fixes #1663 Request/Reply Protocol Throughput and Scalability

This eliminates the req protocols use of nni_timer (and setting
a single timer node per request.  This was problematic because it
devolves into O(n^2) as we wind up inserting timer nodes and having
to scan the list for the timer node.

The solution is to use a single scan - stop worrying about insertion,
but instead use a coarse granularity timer (defaults to 1 second)
for retries.  Then do the O(n) scan just once per interval.

A new option, NNG_OPT_REQ_RESENDTICK, can be used to change the tick
interval for cases (like unit tests) where more fine grained timing
is required.

1 files changed, 1 insertions, 0 deletions

diff --git a/include/nng/protocol/reqrep0/req.h b/include/nng/protocol/reqrep0/req.h
index 3ed80216..0c9fde3f 100644
--- a/include/nng/protocol/reqrep0/req.h
+++ b/include/nng/protocol/reqrep0/req.h
@@ -31,6 +31,7 @@ NNG_DECL int nng_req0_open_raw(nng_socket *);
 #define NNG_REQ0_PEER_NAME "rep"
 
 #define NNG_OPT_REQ_RESENDTIME "req:resend-time"
+#define NNG_OPT_REQ_RESENDTICK "req:resend-tick"
 
 #ifdef __cplusplus
 }