Most often, to avoid the HTTP 504 error in CloudFront we set a higher CloudFront timeout value for the distribution.

Here, at Bobcares, we assist our customers with several AWS queries as part of our AWS Support Services.

Today, let us see how our Support Techs fix this error.

HTTP 504 error in CloudFront

Server timeouts are often the result of either an application taking a very long time to respond or a timeout value that is set too low.

However, before we set a higher CloudFront timeout value we need to address any performance and latency issues with the application and origin server.

Now, let us see the steps our Support Techs take to find performance issues and correct them:

• Measure typical and high-load latency

Initially, we need to verify if one or more backend web application servers are experiencing high latency.

To check, we run this command on each server:

curl -w "Connect time: %{time_connect} Time to first byte: %{time_starttransfer} Total time: %{time_total} \n" -o /dev/null https://www.example.com/yourobject Note

In addition, our Support Techs suggest keeping in mind the following:

1) Though these values are relative to each application, a Time to First Byte in milliseconds rather than seconds or more is reasonable.

2) Even if the application latency under normal load is fine, viewers might still experience timeouts under high load.

To help prevent high-load latency issues, we check the server’s resources.

We run the following Linux command to check the memory Apache processes use:

watch -n 1 "echo -n 'Apache Processes: ' && ps -C apache2 --no-headers | wc -l && free -m"

3) High CPU utilization on the server can significantly reduce an application’s performance.

4) Other potential issues include database queries that run slowly when there’s a high volume of requests.

• Add resources, and tune servers and databases

Once done, we need to ensure that we have sufficient resources in place for typical traffic and high load situations.

1) In the case of own server, it should have enough CPU, memory, and disk space to handle viewer requests.

2) On the other hand, if we have an Amazon EC2 instance as the backend server, the instance type should have appropriate resources to fulfill incoming requests.

In addition, our Support Techs recommend the following steps to avoid timeouts:

1. Suppose, the Time to First Byte value is high. Then we need to take steps to improve the performance of the application.

2. We have to tune database queries so that they can handle high request volumes without slow performance.

3. Also, we need to set up keep-alive (persistent) connections on the backend server.

• If needed, adjust the CloudFront timeout value

Say, we evaluate and address slow application performance, origin server capacity, and other issues, but viewers are still experiencing HTTP 504 errors.

Then we should change the time specified in the distribution for origin response timeout.

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Conclusion

In short, we saw the steps our Support Techs employ in order to fix the HTTP 504 error in CloudFront.