I agree with Nir, it's not as simple as changing a structure to `[]URL`, it's a bigger architectural design question.
How do you plan to mark caches Unavailable if they're unhealthy on one interface, but healthy on another? Right now, Traffic Router needs a boolean for each cache, it doesn't know anything about multiple network interfaces, IPv4 vs IPv6, etc. It only knows the FQDN, which is all the clients it's giving DNS records to will know when they request the cache. Questions: Is a cache marked Unavailable when any interface is unreachable? Or all of them? What if an interface is reachable, but one interface reports different stats than another interface? For example, what if someone configures a different caching proxy (ATS) on each interface? How are stats aggregated? Should the monitor aggregate all stats from different polls and interfaces together, and consider them the same "server"? If not, how do we reconcile the different stats with what the Monitor reports on `CrStates` and `CacheStats`? If so, again, what happens if different interfaces have different ATS instances, so e.g. the byte count on one is 100, and the other is 1000, then 101, then 1001. It simply won't work. Do we handle that? Or just ignore it, and document "all interfaces must report the same stats"? Do we try to detect that and give a useful error or warning? In Traffic Ops, servers have specific data used for polling. Traffic Monitor gets the stats URI path from Parameters, and the URI IP from the Servers table. It doesn't use the FQDN, Server Host or Server Domain. Where would these other interfaces come from? Parameters? Or another table linked to the servers table? (I'd really, really rather we didn't put more data in unsafe Parameters, which can not exist, not be properly formatted, need safety checks in all code that ever uses them, and are confusing and opaque to new users) Would these other interfaces be in addition to using the IP from the Server table? Or replace it? Do we have config options for all of these? Only some of them? In the config file, or Traffic Ops fields? I'd like to hear the use case too, and e.g. why it isn't better to simply make each different interface a different server in Traffic Ops? How is the Traffic Router routing to them, anyway? Are you setting up the same DNS record to point to the IPs of all interfaces? How is that configured in Traffic Ops then? I.e. which interfaces are configured as the Server IP and IP6? Are we certain there aren't other issues in other Traffic Control components, with a Server IP and IP6 not having a one-to-one relationship with the FQDN A/AAAA record? Do we need to take the bigger step, of having a Traffic Ops Server have an array of IPs? That's a lot more work (especially making sure it works everywhere, e.g. Traffic Router), but it solves a lot of questions and hackery, gives us a lot more flexibility, and matches the physical reality better. I'm not opposed to the idea, but we need to think through the architecture, we need to be sure the added complexity is worth it over existing solutions, we need to make all the options (e.g. Unavailable if any vs all) configurable, and we need to make sure the common simple case of a single Server IP and IP6 still work without additional configuration complexity. On Wed, Mar 28, 2018 at 10:19 AM, Nir Sopher <n...@qwilt.com> wrote: > Hi Eric/Neil, > Isn't the question of supporting multi interfaces per server a much wider > question? Architectural wise. > What would be the desired behavior if the monitoring shows that only one of > the interfaces is down? Will the router send traffic to the healthy > interfaces? How? > Nir > > On Wed, Mar 28, 2018, 19:10 Eric Friedrich (efriedri) <efrie...@cisco.com> > wrote: > > > The use case behind this question probably deserves a longer dev@ email. > > > > I will oversimplify: we are extending TC to support multiple IPv4 (or > > multiple IPv6) addresses per edge cache (across 1 or more NICs). > > > > Assume all addresses are reachable from the TM. > > > > —Eric > > > > > > > On Mar 28, 2018, at 11:37 AM, Robert Butts <robert.o.bu...@gmail.com> > > wrote: > > > > > > When you say different interfaces, do you mean IPv4 versus IPv6? Or > > > something else? > > > > > > If you mean IPv4 vs IPv6, we have a PR for that from Dylan Volz > > > https://github.com/apache/incubator-trafficcontrol/pull/1627 > > > > > > I'm hoping to get to it early next week, just haven't found the time to > > > review and test it yet. > > > > > > Or did you mean something else by "interface"? Linux network > interfaces? > > > Ports? > > > > > > > > > On Wed, Mar 28, 2018 at 12:02 AM, Neil Hao (nbaoping) < > > nbaop...@cisco.com> > > > wrote: > > > > > >> Hi, > > >> > > >> Currently, we poll exact one URL request to each cache server for one > > >> interface, but now we’d like to add multiple interfaces support, > > therefore, > > >> we need multiple requests to query each interface of the cache > server, I > > >> check the code of Traffic Monitor, it seems we don’t support this kind > > of > > >> polling, right? > > >> > > >> I figure out different ways to support this: > > >> 1) The first way: change the ‘Urls’ field in the HttpPollerConfig from > > >> ‘map[string]PollConfig’ to ‘map[string][]PollConfig’, so that we can > > have > > >> multiple polling config to query the multiple interfaces info. > > >> > > >> 2) The second way: Change the ‘URL’ field in the PollConfig from > > ‘string’ > > >> to ‘[]string’. > > >> > > >> No matter which way, it seems it will bring a little big change to the > > >> current polling model. I’m not sure if I’m on the right direction, > would > > >> you guys have suggestions for this? > > >> > > >> Thanks, > > >> Neil > > >> > > > > >
