HTTP with TCP keep alive?

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I'm writing a HTTP/1.1 client in (asyncio) Python, and wondering if sockets should be created with the SO_KEEPALIVE option

import socket

sock = socket.socket(family=socket.AF_INET, type=socket.SOCK_STREAM, proto=socket.IPPROTO_TCP)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)

Should it always be enabled or disabled? Are there certain situations where it is better to enable it or not? Are there tradeoffs to be made? It the answer different if it's HTTPS?

I am specifically thinking in reference to connections used for more than one HTTP request (i.e. using HTTP Keep-Alive).

1 Answers

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Steffen Ullrich On Best Solutions

TCP keep-alive is used to detect a loss of connectivity for TCP connection which are idle (i.e. no data transfer) for a longer duration. HTTP/1 usually does not fit this use case and thus it makes not much sense to have TCP keep-alive active. But it also does no harm. In fact, it likely makes no difference at all what shows up on the wire.

In HTTP/1 the client sends a request which more or less immediately is followed by a response from the server. And if HTTP keep-alive is active then another request might follow which again results in a response. The duration between these requests is usually short, i.e. it is not common to keep an idle connection open for long. It is also expected that client and server can close the connection at any time after the request-response was done and that they must also be able to handle such connection close from the peer. Thus it is likely that the connection either got closed or that new data got transferred before the TCP keep-alive timer could trigger the delivery of the empty keep-alive packet.