partitioner: Futurize split_range_to_single_shard
We saw reactor stalls when closing SSTables. The backtrace looks like:
Oct 12 19:00:51 dell-1 scylla[435045]: Backtrace:[Backtrace #0]
void seastar::backtrace<seastar::backtrace_buffer::append_backtrace()::{lambda(seastar::frame)#1}>(seastar::backtrace_buffer::append_backtrace()::{lambda(seastar::frame)#1}&&) at /home/sylla/scylla/seastar/util/backtrace.hh:56
seastar::backtrace_buffer::append_backtrace() at /home/sylla/scylla/seastar/core/reactor.cc:410
(inlined by) print_with_backtrace at /home/sylla/scylla/seastar/core/reactor.cc:431
seastar::reactor::block_notifier(int) at /home/sylla/scylla/seastar/core/reactor.cc:749
_L_unlock_13 at funlockfile.c:?
std::experimental::fundamentals_v1::_Optional_base<range_bound<dht::ring_position>, true>::_Optional_base(std::experimental::fundamentals_v1::_Optional_base<range_bound<dht::ring_position>, true>&&) at /opt/scylladb/include/c++/7/experimental/optional:247
(inlined by) std::experimental::fundamentals_v1::optional<range_bound<dht::ring_position> >::optional(std::experimental::fundamentals_v1::optional<range_bound<dht::ring_position> >&&) at /opt/scylladb/include/c++/7/experimental/optional:493
(inlined by) wrapping_range<dht::ring_position>::wrapping_range(wrapping_range<dht::ring_position>&&) at /home/sylla/scylla/./range.hh:61
(inlined by) nonwrapping_range<dht::ring_position>::nonwrapping_range(nonwrapping_range<dht::ring_position>&&) at /home/sylla/scylla/./range.hh:430
(inlined by) void __gnu_cxx::new_allocator<nonwrapping_range<dht::ring_position> >::construct<nonwrapping_range<dht::ring_position>, nonwrapping_range<dht::ring_position> >(nonwrapping_range<dht::ring_position>*, nonwrapping_range<dht::ring_position>&&) at /opt/scylladb/include/c++/7/ext/new_allocator.h:136
(inlined by) void std::allocator_traits<std::allocator<nonwrapping_range<dht::ring_position> > >::construct<nonwrapping_range<dht::ring_position>, nonwrapping_range<dht::ring_position> >(std::allocator<nonwrapping_range<dht::ring_position> >&, nonwrapping_range<dht::ring_position>*, nonwrapping_range<dht::ring_position>&&) at /opt/scylladb/include/c++/7/bits/alloc_traits.h:475
(inlined by) nonwrapping_range<dht::ring_position>& std::deque<nonwrapping_range<dht::ring_position>, std::allocator<nonwrapping_range<dht::ring_position> > >::emplace_back<nonwrapping_range<dht::ring_position> >(nonwrapping_range<dht::ring_position>&&) at /opt/scylladb/include/c++/7/bits/deque.tcc:167
(inlined by) std::deque<nonwrapping_range<dht::ring_position>, std::allocator<nonwrapping_range<dht::ring_position> > >::push_back(nonwrapping_range<dht::ring_position>&&) at /opt/scylladb/include/c++/7/bits/stl_deque.h:1558
(inlined by) dht::split_range_to_single_shard(dht::i_partitioner const&, schema const&, nonwrapping_range<dht::ring_position> const&, unsigned int) at /home/sylla/scylla/dht/i_partitioner.cc:454
dht::split_range_to_single_shard(schema const&, nonwrapping_range<dht::ring_position> const&, unsigned int) at /home/sylla/scylla/dht/i_partitioner.cc:464
create_sharding_metadata at /home/sylla/scylla/sstables/sstables.cc:2075
(inlined by) sstables::sstable::write_scylla_metadata(seastar::io_priority_class const&, unsigned int, sstables::sstable_enabled_features) at /home/sylla/scylla/sstables/sstables.cc:2435
sstables::sstable_writer_m::consume_end_of_stream() at /home/sylla/scylla/sstables/sstables.cc:3483
