HTTP 504 timeout after exactly 120 seconds

Question

I have a server application which runs in the Amazon EC2 cloud. From my client (the browser) I make a HTTP request which uploads a file to the server which then processes the file. If there is a lot of processing (large file ), the server always times out with a 504 backend continuation error always exactly after 120 seconds. Though I get this error, the server continues to process the request and completes it (verified by checking the database) but I cannot see the final result on my client because of the timeout.

I am clueless as to why this is happening. Has anyone faced a similar 504 timeout ? Is there some intermediate proxy server not in my control which is timing out ?

Answer 1

I have a similar problem and in my case I believe it is due to the connection between the Elastic Load Balancer (ELB) and the EC2 instance.

For a long-term solution I will go with the 303 Status response + back-end processing suggested by james.garriss above.

For short-term solution it may be possible for Amazon support to increase the ELB timeout (see their response in https://forums.aws.amazon.com/thread.jspa?messageID=491594&#491594). Unfortunately there doesn't seem to be any way to change the timeout yourself through either API or console.

[Update] AWS now does allow you to update the idle timeout either through console, CLI or .ebextensions configuration. See http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/config-idle-timeout.html (thanks @Daniel Patz for the update)