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HomeDatabaseMysql Tutorial关于Amoeba读取longblob字段的问题_MySQL

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最近有一个应用使用Amoeba从几个库中读取MySQL中含有longblob字段的表,老是报Session was killed。

经查是Amoeba中可读通道的缓存大小引起的。原来在com.meidusa.amoeba.net.io.PacketInputStream类中,有一个属性maxPacketSize,限制了可读通道的缓存大小,如果当前读取的记录的长度大于maxPacketSize,就会报错。所以我们必须把它调大点。

Java代码 
/** 最大容量 */ 
protected static final int MAX_BUFFER_CAPACITY = 1024 * 1024 * 2; 
private int maxPacketSize = MAX_BUFFER_CAPACITY; 
 
 
public int getMaxPacketSize() { 
    return maxPacketSize; 

 
public void setMaxPacketSize(int maxPacketSize) { 
    this.maxPacketSize = maxPacketSize; 

maxPacketSize默认是2MB,但是发现setMaxPacketSize方法没有在其它地方有调用,应该是不可配置的,因此我直接修改了MAX_BUFFER_CAPACITY,重新打包扔上去就没问题了。


另外,当maxPacketSize大小不足时,用SQLYog连代理时的时候,发现一个有趣的现象。假如我有一表,各字段长度如下:
field1 | field2
1M     | 3M

如果我先执行:SELECT field2 FROM tab
这时出错:Lost connection to MySQL server during query
再执行:SELECT field1 FROM tab
SQLYog就没有响应了,然后amoeba抛OOM异常,屡试不爽。查DUMP文件后,发现AuthingableConnectionManager 和 Log4j的DailyRollingFileAppender塞满了内存。

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