MyCAT报java.lang.OutOfMemoryError: Java heap space

早上同事反映，mycat又假死了，估计还是内存溢出，查看了一下错误日志。INFO | jvm 1 | 2016/03/25 07:09:06 | java.lang.OutOfMemoryError: Java heap space
INFO | jvm 1 | 2016/03/25 07:09:06 | Exception in thread "Timer67" java.lang.OutOfMemoryError: Java heap space
INFO | jvm 1 | 2016/03/25 07:09:06 | Exception in thread "Timer68" java.lang.OutOfMemoryError: Java heap space
INFO | jvm 1 | 2016/03/25 07:09:06 | Exception in thread "Timer69" java.lang.OutOfMemoryError: Java heap space
INFO | jvm 1 | 2016/03/25 07:09:06 | Exception in thread "Timer70" java.lang.OutOfMemoryError: Java heap space
INFO | jvm 1 | 2016/03/25 07:09:06 | Exception in thread "Timer71" java.lang.OutOfMemoryError: Java heap space
INFO | jvm 1 | 2016/03/25 07:09:06 | Exception in thread "Timer72" java.lang.OutOfMemoryError: Java heap space
INFO | jvm 1 | 2016/03/25 07:09:07 | Exception in thread "Timer74" java.lang.OutOfMemoryError: Java heap space
INFO | jvm 1 | 2016/03/25 07:09:07 | Exception in thread "Timer73" java.lang.OutOfMemoryError: Java heap space堆内存溢出，以为是内存不足，但与前几天的报错又不一样INFO | jvm 1 | 2016/03/23 15:38:35 | Exception in thread "$_MyCatServer" java.lang.OutOfMemoryError: Direct buffer memory
INFO | jvm 1 | 2016/03/23 15:38:35 | at java.nio.Bits.reserveMemory（Bits.java:658）
INFO | jvm 1 | 2016/03/23 15:38:35 | at java.nio.DirectByteBuffer.<init>（DirectByteBuffer.java:123）
INFO | jvm 1 | 2016/03/23 15:38:35 | at java.nio.ByteBuffer.allocateDirect（ByteBuffer.java:306）而且，通过查看wrapper.conf，发现MaxDirectMemorySize已经设置为10G了，刚开始一直按默认2G来，偶尔会出现内存溢出。wrapper.java.additional.5=-XX:MaxDirectMemorySize=10G后来，一高人指点，通过jmap -heap pid命令查看，发现MaxHeapSize=16MBHeap Configuration:
MinHeapFreeRatio = 0
MaxHeapFreeRatio = 100
MaxHeapSize = 16777216 （16.0MB）
NewSize = 1310720 （1.25MB）
MaxNewSize = 17592186044415 MB
OldSize = 5439488 （5.1875MB）
NewRatio = 2
SurvivorRatio = 8
PermSize = 21757952 （20.75MB）
MaxPermSize = 536870912 （512.0MB）
G1HeapRegionSize = 0 （0.0MB）不科学啊，wrapper.conf中有关堆内存的设置没这么小啊wrapper.java.additional.10=-Xmx4G
wrapper.java.additional.11=-Xms1G# Initial Java Heap Size （in MB）
wrapper.java.initmemory=4G# Maximum Java Heap Size （in MB）
