117 - Service Unavailable
Episode description
In todays podcast we are going to talk about the 503 HTTP Status Code.
Error 503 = Service Unavailable
From the W3C: The server is currently unable to handle the request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay. If known, the length of the delay MAY be indicated in a Retry-After header. If no Retry-After is given, the client SHOULD handle the response as it would for a 500 response.
Causes
- DDOS attacks will result in high resource usage which will eventually overload the server. As a result the server will respond with a 503 error code.
- A server might be temporarily un available if it is under going maintenance. Its a server issue and not a client issue. So this wouldn’t be an issue with the HTML or CSS or client sided JavaScript Trouble shooting
- Check any monitoring dashboards or graphs for resource hungry trends. - Check the logs to find any server related errors.
- Check the logs for access requests to see if its a spike in traffic.
- Check if the server is going through an unexpected maintenance
- Check for firewall config. Perhaps a firewall on the network is preventing traffic from flowing.
- Check for long running scripts that could be causing memory leaks.
- Check for disk usage. Perhaps you are running out of swap space if that’s configured.
Solutions
- Stop any jobs that are running
- Divert traffic using a load balancer to another server -
- Scale your application horizontally by bring on other servers/containers to handle the traffic
- Have an auto scaler which keeps adding or removing servers/containers when needed - Reboot the server/container
Resources:
https://thevaluable.dev/dry-principle-cost-benefit-example/
https://metova.com/dry-programming-practices/
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