Negative roles add a lot of complexity, I would really want to stay away from them. That’s why I want strict roles up front. It’s maybe ok to push this decision out, but it also seems like the sort of thing we should consider at the start.
On Thu, Dec 2, 2021 at 5:52 PM Noble Paul <[email protected]> wrote: > Yes. Negative roles is not a bad idea. If I start a node for > machine learning purposes, I wouldn't want that node to ever participate in > overseer election > > On Fri, Dec 3, 2021, 6:50 AM Ilan Ginzburg <[email protected]> wrote: > >> If we have non strict roles (like overseer), then it does make sense >> to have negative roles. >> That way I can define which are the two nodes that I'd prefer the >> overseer to run on, and a few other nodes on which it should >> definitely never run for various reasons. And in case these >> "!overseer" are the only nodes left in the cluster, let the cluster >> fail the same way it would if there were no data nodes available. >> >> On Thu, Dec 2, 2021 at 5:11 PM Houston Putman <[email protected]> >> wrote: >> >>> >> >>> With the Strict/Loose option and sensible defaults, users cannot trip >> themselves up by default, but the option is there for people to tinker and >> have an iron grip over their cluster. >> >> >> >> >> >> +1 to sensible defaults so users don't trip themselves. The option to >> tinker for tighter grip can be tackled later, either on a per role basis or >> as a generic concept later. >> > >> > >> > +1 - Can definitely be added later if we so desire, not needed for this >> SIP >> > >> > On Wed, Dec 1, 2021 at 9:14 PM Ishan Chattopadhyaya < >> [email protected]> wrote: >> >> >> >> >> >> >> >> On Thu, Dec 2, 2021 at 1:31 AM Gus Heck <[email protected]> wrote: >> >>> >> >>> I think the key is to let the roles have full control of the >> implications of having/not having that role. No need for even a >> strict/loose designation. The question of do you have the role is yes/no >> with no logic to guess if the role is implied or not, The question of will >> it come up with the role is "have_explicit ? use_defaults : use_defaults. >> >>> >> >>> Once you figure out who has a role (or not) what that means is up to >> the role code. >> >>> >> >>> Corollary: we don't have to change the way overseer works in this >> SIP. We can rework it or not as we see fit separately. >> >> >> >> >> >> +1 >> >> >> >>> >> >>> >> >>> Only thing we need to do is find a wording that makes the above clear >> on first read through the SIP :) >> >>> >> >>> -Gus >> >>> >> >>> On Wed, Dec 1, 2021 at 2:50 PM Houston Putman < >> [email protected]> wrote: >> >>>>> >> >>>>> This doesn't really address my concern around what happens if all >> of our existing OVERSEER candidates are down. When at least one of them is >> up, the overseer will go there, and that is good and expected. But what >> happens if all of the overseer eligible nodes are down. Your comment, and >> the old system, would imply that the overseer election goes to some other >> unrelated, untagged node. I disagree with this implementation choice. This >> sounds like something role specific to determine, but I would like to see >> us be more strict about it. I don't want cores leaking out of my data >> roles, I don't want query processing to leak out of my "query" nodes or >> whatever. Overseer shouldn't be special in this regard. >> >>>> >> >>>> >> >>>> I'm very strongly in favor of not letting users design a system in >> which the cluster can be "live" without an overseer. I understand that the >> overseer can be taxing to the cluster, but honestly what is the point of >> having an untaxed cluster that doesn't have an overseer? I can see >> arguments for the other roles to be stricter about this, but there are also >> a lot of users who wouldn't want those to be strict either (like "query" >> nodes). >> >>>> >> >>>> Maybe we just put in stronger guarantees that if a non-overseer role >> node HAS to be selected to become overseer, it will try to migrate the >> overseer job to a node with the overseer role whenever one becomes live. >> >>>> >> >>>> So maybe we don't have special rules per role, but instead roles can >> either be defined as "Strict" or "Loose" (better names likely exist), and >> the roles come with a default (Overseer -> Loose, Data -> Strict, Query -> >> Loose, etc.). And it is up to each role to define how to behave when >> running in LOOSE mode and a non-role node is used then a role