目录

目录 1

1. 现象描述 1

2. 问题定位 2

3. 解决方案 5

4. 相关代码 5

 

1. 现象描述

外界连接9090端口均超时,但telnet端口总是成功。使用top命令观察,发现单个线程的CPU最高达99.99%,但并不总是99.9%,而是在波动。当迁走往该机器的流量后,能够访问成功,但仍然有超时,读超时比写超时多:

# ./hbase_stress --hbase=110.13.136.207:9090 --test=2 --timeout=10
[2016-11-27 10:15:21/771][139756154767104/31562][ERROR][hbase_stress.cpp:302]TransportException(thrift://110.13.136.207:9090): EAGAIN (timed out)
[2016-11-27 10:15:31/775][139756154767104/31562][ERROR][hbase_stress.cpp:302]TransportException(thrift://110.13.136.207:9090): EAGAIN (timed out)
 
  PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND                                                            
20727 zhangsan    20   0 10.843g 9.263g  26344 R 99.9 26.4   1448:00 java                                                               
20729 zhangsan    20   0 10.843g 9.263g  26344 R 99.9 26.4   1448:00 java                                                               
20730 zhangsan    20   0 10.843g 9.263g  26344 R 99.9 26.4   1449:10 java                                                               
20728 zhangsan    20   0 10.843g 9.263g  26344 R 99.8 26.4   1448:00 java                                                               
20693 zhangsan    20   0 10.843g 9.263g  26344 S  0.0 26.4   0:00.00 java
 
20727 zhangsan    20   0 10.843g 9.263g  26344 R 75.5 26.4   1448:06 java                                                               
20728 zhangsan    20   0 10.843g 9.263g  26344 R 75.2 26.4   1448:06 java                                                               
20729 zhangsan    20   0 10.843g 9.263g  26344 R 75.2 26.4   1448:06 java                                                               
20730 zhangsan    20   0 10.843g 9.263g  26344 R 75.2 26.4   1449:15 java                                                               
20716 zhangsan    20   0 10.843g 9.263g  26344 S 24.9 26.4  93:48.75 java

2. 问题定位

使用ps命令找出CPU最多的线程,和top显示的一致:

$ ps -mp 20693 -o THREAD,tid,time | sort -rn
zhangsan   18.8  19    - -         -      - 20730 1-00:11:23
zhangsan   18.7  19    - -         -      - 20729 1-00:10:13
zhangsan   18.7  19    - -         -      - 20728 1-00:10:13
zhangsan   18.7  19    - -         -      - 20727 1-00:10:13
zhangsan   16.1  19    - futex_    -      - 20731 20:44:51
zhangsan    5.2  19    - futex_    -      - 20732 06:46:39

 

然后借助jstack,发现为GC进程:

"Gang worker#0 (Parallel CMS Threads)" os_prio=0 tid=0x00007fb7200d4000 nid=0x50f7 runnable 
"Gang worker#1 (Parallel CMS Threads)" os_prio=0 tid=0x00007fb7200d5800 nid=0x50f8 runnable 
"Gang worker#2 (Parallel CMS Threads)" os_prio=0 tid=0x00007fb7200d7800 nid=0x50f9 runnable 
"Gang worker#3 (Parallel CMS Threads)" os_prio=0 tid=0x00007fb7200d9000 nid=0x50fa runnable

 

使用jstat工具查看GC,情况很不乐观,问题就是有GC引起的:

$ jstat -gcutil 20693 1000 100 
  S0     S1     E      O      M     CCS    YGC     YGCT    FGC    FGCT     GCT   
  0.00  99.67 100.00 100.00  98.08  94.41  42199  369.132 27084 34869.601 35238.733
  0.00  99.67 100.00 100.00  98.08  94.41  42199  369.132 27084 34870.448 35239.580
  0.00  99.67 100.00 100.00  98.08  94.41  42199  369.132 27084 34870.448 35239.580
  0.00  99.67 100.00 100.00  98.08  94.41  42199  369.132 27084 34870.448 35239.580
 
$ jstat -gccapacity  20693     
YGC    FGC 
191808.0 1107520.0 1107520.0 110720.0 110720.0 886080.0   383680.0  8094144.0  8094144.0  8094144.0      0.0 1077248.0  31584.0      0.0 1048576.0   3424.0  42199 27156
 
