---
id: 1412e177-b23f-4d77-b2e4-d0c86926d5f8
---

# Tomcat Low Available Threads in Connection Pool
---

This incident type is related to the Tomcat server, which is a popular open-source Java application server. It occurs when the available threads in the connection pool are running low, which means that there are not enough resources to serve incoming requests. This can cause delays or even failures in the application's performance, impacting the end-user experience. It is important to monitor and address this issue promptly to ensure that the application runs smoothly and efficiently.

### Parameters
```shell

export PATH_TO_TOMCAT_CONFIG="PLACEHOLDER"

export TOMCAT_PORT="PLACEHOLDER"

export CONNECTION_POOL_NAME="PLACEHOLDER"

export NEW_CONNECTION_POOL_SIZE="PLACEHOLDER"

export PATH_TO_SERVER_XML_FILE="PLACEHOLDER"

export PATH_TO_TOMCAT_DIRECTORY="PLACEHOLDER"

export NEW_MEMORY_SIZE="PLACEHOLDER"
```

## Debug

### Check if Tomcat is running
```shell
systemctl status tomcat
```

### Check Tomcat logs for any errors related to connection pool
```shell
grep -i "connection pool"  /var/log/tomcat/catalina.out
```

### Check the current number of threads being used by Tomcat
```shell
jcmd $(pgrep -f catalina) Thread.print | grep -i "http"
```

### Check the maximum number of threads allowed in the connection pool
```shell
grep -i "maxActive" ${PATH_TO_TOMCAT_CONFIG}
```

### Check the current number of active threads in the connection pool
```shell
curl -s http://localhost:${TOMCAT_PORT}/manager/jolokia/read/org.apache.tomcat.jdbc:name=${CONNECTION_POOL_NAME},type=ConnectionPool/numActive | jq '.value'
```

### Check the current number of idle threads in the connection pool
```shell
curl -s http://localhost:${TOMCAT_PORT}/manager/jolokia/read/org.apache.tomcat.jdbc:name=${CONNECTION_POOL_NAME},type=ConnectionPool/numIdle | jq '.value'
```

## Repair

### Increase the size of the connection pool to allow for more available threads.
```shell
bash

#!/bin/bash



# Define variables

TOMCAT_HOME=${PATH_TO_TOMCAT_DIRECTORY}

SERVER_XML=${PATH_TO_SERVER_XML_FILE}

CONNECTION_POOL_SIZE=${NEW_CONNECTION_POOL_SIZE}



# Stop Tomcat server

$TOMCAT_HOME/bin/shutdown.sh



# Replace connection pool size in server.xml

sed -i "s/maxTotal=\"[0-9]*\"/maxTotal=\"$CONNECTION_POOL_SIZE\"/" $SERVER_XML



# Start Tomcat server

$TOMCAT_HOME/bin/startup.sh


```

### Increase the memory allocation to the Tomcat server to allow for more threads.
```shell


#!/bin/bash



# Stop the Tomcat server

sudo systemctl stop tomcat



# Increase the memory allocation by updating the CATALINA_OPTS environment variable in the Tomcat configuration file

sudo sed -i 's/export CATALINA_OPTS=/export CATALINA_OPTS="-Xms${NEW_MEMORY_SIZE}G -Xmx${NEW_MEMORY_SIZE}G"/g' /etc/tomcat/catalina.sh



# Start the Tomcat server

sudo systemctl start tomcat


```

This incident type is related to the Tomcat server, which is a popular open-source Java application server. It occurs when the available threads in the connection pool are running low, which means that there are not enough resources to serve incoming requests. This can cause delays or even failures in the application's performance, impacting the end-user experience. It is important to monitor and address this issue promptly to ensure that the application runs smoothly and efficiently.


When too many requests are sent to a Tomcat server, the thread pools that handle these requests can run out of available threads. This means that incoming requests will not be processed, leading to service degradation or even a complete outage. This incident type is critical for web applications that rely on Tomcat as their application server.


Tomcat thread pool exhaustion.

Tomcat Server Crash incident type refers to a situation where the Tomcat Server, an open-source web server and servlet container, becomes unresponsive and stops functioning. This can result in a complete or partial system outage, leading to a disruption in the delivery of web applications and services. The root cause of the crash can be attributed to a variety of factors such as misconfiguration, network or hardware issues, software bugs, or excessive server load. It is critical to address this incident quickly to minimize the impact on users and restore normal system functionality.


Tomcat Server Crash

This incident type occurs when the PermGen or Metaspace usage of the Tomcat server exceeds 90%. PermGen and Metaspace are memory pools used for storing class definitions and metadata of the Java virtual machine (JVM). When these memory pools reach their maximum capacity, the server may experience performance issues or even crash. This incident requires immediate attention from the software engineer to investigate the root cause and take appropriate actions to resolve the issue.


