Prevent low-likelihood crash on shutdown (RIPD-1392):

The DatabaseImp has threads that asynchronously call JobQueue to
perform database reads.  Formerly these threads had the same
lifespan as Database, which was until the end-of-life of
ApplicationImp.  During shutdown these threads could call JobQueue
after JobQueue had already stopped.  Or, even worse, occasionally
call JobQueue after JobQueue's destructor had run.

To avoid these shutdown conditions, Database is made a Stoppable,
with JobQueue as its parent.  When Database stops, it shuts down
its asynchronous read threads.  This prevents Database from
accessing JobQueue after JobQueue has stopped, but allows
Database to perform stores for the remainder of shutdown.

During development it was noted that the Database::close()
method was never called.  So that method is removed from Database
and all derived classes.

Stoppable is also adjusted so it can be constructed using either
a char const* or a std::string.

For those files touched for other reasons, unneeded #includes
are removed.

src/ripple/app/main/Application.cpp

@@ -23,7 +23,6 @@
 #include <ripple/app/main/DBInit.h>
 #include <ripple/app/main/BasicApp.h>
 #include <ripple/app/main/Tuning.h>
-#include <ripple/app/ledger/AcceptedLedger.h>
 #include <ripple/app/ledger/InboundLedgers.h>
 #include <ripple/app/ledger/LedgerMaster.h>
 #include <ripple/app/ledger/LedgerToJson.h>
@@ -32,59 +31,29 @@
 #include <ripple/app/ledger/PendingSaves.h>
 #include <ripple/app/ledger/InboundTransactions.h>
 #include <ripple/app/ledger/TransactionMaster.h>
-#include <ripple/app/main/CollectorManager.h>
 #include <ripple/app/main/LoadManager.h>
 #include <ripple/app/main/NodeIdentity.h>
 #include <ripple/app/main/NodeStoreScheduler.h>
 #include <ripple/app/misc/AmendmentTable.h>
 #include <ripple/app/misc/HashRouter.h>
 #include <ripple/app/misc/LoadFeeTrack.h>
-#include <ripple/app/misc/Manifest.h>
 #include <ripple/app/misc/NetworkOPs.h>
 #include <ripple/app/misc/SHAMapStore.h>
 #include <ripple/app/misc/TxQ.h>
-#include <ripple/app/misc/Validations.h>
-#include <ripple/app/misc/ValidatorList.h>
 #include <ripple/app/misc/ValidatorSite.h>
-#include <ripple/app/paths/Pathfinder.h>
 #include <ripple/app/paths/PathRequests.h>
 #include <ripple/app/tx/apply.h>
-#include <ripple/basics/contract.h>
-#include <ripple/basics/Log.h>
 #include <ripple/basics/ResolverAsio.h>
 #include <ripple/basics/Sustain.h>
-#include <ripple/basics/chrono.h>
 #include <ripple/json/json_reader.h>
-#include <ripple/json/to_string.h>
-#include <ripple/core/ConfigSections.h>
 #include <ripple/core/DeadlineTimer.h>
-#include <ripple/core/TimeKeeper.h>
-#include <ripple/ledger/CachedSLEs.h>
-#include <ripple/nodestore/Database.h>
 #include <ripple/nodestore/DummyScheduler.h>
-#include <ripple/nodestore/Manager.h>
 #include <ripple/overlay/Cluster.h>
 #include <ripple/overlay/make_Overlay.h>
-#include <ripple/protocol/Indexes.h>
-#include <ripple/protocol/PublicKey.h>
-#include <ripple/protocol/SecretKey.h>
 #include <ripple/protocol/STParsedJSON.h>
-#include <ripple/protocol/types.h>
-#include <ripple/resource/Charge.h>
-#include <ripple/resource/Consumer.h>
 #include <ripple/resource/Fees.h>
-#include <ripple/rpc/Context.h>
-#include <ripple/rpc/RPCHandler.h>
-#include <ripple/shamap/Family.h>
-#include <ripple/crypto/csprng.h>
 #include <ripple/beast/asio/io_latency_probe.h>
 #include <ripple/beast/core/LexicalCast.h>
-#include <beast/core/detail/ci_char_traits.hpp>
-#include <boost/asio/signal_set.hpp>
-#include <boost/optional.hpp>
-#include <atomic>
-#include <chrono>
-#include <fstream>
 
 namespace ripple {
 
@@ -325,7 +294,6 @@ public:
 
     NodeStoreScheduler m_nodeStoreScheduler;
     std::unique_ptr <SHAMapStore> m_shaMapStore;
-    std::unique_ptr <NodeStore::Database> m_nodeStore;
     PendingSaves pendingSaves_;
     AccountIDCache accountIDCache_;
     boost::optional<OpenLedger> openLedger_;
@@ -333,7 +301,6 @@ public:
     // These are not Stoppable-derived
     NodeCache m_tempNodeCache;
     std::unique_ptr <CollectorManager> m_collectorManager;
-    detail::AppFamily family_;
     CachedSLEs cachedSLEs_;
     std::pair<PublicKey, SecretKey> nodeIdentity_;
 
@@ -341,6 +308,8 @@ public:
 
     // These are Stoppable-related
     std::unique_ptr <JobQueue> m_jobQueue;
+    std::unique_ptr <NodeStore::Database> m_nodeStore;
+    detail::AppFamily family_;
     // VFALCO TODO Make OrderBookDB abstract
     OrderBookDB m_orderBookDB;
     std::unique_ptr <PathRequests> m_pathRequests;
@@ -416,8 +385,6 @@ public:
             logs_->journal ("SHAMapStore"), logs_->journal ("NodeObject"),
             m_txMaster, *config_))
 
-        , m_nodeStore (m_shaMapStore->makeDatabase ("NodeStore.main", 4))
-
         , accountIDCache_(128000)
 
         , m_tempNodeCache ("NodeCache", 16384, 90, stopwatch(),
@@ -426,8 +393,6 @@ public:
         , m_collectorManager (CollectorManager::New (
             config_->section (SECTION_INSIGHT), logs_->journal("Collector")))
 
-        , family_ (*this, *m_nodeStore, *m_collectorManager)
-
         , cachedSLEs_ (std::chrono::minutes(1), stopwatch())
 
         , m_resourceManager (Resource::make_Manager (
@@ -443,6 +408,10 @@ public:
         //
         // Anything which calls addJob must be a descendant of the JobQueue
         //
+        , m_nodeStore (
+            m_shaMapStore->makeDatabase ("NodeStore.main", 4, *m_jobQueue))
+
+        , family_ (*this, *m_nodeStore, *m_collectorManager)
 
         , m_orderBookDB (*this, *m_jobQueue)
 
@@ -1964,9 +1933,9 @@ bool ApplicationImp::updateTables ()
         auto j = logs_->journal("NodeObject");
         NodeStore::DummyScheduler scheduler;
         std::unique_ptr <NodeStore::Database> source =
-            NodeStore::Manager::instance().make_Database ("NodeStore.import", scheduler,
-                j, 0,
-                config_->section(ConfigSection::importNodeDatabase ()));
+            NodeStore::Manager::instance().make_Database ("NodeStore.import",
+                scheduler, 0, *m_jobQueue,
+                config_->section(ConfigSection::importNodeDatabase ()), j);
 
         JLOG (j.warn())
             << "Node import from '" << source->getName () << "' to '"