node comes >> online (like the overseer example given above). >> >>>> >> >>>> With the Strict/Loose option and sensible defaults, users cannot >> trip themselves up by default, but the option is there for people to tinker >> and have an iron grip over their cluster. >> >>>> >> >>>> On Wed, Dec 1, 2021 at 2:24 PM Mike Drob <[email protected]> wrote: >> >>>>> >> >>>>> Noble wrote: >> >>>>> > We are not modifying the way the "overseer role" works today. We >> are just changing the definition and standardizing the configuration & >> discoverability >> >>>>> Ishan wrote: >> >>>>> > As of this SIP, we're not planning to modify the OVERSEER role >> (which currently stands for preferred overseer). We can take a stab at >> refactoring it later. >> >>>>> >> >>>>> Grouping these two comments together, since I think they are saying >> the same thing. I think this is part of my confusion. We have an old system >> that doesn't work the way we want the new system to work. There may be >> people already using the old system. What path do we offer for folks using >> the old system to migrate to the new system? What happens if somebody >> accidentally tries to use both systems at the same time? >> >>>>> >> >>>>> Ishan wrote: >> >>>>> > When I wrote "When one or more such nodes [with OVERSEER role] >> are live, Solr guarantees that one of those nodes becomes the overseer.", I >> meant to somewhat capture the current behaviour as the OVERSEER role >> performs today. Do you see any inconsistency with this statement vs. what >> it does today? >> >>>>> >> >>>>> This doesn't really address my concern around what happens if all >> of our existing OVERSEER candidates are down. When at least one of them is >> up, the overseer will go there, and that is good and expected. But what >> happens if all of the overseer eligible nodes are down. Your comment, and >> the old system, would imply that the overseer election goes to some other >> unrelated, untagged node. I disagree with this implementation choice. This >> sounds like something role specific to determine, but I would like to see >> us be more strict about it. I don't want cores leaking out of my data >> roles, I don't want query processing to leak out of my "query" nodes or >> whatever. Overseer shouldn't be special in this regard. >> >>>>> >> >>>>> Noble wrote: >> >>>>> > If we do that how do we know if xyz is a role or a node in the >> following request? >> >>>>> >> >>>>> You're absolutely correct, thanks for pointing this out. Let's >> leave it as is. >> >>>>> >> >>>>> >> >>>>> >> >>>>> On Tue, Nov 30, 2021 at 2:21 PM Ishan Chattopadhyaya < >> [email protected]> wrote: >> >>>>>> >> >>>>>> >> >>>>>> >> >>>>>> On Tue, Nov 30, 2021 at 12:53 AM Mike Drob <[email protected]> >> wrote: >> >>>>>>> >> >>>>>>> Replying to the top post in this thread because there has been a >> lot of discussion and I don't want to look like I'm continuing any of those >> particular threads. >> >>>>>>> >> >>>>>>> I finally had time to sit down and think about this with the >> attention it deserves and am generally happy with how the conversation has >> shaped the current proposal. >> >>>>>>> >> >>>>>>> GOOD: I think using system properties to define node roles is >> fine and I like that data is the default role when not defined. I think it >> is important to hold on to the guarantee that an active overseer will land >> on an overseer node role. >> >>>>>>> CHANGE REQUEST: I would like to see a migration path for folks >> using the current OVERSEER role. I am not sure that something can be done >> automatically since they need to now specify new properties at startup. >> Maybe we need to include loud warnings or support both approaches for a >> time? >> >>>>>>> CHANGE REQUEST: I do not like that if all of the overseer nodes >> fail, then it is implied the overseer will go to one of the data nodes. The >> specific wording in the SIP - "When one or more such nodes are live, Solr >> guarantees that one of those nodes become the overseer." implies to me that >> failover could go from overseer1 to overseer2 to overseerN to random node. >> I feel like we need to have some recording that there were dedicated >> overseer nodes and stop the cascading failure instead of churning through >> our data nodes. >> >>>>>>> >> >>>>>>> CLARIFICATION: I am slightly confused by the proposed scope of >> "coordinator" roles from a split query/indexing standpoint. I understand >> that these are used as examples, but would like stronger language that new >> roles should also go through their own SIP discussions. >> >>>>>>> >> >>>>>>> CLARIFICATION: I do not like that we are storing node liveness in >> two different places now. We have the live nodes and we have the node roles >> stored in two different places in zookeeper and it feels like this would >> lead to race conditions or split brain or other hard to diagnose bugs when >> those two lists don't agree with each other. This also feels like it >> contradicts the "single source of truth" idea later stated in the proposal. >> I see Gus's arguments for decoupling these and am not strongly opposed, I >> just get a lurking feeling about it. Even if we don't do this, I would like >> this called out explicitly in the alternative approaches section as >> something that we considered and rejected, with details why, >> >>>>>>> >> >>>>>>> GOOD: The API looks pretty clear. I would like an additional call >> out here that all operations are GET because nodes cannot be changed at >> runtime. >> >>>>>>> CLARIFICATION: How does this interact with the previous OVERSEER >> preference role? >> >>>>>>> CHANGE REQUEST: An additional API to get the list of available >> roles for a cluster. I _think_ this could be based on the version that the >> cluster is running? Would be useful to be able to interrogate a cluster in >> the future... we're seeing OOM issues on queries, can we add some query >> nodes? When were they introduced? I don't know what path this API should >> exist at. >> >>>>>> >> >>>>>> >> >>>>>> Added a GET /api/cluster/roles/supported API, updated the SIP >> document. Not sure if there's a better path that we could go for. >> >>>>>> >> >>>>>>> >> >>>>>>> CLARIFICATION: Can we list the APIs to clearly show which parts >> are string literals and which parts are meant to be substituted by the >> operator? GET /api/cluster/roles/data would become GET >> /api/cluster/roles/${rolename} in our SIP/documentation. >> >>>>>>> CHANGE REQUEST: I think GET /api/cluster/roles/nodes/node1 should >> be GET /api/cluster/roles/${nodename} dropping the intermediate "nodes" >> >>>>>>> CHANGE REQUEST: The ZK structure also might not need that >> intermediate "nodes" node. >> >>>>>>> >> >>>>>>> CLARIFICATION: Should listing roles require some permissions? >> Maybe this requirement is too fundamental to the operation of a cluster and >> everybody would have to be able to do it. >> >>>>>>> CLARIFICATION: How do we expect SolrJ (and other clients) to >> treat roles? Implementation detail that the servers will figure out? Or >> strict guidance where the client needs to check where specific roles are >> before sending any further communication to the server? >> >>>>>>> CLARIFICATION: What happens when a node gets a request that it >> can't fulfil? An overseer node gets a query or an update. A data node gets >> a collection creation request. Do they forward it on to an appropriate >> node, or do they reject it? Should this be configurable? If not, then it >> seems like lazy or poorly configured clients will defeat this isolation >> system quite easily. >> >>>>>>> >> >>>>>>> GOOD: Testing the API is very important, yes. >> >>>>>>> CLARIFICATION: What does testing for how nodes behave when roles >> are added mean? I thought we established that they are not dynamic. >> >>>>>>> >> >>>>>>> >> >>>>>>> Thanks, >> >>>>>>> Mike >> >>>>>>> >> >>>>>>> On Wed, Oct 27, 2021 at 2:17 AM Ishan Chattopadhyaya < >> [email protected]> wrote: >> >>>>>>>> >> >>>>>>>> Hi, >> >>>>>>>> >> >>>>>>>> Here's an SIP for introducing the concept of node roles: >> >>>>>>>> https://issues.apache.org/jira/browse/SOLR-15694 >> >>>>>>>> >> https://cwiki.apache.org/confluence/display/SOLR/SIP-15+Node+roles >> >>>>>>>> >> >>>>>>>> We also wish to add first class support for Query nodes that are >> used to process user queries by forwarding to data nodes, >> merging/aggregating them and presenting to users. This concept exists as >> first class citizens in most other search engines. This is a chance for >> Solr to catch up. >> >>>>>>>> https://issues.apache.org/jira/browse/SOLR-15715 >> >>>>>>>> >> >>>>>>>> Regards, >> >>>>>>>> Ishan / Noble / Hitesh >> >>> >> >>> >> >>> >> >>> -- >> >>> http://www.needhamsoftware.com (work) >> >>> http://www.the111shift.com (play) >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: [email protected] >> For additional commands, e-mail: [email protected] >> >>
