> Boiling it down the idea I'm proposing is that roles required for back
compatibility get explicitly added on startup, if not by the user then by
the code. This is more flexible than assuming that no role means every
role, because then every new feature that has a role will end up on legacy
clusters which are also not back compatible.
+1, I totally agree. I even said so, when I said: "This is why I was
advocating that 1) we assume the "data" as a default, 2) not assume
overseer to be implicitly defined (because of the way overseer role is
written today), 3) not assume any future roles to be true by default."
So, basically, I'm proposing that the "roles required for back
compatibility" (that should be explicitly added on startup) be just the
["data"] role, and not the "overseer" role (due to the way overseer role is
currently defined, i.e. it is "preferred overseer").
On Mon, Nov 1, 2021 at 10:19 PM Gus Heck <gus.h...@gmail.com> wrote:
> Very sorry don't mean to sound offended, Frustrated yes offended no :)...
> the most difficult thing about communication is the illusion it has
> occurred :)
>
> If you read back just a few emails you'll see where I talk about roles
> being applied on startup. Boiling it down the idea I'm proposing is that
> roles required for back compatibility get explicitly added on startup, if
> not by the user then by the code. This is more flexible than assuming that
> no role means every role, because then every new feature that has a role
> will end up on legacy clusters which are also not back compatible.
>
> There are points where I said all roles rather than back compatibility
> roles because I was thinking about back compatibility specifically, but you
> can't know that if I don't say that can you :).
>
> On Mon, Nov 1, 2021 at 12:39 PM Ishan Chattopadhyaya <
> ichattopadhy...@gmail.com> wrote:
>
>> > If you read more closely, my way can provide full back compatibility.
>> To say or imply it doesn't isn't helping. Perhaps you need to re-read?
>>
>> I understand e-mails are frustrating, and I'm trying my best. Please
>> don't be offended, and kindly point me to the exact part you want me to
>> re-read.
>>
>> On Mon, Nov 1, 2021 at 10:05 PM Gus Heck <gus.h...@gmail.com> wrote:
>>
>>>
>>>
>>> On Mon, Nov 1, 2021 at 12:22 PM Ishan Chattopadhyaya <
>>> ichattopadhy...@gmail.com> wrote:
>>>
>>>> > Positive - They denote the existence of a capability
>>>>
>>>> Agree, the SIP already reflects this.
>>>>
>>>> > Absolute - Absence/Presence binary identification of a capability;
>>>> no implications, no assumptions
>>>>
>>>> Disagree, we need backcompat handling on nodes running without any
>>>> roles. There has to be an implicit assumption as to what roles are those
>>>> nodes assumed to have. My proposal is that only the "data" role be assumed,
>>>> but not the "overseer" role. For any future roles ("coordinator",
>>>> "zookeeper" etc.), this decision as to what absence of any role implies
>>>> should be left to the implementation of that future role. Documentation
>>>> should reflect clearly about these implicit assumptions.
>>>>
>>>>
>>> If you read more closely, my way can provide full back compatibility. To
>>> say or imply it doesn't isn't helping. Perhaps you need to re-read?
>>>
>>>
>>>> > Focused - Do one thing per role
>>>>
>>>> Agree. However, I disagree with ideas where "query analysis" has a role
>>>> of its own. Where would that lead us to? Separate roles for nodes that do
>>>> "faceting" or "spell correction" etc.? But anyway, that is for discussion
>>>> when we add future roles. This is beyond this SIP.
>>>>
>>>>
>>> I am not asking you to implement every possible role of course :). As a
>>> note I know a company that is running an entire separate cluster to offload
>>> and better serve highlighting on a subset of large docs, so YES I think
>>> there are people who may want such fine grained control.
>>>
>>>
>>>> > Accessible - It should be dead simple to determine the members of
>>>> a role, avoid parsing blobs of json, avoid calculating implications, avoid
>>>> consulting other resources after listing nodes with the role
>>>>
>>>> Agree. I'm open to any implementation details that make it easy. There
>>>> should be a reasonable API to return these node roles, with ability to
>>>> filter by role or filter by node.
>>>>
>>>> > Independent - One role should not require other roles to be present
>>>>
>>>> Do we need to have this hard and fast requirement upfront? There might
>>>> be situations where this is desirable. I feel we can discuss on a case by
>>>> case basis whenever a future role is added.
>>>>
>>>> > Persistent - roles should not be lost across reboot
>>>>
>>>> Agree.
