Java – Out of Memory Issue – Mongo is getting killed as soon as I start the java application

javamongodb

I have a standalone application where I am trying to create 5 threads for each thread I am creating a mongoclient and persisting the details in MongoDB and then closing the mongoclient.

When I start my mongo service it is running but as soon as I start my java application after some time my mongo service is getting killed and I can see the below error in syslog.

Out of memory: Kill process 12715 (mongod) score 433 or sacrifice child\\
kernel: [2946780.340246] Killed process 12715 (mongod) total-vm:6646800kB, anon-rss:6411432kB, file-rss:0kB

I am using Linux server it has 10GB RAM. As far as I know we can do thousands of transactions in MongoDB. And before I start I can see free memory after some time I am getting the above error.

Not sure exactly what to do, Do we need to set anything in linux server to handle multiple mongo requests? or do I need to increase the limit of mongo service any where?

Can any one please suggest me on this?

Thanks in Advance.

o/p of free -m before and after execution of my java application are as follows:

Before: 

             total       used       free     shared    buffers     cached
Mem:         14032       7646       6385         54          4        153
-/+ buffers/cache:       7489       6542
Swap:            0          0          0

After: 

             total       used       free     shared    buffers     cached
Mem:         14032      13845        186         54        106       4131
-/+ buffers/cache:       9607       4425
Swap:            0          0          0

The below are the details from mongod.conf

# mongod.conf

storage:
  dbPath: /xxx/xxx 
  journal:
    enabled: true

systemLog:
  destination: file
  logAppend: true
  path: /var/log/mongodb/mongod.log

net:
  port: 27017    
  bindIp: 127.0.0.1,xx.xx.xx.xx

processManagement:
   fork: true
security:
  authorization: enabled

Output of cat /proc/<PId>/limits:

cat /proc/17694/limits
Limit                     Soft Limit           Hard Limit           Units
Max cpu time              unlimited            unlimited            seconds
Max file size             unlimited            unlimited            bytes
Max data size             unlimited            unlimited            bytes
Max stack size            8388608              unlimited            bytes
Max core file size        0                    unlimited            bytes
Max resident set          unlimited            unlimited            bytes
Max processes             112088               112088               processes
Max open files            1024                 4096                 files
Max locked memory         65536                65536                bytes
Max address space         unlimited            unlimited            bytes
Max file locks            unlimited            unlimited            locks
Max pending signals       112088               112088               signals
Max msgqueue size         819200               819200               bytes
Max nice priority         0                    0
Max realtime priority     0                    0
Max realtime timeout      unlimited            unlimited            us

ps xua | grep java results ::: 

  root     17142  0.4  3.1 5645648 453180 pts/0  Sl   Sep04   2:27 java -d64 -Xms1024m -Xmx2048m -server -cp bin:lib/* javaclassname -resourceDir /xxx/bin -dataDir /xxx/data
   root     17491 22.1 11.2 5653432 1610716 pts/0 Sl   Sep04 115:14 java -d64 -Xms1024m -Xmx2048m -server -cp bin:lib_new/* javaclassname -resourceDir /xxx/bin -dataDir /xxx/data -outConfigPath /xxx/xxx.xml -outCatBrandPath /xxx/xxx.xml -outCatAndSunCatPath /xxx/xxx.xml
   xxx      19223  3.5 22.1 20396560 3184668 ?    Sl   Aug28 398:11 /usr/bin/java -Xms2g -Xmx2g -XX:+UseConcMarkSweepGC -XX:CMSInitiatingOccupancyFraction=75 -XX:+UseCMSInitiatingOccupancyOnly -XX:+DisableExplicitGC -XX:+AlwaysPreTouch -server -Xss1m -Djava.awt.headless=true -Dfile.encoding=UTF-8 -Djna.nosys=true -Djdk.io.permissionsUseCanonicalPath=true -Dio.netty.noUnsafe=true -Dio.netty.noKeySetOptimization=true -Dio.netty.recycler.maxCapacityPerThread=0 -Dlog4j.shutdownHookEnabled=false -Dlog4j2.disable.jmx=true -Dlog4j.skipJansi=true -XX:+HeapDumpOnOutOfMemoryError -Des.path.home=/elasticsearch-5.4.0 -cp /elasticsearch-5.4.0/lib/* org.elasticsearch.bootstrap.Elasticsearch
   root     21617  2.2 21.7 18549248 3124416 ?    Sl   Aug28 247:34 /usr/bin/java -Djava.util.logging.config.file=/opt/apache-tomcat-8.0.30/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.endorsed.dirs=/opt/apache-tomcat-8.0.30/endorsed -classpath /opt/apache-tomcat-8.0.30/bin/bootstrap.jar:/opt/apache-tomcat-8.0.30/bin/tomcat-juli.jar -Dcatalina.base=/opt/apache-tomcat-8.0.30 -Dcatalina.home=/opt/apache-tomcat-8.0.30 -Djava.io.tmpdir=/opt/apache-tomcat-8.0.30/temp org.apache.catalina.startup.Bootstrap start

swapon -s output :

Filename                                Type            Size    Used    Priority

Best Answer

It seems that the OS is running out of physical memory, and since your server doesn't seem to have any swap configured, the kernel's out-of-memory killer (OOM-killer) kicks in and terminates processes to free up some RAM (in this case it's mongodb, but could be any other).

You should create a swap partition on that server.

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