Load Balancer 504 Gateway Timeout | Resolved

Load Balancer 504 Gateway Timeout may impact our online experience. As part of our Server Management Service, Bobcares offer solutions to your server issues.

Load Balancer 504 Gateway Timeout

Load Balancer 504 Gateway Timeout is an HTTP error that indicates a connection was closed by the load balancer because a request did not finish within the idle timeout period. The possible reasons for this error include:

1. A target application takes more time than the default idle timeout to respond.
2. Elastic Load Balancing connection is cut off for registered instances.
3. The load balancer fails to establish a connection to the target before the connection timeout expired.
4. Traffic from the target to the load balancer nodes on the ephemeral ports was blocked by the network ACL for the subnet (1024-65535).
5. A Content-Length header value that is greater than the entity body is returned by the target. While it was awaiting the byte gaps, the load balancer ran out of time.
6. The target is an AWS Lambda function, and the Support team service was unavailable when the connection timed out.

How To Fix The Load Balancer 504 Gateway Timeout Error?

Our Support team provides some easy methods to fix this error.

Method 1: Examine the load balancer’s idle timeout and make any necessary adjustments.

If the backend instance didn’t respond to the request within the configured idle timeout period, it also results in the load balancer HTTP 504 error. The Application Load Balancer’s idle timeout is set by default to 60 seconds.

Modify the load balancer’s idle timeout so that the HTTP request finishes within the allotted time. Alternately, speed up the application’s response to the HTTP request. Verify that the application responds within the configured idle timeout.

Method 2: Confirm that the load balancer allows traffic with registered targets.

Verify that traffic from one another in both directions is permitted on the traffic and health check ports by the network security groups connected to the load balancer and the backend targets. Verify that the network ACL for the subnet allows traffic from the targets to the load balancer nodes on the ephemeral ports (1024-65535).

Method 3: Before the connection timeout expiring, ensure that the Lambda function responds.

Check the performance metric duration with max statistics to confirm how much time is spent processing an event if the target is a Lambda function.

Method 4: Enable keep-alive settings on the EC2 instances in case of Elastic load balancing.

If Registered instances closing the connection to Elastic Load Balancing leads to the error, then enable keep-alive settings on the EC2 instances and make sure that the keep-alive timeout is greater than the idle timeout settings of the load balancer.

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Conclusion

Load Balancer 504 Gateway Timeout is a common HTTP error that can degrade a user’s online experience. To summarize, our Support team offers a few quick fixes to the error to stop it.