pub const SUBSCRIBE_TURNS: u32 = 20;Expand description
How many of a conversation’s newest turns a subscribe carries.
A subscribe is not a request for a whole transcript. A client draws a
window and asks more for what is above it, so handing it the whole
conversation is a transcript’s worth of bytes written per client per
connect and per refresh - measured at 111.7 MB of socket for four
refreshes of a 68.9 MB transcript, which is 99% of that connection’s
traffic - for turns it will not draw.
The window matches the client’s own SUBSCRIBE_TURNS (20), which its seat
record trims to, and the MORE_TURNS page a client asks for: the newest
page a subscribe carries and the newest page a client asks for are the same
page, so a client that asks anyway is handed what it already holds, which it
drops by turn key.
It is a ceiling, not the page. [server] first_frame_cap_kb holds the
same page to its bytes (see page_within), so a conversation whose
turns are large carries fewer than this.