Develop Reference

How can we verify heap size for running ElasticSearch

Am running ElasticSearch Version 6.2.3 and i am increasing heapsize to 4GB in config\jvm.options file. Then am restarting my ES, how i can make sure that my ES is running with my modified heapsize. Is there any command to verify the heap-size of ES.
Am running my ES in Windows machine.
Please find my configuration details.
## JVM configuration
################################################################
## IMPORTANT: JVM heap size
################################################################
##
## You should always set the min and max JVM heap
## size to the same value. For example, to set
## the heap to 4 GB, set:
##
## -Xms2g
## -Xmx2g
##
## See https://www.elastic.co/guide/en/elasticsearch/reference/current/heap-size.html
## for more information
##
################################################################
# Xms represents the initial size of total heap space
# Xmx represents the maximum size of total heap space
-Xms4g
-Xmx4g

You can find out the heap size used by each node using the _cat/nodes endpoint.
It would look like below:
host=localhost:9200 #replace with your Elasticsearch URL
curl $host/_cat/nodes?h=heap*
This would return an output which should look like below:
554.8mb 30 1.8gb
850.9mb 46 1.8gb
1.7gb 95 1.8gb
Column 1 here is heap.current, aka used heap.
Column 2 here is heap.percent, aka used heap in percentage.
Column 3 here is heap.max, aka max heap available to the node.
The h query string param allows you to select the column names to display. We are using the * wildcard to expand to all the columns that start with the heap prefix.
You can read the documentation here to learn more: https://www.elastic.co/guide/en/elasticsearch/reference/current/cat-nodes.html.

You can find the JVM arguments used in elasticsearch instance in INFO logs. Make sure that your elastic logging level shows INFO logs.

You can also check the command line arguments used to launch the instance by using either of the options below:
Use Process Explorer, and hover over the process name for java.exe (launched by elasticsearch.exe). Be sure you have selected "Show Details for All Processes" from the File menu.
Run the following command from an elevated command prompt: WMIC PATH win32_process WHERE "caption='java.exe'" GET Commandline
Both will give you the commandline parameters used to launch the instance. Look for the -Xmx and -Xms values.
For more information about these two options, check out How do I find out command line arguments of a running program?

Increased heap size in java is not reflecting in jconsole

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I am trying to run an java spring boot application by specifying the heap size as argument while starting the jar like below,
java -jar a-1.0.0.jar -Dpidfile=/tmp/a_report.pid -Xmx5196m -Xms512m
-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/tmp/java_heapdump.hprof
Max Heap Space - 4 GB
But when I try to monitor the application after execution in J-Console, I could not see the actual heap size change getting reflected. I could see in Memory tab the following params
Time:  2018-02-13 15:23:42 Used: 
    73,103 kbytes Committed:   1,181,184 kbytes Max:   1,864,192 kbytes
Also the application throws OOM exception when the heap size is around 2 gb so it is clear that the updated heap space memory given during the start of the application is not getting reflected.
So what should I do to make my application pick heap space as 4gb
Configuration :
RAM - 8 gb JDK - 1.8

You need to provide the options before -jar a-1.0.0.jar, otherwise they're interpreted as arguments for the jar, not for the JVM.

MaxHeapSize in Java

I run command in window machine
java -XX:+PrintFlagsFinal -version | findstr /i "HeapSize PermSize ThreadStackSize
and got below value for MaxHeapSize
2118123520
which is 2020MB however, when I call Runtime.getRuntime().maxMemory() , it gives me 259522560 only i.e. 247MB .
Can anyone please suggest why I'm getting this mismatch ?

As per your last comment
I'm using eclipse IDE and didn't change any setting . do you know how to change maximum heap size in eclipse IDE ?
Set the VM arguments found under Run configuration.
VM arguments are typically values that change the behaviour of the Java Virtual Machine (JVM). For example, the -Xmx256M argument allows the Java heap to grow to 256MB.
For more info have a look at Eclipse launching program and VM arguments

Can anyone please suggest why I'm getting this mismatch ?
The Runtime.getRuntime().maxMemory() call is returning the maximum heap size for the current JVM. This is determined by either the -Xmx command line option (e.g. for the java command) or a platform specific default.
The command you are running is giving the maximum allowed value for the -Xmx commandline option on your platform.
Clearly these are different things. Furthermore, the numbers are usually different.