$ jstat -gcold  20693        
   MC       MU      CCSC     CCSU       OC          OU       YGC    FGC    FGCT     GCT   
 31584.0  30978.7   3424.0   3232.7   8094144.0   8094144.0  42199 27174 34964.347 35333.479
 
$ jstat -gcoldcapacity 20693       
   OGCMN       OGCMX        OGC         OC       YGC   FGC    FGCT     GCT   
   383680.0   8094144.0   8094144.0   8094144.0 42199 27192 34982.623 35351.755
 
$ jstat -gcnewcapacity 20693                NGCMN      NGCMX       NGC      S0CMX     S0C     S1CMX     S1C       ECMX        EC      YGC   FGC 
  191808.0  1107520.0  1107520.0 110720.0 110720.0 110720.0 110720.0   886080.0   886080.0 42199 27202
 
$ jstat -gc 20693           
 S0C    S1C    S0U    S1U      EC       EU        OC         OU       MC     MU    CCSC   CCSU   YGC     YGCT    FGC    FGCT     GCT   
110720.0 110720.0  0.0   110395.9 886080.0 886080.0 8094144.0  8094144.0  31584.0 30978.7 3424.0 3232.7  42199  369.132 27206 34996.538 35365.671
 
$ jstat -gcnew 20693
 S0C    S1C    S0U    S1U   TT MTT  DSS      EC       EU     YGC     YGCT  
110720.0 110720.0    0.0 110396.9  6   6 55360.0 886080.0 886080.0  42199  369.132

 

使用lsof显示该进程的连接数不多,完全在安全范围内,问题应当是有对象不能被回收。使用jmap查看内存详情,先看堆的使用情况:

$ jmap -heap 20693
Attaching to process ID 20693, please wait...
Debugger attached successfully.
Server compiler detected.JVM version is 25.77-b03
 
using parallel threads in the new generation.
using thread-local object allocation.
Concurrent Mark-Sweep GC
 
Heap Configuration:
   MinHeapFreeRatio         = 40
   MaxHeapFreeRatio         = 70
   MaxHeapSize              = 9422503936 (8986.0MB)
   NewSize                  = 196411392 (187.3125MB)
   MaxNewSize               = 1134100480 (1081.5625MB)
   OldSize                  = 392888320 (374.6875MB)
   NewRatio                 = 2
   SurvivorRatio            = 8
   MetaspaceSize            = 21807104 (20.796875MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 17592186044415 MB
   G1HeapRegionSize         = 0 (0.0MB)
 
Heap Usage:
New Generation (Eden + 1 Survivor Space):
   capacity = 1020723200 (973.4375MB)
   used     = 1020398064 (973.1274261474609MB)
   free     = 325136 (0.3100738525390625MB)
   99.96814650632022% used
Eden Space:
   capacity = 907345920 (865.3125MB)
   used     = 907345920 (865.3125MB)
   free     = 0 (0.0MB)
   100.0% used
From Space:
   capacity = 113377280 (108.125MB)
   used     = 113052144 (107.81492614746094MB)
   free     = 325136 (0.3100738525390625MB)
   99.71322649476156% used
To Space:
   capacity = 113377280 (108.125MB)
   used     = 0 (0.0MB)
   free     = 113377280 (108.125MB)
   0.0% used
concurrent mark-sweep generation:
   capacity = 8288403456 (7904.4375MB)
   used     = 8288403424 (7904.437469482422MB)
   free     = 32 (3.0517578125E-5MB)
   99.9999996139184% used
 
10216 interned Strings occupying 934640 bytes.

 

进一步查看对象的情况:

