The SIP looks like a good start, and I was already thinking of something
very similar to this as a follow on to my attempts to split the uber filter
(SolrDispatchFilter) into servlets such that roles determine what servlets
are deployed, but I would like to recommend that the roles be all positive
("Can do this") and nodes with no role at all are ineligible for all
activities. (just like standard role permissioning systems). This will make
it much more familiar and easy to think about. Therefore there would be no
need for a role such as !data which I presume was meant to mean "no data on
this node"... rather just don't give the "data" role to the node.Additional node roles I think should exist: I think that we should expand/edit your list of roles to be - QUERY - accepts and analyzes queries up to the point of actually consulting the lucene index (useful if you have a very heavy analysis phase) - UPDATE - accepts update requests, and performs update functionality prior to and including DistributedUpdateProcessorFactory (useful if you have a very heavy analysis phase) - ADMIN - accepts admin/management commands - UI - hosts an admin ui - ZOOKEEPER - hosts embedded zookeeper - OVERSEER - performs overseer related functionality (though IIRC there's a proposal to eliminate overseer that might eliminate this) - DATA - nodes where there is a lucene index and matching against the analyzed results of a query may be conducted to generate a response, also performs update steps that come after DistributedUpdateProcesserFactory I also suggest that these roles each have a node in zookeeper listing the current member nodes (as child nodes) so that code that wants to find a node with an appropriate role does not need to scan the list of all nodes parsing something to discover which nodes apply and also does not have to parse json to do it. I think this will be particularly key for zookeeper nodes which might be 3 out of 100 or more nodes. Similar to how we track live nodes. I think we should have a nodes.json too that tracks what roles a node is ALLOWED to take (as opposed to which roles it currently servicing) So running code consults the zookeeper role list of nodes, and any code seeking to transition a node (an admin operation with much lower performance requirements) consults the json data in the nodes.json node, parses it, finds the node in question and checks what it's eligible for (this will correspond to which servlets/apps have been loaded). I know of a case that would benefit from having separate Query/Update nodes that handle a heavy analysis process which would be deployed to a number of CPU heavy boxes (which might add more in prep for bulk indexing, and remove them when bulk was done), data could then be hosted on cheaper nodes.... Also maybe think about how this relates to NRT/TLOG/PULL which are also maybe role like WDYT? -Gus On Wed, Oct 27, 2021 at 3:17 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)
