HBASE-1447 Take last version of the hbase-1249 design doc. and make documentation out of it
git-svn-id: https://svn.apache.org/repos/asf/hadoop/hbase/trunk@785081 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Michael Stack
parent
78af4ede60
commit
363d81c247
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@ -193,6 +193,8 @@ Release 0.20.0 - Unreleased
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HBASE-1529 familyMap not invalidated when a Result is (re)read as a
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Writable
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HBASE-1528 Ensure scanners work across memcache snapshot
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HBASE-1447 Take last version of the hbase-1249 design doc. and make
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documentation out of it
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IMPROVEMENTS
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HBASE-1089 Add count of regions on filesystem to master UI; add percentage
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@ -35,95 +35,93 @@ Provides HBase Client
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<div style="background-color: #cccccc; padding: 2px">
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<blockquote><pre>
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REPLACE!!!!!!!!
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import java.io.IOException;
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import org.apache.hadoop.hbase.HBaseConfiguration;
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import org.apache.hadoop.hbase.client.Get;
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import org.apache.hadoop.hbase.client.HTable;
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import org.apache.hadoop.hbase.client.Scanner;
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import org.apache.hadoop.hbase.io.BatchUpdate;
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import org.apache.hadoop.hbase.io.Cell;
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import org.apache.hadoop.hbase.io.RowResult;
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import org.apache.hadoop.hbase.client.Put;
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import org.apache.hadoop.hbase.client.Result;
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import org.apache.hadoop.hbase.client.ResultScanner;
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import org.apache.hadoop.hbase.client.Scan;
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import org.apache.hadoop.hbase.util.Bytes;
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public class MyClient {
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public static void main(String args[]) throws IOException {
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// Class that has nothing but a main.
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// Does a Put, Get and a Scan against an hbase table.
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public class MyLittleHBaseClient {
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public static void main(String[] args) throws IOException {
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// You need a configuration object to tell the client where to connect.
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// But don't worry, the defaults are pulled from the local config file.
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// When you create a HBaseConfiguration, it reads in whatever you've set
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// into your hbase-site.xml and in hbase-default.xml, as long as these can
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// be found on the CLASSPATH
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HBaseConfiguration config = new HBaseConfiguration();
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// This instantiates an HTable object that connects you to the "myTable"
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// table.
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HTable table = new HTable(config, "myTable");
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// This instantiates an HTable object that connects you to
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// the "myLittleHBaseTable" table.
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HTable table = new HTable(config, "myLittleHBaseTable");
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// To do any sort of update on a row, you use an instance of the BatchUpdate
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// class. A BatchUpdate takes a row and optionally a timestamp which your
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// updates will affect. If no timestamp, the server applies current time
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// to the edits.
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BatchUpdate batchUpdate = new BatchUpdate("myRow");
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// To add to a row, use Put. A Put constructor takes the name of the row
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// you want to insert into as a byte array. In HBase, the Bytes class has
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// utility for converting all kinds of java types to byte arrays. In the
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// below, we are converting the String "myLittleRow" into a byte array to
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// use as a row key for our update. Once you have a Put instance, you can
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// adorn it by setting the names of columns you want to update on the row,
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// the timestamp to use in your update, etc.If no timestamp, the server
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// applies current time to the edits.
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Put p = new Put(Bytes.toBytes("myLittleRow"));
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// The BatchUpdate#put method takes a byte [] (or String) that designates
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// what cell you want to put a value into, and a byte array that is the
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// value you want to store. Note that if you want to store Strings, you
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// have to getBytes() from the String for HBase to store it since HBase is
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// all about byte arrays. The same goes for primitives like ints and longs
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// and user-defined classes - you must find a way to reduce it to bytes.
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// The Bytes class from the hbase util package has utility for going from
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// String to utf-8 bytes and back again and help for other base types.
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batchUpdate.put("myColumnFamily:columnQualifier1",
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Bytes.toBytes("columnQualifier1 value!"));
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// To set the value you'd like to update in the row 'myRow', specify the
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// column family, column qualifier, and value of the table cell you'd like
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// to update. The column family must already exist in your table schema.
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// The qualifier can be anything. All must be specified as byte arrays as
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// hbase is all about byte arrays. Lets pretend the table
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// 'myLittleHBaseTable' was created with a family 'myLittleFamily'.
