Bdtjtk

I have a DO loadbalancer setup in front of a MySQL Group Replication setup. What I need to do is create a health check for the loadbalancer via an http request.

What I've come up with so far is to create a bash script (code below) that basically checks if MySQL is up and running and then run this via xinetd on port 9201.

However, when I curl to http://ip:port from another server it never reads any output from my bash file and just connection reset by peer (after connecting and timing out).

I'm very new to all this, so I'm not sure if what I'm doing is even correct in the slightest.

service mysqlchk

{ 

        flags           = REUSE

        socket_type     = stream

        protocol        = tcp

        port            = 9201

        wait            = no

        user            = root

        server          = /opt/mysqlchk.sh

        disable         = no

        log_type        = FILE /var/log/xinetd.log

        log_on_success  = DURATION EXIT HOST PID USERID

        log_on_failure  = ATTEMPT HOST USERID

        only_from       = 0.0.0.0/0

}

Bash (Found online)

MYSQL_HOST="ip"

MYSQL_PORT="3306"

MYSQL_USERNAME="user"

MYSQL_PASSWORD="=password"



#

# We perform a simple query that should return a few results :-p



ERROR_MSG=`/usr/bin/mysql --host=$MYSQL_HOST --port=$MYSQL_PORT -- 

user=$MYSQL_USERNAME --password=$MYSQL_PASSWORD -e "show databases;" 

2>/dev/null`



#

# Check the output. If it is not empty then everything is fine and we 

return

# something. Else, we just do not return anything.

#

if [ "$ERROR_MSG" != "" ]

then

        # mysql is fine, return http 200

        /bin/echo -e "HTTP/1.1 200 OKrn"

        /bin/echo -e "Content-Type: Content-Type: text/plainrn"

        /bin/echo -e "rn"

        /bin/echo -e "MySQL is running.rn"

        /bin/echo -e "rn"

else

        # mysql is not fine, return http 503

        /bin/echo -e  "HTTP/1.1 503 Service Unavailablern"

        /bin/echo -e "Content-Type: Content-Type: text/plainrn"

        /bin/echo -e "rn"

        /bin/echo -e "MySQL is *down*.rn"

        /bin/echo -e "rn"

fi

What's returned when I curl:

curl -v http://ip:9201/

*   Trying ip...

* TCP_NODELAY set

* Connected to ip (ip) port 9201 (#0)

> GET / HTTP/1.1

> Host: ip:9201

> User-Agent: curl/7.58.0

> Accept: */*

> 

* Recv failure: Connection reset by peer

* stopped the pause stream!

* Closing connection 0

curl: (56) Recv failure: Connection reset by peer

I'm not sure if the issue is because I'm just responding incorrectly to the request or?

EDIT: Running the bash script manually returns the right output based on if it can connect or not. I don't think there's a syntactical error in the bash itself, just the way it responds to an http request possibly.

xinetd listens for incoming requests over a network and launches the appropriate service for that request. Requests are made using port numbers as identifiers and xinetd usually launches another daemon to handle the request.

In you case, you are launching a script. Make sure it's executable, have the right permission and add the corresponding shebang

#! /bin/bash

Then try

telnet ip 9201