Tomcat PermGen or Metaspace Usage exceeds 90%

In software engineering, a large number of suspended threads in Tomcat is an incident type that occurs when a high number of threads are created but are blocked from executing. This can happen due to a variety of reasons, such as slow database queries, network latency, or resource contention. When this occurs, the system may become unresponsive or slow, causing a degradation in performance or even a complete system failure. It is important to investigate and resolve this issue as quickly as possible to ensure the system can continue to function properly.


Tomcat Large Number of Suspended Threads Incident.

Tomcat JVM OutOfMemory incident occurs when the Java Virtual Machine (JVM) running the Apache Tomcat server runs out of memory, which causes the server to crash or become unresponsive. This type of incident can happen due to a variety of reasons such as incorrect configuration settings, memory leaks, or insufficient memory allocation. When this incident occurs, it can impact the availability and performance of the web application running on the Tomcat server.


Tomcat JVM OutOfMemory Incident

```shell

export PATH_TO_TOMCAT_CONFIG="PLACEHOLDER"

export TOMCAT_PORT="PLACEHOLDER"

export CONNECTION_POOL_NAME="PLACEHOLDER"

export NEW_CONNECTION_POOL_SIZE="PLACEHOLDER"

export PATH_TO_SERVER_XML_FILE="PLACEHOLDER"

export PATH_TO_TOMCAT_DIRECTORY="PLACEHOLDER"

export NEW_MEMORY_SIZE="PLACEHOLDER"
```


### Check if Tomcat is running

```shell
systemctl status tomcat
```

### Check Tomcat logs for any errors related to connection pool

```shell
grep -i "connection pool"  /var/log/tomcat/catalina.out
```

### Check the current number of threads being used by Tomcat

```shell
jcmd $(pgrep -f catalina) Thread.print | grep -i "http"
```

### Check the maximum number of threads allowed in the connection pool

```shell
grep -i "maxActive" ${PATH_TO_TOMCAT_CONFIG}
```

### Check the current number of active threads in the connection pool

```shell
curl -s http://localhost:${TOMCAT_PORT}/manager/jolokia/read/org.apache.tomcat.jdbc:name=${CONNECTION_POOL_NAME},type=ConnectionPool/numActive | jq '.value'
```

### Check the current number of idle threads in the connection pool

```shell
curl -s http://localhost:${TOMCAT_PORT}/manager/jolokia/read/org.apache.tomcat.jdbc:name=${CONNECTION_POOL_NAME},type=ConnectionPool/numIdle | jq '.value'
```


### Increase the size of the connection pool to allow for more available threads.

```shell
bash

#!/bin/bash



# Define variables

TOMCAT_HOME=${PATH_TO_TOMCAT_DIRECTORY}

SERVER_XML=${PATH_TO_SERVER_XML_FILE}

CONNECTION_POOL_SIZE=${NEW_CONNECTION_POOL_SIZE}



# Stop Tomcat server

$TOMCAT_HOME/bin/shutdown.sh



# Replace connection pool size in server.xml

sed -i "s/maxTotal=\"[0-9]*\"/maxTotal=\"$CONNECTION_POOL_SIZE\"/" $SERVER_XML



# Start Tomcat server

$TOMCAT_HOME/bin/startup.sh


```

### Increase the memory allocation to the Tomcat server to allow for more threads.

```shell


#!/bin/bash



# Stop the Tomcat server

sudo systemctl stop tomcat



# Increase the memory allocation by updating the CATALINA_OPTS environment variable in the Tomcat configuration file

sudo sed -i 's/export CATALINA_OPTS=/export CATALINA_OPTS="-Xms${NEW_MEMORY_SIZE}G -Xmx${NEW_MEMORY_SIZE}G"/g' /etc/tomcat/catalina.sh



# Start the Tomcat server

sudo systemctl start tomcat


```


Tomcat Low Available Threads in Connection Pool

Overview

Parameters

Debug

Check if Tomcat is running

Check the current number of threads being used by Tomcat

Check the maximum number of threads allowed in the connection pool

Check the current number of active threads in the connection pool

Check the current number of idle threads in the connection pool

Repair

Increase the size of the connection pool to allow for more available threads.

Increase the memory allocation to the Tomcat server to allow for more threads.

Learn more

Related Runbooks

Tomcat thread pool exhaustion.

Tomcat Server Crash

Tomcat PermGen or Metaspace Usage exceeds 90%

Tomcat Large Number of Suspended Threads Incident.

Support