Revise shutdown proceedure. Rename variables

Author: linas

opencog/persist/proxy/WriteBufferProxy.cc

@@ -92,21 +92,23 @@ void WriteBufferProxy::open(void)
 
 // Start the writer.
 _stop = false;
-_write_thread = std::thread(&WriteBufferProxy::write_loop, this);
+_drain_thread = std::thread(&WriteBufferProxy::drain_loop, this);
 }
 
 void WriteBufferProxy::close(void)
 {
-// Stop writing. The thread may be sleeping, so the join() might
-// hang for a fraction of _decay seconds. It does not seem worthwhile
-// to try to speed this up, e.g. with a condition variable.
+// Close. Threads that are still writing will catch an exception.
+_atom_queue.close();
+_value_queue.close();
+
+// Stop draining. The drain thread may be sleeping, so the join()
+// might hang for a fraction of _ticker seconds. It does not seem
+// worthwhile to try to speed this up, e.g. with a condition variable.
 _stop = true;
-_write_thread.join();
+_drain_thread.join();
 
 // Drain the queues
 barrier();
-_atom_queue.close();
-_value_queue.close();
 
 WriteThruProxy::close();
 }
@@ -279,7 +281,7 @@ std::string WriteBufferProxy::monitor(void)
 // lock contention in the target. But I don't know for sure. Indirect
 // evidence from RocksStorage indicates that bombarding it from multiple
 // threads does not improve throughput. So, for now, just one thread.
-void WriteBufferProxy::write_loop(void)
+void WriteBufferProxy::drain_loop(void)
 {
 // Keep a moving average queue size. This is used to determine
 // when the queue is almost empty, by historical standards, which

opencog/persist/proxy/WriteBufferProxy.h

@@ -57,9 +57,9 @@ class WriteBufferProxy : public WriteThruProxy
 size_t _high_water_mark;
 concurrent_set<Handle> _atom_queue;
 concurrent_set<std::pair<Handle,Handle>> _value_queue;
-std::thread _write_thread;
+std::thread _drain_thread;
 bool _stop;
-void write_loop();
+void drain_loop();
 void erase_recursive(const Handle&);
 
 private: