On 8/10/22 19:54, Mark Michelson wrote: > Hi Dumitru, > Hi Mark,
> I read the patch series, and I think the idea of chassis-specific > variables is a good idea to reduce the number of DB records for certain > things. Aside from load balancers, I suspect this could have a positive > impact for other structures as well. > Thanks for taking a look! Yes, I think this might be applicable to other structures too. > Rather than criticizing the individual lines of code, I'll focus instead > on some higher-level questions/ideas. > Sure, thanks! :) > First, one question I had was what happens when a template variable name > is used in a load balancer, but there is no appropriate value to > substitute? For instance, what if a load balancer applies to chassis-3, > but you only have template variables for chassis-1 and chassis-2? This > might be addressed in the code but I didn't notice if it was. > There are actually two things to consider here: 1. there might be a logical flow that uses a template variable: in this case if template expansion/instantiation fails we currently leave the token untouched (e.g., '^variable' stays '^variable'). That will cause the flow action/match parsing to fail and currently logs a warning. The flow itself is skipped, as it should be. We probably need to avoid logging a warning though. 2. like you pointed out, there might be a load balancer using templates in its backends/vips: if some of those templates cannot be instantiated locally the backend/vip where they're added is skipped. Unless I missed something, the code should already do that. > Second, it seems like template variables are a natural extension of > existing concepts like address sets and port groups. In those cases, > they were an unconditional collection of IP addresses or ports. For You're right to some extent template variables are similar to port groups. The southbound database port group table splits the northbound port group per datapath though not per chassis like template variables. > template variables, they're a collection of untyped values with the > condition of only applying on certain Chassis. I wonder if this could > all be reconciled with a single table that uses untyped values with > user-specified conditions. Right now template variables have a "Chassis" > column, but maybe this could be replaced with a broader "condition", > "when", or "match" column. To get something integrated quickly, this > column could just accept the syntax of "chassis.name == <blah>" or > "chassis.uuid == <blah>" to allow for chassis-specific application of > the values. With this foundation, we could eventually allow > unconditional application of the value, or more complex conditions (e.g. > only apply to logical switch ports that are connected to a router with a > distributed gateway port). Doing this, we could deprecate address sets > and port groups eventually in favor of template variables. This sounds like a good idea to me. I wasn't too happy with the "chassis" string column of the Template_Var table anyway. A generic condition field makes more sense. Regarding deprecating and replacing address sets and port groups, I'm not sure how easy that would be but we can try it when we get to that point. > > Third, I was wondering if there could be some layer that exists between > the IDL and the application that expands the template variables as early > as possible. I'm thinking the application could inject some callback in > the IDL layer that might allow for the values to be substituted. This > way, the variable substitution is taken care of in a single place, and > by the time the application gets the data, it knows that all > substitutions have been made and there is no need to special case > template variable names vs. plain tokens. They should all be plain > tokens. I don't think construction of such a layer should be a barrier > to merging the code, but it's something worth considering as a later > improvement. This could work. I'll think more about it. But like you said, it's probably a longer term goal. It will need some significant changes in the IDL layer (e.g., to re-evaluate some records when template instantiations change). > > Anyway, those were my high-level thoughts on the topic. Let me know what > you think. > I can work on changing the Template_Var schema to add a broader way of specifying conditions (when/match/etc). I'm already working on adding proper nbctl support for templated load balancers and trying to tackle the rest of the todos. I can probably send a v1 sometime in the first half of next week. Do you want to share any specific code related comments that I should already integrate or shall we start a proper review when v1 gets posted? Thanks again for your input on this RFC! Regards, Dumitru > On 8/5/22 12:26, Dumitru Ceara wrote: >> Sometimes network components are compute node-specific. Sometimes such >> components are replicated, almost identically, for multiple nodes >> in the cluster. >> >> One such example is the case of Kubernetes NodePort services which >> translate (in the ovn-kubernetes case) to Load_Balancer >> objects being applied to each and every node's logical gateway router. >> These load balancers are almost identical, the main difference being >> the fact that they use different VIPs (the node's IP). >> >> With the current OVN load balancer design, this becomes a problem at >> scale because the number of load balancers that must be configured is >> N x M (N nodes times M services). >> >> This series proposes a new concept in OVN: virtual network component >> templates. The goal of the templates is to help reduce resource >> consumption in the OVN central components in specific cases like the one >> described above. >> >> To achieve that, the CMS will instead configure a "templated" load >> balancer for every service and apply that single template record to >> the cluster-wide load balancer group. This template is then >> instantiated differently on different compute nodes. This translation >> is controlled through per-chassis "template variables" configured by >> the CMS in the new NB.Template_Var table. >> >> A syntetic benchmark simulating what an OpenShift router (using Node >> Port services) scale test would do shows the following preliminary >> results: >> A. 120 node, 2K NodePort services: >> - before: >> - Southbound DB size on disk (compacted): ~385MB >> - Southbound DB memory usage (RSS): ~3GB >> - Southbound DB logical flows: 720K >> >> - after: >> - Southbound DB size on disk (compacted): ~100MB >> - Southbound DB memory usage (RSS): ~250MB >> - Southbound DB logical flows: 6K >> >> B. 250 node, 2K NodePort services: >> - after (didn't run the "before" test as it was taking way too long): >> - Southbound DB size on disk (compacted): ~155MB >> - Southbound DB memory usage (RSS): ~760MB >> - Southbound DB logical flows: 6K >> >> The series is sent as RFC because there's still the need to add >> some template specific unit tests and the "ovn-nbctl lb-*" helper >> utilities need to be adapted to support templated load balancers. >> >> With these two items addressed the code is self can likely qualify >> for acceptance as a new feature in the upcoming release. >> >> There also exists a more extensive TODO list (also listed in the commit >> log of every patch in the series for now) but these are mainly load >> balancer related functionalities that are not yet implemented for >> templated load balancers but can definitely be implemented as follow ups: >> - No support for LB health check if the LB is templated. >> - No support for VIP ARP responder if the LB is templated. >> - No support for routed VIPs if the LB is templated. >> - Figure out a way to deal with templates in ovn-trace >> - Determine if we need to allow Template_Var to match against chassis >> hostname or other IDs. >> - Make ofctrl_inject_pkt() work with template_vars. >> - Make test-ovn work with template_vars. >> >> A basic example of how to configure a templated load balancer follows: >> $ ovn-nbctl create load_balancer name=lb-test \ >> protocol=tcp options:template=true \ >> vips:\"^vip:4200\"="^backends" >> >> $ ovn-nbctl ls-add ls >> $ ovn-nbctl ls-lb-add ls lb-test >> >> # Instantiate the load balancer on chassis-1 >> $ ovn-nbctl create template_var name=vip value=80.80.80.1 >> chassis=chassis-1 >> $ ovn-nbctl create template_var name=backends >> value='"42.42.42.1:1000"' chassis=chassis-1 >> >> # Instantiate the load balancer on chassis-2 >> $ ovn-nbctl create template_var name=vip value=80.80.80.2 >> chassis=chassis-2 >> $ ovn-nbctl create template_var name=backends >> value='"42.42.42.2:1000"' chassis=chassis-2 >> >> Dumitru Ceara (5): >> Add NB and SB Template_Var tables. >> controller: Add support for templated actions and matches. >> controller: Make resource references more generic. >> lb: Support using templates. >> controller: Add Template_Var <- LB references. >> >> >> controller/lflow.c | 248 ++++++++++++++++++++++++-------- >> controller/lflow.h | 98 +++++++------ >> controller/ofctrl.c | 9 +- >> controller/ofctrl.h | 3 +- >> controller/ovn-controller.c | 277 ++++++++++++++++++++++++++++++++++-- >> include/ovn/expr.h | 4 +- >> include/ovn/lex.h | 14 +- >> lib/actions.c | 9 +- >> lib/expr.c | 14 +- >> lib/lb.c | 201 ++++++++++++++++++++++---- >> lib/lb.h | 36 +++-- >> lib/lex.c | 55 +++++++ >> northd/northd.c | 64 +++++---- >> tests/ovn.at | 2 +- >> tests/test-ovn.c | 16 ++- >> utilities/ovn-trace.c | 26 +++- >> 16 files changed, 869 insertions(+), 207 deletions(-) >> >> _______________________________________________ >> dev mailing list >> d...@openvswitch.org >> https://mail.openvswitch.org/mailman/listinfo/ovs-dev >> > _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
