HBase的行健是 hbase 行锁

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梦里忧郁 2023-06-15 10:06:16

文章标签 HBase的行健是 Hbase java apache hadoop 文章分类 Hbase 数据库

https://github.com/sgp2004/JavaTools 代码地址

HBase客户端的行锁会对相同rowkey的读写造成很大影响，同一个进程并发更新rowkey的计数有可能造成阻塞(场景热门短链点击增加热门微博评论数).

例如一个线上问题：

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所有被删除的微博里短链被引用的计数要减一，结果因为微博内容删除，只剩一个帮助短链，计数都减到帮助短链里，导致服务器响应缓慢

分析行锁关键代码总结一下：

client端：

1 HTable类代码，发现 lockRow 和 unlockRow方法都没有被使用到，0.96某个jira说到的client端去除lock不知道有什么用？只是移除无用代码？

2 HRegionServer类的lockRow方法只在HTable中调用。但是在测试中并没有执行到这个lockRow方法。

推测应用调用jar包时，在client端并不存在锁的问题。

server端：

HRegion 自行生成lockId并阻塞同一行的操作 ,去掉lockid从客户端的传递，增加MVCC，优化请求。

所以只是去掉了显式锁调用。

废话不说，上测试代码

@Test
    public void testMultiAdd() throws InterruptedException {
        for (int i=0;i<100;i++){
            final int finalI = i;
            new Thread(new Runnable() {
                @Override
                public void run() {
                    System.out.println("start thread"+finalI);
                    long  time = System.currentTimeMillis();
                    int loop=0;
                    while (loop++<1000)
                        //commonDao.insert("test1","f1","key","value"+ finalI);         //for one same key test1   1000 loop，100 threads cost 53s   ;if increase to 10000 loop cost 530s and may be timeout
                        //commonDao.insert("test1"+finalI+loop,"f1","key","value"+ finalI); // for different key  1000 loop，100 threads cost 14s，10000loop cost 113s
                        //commonDao.delete("test1");         //for one same key test1   1000 loop，100 threads cost 53s
                        //commonDao.delete("test1"+finalI+loop); // for different key  1000 loop，100 threads cost 13s
                        //commonDao.incr("test2","f1","key",1l);  // for  one same key test2  1000 loop，100 threads cost 59s
                       // commonDao.incr("test2"+finalI+loop,"f1","key",1l);  // for different key  1000 loop，100 threads cost 15s
                        commonDao.getStrValue("test1","f1","key");  // for  one same key test1  100 loop，100 threads cost 59s ??? why is it so slow?
                       // commonDao.getStrValue("test1"+finalI+loop,"f1","key");  // for different key  1000 loop，100 threads cost 12s
                    System.out.println(finalI+"thread stop,use time:"+(System.currentTimeMillis()-time));
                }
            }) .start();
        }

        TimeUnit.DAYS.sleep(3l);
    }

commonDao是对原始HBase client的简单封装，隐藏表名，对常用字符串 整数 长整数进行封装bytes操作，

运行耗时表

100个线程 1000次循环，耗时（单位s）：

操作	单rowkey	变化的rowkey
insert	53	14
delete	53	13
计数加incr	59	15
get	600	12

对单key的写操作会出现超时，get操作比其他要慢10倍。并且get操作必须在delete之后，insert之后可以在10s左右运行完毕。

https://issues.apache.org/jira/browse/HBASE-7263 中描述了 HBase的read/updates 流程：

(1) Acquire RowLock

(1a) BeginMVCC + Finish MVCC

(2) Begin MVCC

(3) Do work

(4) Release RowLock

(5) Append to WAL

(6) Finish MVCC

Write-only operations (e.g. puts) 除了步骤1a，与上相同。

疑问：update和write有何区别？

Remove explicit RowLocks in 0.96

一、insert分析

先分析insert ，重点步骤在 HConnnectionManager 的 processBatchCallback方法

在retry 次数内进行一个循环

1 寻找对应region HRegionLocation loc = locateRegion(tableName, row.getRow());

step1 locateRegion 时首先会加锁 regionLockObject

This block guards against two threads trying to load the meta
          // region at the same time. The first will load the meta region and
          // the second will use the value that the first one found.

step2 生成一个metakey

byte [] metaKey = HRegionInfo.createRegionName(tableName, row,
        HConstants.NINES, false);

step3 查询metakey所在region

// Query the root or meta region for the location of the meta region
            regionInfoRow = server.getClosestRowBefore(
            metaLocation.getRegionInfo().getRegionName(), metaKey,
            HConstants.CATALOG_FAMILY);

得到的regionInfoRow 信息,Result类型，打印为kv：keyvalues={.META.,,1/info:regioninfo/1353046230286/Put/vlen=34/ts=0, .META.,,1/info:server/1353046237800/Put/vlen=40/ts=0, .META.,,1/info:serverstartcode/1353046237800/Put/vlen=8/ts=0, .META.,,1/info:v/1353046230286/Put/vlen=2/ts=0}

转换server信息为region server的ip和端口

value = regionInfoRow.getValue(HConstants.CATALOG_FAMILY,
              HConstants.SERVER_QUALIFIER);
              ipAndPort:75-25-171-yf-core.jpool.sinaimg.cn:60020

这样就得到了row对应regionServer的地址

我们再回到processBatchCallback 的 locateRegion

if (useCache) {
        location = getCachedLocation(tableName, row);
        if (location != null) {
          return location;
        }
      }