>>>>
>>>> > Immutable - roles should not change while the node is running
>>>>
>>>> Agree
>>>>
>>>> > Lively - A node with a capability may not be presently providing
>>>> that capability.
>>>>
>>>> I don't understand, can you please elaborate?
>>>>
>>>
>>>
>>> Specifically imagine the case where there are 100 nodes:
>>> 1-100 ==> DATA
>>> 101-103 ==> OVERSEER
>>> 104-106 ==> ZOOKEEPER
>>>
>>> But you won't have 3 overseers... you'll want only one of those to be
>>> *providing
>>> *overseer functionality and the other two to be *capable*, but not
>>> providing (so that if the current overseer goes down a new one can be
>>> assigned).
>>>
>>> Then you decide you'd ike 5 Zookeepers. You start nodes 107-108 with
>>> that role, but you probably want to ensure that zookeepers require some
>>> sort of command for them to actually join the zookeeper cluster (i.e.
>>> /admin?action=ZKADD&nodes=node107,node18) ... to do that the nodes need to
>>> be up. But oh look I typoed 108... we want that to fail... how? because 18
>>> does not have the *capability* to become a zookeeper.
>>>
>>>
>>>>
>>>> On Mon, Nov 1, 2021 at 9:30 PM Ishan Chattopadhyaya <
>>>> ichattopadhy...@gmail.com> wrote:
>>>>
>>>>> > Ilan: A node not having node.roles defined should be assumed to have
>>>>> all roles. Not only data. I don't see a reason to special case this one or
>>>>> any role.
>>>>> > Gus: There should be no "assumptions" Nothing to figure out. A node
>>>>> has a role or not. For back compatibility reasons, all roles would be
>>>>> assumed on startup if none specified.
>>>>> > Jan: No role == all roles. Explicit list of roles = exactly those
>>>>> roles.
>>>>>
>>>>> Problem with this approach is mainly to do with backcompat.
>>>>>
>>>>> *1. Overseer backcompat:*
>>>>> If we don't make any modifications to how overseer works and adopt
>>>>> this approach (as quoted), then imagine this situation:
>>>>>
>>>>> Solr1-100: No roles param (assumed to be "data,overseer").
>>>>> Solr101: -Dnode.roles=overseer (intention: dedicated overseer)
>>>>>
>>>>> User wants this node Solr101 to be a dedicated overseer, but for that
>>>>> to happen, he/she would need to restart all the data nodes with
>>>>> -Dnode.roles=data. This will cause unnecessary disruption to running
>>>>> clusters where a dedicated overseer is needed. Keep in mind, if a user
>>>>> needs a dedicated overseer, he's likely in an emergency situation and
>>>>> restarting the whole cluster might not be viable for him/her.
>>>>>
>>>>> *2. Future roles might not be compatible with this "assumed to have
>>>>> all roles" idea:*
>>>>> Take the proposed "zookeeper" role for example. Today, regular nodes
>>>>> are not supposed to have embedded ZK running on them. By introducing this
>>>>> artificial limitation ("assumed to have all roles"), we constrain adoption
>>>>> of all future roles to necessarily require a full cluster restart.
>>>>>
>>>>> Keep in mind newer Solr versions can introduce new capabilities and
>>>>> roles. Imagine we have a role that is defined in a new Solr version (and
>>>>> there's functionality to go with that role), and user upgrades to that
>>>>> version. However, his/her nodes all were started with no node.roles param.
>>>>> Hence, if those nodes are "assumed to have all roles", then just by virtue
>>>>> of upgrading to this new version, new capabilities will be turned on for
>>>>> the entire cluster, whether or not the user opted for such a capability.
>>>>> This is totally undesirable.
>>>>>
>>>>> > Gus: I actually don't want a coordinator to do more work, I would
>>>>> prefer small focused roles with names that accurately describe their
>>>>> function. In that light, COORDINATOR might be too nebulous. How about
>>>>> AGREGATOR role? (what I was thinking of would better be called a
>>>>> QUERY_ANALYSIS role)
>>>>>
>>>>> If you want to do specific things like query analysis or query
>>>>> aggregation or bulk indexing etc, all of those can be done on COORDINATOR
>>>>> nodes (as is the case in ElasticSearch). Having tens of of " small focused
>>>>> roles" defined as first class concepts would be confusing to the user. As
>>>>> a
>>>>> remedy to your situation where you want the coordinator role to also do
>>>>> query-analysis for shards, one possible solution is to send such a query
>>>>> to
>>>>> a coordinator node with a parameter like
>>>>> "coordinator.query_analysis=true",
>>>>> and then the coordinator, instead of blindly hitting remote shards, also
>>>>> does some extra work on behalf of the shards.
