building apps with hbase - big data techcon boston

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Headline Goes HereSpeaker Name or Subhead Goes Here

Building applica2ons with HBaseAmandeep Khurana | Solu7ons ArchitectBig Data TechCon, Boston, April 2013

Friday, April 12, 13

About me

•Solu2ons Architect, Cloudera Inc•Amazon Web Services•Interested in large scale distributed systems•Co-‐author, HBase In Ac2on•TwiHer: amansk

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M A N N I N G

Nick DimidukAmandeep Khurana


About the talk

•Setup local HBase environment•Simple client•Deeper dive on API•Data model

3Friday, April 12, 13

What is HBase?

•Scalable, distributed data store•Open source avatar of Google’s Bigtable•Sorted map of maps•Sparse•Mul2 dimensional•Tightly integrated with Hadoop•Not a RDBMS


So, what’s the big deal?

•Give up system complexity and sophis2cated features for ease of scale and manageability

•Simple system != easy to build applica2ons on top•Goal: predictable read and write performance at scale

•Effec2ve API usage•Op2mal schema design•Understand internals and leverage at scale


Use cases

•Canonical use case: storing crawl data and indices for search

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1

1 Crawlers constantly scour the Internet for new pages.Those pages are stored as individual records in Bigtable. 3

2 A MapReduce job runs over the entire table, generatingsearch indexes for the Web Search application.

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2

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Web Searchpowered by Bigtable

Indexing the Internet

3 The user initiates a Web Search request.

4 The Web Search application queries the Search Indexesand retries matching documents directly from Bigtable.

5 Search results are presented to the user.

Searching the Internet

BigtableInternetsCrawlers

CrawlersCrawlers

Crawlers

MapReduce

You

Search IndexSearch

IndexSearch Index

Web Search


Use cases (con2nued)

•Capturing incremental trickle data•Content serving / OLTP•Blob store


Installing HBase

•Get it here -‐> hHp://hbase.apache.org/•Downloads -‐> Choose a mirror -‐> Choose a release•Download the tarball•Untar it and run it


http://hbase.apache.org/

http://hbase.apache.org/

Basics

•Modes of opera2on•Standalone•Pseudo-‐distributed•Fully distributed

•Start up in standalone mode•cd hbase-‐0.94.1•bin/start-‐hbase.sh•Logs are in ./logs/

•Check out hHp://localhost:60010 in your browser


Ways to interact

•Shell•Java client•Thrid interface•REST interface•Asynchbase


Shell

•Basic interac2on tool•WriHen in JRuby•Uses the Java client library•Good place to start poking around


Shell (con2nued)

•bin/hbase shell•Create table

•create ‘users’ , ‘info’•List tables

•list•Describe table

•describe ‘users’


Shell (con2nued)

•Put a row•put ‘users’ , ‘u1’, ‘info:name’ , ‘Mr. Rogers’

•Get a row•get ‘users’ , ‘u1’

•Put more•put ‘users’ , ‘u1’ , ‘info:email’ , ‘[email protected]’•put ‘users’ , ‘u1’ , ‘info:password’ , ‘foobar’

•Get a row•get ‘users’ , ‘u1’

•Scan table• scan ‘users’


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Demo-‐ Standalone mode-‐ Shell


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... can’t really build an applica7on just with the shell

Java API


Important terms

• Table• Consists of rows and columns

• Row• Has a bunch of columns.• Iden2fied by a rowkey (primary key)

• Column Qualifier• Dynamic column name

• Column Family• Column groups -‐ logical and physical (Similar access paHern)

• Cell• The actual element that contains the data for a row-‐column intersec2on

• Version• Every cell has mul2ple versions.


Introducing TwitBase

•TwiHer clone built on HBase•Designed to scale• It’s an example, not a produc2on app•Start with users and twits for now•Users

•Have profiles•Post twits

•Twits•Have text posted by users

•Get sample code at: hHps://github.com/hbaseinac2on/twitbase


https://github.com/hbaseinaction/twitbase

https://github.com/hbaseinaction/twitbase

Java API

•Configura)on -‐ holds config informa2on about the cluster. Roughly equivalent to JDBC connec2on string

•HConnec)on -‐ represents connec2on to a cluster•HBaseAdmin -‐ admin tool to handle DDL opera2ons

•HTablePool -‐ pool of connec2ons to cluster•HTable (HTableInterface) -‐ handle on a single HBase table. Sends commands to table


Connec2ng to HBase

•Using default confs:HTableInterface usersTable = new HTable("users");

•Passing custom conf:Configuration myConf = HBaseConfiguration.create();myConf.set("parameter_name", "parameter_value");HTableInterface usersTable = new HTable(myConf, "users");

