hbase快速入门
hbase 是什么？
Apache HBase is an open-source, distributed, versioned, non-relational database modeled after Google's Bigtable: A Distributed Storage System for Structured Data by Chang et al. Just as Bigtable leverages the distributed data storage provided by the Google File System, Apache HBase provides Bigtable-like capabilities on top of Hadoop and HDFS.hbase的應用場景
Use Apache HBase? when you need random, realtime read/write access to your Big Data. This project's goal is the hosting of very large tables -- billions of rows X millions of columns -- atop clusters of commodity hardware.hbase的特性
>>>Linear and modular scalability. >>>Strictly consistent reads and writes. >>>Automatic and configurable sharding of tables >>>Automatic failover support between RegionServers. >>>Convenient base classes for backing Hadoop MapReduce jobs with Apache HBase tables. >>>Easy to use Java API for client access. >>>Block cache and Bloom Filters for real-time queries. >>>Query predicate push down via server side Filters >>>Thrift gateway and a REST-ful Web service that supports XML, Protobuf, and binary data encoding options >>>Extensible jruby-based (JIRB) shell >>>Support for exporting metrics via the Hadoop metrics subsystem to files or Ganglia; or via JMXhbase 有哪些操作？
先看一下hbase的基本操作：創建一個表，刪除一個表，增加一條記錄，刪除一條記錄，遍歷一條記錄。
import java.io.IOException; import java.util.ArrayList; import java.util.List;import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.hbase.HBaseConfiguration; import org.apache.hadoop.hbase.HColumnDescriptor; import org.apache.hadoop.hbase.HTableDescriptor; import org.apache.hadoop.hbase.KeyValue; import org.apache.hadoop.hbase.MasterNotRunningException; import org.apache.hadoop.hbase.ZooKeeperConnectionException; import org.apache.hadoop.hbase.client.Delete; import org.apache.hadoop.hbase.client.Get; import org.apache.hadoop.hbase.client.HBaseAdmin; import org.apache.hadoop.hbase.client.HTable; import org.apache.hadoop.hbase.client.Result; import org.apache.hadoop.hbase.client.ResultScanner; import org.apache.hadoop.hbase.client.Scan; import org.apache.hadoop.hbase.client.Put; import org.apache.hadoop.hbase.util.Bytes;public class HBaseTest {private static Configuration conf = null;/*** Initialization*/static {conf = HBaseConfiguration.create();}/*** Create a table*/public static void creatTable(String tableName, String[] familys)throws Exception {HBaseAdmin admin = new HBaseAdmin(conf);if (admin.tableExists(tableName)) {System.out.println("table already exists!");} else {HTableDescriptor tableDesc = new HTableDescriptor(tableName);for (int i = 0; i < familys.length; i++) {tableDesc.addFamily(new HColumnDescriptor(familys[i]));}admin.createTable(tableDesc);System.out.println("create table " + tableName + " ok.");}}/*** Delete a table*/public static void deleteTable(String tableName) throws Exception {try {HBaseAdmin admin = new HBaseAdmin(conf);admin.disableTable(tableName);admin.deleteTable(tableName);System.out.println("delete table " + tableName + " ok.");} catch (MasterNotRunningException e) {e.printStackTrace();} catch (ZooKeeperConnectionException e) {e.printStackTrace();}}/*** Put (or insert) a row*/public static void addRecord(String tableName, String rowKey,String family, String qualifier, String value) throws Exception {try {HTable table = new HTable(conf, tableName);Put put = new Put(Bytes.toBytes(rowKey));put.add(Bytes.toBytes(family), Bytes.toBytes(qualifier), Bytes.toBytes(value));table.put(put);System.out.println("insert recored " + rowKey + " to table "+ tableName + " ok.");} catch (IOException e) {e.printStackTrace();}}/*** Delete a row*/public static void delRecord(String tableName, String rowKey)throws IOException {HTable table = new HTable(conf, tableName);List<Delete> list = new ArrayList<Delete>();Delete del = new Delete(rowKey.getBytes());list.add(del);table.delete(list);System.out.println("del