This fixes a possible cause of #4614.
From the backtrace in that issue, it looks like a file is being closed
twice. The first point in the backtrace where that seems likely is in
the MC writer.
My first idea was to add a writer::close and make it the responsibility
of the code using the writer to call it. That way we would move work
out of the destructor.
That is a bit hard since the writer is destroyed from
flat_mutation_reader::impl::~consumer_adapter and that would need to
get a close function too.
This patch instead just fixes an exception safety issue. If
_index_writer->close() throws, _index_writer is still valid and
~writer will try to close it again.
If the exception was thrown after _completed.set_value(), that would
explain the assert about _completed.set_value() being called twice.
With this patch the path outside of the destructor now moves the
writer to a local variable before trying to close it.
Fixes#4614
Message-Id: <20190710171747.27337-1-espindola@scylladb.com>
281f3a69f8