•Connection poolingHTablePool pool = new HTablePool();HTableInterface usersTable = pool.getTable("users"); // work with the tableusersTable.close();


Inser2ng data

•Put call on HTablePut p = new Put(Bytes.toBytes("TheRealMT")); p.add(Bytes.toBytes("info"), Bytes.toBytes("name"), Bytes.toBytes("Mark Twain")); p.add(Bytes.toBytes("info"), Bytes.toBytes("email"), Bytes.toBytes("[email protected]")); p.add(Bytes.toBytes("info"), Bytes.toBytes("password"), Bytes.toBytes("Langhorne"));

usersTable.put(p);


mailto:[email protected]

mailto:[email protected]

Data coordinates

•Row is addressed using rowkey•Cell is addressed using [rowkey + family + qualifier]


Upda2ng data

•Update == WritePut p = new Put(Bytes.toBytes("TheRealMT"));

p.add(Bytes.toBytes("info"),

Bytes.toBytes("password"),

Bytes.toBytes("abc123"));

usersTable.put(p);


Write path

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Memstore

HFile

HFile

WAL

Write goes to the write-ahead log (WAL)as well as the in memory write buffer called

the Memstore.Client's don't interact directly with the

underlying HFiles during writes.Client

Memstore

New HFile

HFile

Memstore gets flushed to disk toform a new HFile

when filled up with writes.

HFile


Reading data

•Get the en2re rowGet g = new Get(Bytes.toBytes("TheRealMT"));

Result r = usersTable.get(g);

•Get selected columnsGet g = new Get(Bytes.toBytes("TheRealMT"));

g.addColumn(Bytes.toBytes("info"),

Bytes.toBytes("password"));

Result r = usersTable.get(g);

•Extract the value out of the Result objectbyte[] b = r.getValue(Bytes.toBytes("info"),

Bytes.toBytes("email"));

String email = Bytes.toString(b);


Reading data (con2nued)

•ScanScan s = new Scan(startRow, stopRow);

ResultsScanner rs = twits.getScanner(s);

for(Result r : rs) {

// iterate over scanner results

}

•Single threaded iteration over defined set of rows. Could be the entire table too.


What happens when you read data?

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Memstore

HFile

HFile

Client

BlockCache


Dele2ng data

•Another simple API call•Delete en2re rowDelete d = new Delete(Bytes.toBytes("TheRealMT"));

usersTable.delete(d);

•Delete selected columnsDelete d = new Delete(Bytes.toBytes("TheRealMT"));

d.deleteColumns(Bytes.toBytes("info"),

Bytes.toBytes("email"));

usersTable.delete(d);


Delete internals

•Tombstone markers•Dele2on only happens during major compac2ons•Compac2ons

•Minor•Major


Compac2ons

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Memstore

HFile

HFile

Memstore

CompactedHFile

Two or more HFiles get combinedto form a single HFile during

a compaction.

HFile HFile


DAO

•Like any other applica2on•Makes data access management easy

•Cleaner code•Table info at a single place

•Op2miza2ons like connec2on pooling etc•Easier management of database configs


AdminHBaseAdmin

• Administra2ve API to the cluster.

• Provides an interface to manage HBase database tables metadata and general administra2ve func2ons.

Table Opera2ons

• createTable()

• deleteTable()

• addColumn()

• modifyColumn()

• deleteColumn()

• listTables()


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Demo-‐ Java client


More API features

•Filters•Compare and Swap•Coprocessors


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It’s not a rela7onal database system

Data Model


HBase is ...

•Column family oriented database•Column family oriented•Tables consis2ng of rows and columns

•Persisted Map•Sparse•Mul2 dimensional•Sorted• Indexed by rowkey, column and 2mestamp

•Key Value store• [rowkey, col family, col qualifier, 2mestamp] -‐> cell value


HBase is not ...

•A rela2onal database•No SQL query language•No joins•No secondary indexing•No transac2ons


Tabular representa2on

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Column Family - Info

password

abc123

abc123

abc123

[email protected]

TheRealMT

HMS_Surprise

[email protected]

Sir Arthur Conan Doyle [email protected]

[email protected]

SirDoyle

GrandpaD

Fyodor Dostoyevsky

Patrick O'Brien

Mark Twain

Rowkey name email

Cells

Each cell has multiple versions,

typically represented by the timestamp

of when they were inserted into the table

(ts2>ts1)

ts1=1329088321289 ts2=1329088818321

The table is lexicographicallysorted on the rowkeys

Langhorneabc123

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3

4

The coordinates used to identify data in an HBase table are:(1) rowkey, (2) column family, (3) column qualifier, (4) version


Key-‐Value store

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[TheRealMT, info, password, 1329088818321]

