The query processor is present in the global namespace and is
widely accessed with global get(_local)?_query_processor().
There's a long-term task to get rid of this globality and make
services and componenets reference each-other and, for and
due-to this, start and stop in specific order. This set makes
this for the query processor.
The remaining users of it are -- alternator, controllers for
client services, schema_tables and sys_dist_ks. All of them
except for the schema_tables are fixed just by passing the
reference on query processor with small patches. The schema
tables accessing qp sit deep inside the paxos code, but can
be "fixed" with the qctx thing until the qctx itself is
de-globalized.
* https://github.com/xemul/scylla/tree/br-rip-global-query-processor:
code: RIP global query processor instance
cql test env: Keep query processor reference on board
system distributed keyspace: Start sharded service erarlier
schema_tables: Use qctx to make internal requests
transport: Keep sharded query processor reference on controller
thrift: Keep sharded query processor reference on controller
alternator: Use local query processor reference to get keys
alternator: Keep local query processor reference in server
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