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p.add(Bytes.toBytes("myLittleFamily"), Bytes.toBytes("someQualifier"),
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Bytes.toBytes("Some Value"));
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// Deletes are batch operations in HBase as well.
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batchUpdate.delete("myColumnFamily:cellIWantDeleted");
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// Once you've done all the puts you want, you need to commit the results.
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// The HTable#commit method takes the BatchUpdate instance you've been
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// building and pushes the batch of changes you made into HBase.
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table.commit(batchUpdate);
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// Once you've adorned your Put instance with all the updates you want to
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// make, to commit it do the following (The HTable#put method takes the
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// Put instance you've been building and pushes the changes you made into
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// hbase)
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table.put(p);
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// Now, to retrieve the data we just wrote. The values that come back are
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// Cell instances. A Cell is a combination of the value as a byte array and
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// the timestamp the value was stored with. If you happen to know that the
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// value contained is a string and want an actual string, then you must
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// convert it yourself.
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Cell cell = table.get("myRow", "myColumnFamily:columnQualifier1");
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// This could throw a NullPointerException if there was no value at the cell
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// location.
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String valueStr = Bytes.toString(cell.getValue());
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// Result instances. Generally, a Result is an object that will package up
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// the hbase return into the form you find most palatable.
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Get g = new Get(Bytes.toBytes("myLittleRow"));
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Result r = table.get(g);
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byte [] value = r.getValue(Bytes.toBytes("myLittleFamily"),
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Bytes.toBytes("someQualifier"));
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// If we convert the value bytes, we should get back 'Some Value', the
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// value we inserted at this location.
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String valueStr = Bytes.toString(value);
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System.out.println("GET: " + valueStr);
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// Sometimes, you won't know the row you're looking for. In this case, you
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// use a Scanner. This will give you cursor-like interface to the contents
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// of the table.
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Scanner scanner =
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// we want to get back only "myColumnFamily:columnQualifier1" when we iterate
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table.getScanner(new String[]{"myColumnFamily:columnQualifier1"});
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// Scanners return RowResult instances. A RowResult is like the
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// row key and the columns all wrapped up in a single Object.
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// RowResult#getRow gives you the row key. RowResult also implements
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// Map, so you can get to your column results easily.
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// Now, for the actual iteration. One way is to use a while loop like so:
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RowResult rowResult = scanner.next();
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while (rowResult != null) {
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// print out the row we found and the columns we were looking for
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System.out.println("Found row: " + Bytes.toString(rowResult.getRow()) +
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" with value: " + rowResult.get(Bytes.toBytes("myColumnFamily:columnQualifier1")));
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rowResult = scanner.next();
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// of the table. To set up a Scanner, do like you did above making a Put
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// and a Get, create a Scan. Adorn it with column names, etc.
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Scan s = new Scan();
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s.addColumn(Bytes.toBytes("myLittleFamily"), Bytes.toBytes("someQualifier"));
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ResultScanner scanner = table.getScanner(s);
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try {
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// Scanners return Result instances.
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// Now, for the actual iteration. One way is to use a while loop like so:
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for (Result rr = scanner.next(); rr != null; rr = scanner.next()) {
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// print out the row we found and the columns we were looking for
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System.out.println("Found row: " + rr);
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}
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// The other approach is to use a foreach loop. Scanners are iterable!
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// for (Result rr : scanner) {
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// System.out.println("Found row: " + rr);
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// }
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} finally {
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// Make sure you close your scanners when you are done!
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// Thats why we have it inside a try/finally clause
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scanner.close();
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}
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// The other approach is to use a foreach loop. Scanners are iterable!
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for (RowResult result : scanner) {
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// print out the row we found and the columns we were looking for
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System.out.println("Found row: " + Bytes.toString(rowResult.getRow()) +
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" with value: " + rowResult.get(Bytes.toBytes("myColumnFamily:columnQualifier1")));
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}
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// Make sure you close your scanners when you are done!
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// Its probably best to put the iteration into a try/finally with the below
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// inside the finally clause.
