---
id: debf9078-39e9-47be-ae10-03650feee33c
---

# Apache server Mod_JK Worker Failures.
---

This incident type refers to failures with the Apache server's Mod_JK Worker, which is a module used to connect Apache to applications running on Tomcat. When this module fails, it can lead to issues with serving web pages and accessing web applications. This incident requires investigation and resolution to restore the proper functioning of the Apache server.

### Parameters
```shell
export APACHE_PORT_NUMBER="PLACEHOLDER"

export PATH_TO_WORKERS_PROPERTIES="PLACEHOLDER"

export WORKER_NAME="PLACEHOLDER"

export TOMCAT_PORT_NUMBER="PLACEHOLDER"

export PATH_TO_TOMCAT_LOGS="PLACEHOLDER"
```

## Debug

### Check if Apache is running
```shell
systemctl status apache2
```

### Check if the Apache server is listening on the correct port
```shell
netstat -tulpen | grep ${APACHE_PORT_NUMBER}
```

### Check if the Mod_JK module is loaded in Apache
```shell
apachectl -M | grep mod_jk
```

### Check the Mod_JK configuration file for errors
```shell
apachectl configtest
```

### Check if the workers.properties file is correctly configured
```shell
cat ${PATH_TO_WORKERS_PROPERTIES} | grep worker.${WORKER_NAME}
```

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

### Check if the Tomcat server is listening on the correct port
```shell
netstat -tulpen | grep ${TOMCAT_PORT_NUMBER}
```

### Check the Tomcat server logs for errors
```shell
tail -f ${PATH_TO_TOMCAT_LOGS}
```

### Check if the firewall is blocking traffic to/from Apache or Tomcat
```shell
systemctl status firewalld
```

## Repair

### Restart the Apache server to see if that resolves the issue.
```shell


#!/bin/bash

sudo systemctl restart apache2

echo "Apache server has been restarted."


```

This incident type refers to failures with the Apache server's Mod\_JK Worker, which is a module used to connect Apache to applications running on Tomcat. When this module fails, it can lead to issues with serving web pages and accessing web applications. This incident requires investigation and resolution to restore the proper functioning of the Apache server.


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 usually occurs when there is a failure in the SSL Handshake process between a client and server running on a Tomcat web server. This can happen for various reasons such as incorrect SSL certificate configuration, cipher suite mismatches, or network connectivity issues. When this type of incident is not resolved quickly, it can lead to downtime or service disruptions for users trying to access the affected service.


Tomcat SSL Handshake Failure Incident

This incident type refers to a situation where the Tomcat server's JDBC connection pool usage surpasses its configured limits. This can lead to a shortage of available connections for incoming requests, resulting in slow response times or even server crashes. It is important to monitor and manage the JDBC connection pool usage to prevent such incidents from occurring.


Tomcat High JDBC Connection Pool Usage Incident.

This incident type refers to an increase in the number of errors per second on a Tomcat server, which could indicate an issue with the server itself, the host, a deployed application, or an application servlet. This could include errors generated when the Tomcat server runs out of memory, can't find a requested file or servlet, or is unable to serve a JSP due to syntax errors in the servlet codebase. This incident type requires immediate attention to diagnose and address the underlying issue.


Increase of the errors/second rate for Tomcat server

```shell
export APACHE_PORT_NUMBER="PLACEHOLDER"

export PATH_TO_WORKERS_PROPERTIES="PLACEHOLDER"

export WORKER_NAME="PLACEHOLDER"

export TOMCAT_PORT_NUMBER="PLACEHOLDER"

export PATH_TO_TOMCAT_LOGS="PLACEHOLDER"
```


### Check if Apache is running

```shell
systemctl status apache2
```

### Check if the Apache server is listening on the correct port

```shell
netstat -tulpen | grep ${APACHE_PORT_NUMBER}
```

### Check if the Mod\_JK module is loaded in Apache

```shell
apachectl -M | grep mod_jk
```

### Check the Mod\_JK configuration file for errors

```shell
apachectl configtest
```

### Check if the workers.properties file is correctly configured

```shell
cat ${PATH_TO_WORKERS_PROPERTIES} | grep worker.${WORKER_NAME}
```

### Check if the Tomcat server is running

```shell
systemctl status tomcat
```

### Check if the Tomcat server is listening on the correct port

```shell
netstat -tulpen | grep ${TOMCAT_PORT_NUMBER}
```

### Check the Tomcat server logs for errors

```shell
tail -f ${PATH_TO_TOMCAT_LOGS}
```

### Check if the firewall is blocking traffic to/from Apache or Tomcat

```shell
systemctl status firewalld
```


### Restart the Apache server to see if that resolves the issue.

```shell


#!/bin/bash

sudo systemctl restart apache2

echo "Apache server has been restarted."


```


Apache server Mod_JK Worker Failures.

Overview

Parameters

Debug

Check if Apache is running

Check if the Apache server is listening on the correct port

Check if the Mod_JK module is loaded in Apache

Check the Mod_JK configuration file for errors

Check if the workers.properties file is correctly configured

Check if the Tomcat server is running

Check if the Tomcat server is listening on the correct port

Check the Tomcat server logs for errors

Check if the firewall is blocking traffic to/from Apache or Tomcat

Repair

Restart the Apache server to see if that resolves the issue.

Learn more

Related Runbooks

Tomcat thread pool exhaustion.

Tomcat Server Crash

Tomcat SSL Handshake Failure Incident

Tomcat High JDBC Connection Pool Usage Incident.

Support