recored " + rowKey + " ok.");}/*** Get a row*/public static void getOneRecord (String tableName, String rowKey) throws IOException{HTable table = new HTable(conf, tableName);Get get = new Get(rowKey.getBytes());Result rs = table.get(get);for(KeyValue kv : rs.raw()){System.out.print(new String(kv.getRow()) + " " );System.out.print(new String(kv.getFamily()) + ":" );System.out.print(new String(kv.getQualifier()) + " " );System.out.print(kv.getTimestamp() + " " );System.out.println(new String(kv.getValue()));}}/*** Scan (or list) a table*/public static void getAllRecord (String tableName) {try{HTable table = new HTable(conf, tableName);Scan s = new Scan();ResultScanner ss = table.getScanner(s);for(Result r:ss){for(KeyValue kv : r.raw()){System.out.print(new String(kv.getRow()) + " ");System.out.print(new String(kv.getFamily()) + ":");System.out.print(new String(kv.getQualifier()) + " ");System.out.print(kv.getTimestamp() + " ");System.out.println(new String(kv.getValue()));}}} catch (IOException e){e.printStackTrace();}}public static void main(String[] agrs) {try {String tablename = "scores";String[] familys = { "grade", "course" };HBaseTest.creatTable(tablename, familys);// add record zkbHBaseTest.addRecord(tablename, "zkb", "grade", "", "5");HBaseTest.addRecord(tablename, "zkb", "course", "", "90");HBaseTest.addRecord(tablename, "zkb", "course", "math", "97");HBaseTest.addRecord(tablename, "zkb", "course", "art", "87");// add record baoniuHBaseTest.addRecord(tablename, "baoniu", "grade", "", "4");HBaseTest.addRecord(tablename, "baoniu", "course", "math", "89");System.out.println("===========get one record========");HBaseTest.getOneRecord(tablename, "zkb");System.out.println("===========show all record========");HBaseTest.getAllRecord(tablename);System.out.println("===========del one record========");HBaseTest.delRecord(tablename, "baoniu");HBaseTest.getAllRecord(tablename);System.out.println("===========show all record========");HBaseTest.getAllRecord(tablename);} catch (Exception e) {e.printStackTrace();}} }基本概念
HTable核心概念，實現了Table，用來和hbase的一個單表進行通信。輕量級的，提供獲取和關閉方法。
這個類不能通過構造函數直接構建出來。可以通過Connection獲取該類的一個實例。參考ConnectionFactory類生成實例： Connection connection = ConnectionFactory.createConnection(config);Table table = connection.getTable(TableName.valueOf("table1"));try {// Use the table as needed, for a single operation and a single thread} finally {table.close();connection.close();}
Htable的字段有哪些呢？
public class HTable implements HTableInterface, RegionLocator {private static final Log LOG = LogFactory.getLog(HTable.class);protected ClusterConnection connection;private final TableName tableName;private volatile Configuration configuration;private TableConfiguration tableConfiguration;protected BufferedMutatorImpl mutator;private boolean autoFlush = true;private boolean closed = false;protected int scannerCaching;private ExecutorService pool; // For Multi & Scanprivate int operationTimeout;private final boolean cleanupPoolOnClose; // shutdown the pool in close()private final boolean cleanupConnectionOnClose; // close the connection in close()private Consistency defaultConsistency = Consistency.STRONG;/** The Async process for batch */protected AsyncProcess multiAp;private RpcRetryingCallerFactory rpcCallerFactory;private RpcControllerFactory rpcControllerFactory; }HTableDescriptor包含了HBase表的詳細信息，例如所有列家族的描述，該表是否一個分類表，ROOT或者hbase:meta，該表是否只讀，當region分片時memstore的最大值，關聯的coprocessor等等。
Htable繼承并實現了Table，Table用來和一個hbase單表進行通信，從表中獲取，插入，刪除或者掃描數據。使用Connection來獲取Table實例，使用完畢后調用close()方法。
Htable也繼承實現了RegionLocator，RegionLocator用來定位一張Hbase單表的區域位置信息，可以通過Connection獲取該類的實例，RegionLocator的getRegionLocation方法返回HRegionLocation。
HRegionLocation記錄HRegionInfo和HRegionServer的主機地址的數據結構。
構造函數：
public HRegionLocation(HRegionInfo regionInfo, ServerName serverName) {this(regionInfo, serverName, HConstants.NO_SEQNUM);}public HRegionLocation(HRegionInfo regionInfo, ServerName serverName, long seqNum) {this.regionInfo = regionInfo;this.serverName = serverName;this.seqNum = seqNum;} HRegionInfo一個區域的信息。區域是在一張表的整個鍵空間中一系列的鍵，一個標識(時間戳)區分不同子序列(在區間分隔之后)，一個復制ID區分同一序列和同一區域狀態信息的不同實例。
一個區域有一個位于的名稱，名稱由下列的字段組成：
表名(tableName)：表的名稱。
開始鍵(startKey)：一個區間的開始鍵。
區域ID(regionId)：創建區域的時間戳。
復制ID(replicaId)：一個區分同一區域序列的Id，從0開始，保存到不同的服務器，同一個區域的序列可以保存在多個位置中。
加密后的名稱(encodedName):md5加密后的區域名稱。
除了區域名稱外，區域信息還包含：結束鍵(endkey):區域的結束鍵(獨有的)
分片(split)：區域是否分片
離線(offline)：區域是否離線
在0.98版本或者之前，一組表的區域會完全包含所有的鍵空間，在任何時間點，一個行鍵通常屬于一個單獨的區域，該單獨區域又屬于一個單獨的服務器。在0.99+版本，一個區域可以有多個實例（叫做備份），因此一行可以對應多個HRegionInfo。這些HRI除了備份Id字段外都可以共用字段。若備份Id未設置，默認為0。 /*** The new format for a region name contains its encodedName at the end.* The encoded name also serves as the directory name for the region* in the filesystem.** New region name format:* <tablename>,,<startkey>,<regionIdTimestamp>.<encodedName>.* where,* <encodedName> is a hex version of the MD5 hash of* <tablename>,<startkey>,<regionIdTimestamp>** The old region name format:* <tablename>,<startkey>,<regionIdTimestamp>* For region names in the old format, the encoded name is a 32-bit* JenkinsHash integer value (in its decimal notation, string form).*<p>* **NOTE**** The first hbase:meta region, and regions created by an older* version of HBase (0.20 or prior) will continue to use the* old region name format.*//** Separator used to demarcate the encodedName in a region name* in the new format. See description on new format above.*/private static final int ENC_SEPARATOR = '.';public static final int MD5_HEX_LENGTH = 32;/** A non-capture group so that this can be embedded. */public static final String ENCODED_REGION_NAME_REGEX = "(?:[a-f0-9]+)";// to keep appended int's sorted in string format. Only allows 2 bytes to be// sorted for replicaIdpublic static final String REPLICA_ID_FORMAT = "%04X";public static final byte REPLICA_ID_DELIMITER = (byte)'_';private static final int MAX_REPLICA_ID = 0xFFFF;static final int DEFAULT_REPLICA_ID = 0;private byte [] endKey = HConstants.EMPTY_BYTE_ARRAY;// This flag is in the parent of a split while the parent is still referenced// by daughter regions. We USED to set this flag when we disabled a table// but now table state is kept up in zookeeper as of 0.90.0 HBase.private boolean offLine = false;private long regionId = -1;private transient byte [] regionName = HConstants.EMPTY_BYTE_ARRAY;private boolean split = false;private byte [] startKey = HConstants.EMPTY_BYTE_ARRAY;private int hashCode = -1;//TODO: Move NO_HASH to HStoreFile which is really the only place it is used.public static final String NO_HASH = null;private String encodedName = null;private byte [] encodedNameAsBytes = null;private int replicaId = DEFAULT_REPLICA_ID;// Current TableNameprivate TableName tableName = null;/** HRegionInfo for first meta region */public static final HRegionInfo FIRST_META_REGIONINFO =new HRegionInfo(1L, TableName.META_TABLE_NAME);
先了解一下HBase的數據結構：
組成部件說明：
Row Key： Table主鍵 行鍵 Table中記錄按照Row Key排序
Timestamp：? ? 每次對數據操作對應的時間戳，也即數據的version number
Column Family： 列簇，一個table在水平方向有一個或者多個列簇，列簇可由任意多個Column組成，列簇支持動態擴展，無須預定義數量及類型，二進制存儲，用戶需自行進行類型轉換。
行操作
Get用來對一個單獨的行進行Get操作：
獲取一個row的所有信息前，需要實例化一個Get對象。
獲取特定家族的所有列，使用addFamily(byte[])。
獲取特定列，使用addColumn(byte[], byte[])
獲取在特定的時間戳內的一系列列，使用setTimeRange(long, long)
獲取在特定時間戳的列，使用setTimeStamp(long)
限制返回的列數，使用setMaxVersions(int)
增加過濾器，使用setFilter(Filter)。
Put用來對一個單獨的列進行Put操作：
使用Put前需初始化Put對象，來插入一行使用add(byte[], byte[], byte[])，若設定時間戳則使用add(byte[], byte[], long, byte[])。
Append 操作：
對一行增加多個列，使用add(byte[], byte[], byte[])；
?參考文獻：
【1】http://hbase.apache.org/
【2】https://autofei.wordpress.com/2012/04/02/java-example-code-using-hbase-data-model-operations/
【3】http://www.cnblogs.com/shitouer/archive/2012/06/04/2533518.html
轉載于:https://www.cnblogs.com/davidwang456/p/4795608.html
《新程序員》：云原生和全面數字化實踐50位技術專家共同創作，文字、視頻、音頻交互閱讀總結
- 上一篇： 使用solr的DIHandler 构建m
- 下一篇： RPC调用框架比较分析--转载