ELB Dropping Cors headers from Lambda

Question

Hi ,

We are using ELB infront of lambda function (API Gateway has been substituted by ELB due to API gateway timeout at 20 secs)  , We are setting specific CORS headers for browser preflight in lambda and when we hit this , we are still facing cors errors , and we see ELB is dropping the CORS headers sent by lambda.

we are only getting back date and Server - awselb2.0 headers back from ELB

Any help would be appreciated

Daniel ABIB · Answer

I did manage to get everything working.

All the CORS configuration values default to being locked down. During testing to try and open everything up, I had tried * for all the values, but did not set the Max age configuration value (which defaults to blank). A blank max age by the spec should be equivalent to a 0 value, but that doesn't seem to be the case.

With all setting properly filled out to the origins, methods, and headers that I am using AND Max age set to 0 everything started behaving itself.

ELB Dropping Cors headers from Lambda

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