Read pdf using java

i have a problem with reading PDF file content in java using itextpdf.jar ,
if i read a small sized(5-15MB) PDF file means its working well, it is possible to read it's contents
but when i read large sized(200MB) PDF file means its showing Run time exception like following
enter code hereException in thread "main" java.lang.OutOfMemoryError: Java heap space
at java.util.Arrays.copyOf(Arrays.java:2786)
at java.io.ByteArrayOutputStream.write(ByteArrayOutputStream.java:94)
at com.itextpdf.text.pdf.RandomAccessFileOrArray.InputStreamToArray(RandomAccessFileOrArray.java:213)
at com.itextpdf.text.pdf.RandomAccessFileOrArray.<init>(RandomAccessFileOrArray.java:203)
at com.itextpdf.text.pdf.PdfReader.<init>(PdfReader.java:235)
at com.itextpdf.text.pdf.PdfReader.<init>(PdfReader.java:246)
at general.FileStreamClose.main(FileStreamClose.java:28)
Java Result: 1enter code here
any solution for this , how to increase heap size in tomcat

You can tune your Java Application Runtime settings:
maximize heap size to high value with -Xmx say 500M
tune -XX:MaxHeapFreeRatio and -XX:MinHeapFreeRatio to make sure that the application will not becomes irresponsive when consuming lot of memory when the heap reduces.

to increase heap size for tomcat you'll have to set the evnirenment variable JAVA_OPTS and have it contain the -Xmx option for example -Xmx512m
here is a sample script how you can run tomcat
#echo off
set JAVA_HOME=C:\Program Files\Java\jdk1.6.0_33
set CATALINA_HOME=C:\Program Files\apache-tomcat-7.0
set JAVA_OPTS=-XX:MaxPermSize=128m -Xmx512m -server
call %CATALINA_HOME%\bin\catalina.bat run

for additional info, as far as i know, if your machine is 32 bit increase xmx and xms heap size will limited around 1k++. If you need more than that you need to install java 64 bit (of course in 64 machine and 64 OS).

Java Increase Heap size

I have a java application form which i am accessing records from database,processing it and again updaing the database.
I am doing this by converting my java application to JAR and executing it from command prompt.During testing there are only 20 records
per table in database.For that i am executing the jar as follows to avoid out of memory error,
java -jar -Xmx512m MyApp.jar
If database contains much record(50,000),how to increase the heap size while executing jar or How to increase the heap size dynamically based on needs while executing the jar.
Thanks

The maximal heap size is set before running the program by using the -Xmx option you already used. Based on this information, the JVM will use as much heap size as it needs, up to the given amount. So if your program only needs 1 MB of RAM, the JVM will only use that amount, if it needs 1G and you only gave it 512M, you will get an OutOfMemoryError.
So, basically, you can give your program more heap space if you need to, and the JVM will dynamically adjust the used heap size according to its needs.
Sometimes this is not the intended behavior, and the lower bound for heap size can be set with -Xms. Then the JVM will always reserve a heap of the size between Xms and Xmx.

The maximum is the maximum heap you would need ever not how much it will actually use. It's the point at which you would rather than application crash than keep running. The JVM will dynamically manage the memory used up to this point.
How to increase the heap size dynamically based on needs while executing the jar.
So if you want the JVM to use 256 MB, but you want it to dynamically grow up to 30 GB you would set it like this
java -ms256m -mx30g -jar MyApp.jar
Even the minimum is not guaranteed to be used. The JVM will do minimal effort to keep the memory usage up to this level. A Hello World program will not use 256 MB of heap no matter what you set the minimum to.

-Xmx2048m -XX:-UseGCOverheadLimit
Set this in your VM Arguement.
You can set less memory size in place of 2048

This will increase your max heapSize to 1Gb.
java -Xms256m -Xmx1024m -jar MyApp.jar
where -Xms specifies the initial Java heap size and -Xmx the maximum Java heap size.
Parameters to the JVM must be passed before the -jar part. The reason for that can be seen when we execute "java -version" :
Usage:
java [-options] class [args...]
(to execute a class)
or java [-options] -jar jarfile [args...]
(to execute a jar file)