wrapper.java.maxmemory=15G复制代码最后才发现，问题出在wrapper.java.initmemory=4G和wrapper.java.maxmemory=15G上了。原来，这两个参数直接设置数值就可以了，因为它的单位已经已经指明了，为MB。如果设置为15G，jvm会直接屏蔽掉后面的G，使用15，然后MaxHeapSize将会被设置为16MB（后来测试了一下，如果设置为17，MaxHeapSize则会被设置为18MB，至于为什么每次都分配为偶数，这个就不太清楚了）。后来测试了一下，得出以下结论：1. wrapper.java.maxmemory参数会覆盖wrapper.java.additional.10参数。2. 即便wrapper.java.maxmemory的值超过了4096，MaxHeapSize最大为4096MB。3. 如果堆大小要超过4096MB，可设置wrapper.java.maxmemory，同时注释掉wrapper.java.maxmemory。建议，只使用wrapper.java.additional.10=-Xmx4G和wrapper.java.additional.11=-Xms1G配置堆内存的大小。总结：mycat的启动方式有两种1. mycat/bin/mycat start这种方式会使用mycat/conf/wrapper.conf作为配置文件通过 sh -x mycat start即可发现+ eval ""/usr/local/mycat/bin/./wrapper-linux-x86-64"" ""/usr/local/mycat/conf/wrapper.conf"" wrapper.syslog.ident=mycat "wrapper.pidfile="/usr/local/mycat/logs/mycat.pid"" wrapper.daemonize=TRUE "wrapper.lockfile="/var/lock/subsys/mycat""
++ /usr/local/mycat/bin/./wrapper-linux-x86-64 /usr/local/mycat/conf/wrapper.conf wrapper.syslog.ident=mycat wrapper.pidfile=/usr/local/mycat/logs/mycat.pid wrapper.daemonize=TRUE wrapper.lockfile=/var/lock/subsys/myca2. mycat/bin/startup_nowrap.sh这个脚本里面同样有关于jvm的配置JAVA_OPTS="-server -Xms2G -Xmx2G -XX:MaxPermSize=64M -XX:+AggressiveOpts -XX:MaxDirectMemorySize=2G"# ./startup_nowrap.sh
"/usr/local/jdk1.7.0_79/bin/java" -DMYCAT_HOME="/usr/local/mycat" -classpath "/usr/local/mycat/conf:/usr/local/mycat/lib/classes:/usr/local/mycat/lib/curator-client-2.9.0.jar:/usr/local/mycat/lib/curator-framework-2.9.0.jar:/usr/local/mycat/lib/dom4j-1.6.1.jar:/usr/local/mycat/lib/druid-1.0.14.jar:/usr/local/mycat/lib/ehcache-core-2.6.11.jar:/usr/local/mycat/lib/fastjson-1.2.7.jar:/usr/local/mycat/lib/guava-18.0.jar:/usr/local/mycat/lib/jline-0.9.94.jar:/usr/local/mycat/lib/json-20151123.jar:/usr/local/mycat/lib/leveldb-0.7.jar:/usr/local/mycat/lib/leveldb-api-0.7.jar:/usr/local/mycat/lib/log4j-1.2.17.jar:/usr/local/mycat/lib/mapdb-1.0.7.jar:/usr/local/mycat/lib/mongo-java-driver-2.11.4.jar:/usr/local/mycat/lib/Mycat-server-1.5-GA.jar:/usr/local/mycat/lib/netty-3.7.0.Final.jar:/usr/local/mycat/lib/ojdbc14-10.2.0.3.0.jar:/usr/local/mycat/lib/sequoiadb-java-driver-1.0-20150615.070208-1.jar:/usr/local/mycat/lib/slf4j-api-1.7.12.jar:/usr/local/mycat/lib/slf4j-log4j12-1.7.12.jar:/usr/local/mycat/lib/snakeyaml-1.16.jar:/usr/local/mycat/lib/univocity-parsers-1.5.4.jar:/usr/local/mycat/lib/wrapper.jar:/usr/local/mycat/lib/xml-apis-1.0.b2.jar:/usr/local/mycat/lib/zookeeper-3.4.6.jar" -server -Xms2G -Xmx2G -XX:MaxPermSize=64M -XX:+AggressiveOpts -XX:MaxDirectMemorySize=2G org.opencloudb.MycatStartup >> "/usr/local/mycat/logs/console.log" 2>&1 &MyCAT实现MySQL读写分离实践 http://www.linuxidc.com/Linux/2016-01/127957.htmMyCAT实现MySQL的读写分离 http://www.linuxidc.com/Linux/2016-01/127555.htmMyCAT ER分片的验证 http://www.linuxidc.com/Linux/2016-02/128636.htmLVS+Keepalived搭建MyCAT高可用负载均衡集群 http://www.linuxidc.com/Linux/2016-03/129231.htm本文永久更新链接地址