>>>>>
>>>>>
>>>>> On Mon, Nov 1, 2021 at 9:01 PM Ishan Chattopadhyaya <
>>>>> ichattopadhy...@gmail.com> wrote:
>>>>>
>>>>>> > If we make collections role-aware for example (replicas of that
>>>>>> collection can only be
>>>>>> > placed on nodes with a specific role, in addition to the other role
>>>>>> based constraints),
>>>>>> > the set of roles should be user extensible and not fixed.
>>>>>> > If collections are not role aware, the constraints introduced by
>>>>>> roles apply to all collections
>>>>>> > equally which might be insufficient if a user needs for example a
>>>>>> heavily used collection to
>>>>>> > only be placed on more powerful nodes.
>>>>>>
>>>>>> I feel node roles and role-aware collections are orthogonal topics.
>>>>>> What you describe above can be achieved by the autoscaling+replica
>>>>>> placement framework where the placement plugins take the node roles as
>>>>>> one
>>>>>> of the inputs.
>>>>>>
>>>>>> > It does impact the design from early on: the set of roles need to
>>>>>> be expandable by a user
>>>>>> > by creating a collection with new roles for example (consumed by
>>>>>> placement plugins) and be
>>>>>> > able to start nodes with new (arbitrary) roles. Should such roles
>>>>>> follow some naming syntax to
>>>>>> > differentiate them from built in roles? To be able to fail on typos
>>>>>> on roles - that otherwise can be
>>>>>> > crippling and hard to debug. This implies in any case that the
>>>>>> current design can't assume all
>>>>>> > roles are known at compile time or define them in a Java enum.
>>>>>>
>>>>>> I think this should be achieved by something different from roles.
>>>>>> Something like node *labels* (user defined) which can then be used
>>>>>> in a replica placement plugin to assign replicas. I see roles as more
>>>>>> closely associated with kinds of functionality a node is designated for.
>>>>>> Therefore, I feel that replica placements and user defined node labels is
>>>>>> out of scope for this SIP. It can be added later in a separate SIP,
>>>>>> without
>>>>>> being at odds with this proposal.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Mon, Nov 1, 2021 at 8:42 PM Jan Høydahl <jan....@cominvent.com>
>>>>>> wrote:
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> > 1. nov. 2021 kl. 14:46 skrev Ilan Ginzburg <ilans...@gmail.com>:
>>>>>>> > A node not having node.roles defined should be assumed to have all
>>>>>>> roles. Not only data. I don't see a reason to special case this one or
>>>>>>> any
>>>>>>> role.
>>>>>>>
>>>>>>> +1, make it simple and transparent. No role == all roles. Explicit
>>>>>>> list of roles = exactly those roles.
>>>>>>>
>>>>>>> > (Gus) See my comment above, but maybe preference is something
>>>>>>> handled as a feature of the role rather than via role designation?
>>>>>>>
>>>>>>> Yea, we always need an overseer, so that feature can decide to use
>>>>>>> its list of nodes as a preference if it so chooses.
>>>>>>>
>>>>>>>
>>>>>>> Aside: I think it makes it easier if we always prefix Solr env.vars
>>>>>>> and sys.props with "SOLR_" or "solr.", i.e. -Dsolr.node.roles=foo. That
>>>>>>> way
>>>>>>> we can get away from having to have explicit code in bin/solr,
>>>>>>> bin/solr.cmd
>>>>>>> and SolrCLI to manage every single property. Instead we can parse all
>>>>>>> ENVs
>>>>>>> and Props with the solr prefix in our bootstrap code. And we can by
>>>>>>> convention allow e.g. docker run -e SOLR_NODE_ROLES=foo solr:9 and it
>>>>>>> would
>>>>>>> be the same ting...
>>>>>>>
>>>>>>> Jan
>>>>>>> ---------------------------------------------------------------------
>>>>>>> To unsubscribe, e-mail: dev-unsubscr...@solr.apache.org
>>>>>>> For additional commands, e-mail: dev-h...@solr.apache.org
>>>>>>>
>>>>>>>
>>>
>>> --
>>> http://www.needhamsoftware.com (work)
>>> http://www.the111shift.com (play)
>>>
>>
>
> --
> http://www.needhamsoftware.com (work)
> http://www.the111shift.com (play)
>
