Connection hangs/does not timeout after 350 seconds.

[mittalsuraj18]

Discussed in https://github.com/encode/httpx/discussions/2968

^{Originally posted by **mittalsuraj18** December 1, 2023} When an application is running on an AWS VPC and using NAT gateway to communicate, there is a specific behavior in NAT gateway which is described here https://docs.aws.amazon.com/vpc/latest/userguide/nat-gateway-troubleshooting.html as such ``` Internet connection drops after 350 seconds Problem Your instances can access the internet, but the connection drops after 350 seconds. Cause If a connection that's using a NAT gateway is idle for 350 seconds or more, the connection times out. When a connection times out, a NAT gateway returns an RST packet to any resources behind the NAT gateway that attempt to continue the connection (it does not send a FIN packet). Solution To prevent the connection from being dropped, you can initiate more traffic over the connection. Alternatively, you can enable TCP keepalive on the instance with a value less than 350 seconds. ``` For example, if i have a single connection. and do something like, ``` client = AsyncClient(base_url=BASE_URL, http2=True) _ = await client.get("/", timeout=1200) ``` The connection does not respond to RST packet. And times out after 1200 seconds instead of 350 seconds. The behavior should have been either of the following 1. Timeout at 350 seconds 2. Periodically send keepalive packet to make sure NAT gateway does not timeout. How i currently have solved it is by doing a periodic call every 60 seconds, which just calls a healtcheck endpoint of the same baseurl, to use the same connection.

[tomchristie]

Closing in favor of the discussion, we can escalate if neccessary.