Pre-sul, checking for interval to next pending scheduled event was expensive and
iterative, so the service avoided it if the wait was already 0.
With sul though, the internal "check" function also services ripe events and
removes them, and finding the interval to the next one is really cheap.
Rename the "check" function to __lws_sul_service_ripe() to make it clear it's
not just about returning the interval to the next pending one. And call it
regardless of if we already decided we are not going to wait in the poll.
After https://github.com/warmcat/libwebsockets/pull/1745
There's no longer any reason to come out of sleep for periodic service
which has been eliminated by lws_sul.
With event libs, there is no opportunity to do it anyway since their
event loop is atomic and makes callbacks and sleeps until it is stopped.
But some users are relying on the old poll() service loop as
glue that's difficult to replace. So for now help that happen by
accepting the timeout_ms of -1 as meaning sample poll and service
what's there without any wait.
Remove LWS_LATENCY.
Add the option LWS_WITH_DETAILED_LATENCY, allowing lws to collect very detailed
information on every read and write, and allow the user code to provide
a callback to process events.
This adds the option to have lws do its own dns resolution on
the event loop, without blocking. Existing implementations get
the name resolution done by the libc, which is blocking. In
the case you are opening client connections but need to carefully
manage latency, another connection opening and doing the name
resolution becomes a big problem.
Currently it supports
- ipv4 / A records
- ipv6 / AAAA records
- ipv4-over-ipv6 ::ffff:1.2.3.4 A record promotion for ipv6
- only one server supported over UDP :53
- nameserver discovery on linux, windows, freertos
It also has some nice advantages
- lws-style paranoid response parsing
- random unique tid generation to increase difficulty of poisoning
- it's really integrated with the lws event loop, it does not spawn
threads or use the libc resolver, and of course no blocking at all
- platform-specific server address capturing (from /etc/resolv.conf
on linux, windows apis on windows)
- it has LRU caching
- piggybacking (multiple requests before the first completes go on
a list on the first request, not spawn multiple requests)
- observes TTL in cache
- TTL and timeout use lws_sul timers on the event loop
- ipv6 pieces only built if cmake LWS_IPV6 enabled
