks Riyad.
>
> Right now I am just testing Cassandra on single node. The server and
client
> are running on the same machine. I tried the read test again on two
> machines, on one machine the cpu usage is around 30% most of the time and
> another is 90%.
>
> Pelops is one way to access Cassandra, there are also other java client
like
> hector and jassandra, will these java clients have significant different
> performance?
>
> Also I once tried to change the storage configure file, like change
> CommitLogDirectory and DataFileDirectory to different disks, change
> DiskAccessMode to mmap for a 64bit machine, and change ConcurrentReads
from
> 8 to 2. All of these do not change performance much.
>
> For other users who use different access client, like using php, c++,
> python, etc, if you have any experience in boosting the read performance,
> you are more than welcome to share with me. Thanks,
>
> On Fri, Jun 11, 2010 at 8:19 AM, Riyad Kalla <rkalla@gmail.com> wrote:
>>
>> Caribbean410,
>>
>> This comes up on the Redis list alot as well -- what you are actually
>> measuring is the client sending a network connection to the Cas server
and
>> it replying -- so the performance numbers you are getting can easily be
70%
>> network wait time and not necessarily hardcore read/write server
>> performance.
>> One way to see if this is the case, run your read test, then watch the
CPU
>> on the server for the Cassandra process and see if it's pegging the CPU
--
>> if it's just sitting there banging between 0-10%, the you are spending
most
>> of your time waiting on network i/o (open/close sockets, etc.)
>> If you can parallelize your test to spawn say 5 threads that all do the
>> same thing, see if the performance for each thread increases linearly --
>> which would indicate Cassandra is plenty fast in your setup, you just
need
>> to utilize more client threads over the network.
>> That new Java library, Pelops by Dominic
>>
(http://ria101.wordpress.com/2010/06/11/pelops-the-beautiful-cassandra-datab
ase-client-for-java/)
>> has a nice intrinsic node-balancing design that could be handy IF you are
>> using multiple nodes. If you are just testing against 1 node, then spawn
>> multiple threads of your code above and see how each thread's performance
>> scales.
>> -R
>> On Thu, Jun 10, 2010 at 2:39 PM, Caribbean410 <caribbean410@gmail.com>
>> wrote:
>>>
>>> Hello,
>>>
>>> I am testing the performance of cassandra. We write 200k records to
>>> database and each record is 1k size. Then we read these 200k records.
>>> It takes more than 400s to finish the read which is much slower than
>>> mysql (20s around). I read some discussion online and someone suggest
>>> to make multiple connections to make it faster. But I am not sure how
>>> to do it, do I need to change my storage setting file or just change
>>> the java client code?
>>>
>>> Here is my read code,
>>>
>>>                     Properties info = new Properties();
>>>                     info.put(DriverManager.CONSISTENCY_LEVEL,
>>>                               ConsistencyLevel.ONE.toString());
>>>
>>>                     IConnection connection =
DriverManager.getConnection(
>>>                                 "thrift://localhost:9160", info);
>>>
>>>                       // 2. Get a KeySpace by name
>>>                       IKeySpace keySpace =
>>> connection.getKeySpace("Keyspace1");
>>>
>>>                       // 3. Get a ColumnFamily by name
>>>                       IColumnFamily cf =
>>> keySpace.getColumnFamily("Standard2");
>>>
>>>                       ByteArray nameFirst = ByteArray.ofASCII("first");
>>>                       ICriteria criteria = cf.createCriteria();
>>>                       long readBytes = 0;
>>>                       long start = System.currentTimeMillis();
>>>                           for (int i = 0; i < numOfRecords; i++) {
>>>                                   int n = random.nextInt(numOfRecords);
>>>                                       userName = keySet[n];
>>>
>>> criteria.keyList(Lists.newArrayList(userName)).columnRange(nameFirst,
>>> nameFirst, 10);
>>>                                       Map<String, List<IColumn>>
map =
>>> criteria.select();
>>>                                       List<IColumn> list =
>>> map.get(userName);
>>>                                       ByteArray bloc =
>>> list.get(0).getValue();
>>>                                       byte[] byteArrayloc =
>>> bloc.toByteArray();
>>>                                       loc = new String(byteArrayloc);
>>> //                                    System.out.println(userName+"
>>> "+loc);
>>>                                       readBytes = readBytes +
>>> loc.length();
>>>                           }
>>>
>>>                         long finish=System.currentTimeMillis();
>>>
>>> I once commented these lines
>>>
>>>                                       ByteArray bloc =
>>> list.get(0).getValue();
>>>                                       byte[] byteArrayloc =
>>> bloc.toByteArray();
>>>                                       loc = new String(byteArrayloc);
>>> //                                    System.out.println(userName+"
>>> "+loc);
>>>                                       readBytes = readBytes +
>>> loc.length();
>>>
>>> And the performance doesn't improve much.
>>>
>>> Any suggestion is welcome. Thanks,
>
>

--
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano, the source for professional Cassandra support
http://riptano.com

 

 

 


Mime
View raw message