Production Tomcat (Java 8) parameter

✔ JVM tuning (temporary mitigation)

-Xms8g
-Xmx8g
-XX:+UseG1GC

⚠️ JVM tuning does not fix leaks, only delays failure.

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🧪 Validation

jcmd <PID> GC.run

Check memory release:

jmap -histo <PID>

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✅ Best Practices (Production / Bank / ISO)

✔ Code review for static leaks
✔ Mandatory resource closing
✔ Regular heap dump analysis
✔ Scheduled Tomcat restart (only if unavoidable)
✔ Monitoring via Prometheus / JMX

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Summary

Area	Action
Root cause	Application code
Detection	Heap dump + GC logs
Fix	Code cleanup
Prevention	Monitoring & best practices

If you want, I can provide:

• Tomcat memory leak SOP

• Heap dump analysis checklist

• Production JVM tuning template

Just let me know.

tomcat memory perameter

Below are the commonly used and recommended Tomcat (JVM) memory parameters, with clear explanations and production-ready examples.

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🔹 Core Tomcat JVM Memory Parameters

1️⃣ Heap Memory

-Xms4g     # Initial heap size
-Xmx4g     # Maximum heap size

Best practice: Keep -Xms = -Xmx for stable performance.

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2️⃣ Metaspace (Java 8+)

-XX:MetaspaceSize=256m
-XX:MaxMetaspaceSize=512m

Controls class metadata memory (important for Tomcat apps).

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3️⃣ Stack Memory (per thread)

-Xss512k

Too many threads + large stack = OutOfMemoryError.

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4️⃣ Garbage Collector (Recommended)

For Java 8+

-XX:+UseG1GC

Optional tuning:

-XX:MaxGCPauseMillis=200
-XX:InitiatingHeapOccupancyPercent=45

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🔹 Memory Leak & Stability Parameters

-XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=/opt/tomcat/heapdump
-XX:+ExitOnOutOfMemoryError

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🔹 GC Logging (Java 8)

-XX:+PrintGCDetails
-XX:+PrintGCDateStamps
-Xloggc:/opt/tomcat/logs/gc.log

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🔹 Example: Production Tomcat (Java 8)

Add to setenv.sh:

export CATALINA_OPTS="
-Xms8g
-Xmx8g
-XX:MetaspaceSize=256m
-XX:MaxMetaspaceSize=512m
-Xss512k
-XX:+UseG1GC
-XX:MaxGCPauseMillis=200
-XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=/opt/tomcat/heapdump
"

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🔹 Check Memory at Runtime

jmap -heap <PID>

jstat -gc <PID> 5s

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✅ Recommended Sizing (Rule of Thumb)

Server RAM	Tomcat Heap
8 GB	4–5 GB
16 GB	8–10 GB
32 GB	16–20 GB

Leave memory for:

• OS

• File cache

• Other services

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⚠️ Common Mistakes

❌ Setting heap larger than system RAM
❌ Ignoring Metaspace
❌ Relying only on JVM tuning for leaks

cat /u01/ocastomcat/tomcat/apache-tomcat-9.0.65/bin/setenv.sh

#java.awt.headles=strue

export CATALINA_OPTS="$CATALINA_OPTS -Djava.awt.headless=true"

#export CATALINA_OPTS="$CATALINA_OPTS -Xms24576m"

#export CATALINA_OPTS="$CATALINA_OPTS -Xmx24576m"

#export CATALINA_OPTS="$CATALINA_OPTS -Xms8g -Xmx16g"

### ================================

### Memory & Heap Settings

### ================================

export CATALINA_OPTS="$CATALINA_OPTS -Xms32g"

export CATALINA_OPTS="$CATALINA_OPTS -Xmx48g"

# Why? Large application benefits from higher initial heap for stability.

### ================================

### Garbage Collector (G1)

### ================================

export CATALINA_OPTS="$CATALINA_OPTS -XX:+UseG1GC"

export CATALINA_OPTS="$CATALINA_OPTS -XX:MaxGCPauseMillis=200"

export CATALINA_OPTS="$CATALINA_OPTS -XX:+ParallelRefProcEnabled"

### ================================

### Heap Region Tuning (for 16–32GB heaps)

### ================================

export CATALINA_OPTS="$CATALINA_OPTS -XX:G1HeapRegionSize=32m"

### ================================

### Metaspace Tuning (large WAR needs more)

### ================================

export CATALINA_OPTS="$CATALINA_OPTS -XX:MetaspaceSize=512m"

export CATALINA_OPTS="$CATALINA_OPTS -XX:MaxMetaspaceSize=2048m"

### ================================

### JVM Startup Optimization

### ================================

export CATALINA_OPTS="$CATALINA_OPTS -XX:+AlwaysPreTouch"

export CATALINA_OPTS="$CATALINA_OPTS -XX:+DisableExplicitGC"

# --------------------------------

# Heap Dump on OutOfMemoryError

# --------------------------------

export CATALINA_OPTS="$CATALINA_OPTS -XX:+HeapDumpOnOutOfMemoryError"

export CATALINA_OPTS="$CATALINA_OPTS -XX:HeapDumpPath=/u01/ocastomcat/tomcat/apache-tomcat-9.0.65/heapdump"

# --------------------------------

# GC Logging (Java 8 syntax)

# --------------------------------

export CATALINA_OPTS="$CATALINA_OPTS -XX:+PrintGCDetails"

export CATALINA_OPTS="$CATALINA_OPTS -XX:+PrintGCDateStamps"

export CATALINA_OPTS="$CATALINA_OPTS -XX:+PrintTenuringDistribution"

export CATALINA_OPTS="$CATALINA_OPTS -Xloggc:/opt/tomcat/logs/gc.log"

export CATALINA_OPTS="$CATALINA_OPTS -XX:+UseGCLogFileRotation"

export CATALINA_OPTS="$CATALINA_OPTS -XX:NumberOfGCLogFiles=10"

export CATALINA_OPTS="$CATALINA_OPTS -XX:GCLogFileSize=100M"

Example: Production Tomcat (Java 8)

Add to setenv.sh:

export CATALINA_OPTS="
-Xms8g
-Xmx8g
-XX:MetaspaceSize=256m
-XX:MaxMetaspaceSize=512m
-Xss512k
-XX:+UseG1GC
-XX:MaxGCPauseMillis=200
-XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=/opt/tomcat/heapdump

Enable Remote Access to Tomcat Manager

 

Step 1: Install Apache Tomcat

Before we start, make sure you have Apache Tomcat installed on your server or computer. If you haven’t installed it yet, you can download it from the official Tomcat website and follow the installation instructions.

Step 2: Locate the Tomcat Configuration File

1. Open the folder where Tomcat is installed.
2. Find the conf directory.
3. In this directory, locate the tomcat-users.xml file. This file is used to manage users and roles.

Step 3: Edit the tomcat-users.xml File

1. Open the tomcat-users.xml file with a text editor.
2. Add the following lines inside the <tomcat-users> tags to create a user with the manager role:

   
   <role rolename="manager-gui"/>
   <user username="admin" password="admin_password" roles="manager-gui"/>
   
   

Replace admin with your desired username and admin_password with a strong password.

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3. Save the changes and close the file.

Step 4: Allow Remote Access To Manager App

1. Go to the webapps/manager/META-INF/ directory.
2. Open the context.xml file located in that directory with a text editor.
3. Find the section that looks like this:

   
   <Valve className="org.apache.catalina.valves.RemoteAddrValve"
       allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1" />
   
   
4. Change the allow attribute to include your IP address or a range of IP addresses from which you want to allow access. For example:

   
   <Valve className="org.apache.catalina.valves.RemoteAddrValve"
       allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1|192\.168\.1\.\d+" />
   
   

   This example allows access from any IP address in the 192.168.1.x range.

5. Save the changes and close the file.

Step 5: Allow Remote Access To Host Manager

1. Go to the webapps/host-manager/META-INF/ directory.
2. Open the context.xml file located in webapps/host-manager/META-INF/ directory with a text editor.
3. Find the section that looks like this:

   
   <Valve className="org.apache.catalina.valves.RemoteAddrValve"
       allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1" />
   
   
4. Change the allow attribute to include your IP address or a range of IP addresses from which you want to allow access. For example:

   
   <Valve className="org.apache.catalina.valves.RemoteAddrValve"
       allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1|192\.168\.1\.\d+" />
   
   

   This example allows access from any IP address in the 192.168.1.x range.

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5. Save the changes and close the file.

Step 6: Restart Tomcat

For the changes to take effect, you need to restart Tomcat. You can do this by running the shutdown script followed by the startup script located in the bin directory of your Tomcat installation:

• For Windows:

  
  shutdown.bat
  startup.bat
  
  
• For Linux:
  Linux server distribution

  
  ./shutdown.sh
  ./startup.sh
  
  

Step 7: Access Tomcat Manager Remotely

Open a web browser and go to http://<your-server-ip>:8080/manager. You should see the Tomcat Manager login page. Enter the username and password you created in the tomcat-users.xml file.

======================

file edit

setenv.sh

export CATALINA_OPTS="$CATALINA_OPTS -Xms28672m"

export CATALINA_OPTS="$CATALINA_OPTS -Xmx28672m"

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