分析版本为hbase 0.94
附上趋势团队画的图：
rpc角色表：
| HBase通信信道 | HBase的通信接口 | |
| 客户端 | 服务端 | |
| HBase Client | Master Server | HMasterInterface |
| HBase Client | Region Server | HRegionInterface |
| Region Server | Master Server | HMasterRegionInterface |
客户端发起请求：
htable.get(Get)
public Result get(final Get get) throws IOException { return new ServerCallable<Result>(connection, tableName, get.getRow(), operationTimeout) { public Result call() throws IOException { return server.get(location.getRegionInfo().getRegionName(), get); } }.withRetries(); }
调用get方法后，客户端进入睡眠，睡眠时间为pause * HConstants.RETRY_BACKOFF[ntries];
pause= HBASE_CLIENT_PAUSE（1秒）
RETRY_BACKOFF[] = { 1, 1, 1, 2, 2, 4, 4, 8, 16, 32 };
有结果则中断执行返回rpc结果，否则重试十次（默认DEFAULT_HBASE_CLIENT_RETRIES_NUMBER=10）
第一次进行get时，客户端需要先进行rpc通信，获得root表 meta表信息，确定row对应的location
通过ServerCallable维持HRegionInterface 的server实例 ，server为HConnectionManager的getHRegionConnection方法获取的HBaseRPC的VersionedProtocol代理，其实是
WritableRpcEngine实例，call方法则会调用成员HbaseClient的call方法与regionserver进行远程通信
服务器端：
当regionserver 收到来自客户端的Get请求时，调用接口
public Result get(byte[] regionName, Get get) { ... HRegion region = getRegion(regionName); return region.get(get, getLockFromId(get.getLockId())); ... }
在HRegion中
Scan scan = new Scan(get);
会先根据设置的columnFamily存放familyMap对 ---- columnFamily:null
public Get addFamily(byte [] family) { familyMap.remove(family); familyMap.put(family, null); return this; }
如果查询的family不在htableDescriptor中，返回错误
scanner = getScanner(scan); public RegionScanner getScanner(Scan scan) throws IOException { return getScanner(scan, null); }
additionalScanners为null 所以在RegionScannerImpl的构造中只会使用StoreScanner
return instantiateRegionScanner(scan, additionalScanners);
return new RegionScannerImpl(scan, additionalScanners);
RegionScannerImpl 是 HRegion中的子类
for (Map.Entry<byte[], NavigableSet<byte[]>> entry : scan.getFamilyMap().entrySet()) { Store store = stores.get(entry.getKey()); StoreScanner scanner = store.getScanner(scan, entry.getValue()); scanners.add(scanner); }
按照familyMap的数量存放对应数量的 StoreScanner
Hregion initialize时会对应每个columnFamily存放一个stores
Future<Store> future = completionService.take();
Store store = future.get();
this.stores.put(store.getColumnFamilyName().getBytes(), store);
scanners 添加从Store中获取的scanner
store.getScanners(cacheBlocks, isGet,
isCompaction, matcher)
Store 类：
memStoreScanners = this.memstore.getScanners(); List<StoreFileScanner> sfScanners = StoreFileScanner .getScannersForStoreFiles(storeFiles, cacheBlocks, isGet, isCompaction, matcher); List<KeyValueScanner> scanners = new ArrayList<KeyValueScanner>(sfScanners.size()+1); scanners.addAll(sfScanners); // Then the memstore scanners scanners.addAll(memStoreScanners); return scanners;
memStoreScanners 为Collections.<KeyValueScanner>singletonList(
new MemStoreScanner())
Store中为StoreScanner添加了StoreFileScanner和 memStoreScanner
进行scan时
scanner = getScanner(scan);
scanner.next(results);
现在分析RegionScannerImpl中的next方法，此时正式进入获取数据流程
@Override public synchronized boolean next(List<KeyValue> outResults) throws IOException { // apply the batching limit by default return next(outResults, batch); }
batch默认为-1
startRegionOperation();
outResults.addAll(results);
startRegionOperation 会为操作加读锁，lock.readLock().lock();
然后遍历storeHeap，找到对应Row
do {
this.storeHeap.next(results, limit - results.size());
} while (Bytes.equals(currentRow, nextRow = peekRow()));
this.storeHeap 会不断poll出存储的scanner
因RegionScannerImpl 中 memStoreScanners后添加，所以会先从memStoreScanners中查询，如果没有则从StoreFileScanner中查询
RegionScannerImpl 的 storeHeap为KeyValueHeap，会强制转型scanner为 InternalScanner
InternalScanner currentAsInternal = (InternalScanner)this.current;
总结下目前流程get request -> regionServer -> region -> storeHeap -> scanner -> find row
但上述流程没有解释reguest是怎么找到regionServer去处理请求的，下边我们在分析下
服务器端服务在HMaster和HRegionServer启动时，中都会生成一个全局的RpcServer
hmaster的rpc server：
hmaster会使用org.apache.hadoop.hbase.executor.ExecutorService启动多种线程服务 （This is a generic executor service. This component abstracts a threadpool, a queue to which EventHandler.EventTypes can be submitted, and a Runnable that handles the object that is added to the queue. ）：
MASTER_OPEN_REGION （默认5）
MASTER_CLOSE_REGION （默认5）
MASTER_SERVER_OPERATIONS （默认3）
MASTER_META_SERVER_OPERATIONS （默认5）
MASTER_TABLE_OPERATIONS （单线程）
logCleaner （单线程）
infoServer (master-status 等信息展示)
rpcServer （我们需要用的rpc服务）
RpcServer是个接口，实现类为HBaseServer，启动时会开启responder listener handlers几种类去响应请求，如设置了priorityHandlers的数目，会另外启动priorityHandlers，listener监听端口，提供请求给handlers，handlers则调用RpcEngine，反射出需要的方法并执行，通过responder写结果回去（this.responder.doRespond）。
HMaster的 handlers的个数由hbase.master.handler.count
HRegionServer的 handlers的个数由 hbase.regionserver.handler.count 指定
HRegionServer的启动和HMaster类似，它启动以下线程：
this.service = new ExecutorService(getServerName().toString()); this.service.startExecutorService(ExecutorType.RS_OPEN_REGION, conf.getInt("hbase.regionserver.executor.openregion.threads", 3)); this.service.startExecutorService(ExecutorType.RS_OPEN_ROOT, conf.getInt("hbase.regionserver.executor.openroot.threads", 1)); this.service.startExecutorService(ExecutorType.RS_OPEN_META, conf.getInt("hbase.regionserver.executor.openmeta.threads", 1)); this.service.startExecutorService(ExecutorType.RS_CLOSE_REGION, conf.getInt("hbase.regionserver.executor.closeregion.threads", 3)); this.service.startExecutorService(ExecutorType.RS_CLOSE_ROOT, conf.getInt("hbase.regionserver.executor.closeroot.threads", 1)); this.service.startExecutorService(ExecutorType.RS_CLOSE_META, conf.getInt("hbase.regionserver.executor.closemeta.threads", 1));
hlogRoller(daemon)
cacheFlusher(daemon)
compactionChecker(daemon)
Leases(它不是线程，会启动后台线程)
splitLogWorker
rpcServer
HBaseClient 和 HMaster关系由HMasterInterface描述：
Clients interact with the HMasterInterface to gain access to meta-level
HBase functionality, like finding an HRegionServer and creating/destroying
tables.
HBaseClient 和 HRegionServer关系由HRegionInterface描述：
Clients interact with HRegionServers using a handle to the HRegionInterface
参考资料：
