cassandra学习笔记5--使用Binary Memtable将大量数据导入Cassandra
在Cassandra的客户端中，我们谈到了如何使用Thrift API以及更加高级的封装（Hector）如果将数据导入到到Cassandra中，但是在导入大量数据的时候这会遇到很多的问题，比如插入失败，超时等等问题。为了解决这个问题，我们可以尝试使用Binary Memtable。
在Cassandra的wiki上，对Binary Memtable的描述如下：
Binary Memtable is the name of Cassandra's bulk-load interface. It avoids several kinds of overhead associated with the normal Thrift API:
Converting to Thrift from the internal structures and back Routing (copying) from a coordinator node to the replica nodes Writing to the commitlog Serializing the internal structures to on-disk formatThe tradeoff you make is that it is considerably less convenient to use than Thrift:
You must use the StorageProxy API, only available as Java code
You must pre-serialize the rows yourselfThe rows you send are not live for querying until a flush occurs (either normally because the Binary Memtable fills up, or because you request one with nodetool)
You must write an entire row at once
具体的实现我们可以参考https://svn.apache.org/repos/asf/cassandra/trunk/contrib/bmt_example/.但是这个示例结合了Hadoop，如何没有这个环境，也可以参考我的测试代码：
package com.alibaba.dw.thrift.client;
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import java.io.IOException;
import java.io.UnsupportedEncodingException;
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import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.db.Column;
import org.apache.cassandra.db.ColumnFamily;
import org.apache.cassandra.db.RowMutation;
import org.apache.cassandra.db.filter.QueryPath;
import org.apache.cassandra.io.util.DataOutputBuffer;
import java.net.InetAddress;
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import org.apache.cassandra.net.Message;
import org.apache.cassandra.net.MessagingService;
import org.apache.cassandra.service.StorageService;
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/**
* TODO Comment of BinaryMemtableTest
*
* @author aaron.guop
*/
public class BinaryMemtableTest {?
????/**
???? * @param args
???? * @throws IOException
???? * @throws InterruptedException
???? */
????public static void main(String[] args) throws IOException, InterruptedException {????????System.setProperty("storage-config", "D:\\apache-cassandra-0.6.1\\conf");?
????????StorageService.instance.initClient();
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????????while (StorageService.instance.getNaturalEndpoints("Keyspace1", "bmt").isEmpty()) {????????????Thread.sleep(1 * 1000);
????????}
????????
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????????doInsert();
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????????StorageService.instance.stopClient();
????}
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????/**
???? * @throws UnsupportedEncodingException
???? */
????private static void doInsert() throws UnsupportedEncodingException {????????String keyspace = "Keyspace1";
????????String cfName = "Member";
????????String memberID = "bmt";
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????????/* Create a column family */
????????ColumnFamily columnFamily = ColumnFamily.create(keyspace, cfName);
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????????//while (values.hasNext()) {????????String SuperColumnName = "SuperColumnName";
????????String ColumnName = "ColumnName";
????????String ColumnValue = "ColumnValue";
????????long timestamp = 0;
????????columnFamily.addColumn(new QueryPath(cfName, SuperColumnName.getBytes("UTF-8"), ColumnName????????????????.getBytes("UTF-8")), ColumnValue.getBytes(), timestamp);????????//}
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????????/* Get serialized message to send to cluster */
????????Message message = createMessage(keyspace, memberID, cfName, columnFamily);
????????for (InetAddress endpoint : StorageService.instance.getNaturalEndpoints(keyspace, memberID)) {????????????/* Send message to end point */
????????????MessagingService.instance.sendOneWay(message, endpoint);
????????????System.out.println("Send message to " + endpoint.toString());????????}
????}
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????public static Message createMessage(String Keyspace, String Key, String CFName,
????????????????????????????????????????ColumnFamily columnFamile) {????????DataOutputBuffer bufOut = new DataOutputBuffer();
????????Column column;
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????????/*
???????? * Get the first column family from list, this is just to get past
???????? * validation
???????? */
????????ColumnFamily baseColumnFamily = new ColumnFamily(CFName, "Standard", DatabaseDescriptor
????????????????.getComparator(Keyspace, CFName), DatabaseDescriptor.getSubComparator(Keyspace,
????????????????CFName));
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????????bufOut.reset();
????????try {????????????ColumnFamily.serializer().serializeWithIndexes(columnFamile, bufOut);
????????????byte[] data = new byte[bufOut.getLength()];
????????????System.arraycopy(bufOut.getData(), 0, data, 0, bufOut.getLength());
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????????????column = new Column(columnFamile.name().getBytes("UTF-8"), data, 0, false);????????????baseColumnFamily.addColumn(column);
????????} catch (IOException e) {????????????throw new RuntimeException(e);
????????}
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????????RowMutation rm = new RowMutation(Keyspace, Key);
????????rm.add(baseColumnFamily);
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????????try {????????????/* Make message */
????????????return rm.makeRowMutationMessage(StorageService.Verb.BINARY);
????????} catch (IOException e) {????????????throw new RuntimeException(e);
????????}
????}
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}
在运行这个代码之前，我们还必须注意以下事项：
1 运行这个程序的机器不能运行Cassandra Server。
2 在storage-conf.xml的seed中指定其他Cassandra Server的地址。
3 使用nodetool的getcachecapacity得到当前的压缩设置，记录下来，供完成导入后恢复使用。
4 使用nodetool的setcachecapacity设置当前的压缩设置为0，即取消压缩功能。
5 运行导入程序。
6 使用nodetool的flush。
7 使用nodetool的setcompactionthreshold设置回之前在第三步获得的值。?
经过这些操作后，数据就导入到我们的Cassandra中了