Many of us have come across the error “503 service unavailable” while working with web servers. It simply says the server is unable to serve the HTTP request given at the time. There can be numerous reasons for 503 status code. Let’s discuss some possibilities, and see what are the possible tweaks we can do to fix it.
1. Server is overloaded
This is the first possibility of the status code 503. You can check the server load using top command in a SSH prompt, and see what if there is any high load on the server (and if so, what process is causing it). The performance of the server depends on many factors like resources, firewall, CMS setup etc.
If you utilize a reliable shared hosting service such as RackNerd’s Shared Hosting solutions, you do not need to worry about maintaining the server load as this is fully managed and optimized in real time by our expert staff.
2. Server is down
It can be said like server is down for maintenance or a related reason. Ensure the server is online and reachable via ping and SSH. If it is up, then you will need to troubleshoot further. Otherwise, contact the hosting provider for assistance.
If you are utilizing an unmanaged server, as a first measure, you can try rebooting the server (if your provider provides you with power controls to your server).
3. Improper firewall setup
The firewall is a crucial part of the web server security and it can’t be ignored at any point. This is basically used to allow genuine traffic getting in and block the malicious traffic, DDoS attacks, etc. However, there can be false positive block if it’s not properly configured. To check if firewall is causing the issue, you will need to temporarily disable the firewall and check the website.
4. Application errors
Websites can be made of different applications like WordPress, Magento, Joomla, PHP etc. Application misconfiguration can trigger such errors as well. Check the application logs and see if there is anything that stands out.
5. Resource outage
It’s common to show 503 service unavailable if the domain’s PHP memory settings (resources defined) has exceeded its limit. If this is the case, try raising the respective values within your php.ini configuration.
In short, there are various reasons behind 503 service temporary unavailable. Not one explanation can cover it all, and the possibilities can greatly vary (and sometimes, it can even be a mix of various items). As a systems administrator, you will need throughly look into each one of it and troubleshoot then fix it permanently. Remember, the status code 503 says the server host itself is up, but web server software is unable to handle the request.
If you do not want to worry about managing these kinds of issues, you can consider using a hosting provider like RackNerd who offers shared hosting services and managed services. Check out our server hosting solutions below, and feel free to contact us if you have any questions.