MyCAT reports java. lang. OutOfMemoryError: Java heap space

MyCAT reports java. lang. OutOfMemoryError: Java heap space

In the morning, my colleague reported that mycat was suspended again. It was estimated that the memory was still overflow and I checked the error log.

INFO | jvm 1 | 07:09:06 | java. lang. OutOfMemoryError: Java heap space
INFO | jvm 1 | 07:09:06 | Exception in thread "Timer67" java. lang. OutOfMemoryError: Java heap space
INFO | jvm 1 | 07:09:06 | Exception in thread "Timer68" java. lang. OutOfMemoryError: Java heap space
INFO | jvm 1 | 07:09:06 | Exception in thread "Timer69" java. lang. OutOfMemoryError: Java heap space
INFO | jvm 1 | 07:09:06 | Exception in thread "Timer70" java. lang. OutOfMemoryError: Java heap space
INFO | jvm 1 | 07:09:06 | Exception in thread "Timer71" java. lang. OutOfMemoryError: Java heap space
INFO | jvm 1 | 07:09:06 | Exception in thread "Timer72" java. lang. OutOfMemoryError: Java heap space
INFO | jvm 1 | 07:09:07 | Exception in thread "Timer74" java. lang. OutOfMemoryError: Java heap space
INFO | jvm 1 | 07:09:07 | Exception in thread "Timer73" java. lang. OutOfMemoryError: Java heap space

Heap memory overflow, which is considered to be insufficient memory, but different from the error reported in the previous days.

INFO | jvm 1 | 15:38:35 | Exception in thread "$ _ MyCatServer" java. lang. OutOfMemoryError: Direct buffer memory
INFO | jvm 1 | 15:38:35 | at java. nio. Bits. reserveMemory (Bits. java: 658)
INFO | jvm 1 | 15:38:35 | at java. nio. DirectByteBuffer. <init> (DirectByteBuffer. java: 123)
INFO | jvm 1 | 15:38:35 | at java. nio. ByteBuffer. allocateDirect (ByteBuffer. java: 306)

In addition, by checking wrapper. conf, we found that the MaxDirectMemorySize has been set to 10 Gb. At the beginning, the default value is 2 GB, and occasionally memory overflow occurs.

Wrapper. java. additional.5 =-XX: MaxDirectMemorySize = 10G

Later, a high-level expert pointed out that MaxHeapSize = 16 MB was found through the jmap-heap pid command.

Heap Configuration:
MinHeapFreeRatio = 0
MaxHeapFreeRatio = 100
MaxHeapSize = 16777216 (16.0 MB)
NewSize = 1310720 (1.25 MB)
MaxNewSize = 17592186044415 MB
OldSize = 5439488 (5.1875 MB)
NewRatio = 2
Required vorratio = 8
PermSize = 21757952 (20.75 MB)
MaxPermSize = 536870912 (512.0 MB)
G1HeapRegionSize = 0 (0.0 MB)

Unscientific. The heap memory settings in wrapper. conf are not that small.

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

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Finally, we found that the problem lies in wrapper. java. initmemory = 4G and wrapper. java. maxmemory = 15g.

It turns out that the two parameters can be set directly to the value, because the Unit of the parameter has been specified, which is MB.

If it is set to 15 GB, the jvm will directly block the subsequent G and use 15, and then the MaxHeapSize will be set to 16 MB (after testing, if it is set to 17, maxHeapSize is set to 18 MB. It is not clear why an even number is allocated each time ).

I tested it and came to the following conclusion:

1. the wrapper. java. maxmemory parameter will overwrite the wrapper. java. additional.10 parameter.

2. Even if the value of wrapper. java. maxmemory exceeds 4096, MaxHeapSize is up to 4096 MB.

3. If the heap size exceeds 4096 MB, you can set wrapper. java. maxmemory and comment out wrapper. java. maxmemory.

We recommend that you only use wrapper. java. additional.10 =-Xmx4G and wrapper. java. additional.11 =-Xms1G to configure the heap memory size.

Summary:

Mycat can be started in two ways.

1. mycat/bin/mycat start

In this way, mycat/conf/wrapper. conf is used as the configuration file.

Use sh-x mycat start to find out

+ 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/myca

2. mycat/bin/startup_nowrap.sh

This script also contains jvm configurations.

JAVA_OPTS = "-server-Xms2G-Xmx2G-XX: MaxPermSize = 64 M-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 = 64 M-XX: + AggressiveOpts-XX: MaxDirectMemorySize = 2G org. opencloudb. mycatStartup> "/usr/local/mycat/logs/console. log "2> & 1 &

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