Troubleshooting the 503 Error

C.

In this scenario, a retail company's online shopping platform runs on Oracle Cloud Infrastructure (OCI), and it is a 3-tier web application that includes a Load Balancer, Virtual Machine Instances for web and application tiers, and an Oracle DB Systems Virtual Machine. Due to unprecedented growth, the company noticed an increase in incoming traffic to their website, and users start getting 503 (Service Unavailable) errors.

The potential problem in this scenario can be identified by analyzing each answer option:

A. You did not configure a Service Gateway to allow connection between web servers and Load Balancer. This answer is unlikely to be the problem because Service Gateways are typically used to connect resources in a VCN to services outside the VCN.

B. The Traffic Management Policy is not set to Load Balancer the traffic to the web servers. This answer is also unlikely to be the problem because the Load Balancer is part of the architecture and should be routing traffic to the web servers.

C. The Load Balancer health check status indicates a critical situation for half of the backend web servers. This answer is the most likely problem in this scenario. If half of the backend web servers are down or not responding to the Load Balancer health check, then the Load Balancer may not be able to distribute the incoming traffic effectively. This could cause the Load Balancer to overload the remaining healthy web servers, resulting in 503 (Service Unavailable) errors for users.

D. The Database is down, and users cannot access the website. This answer is unlikely to be the problem because the database is not directly involved in handling incoming traffic or serving web pages to users. However, if the web servers are unable to access the database, this could contribute to the issue.

E. All the web servers are too busy and not able to answer any request from users. This answer is also a possible problem, but it is less likely than answer C. If all the web servers are too busy, then the Load Balancer may not be able to distribute the incoming traffic effectively, resulting in 503 (Service Unavailable) errors for users.

In conclusion, the potential problem in this scenario is that the Load Balancer health check status indicates a critical situation for half of the backend web servers. The Load Balancer may not be able to distribute the incoming traffic effectively, causing the Load Balancer to overload the remaining healthy web servers and resulting in 503 (Service Unavailable) errors for users.