hbase0.98.9中实现endpoints

在我的前面一篇博客中，抄录了hbase官网的一段话，讲的是0.96.0以后版本中endpoint的实现机制由于引进了protobuf框架，有了比较彻底的改变。本文承接上面一篇博客，给出定制一个endpoint的过程。

下面是实现过程：

1、定义接口描述文件（该功能有protobuf提供出来）

option java_package = "coprocessor.endpoints.generated";
option java_outer_classname = "RowCounterEndpointProtos";
option java_generic_services = true;
option java_generate_equals_and_hash = true;
option optimize_for = SPEED;

message CountRequest {
}

message CountResponse {
  required int64 count = 1 [default = 0];
}

service RowCountService {
  rpc getRowCount(CountRequest)
    returns (CountResponse);
  rpc getKeyValueCount(CountRequest)
    returns (CountResponse);
}

这个文件我直接拿的hbase提供的example中的例子。其中的语法应该有过类似经验的一看就清楚了，实在不清楚就请查查protobuf的帮助手册吧。

2、根据接口描述文件生成java接口类（该功能有protobuf提供出来）

有了接口描述文件，还需要生成java语言的接口类。这个需要借助protobuf提供的工具protoc。

$protoc --java_out=./ Examples.proto

简单解释下，protoc这个命令在你装了protobuf后就有了。Examples.proto这个是文件名，也就是刚才编写的那个接口描述文件。“--java_out”这个用来指定生成后的java类放的地方。

所以，这地方如果你没有装protobuf，你需要装一个，window和linux版都有，多说一句，如果你去装hadoop64位的编译环境的话，应该是要装protobuf。

3、实现接口

package coprocessor;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellUtil;
import org.apache.hadoop.hbase.Coprocessor;
import org.apache.hadoop.hbase.CoprocessorEnvironment;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.coprocessor.CoprocessorException;
import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
import org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter;
import org.apache.hadoop.hbase.protobuf.ResponseConverter;
import org.apache.hadoop.hbase.regionserver.InternalScanner;
import org.apache.hadoop.hbase.util.Bytes;

import com.google.protobuf.RpcCallback;
import com.google.protobuf.RpcController;
import com.google.protobuf.Service;

import coprocessor.endpoints.generated.RowCounterEndpointProtos.CountRequest;
import coprocessor.endpoints.generated.RowCounterEndpointProtos.CountResponse;
import coprocessor.endpoints.generated.RowCounterEndpointProtos.RowCountService;

public class RowCounterEndpointExample extends RowCountService implements
		Coprocessor, CoprocessorService {
	private RegionCoprocessorEnvironment env;

	public RowCounterEndpointExample() {
	}

	@Override
	public Service getService() {
		return this;
	}

	@Override
	public void getRowCount(RpcController controller, CountRequest request,
			RpcCallback<CountResponse> done) {
		Scan scan = new Scan();
		scan.setFilter(new FirstKeyOnlyFilter());
		CountResponse response = null;
		InternalScanner scanner = null;
		try {
			scanner = env.getRegion().getScanner(scan);
			List<Cell> results = new ArrayList<Cell>();
			boolean hasMore = false;
			byte[] lastRow = null;
			long count = 0;
			do {
				hasMore = scanner.next(results);
				for (Cell kv : results) {
					byte[] currentRow = CellUtil.cloneRow(kv);
					if (lastRow == null || !Bytes.equals(lastRow, currentRow)) {
						lastRow = currentRow;
						count++;
					}
				}
				results.clear();
			} while (hasMore);

			response = CountResponse.newBuilder().setCount(count).build();
		} catch (IOException ioe) {
			ResponseConverter.setControllerException(controller, ioe);
		} finally {
			if (scanner != null) {
				try {
					scanner.close();
				} catch (IOException ignored) {
				}
			}
		}
		done.run(response);
	}

	@Override
	public void getKeyValueCount(RpcController controller,
			CountRequest request, RpcCallback<CountResponse> done) {
		CountResponse response = null;
		InternalScanner scanner = null;
		try {
			scanner = env.getRegion().getScanner(new Scan());
			List<Cell> results = new ArrayList<Cell>();
			boolean hasMore = false;
			long count = 0;
			do {
				hasMore = scanner.next(results);
				for (Cell kv : results) {
					count++;
				}
				results.clear();
			} while (hasMore);

			response = CountResponse.newBuilder().setCount(count).build();
		} catch (IOException ioe) {
			ResponseConverter.setControllerException(controller, ioe);
		} finally {
			if (scanner != null) {
				try {
					scanner.close();
				} catch (IOException ignored) {
				}
			}
		}
		done.run(response);
	}

	@Override
	public void start(CoprocessorEnvironment env) throws IOException {
		if (env instanceof RegionCoprocessorEnvironment) {
			this.env = (RegionCoprocessorEnvironment) env;
		} else {
			throw new CoprocessorException("Must be loaded on a table region!");
		}
	}

	@Override
	public void stop(CoprocessorEnvironment env) throws IOException {
		// TODO Auto-generated method stub

	}

}

4、注册接口（Hbase功能，通过配置文件或者表模式方式注册）

这部分，可以看hbase权威指南了，我就看这部分做的。

5、测试调用

package coprocessor;

import java.io.IOException;
import java.util.Map;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.client.HTable;
import org.apache.hadoop.hbase.client.coprocessor.Batch;
import org.apache.hadoop.hbase.ipc.BlockingRpcCallback;
import org.apache.hadoop.hbase.ipc.ServerRpcController;
import org.apache.hadoop.hbase.util.Bytes;

import com.google.protobuf.ServiceException;

import coprocessor.endpoints.generated.RowCounterEndpointProtos.CountRequest;
import coprocessor.endpoints.generated.RowCounterEndpointProtos.CountResponse;
import coprocessor.endpoints.generated.RowCounterEndpointProtos.RowCountService;
import util.HBaseHelper;

public class RowCounterEndpointClientExample {
	public static void main(String[] args) throws ServiceException, Throwable {
		Configuration conf = HBaseConfiguration.create();
		HBaseHelper helper = HBaseHelper.getHelper(conf);
		//helper.dropTable("testtable");
		//helper.createTable("testtable", "colfam1", "colfam2");
		System.out.println("Adding rows to table...");
		helper.fillTable("testtable", 1, 10, 10, "colfam1", "colfam2");

		HTable table = new HTable(conf, "testtable");

		final CountRequest request = CountRequest.getDefaultInstance();
		
		final Batch.Call<RowCountService, Long> call =new Batch.Call<RowCountService, Long>() {
			public Long call(RowCountService counter)
					throws IOException {
				ServerRpcController controller = new ServerRpcController();
				BlockingRpcCallback<CountResponse> rpcCallback = new BlockingRpcCallback<CountResponse>();
				counter.getRowCount(controller, request, rpcCallback);
				CountResponse response = rpcCallback.get();
				if (controller.failedOnException()) {
					throw controller.getFailedOn();
				}
				return (response != null && response.hasCount()) ? response
						.getCount() : 0;
			}
		};
		
		Map<byte[], Long> results = table.coprocessorService(
				RowCountService.class, null, null, call);
		
		for(byte[] b : results.keySet()){
			System.err.println(Bytes.toString(b) + ":" + results.get(b));
		} 
	}
}