第二次获取时会从cache中获取，不存在以上的锁的问题。所以第二次调用时可以回到processBatchCallback方法往下进行

1 生成action

Action<R> action = new Action<R>(row, i);
            lastServers[i] = loc;
            actions.add(regionName, action);

2 发送请求

Map<HRegionLocation, Future<MultiResponse>> futures =
            new HashMap<HRegionLocation, Future<MultiResponse>>(
                actionsByServer.size());

        for (Entry<HRegionLocation, MultiAction<R>> e: actionsByServer.entrySet()) {
          futures.put(e.getKey(), pool.submit(createCallable(e.getKey(), e.getValue(), tableName)));
        }

3 收集结果

没有发现有rowLock使用

HTablePool代码：

class PooledHTable implements HTableInterface {

private HTableInterface table; // actual table implementation

@Override
public RowLock lockRow(byte[] row) throws IOException {
return table.lockRow(row);
}

搜索lockRow 只找到在 “return table.lockRow(row);” 中调用，搜索HTable的lockRow方法也只在PooledHTable中使用，没发现外部使用，困惑。

lockRow方法调用了HRegionServer的lockRow方法。两个方法都在“1 Remove rowlocks as a client side API (https://issues.apache.org/jira/browse/HBASE-7315 )” 被移除。测试屏蔽掉这部分代码也没有任何异常，debug也没有打印，说明没有执行到。

client.Put

public Put(byte [] row, long ts, RowLock rowLock) {
if(row == null || row.length > HConstants.MAX_ROW_LENGTH) {
throw new IllegalArgumentException("Row key is invalid");
}
this.row = Arrays.copyOf(row, row.length);
this.ts = ts;
if(rowLock != null) {
this.lockId = rowLock.getLockId();
}
}

去掉rowLock.getLockId(); 也没有影响

至此看出在client端是没有锁的，只会设置lockId，也需要传入RowLock才设置。生成Get时，我们的调用代码默认也只生成无锁的Get对象。0.96中计划把无用代码去除。

那么对客户端设置lockId是否有用？

服务器端代码 HRegion.java：

public Integer getLock(Integer lockid, byte [] row, boolean waitForLock)
  throws IOException {
    Integer lid = null;
    if (lockid == null) {
      lid = internalObtainRowLock(row, waitForLock);
    } else {
      if (!isRowLocked(lockid)) {
        throw new IOException("Invalid row lock");
      }
      lid = lockid;
    }
    return lid;
  }

传入的lockid需要在服务器端lockIds注册，传入null时服务器端会生成id，存入lockIds，传入lockid则会因为没有入口存入lockIds抛异常，经试验测试

Get get = new Get(row,new RowLock(row,1l));

Put put = new Put(Bytes.toBytes(rowkey),new RowLock(Bytes.toBytes(rowkey),1l));

确实是会抛异常，很坑爹的public 构造方法, 不过没有在HRegion抛，而是在HRegionServer?lockid在服务器端何时被初始化的？

Caused by: org.apache.hadoop.ipc.RemoteException: org.apache.hadoop.hbase.UnknownRowLockException: Invalid row lock
    at org.apache.hadoop.hbase.regionserver.HRegionServer.getLockFromId(HRegionServer.java:2349)
    at org.apache.hadoop.hbase.regionserver.HRegionServer.delete(HRegionServer.java:2259)
    at sun.reflect.GeneratedMethodAccessor30.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.hadoop.hbase.ipc.WritableRpcEngine$Server.call(WritableRpcEngine.java:364)
    at org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:1326)

    at org.apache.hadoop.hbase.ipc.HBaseClient.call(HBaseClient.java:1021)
    at org.apache.hadoop.hbase.ipc.WritableRpcEngine$Invoker.invoke(WritableRpcEngine.java:150)
    at $Proxy6.delete(Unknown Source)
    at org.apache.hadoop.hbase.client.HTable$4.call(HTable.java:714)
    at org.apache.hadoop.hbase.client.HTable$4.call(HTable.java:712)
    at org.apache.hadoop.hbase.client.ServerCallable.withRetries(ServerCallable.java:163)

HRegionServer.java:

Integer getLockFromId(long lockId) throws IOException {
    if (lockId == -1L) {
      return null;
    }
    String lockName = String.valueOf(lockId);
    Integer rl = rowlocks.get(lockName);
    if (rl == null) {
      throw new UnknownRowLockException("Invalid row lock");
    }
    this.leases.renewLease(lockName);
    return rl;
  }

我们接下来看，server端 HRegion的put方法（未完待续）

HBase 0.96进行了很大的变动，rpc调用通过hbase－protocol模块实现，在其中重写了锁方法

Over in HBASE-7263 there has been some discussion about removing support

for explicit RowLocks in 0.96. This would involve the following:

- Remove lockRow/unlockRow functions in HTable and similar 。 replaces instances of RowLock with NullType.

- Remove constructors for Put/Delete/Increment/Get that take RowLocks

- functions in HRegion no longer take lockIds (checkAndPut, append,

increment, etc). This would affect coprocessors that call directly into

those functions.

1 Remove rowlocks as a client side API (https://issues.apache.org/jira/browse/HBASE-7315 )

2. Remove rowlocks from server code and replace it with better mechanism (https://issues.apache.org/jira/browse/HBASE-7263 )

The reasoning is as follows: