Send “Connection” headers only when keepAlive == false

[fabianfett]

Motivation

• after some investigation I discovered that the lambda control plane, does not expect a request header "Connection" = "keep-alive" and does not send a response header "Connection" = "keep-alive"
• http/1.1 specifies in RFC 2616, Section 8.1.2:

[...] unless otherwise indicated, the client SHOULD assume that the server will maintain a persistent connection, even after error responses from the server.

Further, for the response it defines:

An HTTP/1.1 client MAY expect a connection to remain open, but would decide to keep it open based on whether the response from a server contains a Connection header with the connection-token close. In case the client does not want to maintain a connection for more than that request, it SHOULD send a Connection header including the connection-token close.

• since we have been expecting "Connection" = "keep-alive" in the response until now, we where tearing down our connection after every request

Changes

• We only send the "Connection" = "close" header if we don't want to keep the connection alive.
• The MockServer does send the "Connection" = "close" header only if it want's to close the connection
• We check if the response is HTTP/1.1 to close the connection otherwise.

[fabianfett]

This fixes: #25.

[fabianfett]

Performance

It looks like we are saving an average of 50ms with this improvement.

master:

connection-pooling:

Taking this into account we're currently only outperformed by Go and C#.

[tomerd]

wonderful great catch