Is ALB doing request buffering or not?

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I haven't found definite answer so far. I have gunicorn running inside private subnet behind ALB (AWS::ElasticLoadBalancingV2::LoadBalancer) and would like to know if I also need nginx for request buffering or not.

For example in this answer: https://repost.aws/questions/QU30xNhGZWRM6zzt1lD0Colw/web-service-buffer-and-read-quota-settings?sc_ichannel=ha&sc_ilang=en&sc_isite=repost&sc_iplace=hp&sc_icontent=QU30xNhGZWRM6zzt1lD0Colw&sc_ipos=9 they say to check if buffering is ON in ALB settings, but I don't see any settings related to buffering.

Does ALB do request buffering or not?

asked 10 months ago823 views
3 Answers
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No, there is no attribute in an Application Load Balancer(ALB) to enable buffering, it is not a feature that they talk about.

The only time we've had issues with request buffering was because nginx sat behind an ALB had buffering enabled, the ALB itself performed no such buffering.

https://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-target-groups.html#target-group-attributes

profile picture
answered 10 months ago
  • Ok, so you never had any problem with request buffering except the one case when you had Nginx behind ALB - then there was a problem?

  • Yes, we had an application that I think had a race condition, I just looked up the ticket (it was from 2017!) and it related to the application's expectation of not having chunked encoding, with request buffering enabled in nginx it got the request (POST data) all at once. In dev/vagrant, we used nginx as a proxy/loadbalancer. That nginx instance had request buffering enabled. In pre-production and production the application sat behind an ALB in AWS and got the chunked request and the code didn't handle it correctly.

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Hello, There are no clear sources that show ALB's request buffering capability and available configuration settings.

AWS
answered 10 months ago
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Hi - this discussion suggests that ALB does indeed buffer requests: https://github.com/benoitc/gunicorn/issues/2568

peteror
answered 5 months ago

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