> Is there any specific best practice on how many regions one > should split a table into?
As always, "it depends". Usually you don't want your RegionServers to serve more than 50 regions or so. The fewer the better. But at the same time you usually want your regions to be distributed over the whole cluster (so that you use all power). So, it might make sense to start with one region per RS (if your writes are more or less evenly distributed across pre-splitted regions) if you don't know about you data size. If you know that you'll need to have more regions because of how big is your data, then you might create more regions at the start (with pre-splitting), so that you avoid region splits operations (you really want to avoid them if you can). Of course, you need to take into account other tables in your cluster as well. I.e. "usually not more than 50 regions" total per regionserver. > Just one more question, in the split keys that you described below, is it > based on the first byte value of the Key? yes. And the first byte contains readable char, because of Bytes.ToBytes(String.valueOf(i)). If you want to prefix with (byte) 0, ..., (byte) 9 (i.e. with 0x00, 0x01, ..., 0x09) then no need to convert to String. Alex Baranau ------ Sematext :: http://blog.sematext.com/ :: Hadoop - HBase - ElasticSearch - Solr On Thu, Jul 26, 2012 at 11:43 AM, Mohit Anchlia <[email protected]>wrote: > On Thu, Jul 26, 2012 at 7:16 AM, Alex Baranau <[email protected] > >wrote: > > > Looks like you have only one region in your table. Right? > > > > If you want your writes to be distributed from the start (without waiting > > for HBase to fill table enough to split it in many regions), you should > > pre-split your table. In your case you can pre-split table with 10 > regions > > (just an example, you can define more), with start keys: "", "1", "2", > ..., > > "9" [1]. > > > > Just one more question, in the split keys that you described below, is it > based on the first byte value of the Key? > > > > Btw, since you are salting your keys to achieve distribution, you might > > also find this small lib helpful which implements most of the stuff for > you > > [2]. > > > > Hope this helps. > > > > Alex Baranau > > ------ > > Sematext :: http://blog.sematext.com/ :: Hadoop - HBase - ElasticSearch > - > > Solr > > > > [1] > > > > byte[][] splitKeys = new byte[9][]; > > // the first region starting with empty key will be created > > automatically > > for (int i = 1; i < splitKeys.length; i++) { > > splitKeys[i] = Bytes.toBytes(String.valueOf(i)); > > } > > > > HBaseAdmin admin = new HBaseAdmin(conf); > > admin.createTable(tableDescriptor, splitKeys); > > > > [2] > > https://github.com/sematext/HBaseWD > > > > > http://blog.sematext.com/2012/04/09/hbasewd-avoid-regionserver-hotspotting-despite-writing-records-with-sequential-keys/ > > > > On Wed, Jul 25, 2012 at 7:54 PM, Mohit Anchlia <[email protected] > > >wrote: > > > > > On Wed, Jul 25, 2012 at 6:53 AM, Alex Baranau < > [email protected] > > > >wrote: > > > > > > > Hi Mohit, > > > > > > > > 1. When talking about particular table: > > > > > > > > For viewing rows distribution you can check out how regions are > > > > distributed. And each region defined by the start/stop key, so > > depending > > > on > > > > your key format, etc. you can see which records go into each region. > > You > > > > can see the regions distribution in web ui as Adrien mentioned. It > may > > > also > > > > be handy for you to query .META. table [1] which holds regions info. > > > > > > > > In cases when you use random keys or when you just not sure how data > is > > > > distributed in key buckets (which are regions), you may also want to > > look > > > > at HBase data on HDFS [2]. Since data is stored for each region > > > separately, > > > > you can see the size on the HDFS each one occupies. > > > > > > > > I did a scan and the data looks like as pasted below. It appears all > my > > > writes are going to just one server. My keys are of this type > > > [0-9]:[current timestamp]. Number between 0-9 is generated randomly. I > > > thought by having this random number I'll be able to place my keys on > > > multiple nodes. How should I approach this such that I am able to use > > other > > > nodes as well? > > > > > > > > > > > > SESSION_TIMELINE1,,1343074465420.5831bbac53e59 column=info:regioninfo, > > > timestamp=1343170773523, value=REGION => {NAME => > > > 'SESSION_TIMELINE1,,1343074465420.5831bbac53e591c609918c0e2d7da7 > > > 1c609918c0e2d7da7bf. bf.', STARTKEY => '', > > > ENDKEY => '', ENCODED => 5831bbac53e591c609918c0e2d7da7bf, TABLE => > > {{NAME > > > => 'SESSION_TIMELINE1', FAMILIES => [{NAM > > > E => 'S_T_MTX', > > BLOOMFILTER > > > => 'NONE', REPLICATION_SCOPE => '0', COMPRESSION => 'GZ', VERSIONS => > > '1', > > > TTL => '2147483647', BLOCKSIZE => ' > > > 65536', IN_MEMORY => > > > 'false', BLOCKCACHE => 'true'}]}} > > > SESSION_TIMELINE1,,1343074465420.5831bbac53e59 column=info:server, > > > timestamp=1343178912655, value=dsdb3.:60020 > > > 1c609918c0e2d7da7bf. > > > > > > > 2. When talking about whole cluster, it makes sense to use cluster > > > > monitoring tool [3], to find out more about overall load > distribution, > > > > regions of multiple tables distribution, requests amount, and many > more > > > > such things. > > > > > > > > And of course, you can use HBase Java API to fetch some data of the > > > cluster > > > > state as well. I guess you should start looking at it from HBaseAdmin > > > > class. > > > > > > > > Alex Baranau > > > > ------ > > > > Sematext :: http://blog.sematext.com/ :: Hadoop - HBase - > > ElasticSearch > > > - > > > > Solr > > > > > > > > [1] > > > > > > > > hbase(main):001:0> scan '.META.', {LIMIT=>1, STARTROW=>"mytable,,"} > > > > ROW > > > > COLUMN+CELL > > > > > > > > > > > > mytable,,1341279432683.8fd61cd7ef426d2f233a4cd7e8b73845. > > > > column=info:regioninfo, timestamp=1341279432625, value=REGION => > {NAME > > > => > > > > 'mytable,,1341279432683.8fd61cd7ef426d2f233a4cd7e8b73845.', STARTKEY > => > > > > 'chicago', ENDKEY => 'new_york', ENCODED => > > > > fd61cd7ef426d2f233a4cd7e8b73845, TABLE => {{NAME => 'mytable', > FAMILIES > > > => > > > > [{NAME => 'job', BLOOMFILTER => 'NONE', REPLICATION_SCOPE => '0', > > > > COMPRESSION => 'NONE', VERSIONS => '1', TTL => '2147483647', > BLOCKSIZE > > => > > > > '65536', IN_MEMORY => 'false', BLOCKCACHE => 'true'}]}} > > > > > > > > > > > > > > > > mytable,,1341279432683.8fd61cd7ef426d2f233a4cd7e8b73845. > > > > column=info:server, timestamp=1341279432673, value=myserver:60020 > > > > > > > > > > > > mytable,,1341279432683.8fd61cd7ef426d2f233a4cd7e8b73845. > > > > column=info:serverstartcode, timestamp=1341279432673, > > > value=1341267474257 > > > > > > > > > > > > 1 row(s) in 0.1980 seconds > > > > > > > > [2] > > > > > > > > ubuntu@ip-10-80-47-73:~$ sudo -u hdfs hadoop fs -du /hbase/mytable > > > > Found 130 items > > > > 3397 hdfs://hbase.master/hbase/mytable > > > > /02925d3c335bff7e273f392324f16dca > > > > 2682163424 hdfs://hbase.master/hbase/mytable > > > > /03231b8ae2b73317c4858b1a85c09ad2 > > > > 1038862956 hdfs://hbase.master/hbase/mytable > > > > /04f911571593e931a9a3d9e2a6616236 > > > > 1039181555 hdfs://hbase.master/hbase/mytable > > > > /0a177633196cae7b158836181d69dc0f > > > > 1076888812 hdfs://hbase.master/hbase/mytable > > > > /0d52fc477c41a9a236803234d44c7c06 > > > > > > > > [3] > > > > You can get data from JMX directly using any tool you like or use: > > > > * Ganglia > > > > * SPM monitoring ( > > > > http://sematext.com/spm/hbase-performance-monitoring/index.html) > > > > * others > > > > > > > > > > > > On Wed, Jul 25, 2012 at 1:59 AM, Adrien Mogenet < > > > [email protected] > > > > >wrote: > > > > > > > > > From the web-interface, you can have such statistics when viewing > the > > > > > details of a table. > > > > > You can also develop your own "balance viewer" through the HBase > API > > > > (list > > > > > of RS, regions, storeFiles, their size, etc.) > > > > > > > > > > On Wed, Jul 25, 2012 at 7:32 AM, Mohit Anchlia < > > [email protected] > > > > > >wrote: > > > > > > > > > > > Is there an easy way to tell how my nodes are balanced and how > the > > > rows > > > > > are > > > > > > distributed in the cluster? > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > Adrien Mogenet > > > > > 06.59.16.64.22 > > > > > http://www.mogenet.me > > > > > > > > > > > > > > > > > > > > > -- > > > > Alex Baranau > > > > ------ > > > > Sematext :: http://blog.sematext.com/ :: Hadoop - HBase - > > ElasticSearch > > > - > > > > Solr > > > > > > > > > > > > > > > -- > > Alex Baranau > > ------ > > Sematext :: http://blog.sematext.com/ :: Hadoop - HBase - ElasticSearch > - > > Solr > > > -- Alex Baranau ------ Sematext :: http://blog.sematext.com/ :: Hadoop - HBase - ElasticSearch - Solr
