Q: Issues in monitoring apache tomcat server using Monit I have installed Monit using the following command in Ubuntu Linux 12.04.1 server
sudo apt-get install monit

My main goal in using Monit is to restart my - MySQL and Apache tomcat services automatically when they are killed/stopped.
#Check and restart mysql service
check process mysqld with pidfile "/run/mysqld/mysqld.pid"
group database
start program = "/etc/init.d/mysql start"
stop program = "/etc/init.d/mysql stop"
if failed host 127.0.0.1 port 3306 protocol mysql then restart
if 5 restarts within 5 cycles then timeout

The above code works perfectly and Monit restarts MySQL service (when its killed/stopped).
I have actually configured tomcat as follows: 
- Downloaded the tomcat zip and extracted to a particular location
- Configured this as my daemon service (and my tomcat server works properly).
As I don't have pid file for this tomcat setup, I am planning to check tomcat's status and start it using the following code:
#Check and restart tomcat service
check host tomcat with address 127.0.0.1
stop program = "/etc/init.d/tomcat stop"
start program = "/etc/init.d/tomcat start"
if failed port 8080 and protocol http
then start

However, I was unable to start tomcat successfully (when its killed). On investigating the Monit logs I found the following message:
[UTC Dec 24 12:08:23] error    : 'tomcat' failed, cannot open a connection to INET[127.0.0.1:8080] via TCP
[UTC Dec 24 12:08:23] info     : 'tomcat' start: /etc/init.d/tomcat

Through above logs, I found Monit is trying to start tomcat automatically for every particular time (when it finds tomcat service was killed). However, some inner conflicts stops this!
Other Information:
Tomcat server is properly running by using the port 8080:
netstat -an | grep 8080
tcp6       0      0 :::8080                 :::*                    LISTEN     
tcp6       0      0 127.0.0.1:8080          127.0.0.1:53582         TIME_WAIT  


ps -ef|grep tomcat
root     16237     1  9 12:10 ?        00:00:37 /usr/lib/jvm/java-6-oracle/bin/java -Djava.util.logging.config.file=/usr/share/apache-tomcat-7.0.40/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.awt.headless=true -Dfile.encoding=UTF-8 -server -Xms1024m -Xmx1530m -XX:NewSize=512m -XX:MaxNewSize=1024m -XX:PermSize=512m -XX:MaxPermSize=1024m -Djava.endorsed.dirs=/usr/share/apache-tomcat-7.0.40/endorsed -classpath /usr/share/apache-tomcat-7.0.40/bin/bootstrap.jar:/usr/share/apache-tomcat-7.0.40/bin/tomcat-juli.jar -Dcatalina.base=/usr/share/apache-tomcat-7.0.40 -Dcatalina.home=/usr/share/apache-tomcat-7.0.40 -Djava.io.tmpdir=/usr/share/apache-tomcat-7.0.40/temp org.apache.catalina.startup.Bootstrap start
root     16851 16847  0 12:17 ?        00:00:00 sh -c su root -c ps\ \-ef\|grep\ tomcat 2>&1 2>/dev/null
root     16852 16851  0 12:17 ?        00:00:00 su root -c ps -ef|grep tomcat
root     16853 16852  0 12:17 ?        00:00:00 bash -c ps -ef|grep tomcat
root     16855 16853  0 12:17 ?        00:00:00 grep tomcat

Adding preferIPv4Addresses and preferIPv4Stack in catalina.sh file:
JAVA_OPTS="-Djava.awt.headless=true -Dfile.encoding=UTF-8 -server -Xms1024m -Xmx1530m
-XX:NewSize=512m -XX:MaxNewSize=1024m -XX:PermSize=512m -XX:MaxPermSize=1024m -Djava.net.preferIPv4Stack=true -Djava.net.preferIPv4Addresses=true"

Monit log:
[UTC Dec 24 12:48:39] error    : 'tomcat' failed protocol test [HTTP] at INET[127.0.0.1:8080] via TCP -- HTTP: Error receiving data -- Resource temporarily unavailable

Can anyone please guide me on this?
Thank You.

A: Seems that Tomcat binds itself to an ipv6 address for 127.0.0.1.
You can try to use preferIPv4Stack=true and preferIPv4Addresses=true directives in Java options to bind to an ipv4 address
Edit catalina.sh Tomcat startup script and add the following :
JAVA_OPTS="$JAVA_OPTS -Djava.net.preferIPv4Stack=true -Djava.net.preferIPv4Addresses=true"