sstables::compaction::finish_new_sstable(std::experimental::fundamentals_v1::optional<sstables::sstable_writer>&, seastar::lw_shared_ptr<sstables::sstable>&) at /home/sylla/scylla/sstables/compaction.cc:338
(inlined by) sstables::regular_compaction::stop_sstable_writer() at /home/sylla/scylla/sstables/compaction.cc:579
(inlined by) sstables::regular_compaction::finish_sstable_writer() at /home/sylla/scylla/sstables/compaction.cc:585
sstables::compacting_sstable_writer::consume_end_of_stream() at /home/sylla/scylla/sstables/compaction.cc:494
(inlined by) auto compact_mutation_state<(emit_only_live_rows)0, (compact_for_sstables)1>::consume_end_of_stream<sstables::compacting_sstable_writer>(sstables::compacting_sstable_writer&) at /home/sylla/scylla/./mutation_compactor.hh:292
(inlined by) compact_mutation<(emit_only_live_rows)0, (compact_for_sstables)1, sstables::compacting_sstable_writer>::consume_end_of_stream() at /home/sylla/scylla/./mutation_compactor.hh:397
(inlined by) stable_flattened_mutations_consumer<compact_for_compaction<sstables::compacting_sstable_writer> >::consume_end_of_stream() at /home/sylla/scylla/./mutation_reader.hh:366
(inlined by) auto flat_mutation_reader::impl::consume_in_thread<stable_flattened_mutations_consumer<compact_for_compaction<sstables::compacting_sstable_writer> >, std::function<bool (dht::decorated_key const&)> >(stable_flattened_mutations_consumer<compact_for_compaction<sstables::compacting_sstable_writer> >, std::function<bool (dht::decorated_key const&)>, std::chrono::time_point<seastar::lowres_clock, std::chrono::duration<long, std::ratio<1l, 1000l> > >) at /home/sylla/scylla/./flat_mutation_reader.hh:288
(inlined by) auto flat_mutation_reader::consume_in_thread<stable_flattened_mutations_consumer<compact_for_compaction<sstables::compacting_sstable_writer> >, std::function<bool (dht::decorated_key const&)> >(stable_flattened_mutations_consumer<compact_for_compaction<sstables::compacting_sstable_writer> >, std::function<bool (dht::decorated_key const&)>, std::chrono::time_point<seastar::lowres_clock, std::chrono::duration<long, std::ratio<1l, 1000l> > >) at /home/sylla/scylla/./flat_mutation_reader.hh:370
(inlined by) operator() at /home/sylla/scylla/sstables/compaction.cc:757
(inlined by) apply at /home/sylla/scylla/seastar/core/apply.hh:35
(inlined by) apply<sstables::compaction::run(std::unique_ptr<sstables::compaction>)::<lambda()> > at /home/sylla/scylla/seastar/core/apply.hh:43
(inlined by) apply<sstables::compaction::run(std::unique_ptr<sstables::compaction>)::<lambda()> > at /home/sylla/scylla/seastar/core/future.hh:1309
(inlined by) operator() at /home/sylla/scylla/./seastar/core/thread.hh:315
(inlined by) _M_invoke at /opt/scylladb/include/c++/7/bits/std_function.h:316
std::function<void ()>::operator()() const at /opt/scylladb/include/c++/7/bits/std_function.h:706
(inlined by) seastar::thread_context::main() at /home/sylla/scylla/seastar/core/thread.cc:313
The call chain is:
sstable_writer_k_l::consume_end_of_stream and mc::writer::consume_end_of_stream
-> sstable::write_scylla_metadata -> create_sharding_metadata -> dht::split_range_to_single_shard
Since sstable writer assumes a thread context. We can futurize dht::split_range_to_single_shard.
Fixes: #3846
Tests: dtest + build/dev/tests/partitioner_test
58fae5f4c1