Wrong definition of keepAliveMsecs in http.Agent documentation

[calibr]

Documentation for keepAliveMsecs says:

 When using HTTP KeepAlive,
 how often to send TCP KeepAlive packets over sockets being kept alive.

But internally http.Agent just uses keepAliveMsecs in socket.setKeepAlive(true, self.keepAliveMsecs); (https://github.com/nodejs/node/blob/master/lib/_http_agent.js#L73)

From docs for socket.setKeepAlive([enable][, initialDelay]):

Set initialDelay (in milliseconds) to set the delay between
the last data packet received and the first keepalive probe.

So really keepAliveMsecs doesn't mean how often keep alive probe will be sent, it means delay between the last data received and the first keep alive probe.

[jasnell]

@nodejs/http @nodejs/documentation

[dougwilson]

This is correct, in that the HTTP client documentation is not correct, as the time is only the initial delay of the keep alive probe, not the interval between the probes. nodejs/node-v0.x-archive#4109 has a good discussion about this, though all Node.js documentation (and even the libuv documentation) are very terse on this subject and not very clear :)

[calibr]

doc fixed by 3b9e8ad