HTTP Load Balancer - client_disconnected_before_any_response

[Bilal Haidar]

Hello,

My app is hosted on App Engine. After a while, I started seeing logs under the Cloud HTTP Load Balancer with status of:

statusDetails: "client_disconnected_before_any_response"

@type: "type.googleapis.com/google.cloud.loadbalancing.type.LoadBalancerLogEntry"

A few of these errors, then my app started responding with 502 as follows:

@type: "type.googleapis.com/google.cloud.loadbalancing.type.LoadBalancerLogEntry"

statusDetails: "failed_to_pick_backend"

Any idea what this might be happening?

Thanks

Bill

[Sergi (Google Cloud Platform Support)]

Hello Bill,

The error “client_disconnected_before_any_response” means that the client closed the connection before the LB was able to provide a response, and the error "failed_to_pick_backend" means that to handle the request, the Load Balancer (LB) couldn’t pick a healthy backend [1].

One of the reasons for these errors could be because of the TCP session timeout value on your web server software. This value is fixed to 600 seconds on your backend and it is not configurable. You could try to change this value on your web server software by assigning a value greater than 600 seconds. In this documentation you can find more information about this and also a table with the recommended settings [2].

[1] https://cloud.google.com/load-balancing/docs/https/https-logging-monitoring#statusdetail_http_failure_messages

[2] https://cloud.google.com/load-balancing/docs/https/#timeouts_and_retries