Haproxy LBR Troubleshooting Linux Server KodeKloud Engineer Task

Question :  xFusionCorp Industries has an application running on Nautlitus infrastructure in Stratos Datacenter. The monitoring tool recognised that there is an issue with the haproxy service on LBR server. That needs to fixed to make the application work properly.

Troubleshoot and fix the issue, and make sure haproxy service is running on Nautilus LBR server. 

Solution:  

1. At first login to one of the App server  &  Switch to  root user

thor@jump_host /$ ssh loki@stlb01 The authenticity of host 'stlb01 (172.16.238.14)' can't be established. ECDSA key fingerprint is SHA256:SySamszyWhhLGFiybhGBqfrr8g55wS/3e37ZpBOvICs. ECDSA key fingerprint is MD5:6d:31:18:2a:f9:07:f3:29:dd:0a:d3:1f:6e:04:0a:db. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added 'stlb01,172.16.238.14' (ECDSA) to the list of known hosts. loki@stlb01's password: [loki@stlb01 ~]$ sudo su - We trust you have received the usual lecture from the local System Administrator. It usually boils down to these three things:     #1) Respect the privacy of others.     #2) Think before you type.     #3) With great power comes great responsibility. [sudo] password for loki: [root@stlb01 ~]#

2.  Verify the status of haproxy service 

[root@stlb01 ~]# systemctl status haproxy ● haproxy.service - HAProxy Load Balancer    Loaded: loaded (/usr/lib/systemd/system/haproxy.service; disabled; vendor preset: disabled)    Active: inactive (dead)  Jul 06 07:21:47 stlb01.stratos.xfusioncorp.com systemd[1]: Collecting haproxy.service [root@stlb01 ~]#

4.  First validate the existing the haproxy config file using the below command     

[root@stlb01 ~]# haproxy -c -f /etc/haproxy/haproxy.cfg [ALERT] 186/072231 (109) : Proxy 'main': unable to find required default_backend: 'app'. [ALERT] 186/072231 (109) : Fatal errors found in configuration. [root@stlb01 ~]# root@stlb01 ~]# cat /etc/haproxy/haproxy.cfg |grep app # Example configuration for a possible web application.  See the     default_backend             app #backend app     server  app1 127.0.0.1:5001 check     server  app2 127.0.0.1:5002 check     server  app3 127.0.0.1:5003 check     server  app4 127.0.0.1:5004 check [root@stlb01 ~]#

5.  Correct the typo error in the file haproxy.cfg  

[root@stlb01 ~]# vi /etc/haproxy/haproxy.cfg [root@stlb01 ~]# cat /etc/haproxy/haproxy.cfg |grep app # Example configuration for a possible web application.  See the     default_backend             app backend app     server  app1 127.0.0.1:5001 check     server  app2 127.0.0.1:5002 check     server  app3 127.0.0.1:5003 check     server  app4 127.0.0.1:5004 check [root@stlb01 ~]#

6.   After changes  validate the existing the haproxy config file

    

[root@stlb01 ~]# haproxy -c -f /etc/haproxy/haproxy.cfg Configuration file is valid [root@stlb01 ~]#

7.  Start service &   Check service status

[root@stlb01 ~]# systemctl start haproxy [root@stlb01 ~]# systemctl status haproxy ● haproxy.service - HAProxy Load Balancer    Loaded: loaded (/usr/lib/systemd/system/haproxy.service; disabled; vendor preset: disabled)    Active: active (running) since Tue 2021-07-06 07:30:06 UTC; 8s ago  Main PID: 133 (haproxy-systemd)    CGroup: /docker/2217d113ad079d15fae356db49ef8ee02d60408c7010cd914998c9b770aca1a8/system.slice/haproxy.service            ├─133 /usr/sbin/haproxy-systemd-wrapper -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid            ├─134 /usr/sbin/haproxy -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid -Ds            └─135 /usr/sbin/haproxy -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid -Ds   Jul 06 07:30:06 stlb01.stratos.xfusioncorp.com systemd[1]: Enqueued job haproxy.service/start as 107 Jul 06 07:30:06 stlb01.stratos.xfusioncorp.com systemd[1]: About to execute: /usr/sbin/haproxy-systemd-wrapper -f /etc...IONS Jul 06 07:30:06 stlb01.stratos.xfusioncorp.com systemd[1]: Forked /usr/sbin/haproxy-systemd-wrapper as 133 Jul 06 07:30:06 stlb01.stratos.xfusioncorp.com systemd[1]: haproxy.service changed dead -> running Jul 06 07:30:06 stlb01.stratos.xfusioncorp.com systemd[1]: Job haproxy.service/start finished, result=done Jul 06 07:30:06 stlb01.stratos.xfusioncorp.com systemd[1]: Started HAProxy Load Balancer. Jul 06 07:30:06 stlb01.stratos.xfusioncorp.com systemd[133]: Executing: /usr/sbin/haproxy-systemd-wrapper -f /etc/hapr....pid Jul 06 07:30:06 stlb01.stratos.xfusioncorp.com haproxy-systemd-wrapper[133]: haproxy-systemd-wrapper: executing /usr/sbi...Ds Hint: Some lines were ellipsized, use -l to show in full. [root@stlb01 ~]#

8.  Click on Finish & Confirm to complete the task successful

Happy Learning!!!!

Apart from this if you need more clarity,  I have made a  tutorial video on this , please go through and share your comments. Like and share the knowledge