[TheRealMT, info, password, 1329088321289]

abc123

Langhorne

Keys Values

A single KeyValue instance


Key-‐Value store

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[TheRealMT, info, password, 1329088818321] abc123

[TheRealMT, info, password] 1329088818321 : "abc123",1329088321289 : "Langhorne"

}

{

[TheRealMT, info] },

"name" : { 1329088321289 : "Mark Twain"

"email" : { 1329088321289 : "[email protected]" },

"password" : { 1329088818321 : "abc123", 1329088321289 : "Langhorne" } }

{

},

"info" : {

"name" : { 1329088321289 : "Mark Twain"


"password" : { 1329088818321 : "abc123", 1329088321289 : "Langhorne" } } }

{

[TheRealMT]

Keys

Values

Start with coordinates of full precision1

Drop version and you're left with a map of version to values2

Omit qualifier and you have a map of qualifiers to the previous maps3

Finally, drop the column family and you have a row, a map of maps4


Sorted map of maps

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Rowkey

Column family

Column qualifiers

Versions

Values

{

},

"TheRealMT" : { "info" : {

"name" : { 1329088321289 : "Mark Twain"


"password" : { 1329088818321 : "abc123", 1329088321289 : "Langhorne" } } }}


HFiles and physical data model

•HFiles are•Immutable•Sorted on rowkey + qualifier + 2mestamp•In the context of a column family per region

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, , , "TheRealMT" "info" "password" , 1329088321289 "Langhorne", , , "TheRealMT" "info" "password" , 1329088818321 "abc123",

, , , , "TheRealMT" "info" "email" 1329088321289 "[email protected]", , , , "TheRealMT" "info" "name" 1329088321289 "Mark Twain"

HFile for the info column family in the users table


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... what really goes on under the hood

HBase in distributed mode


Distributed mode

•Table is split into Regions

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00001 John 415-111-123400002 Paul 408-432-992200003 Ron 415-993-212400004 Bob 818-243-998800005 Carly 206-221-912300006 Scott 818-231-256600007 Simon 425-112-987700008 Lucas 415-992-443200009 Steve 530-288-983200010 Kelly 916-992-123400011 Betty 650-241-119200012 Anne 206-294-1298

00001 John 415-111-123400002 Paul 408-432-992200003 Ron 415-993-212400004 Bob 818-243-9988

00005 Carly 206-221-912300006 Scott 818-231-256600007 Simon 425-112-987700008 Lucas 415-992-4432

00009 Steve 530-288-983200010 Kelly 916-992-123400011 Betty 650-241-119200012 Anne 206-294-1298

00001 John 415-111-123400002 Paul 408-432-992200003 Ron 415-993-212400004 Bob 818-243-9988



Full table T1 Table T1 split into 3 regions - R1, R2 and R3

T1R1

T1R2

T1R3


Distributed mode (con2nued)

•Regions are served by RegionServers

•RegionServers are Java processes, typically collocated with the DataNodes

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DataNode RegionServer



00001 John 415-111-123400002 Paul 408-432-992200003 Ron 415-993-212400004 Bob 818-243-9988



Host1

Host2

Host3

T1R1

T1R2

T1R3


Finding your region

•Two special tables: -‐ROOT-‐ and .META.

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-ROOT-

M1 M2 M3

-ROOT- table, consisting of only 1 regionhosted on region server RS1

.META. table, consisting of 3 regions,hosted on RS1, RS2 and RS3

User tables T1 and T2, consisting of4 and 3 regions respectively,

distributed amongst RS1, RS2 and RS3

RS1

RS2

T2R1

RS2

T2R2

RS2

T2R3

RS1

RS1RS3

T1R1

RS3

T1R3

RS3

T1R2

RS1

T2R4

RS1


Regions distributed across the cluster

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00001 John 415-111-123400002 Paul 408-432-992200003 Ron 415-993-212400004 Bob 818-243-9988



Host1

Host2

M:T100001-M:T100009 M1 RS2M:T100010-M:T100012 M2 RS1

T1:00001-T1:00004 R1 RS1T1:00005-T1:00008 R2 RS2

T1:00009-T1:00012 R3 RS2

T1-R1

T1-R2

T1-R3

.META. - M1

-ROOT-

.META. - M2

RegionServer 1 (RS1), hosting regions R1 of the user table T1 and M2 of .META.

RegionServer 2 (RS2), hosting regions R2, R3 of the user table and M1 of .META.

RegionServer 3 (RS3), hosting just -ROOT-

Host3




What the client does

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ZooKeeper

TheRealMT

-ROOT-

.META.

MyTable



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ZooKeeper

TheRealMT

-ROOT-

.META.

MyTable

Row per META region



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ZooKeeper

TheRealMT

-ROOT-

.META.

MyTable

Row per META region

Row per table region


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