$ jmap -histo 20693
 
 num     #instances         #bytes  class name
----------------------------------------------
2518411456  [B
49827147     1993085880  java.util.TreeMap$Entry
   3:      12855993      617087664  java.util.TreeMap
ClientScanner
   5:       4285222      377099536  org.apache.hadoop.hbase.client.Scan
   6:       4284875      377069000  org.apache.hadoop.hbase.client.ScannerCallable
   7:       4285528      342921344  [Ljava.util.HashMap$Node;
:     4284880      308511360  org.apache.hadoop.hbase.client.ScannerCallableWithReplicas
   9:       8570671      274261472  java.util.LinkedList
  10:       4285579      205707792  java.util.HashMap
  11:       4285283      205693584  org.apache.hadoop.hbase.client.RpcRetryingCaller
  12:       3820914      152836560  org.apache.hadoop.hbase.filter.SingleColumnValueFilter
  13:       4291904      137340928  java.util.concurrent.ConcurrentHashMap$Node
  14:       8570636      137130176  java.util.TreeMap$EntrySet
  15:       4285278      137128896  org.apache.hadoop.hbase.io.TimeRange
  16:       8570479      137127664  java.util.concurrent.atomic.AtomicBoolean
  17:       2891409       92525088  org.apache.hadoop.hbase.NoTagsKeyValue
  18:       4286540       68584640  java.lang.Integer
  19:       4285298       68564768  java.util.TreeMap$KeySet
  20:       4285275       68564400  java.util.TreeSet
  21:       4285006       68560096  java.util.HashSet
  22:       4284851       68557616  java.util.HashMap$KeySet
  23:       3176118       50817888  org.apache.hadoop.hbase.filter.BinaryComparator
  24:           109       33607600  [Ljava.util.concurrent.ConcurrentHashMap$Node;
  25:        418775       18479112  [Lorg.apache.hadoop.hbase.Cell;
  26:        671443       17693224  [C
  27:        418781       16751240  org.apache.hadoop.hbase.client.Result
  28:        669739       16073736  java.lang.String
  29:        644796       15475104  org.apache.hadoop.hbase.filter.SubstringComparator
  30:        419134       10059216  java.util.LinkedList$Node

 

为使系统能够正常工作,先实施治标不治本的方案:监控GC,定时重启HBase Thrift2进程,然后再找出根本原因达到治本的目的。

 

从上面jmap的输出来看,猜测是不是因为额scanner没有被关闭导致的。而scanner没有被关闭的原因有两个:一是客户端程序问题没有关闭,也就是有内存泄漏了,二是客户端程序异常导致没机会关闭。

 

查看客户端源代码,确实存在openScanner的异常时未关闭。另外客户端被kill掉或断电等,也会导致无法释放,这一点是HBase Thrift2得解决的问题。

3. 解决方案

针对前面分析出的问题分别加以解决:

1) 客户端保证scanner全部释放;

2) HBase Thrift2增加自动释放长时间未操作的scanner;

3) 另外也可以使用getScannerResults替代getScannerRows来规避此问题。

 

补丁:

https://issues.apache.org/jira/browse/HBASE-17182

4. 相关代码

private final Map<Integer, ResultScanner> scannerMap
    = new ConcurrentHashMap<Integer, ResultScanner>();
 
@Override
public int openScanner(ByteBuffer table, TScan scan) throws TIOError, TException {
Table htable = getTable(table);
ResultScanner resultScanner = null;
try {
resultScanner = htable.getScanner(scanFromThrift(scan));
} catch (IOException e) {
throw getTIOError(e);
} finally {
closeTable(htable);
}

// 将scanner放入到scannerMap中,
// 如果客户端没有调用closeScanner,则导致该scanner泄漏,GC无法回收改部分内存
return addScanner(resultScanner);
}
 
/**
* Assigns a unique ID to the scanner and adds the mapping to an internal HashMap.
* @param scanner to add
* @return Id for this Scanner
*/
private int addScanner(ResultScanner scanner) {
int id = nextScannerId.getAndIncrement();
scannerMap.put(id, scanner); // 将scanner放入到scannerMap中
return id;
}
 
/**
* Returns the Scanner associated with the specified Id.
* @param id of the Scanner to get
* @return a Scanner, or null if the Id is invalid
*/
private ResultScanner getScanner(int id) {
return scannerMap.get(id);
}
 
@Override
public void closeScanner(int scannerId) throws TIOError, TIllegalArgument, TException {
LOG.debug("scannerClose: id=" + scannerId);
ResultScanner scanner = getScanner(scannerId);
if (scanner == null) {
String message = "scanner ID is invalid";
LOG.warn(message);
TIllegalArgument ex = new TIllegalArgument();
ex.setMessage("Invalid scanner Id");
throw ex;
}
scanner.close(); // 关闭scanner
removeScanner(scannerId); // 从scannerMap中移除scanner
}
 
/**
* Removes the scanner associated with the specified ID from the internal HashMap.
* @param id of the Scanner to remove
* @return the removed Scanner, or <code>null</code> if the Id is invalid
*/
protected ResultScanner removeScanner(int id) {
return scannerMap.remove(id); // 从scannerMap中移除scanner
}