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scanner.close();
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}
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}
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</pre></blockquote>
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@ -142,7 +142,7 @@ implements InputFormat<ImmutableBytesWritable, Result> {
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}
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/**
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* @param inputColumns the columns to be placed in {@link RowResult}.
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* @param inputColumns the columns to be placed in {@link Result}.
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*/
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public void setInputColumns(final byte [][] inputColumns) {
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this.trrInputColumns = inputColumns;
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@ -304,7 +304,7 @@ implements InputFormat<ImmutableBytesWritable, Result> {
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}
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/**
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* @param inputColumns to be passed in {@link RowResult} to the map task.
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* @param inputColumns to be passed in {@link Result} to the map task.
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*/
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protected void setInputColumns(byte [][] inputColumns) {
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this.inputColumns = inputColumns;
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@ -47,7 +47,6 @@ public class GetDeleteTracker implements DeleteTracker {
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/**
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* Constructor
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* @param comparator
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*/
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public GetDeleteTracker() {}
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@ -82,7 +82,7 @@ public class MinorCompactingStoreScanner implements KeyValueScanner, InternalSca
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/**
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* High performance merge scan.
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* @param writer
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* @return
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* @return True if more.
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* @throws IOException
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*/
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public boolean next(HFile.Writer writer) throws IOException {
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@ -35,6 +35,14 @@
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ssh must be installed and sshd must be running to use Hadoop's
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scripts to manage remote Hadoop daemons.
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</li>
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<li>HBase depends on <a href="http://hadoop.apache.org/zookeeper/">ZooKeeper</a> as of release 0.20.0.
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Clients and Servers now must know where their ZooKeeper Quorum locations before
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they can do anything else.
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In basic standalone and pseudo-distributed modes, HBase manages a ZooKeeper instance
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for you but it is required that you run a ZooKeeper Quorum when running HBase
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fully distributed (More on this below). The Zookeeper addition changes
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how some core HBase configuration is done.
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</li>
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<li>HBase currently is a file handle hog. The usual default of
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1024 on *nix systems is insufficient if you are loading any significant
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amount of data into regionservers. See the
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@ -46,11 +54,6 @@
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<li>The clocks on cluster members should be in basic alignments. Some skew is tolerable but
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wild skew can generate odd behaviors. Run <a href="http://en.wikipedia.org/wiki/Network_Time_Protocol">NTP</a>
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on your cluster, or an equivalent.</li>
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<li>HBase depends on <a href="http://hadoop.apache.org/zookeeper/">ZooKeeper</a> as of release 0.20.0.
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In basic standalone and pseudo-distributed modes, HBase manages a ZooKeeper instance
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for you but it is required that you run a ZooKeeper Quorum when running HBase
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fully distributed (More on this below).
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</li>
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<li>This is a list of patches we recommend you apply to your running Hadoop cluster:
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<ul>
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<li><a hef="https://issues.apache.org/jira/browse/HADOOP-4681">HADOOP-4681 <i>"DFSClient block read failures cause open DFSInputStream to become unusable"</i></a>. This patch will help with the ever-popular, "No live nodes contain current block".
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@ -86,6 +89,9 @@ What follows presumes you have obtained a copy of HBase,
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see <a href="http://hadoop.apache.org/hbase/releases.html">Releases</a>, and are installing
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for the first time. If upgrading your
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HBase instance, see <a href="#upgrading">Upgrading</a>.
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If you have used HBase in the past,
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please read carefully. Some core configuration has changed in 0.20.x HBase.
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</p>
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<p>Three modes are described: standalone, pseudo-distributed (where all servers are run on
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a single host), and distributed. If new to hbase start by following the standalone instruction.
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</p>
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@ -38,9 +38,6 @@ import org.apache.hadoop.hbase.client.Get;
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import org.apache.hadoop.hbase.client.Put;
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import org.apache.hadoop.hbase.client.Result;
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import org.apache.hadoop.hbase.client.Scan;
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import org.apache.hadoop.hbase.filter.StopRowFilter;
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import org.apache.hadoop.hbase.filter.WhileMatchRowFilter;
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import org.apache.hadoop.hbase.io.BatchUpdate;
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import org.apache.hadoop.hbase.io.hfile.Compression;
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import org.apache.hadoop.hbase.util.Bytes;
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import org.apache.hadoop.hbase.util.Writables;
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