Apply transaction batches in periodic intervals (XRPLF#4504)

Add new transaction submission API field, "sync", which
determines behavior of the server while submitting transactions:
1) sync (default): Process transactions in a batch immediately,
   and return only once the transaction has been processed.
2) async: Put transaction into the batch for the next processing
   interval and return immediately.
3) wait: Put transaction into the batch for the next processing
   interval and return only after it is processed.

Builds/CMake/RippledCore.cmake

@@ -199,6 +199,7 @@ install (
     src/ripple/basics/StringUtilities.h
     src/ripple/basics/TaggedCache.h
     src/ripple/basics/tagged_integer.h
+    src/ripple/basics/SubmitSync.h
     src/ripple/basics/ThreadSafetyAnalysis.h
     src/ripple/basics/ThreadUtilities.h
     src/ripple/basics/ToString.h

cfg/rippled-example.cfg

@@ -480,7 +480,7 @@
 #
 #   Configure the maximum number of transactions to have in the job queue
 #
-#   Must be a number between 100 and 1000, defaults to 250
+#   Must be a number between 1000 and 100000, defaults to 10000
 #
 #
 # [overlay]

cfg/rippled-reporting.cfg

@@ -467,7 +467,7 @@
 #
 #   Configure the maximum number of transactions to have in the job queue
 #
-#   Must be a number between 100 and 1000, defaults to 250
+#   Must be a number between 1000 and 100000, defaults to 10000
 #
 #
 # [overlay]

src/ripple/app/ledger/impl/LedgerMaster.cpp

@@ -549,22 +549,25 @@ void
 LedgerMaster::applyHeldTransactions()
 {
     std::lock_guard sl(m_mutex);
+    // It can be expensive to modify the open ledger even with no transactions
+    // to process. Regardless, make sure to reset held transactions with
+    // the parent.
+    if (mHeldTransactions.size())
+    {
+        app_.openLedger().modify([&](OpenView& view, beast::Journal j) {
+            bool any = false;
+            for (auto const& it : mHeldTransactions)
+            {
+                ApplyFlags flags = tapNONE;
+                auto const result =
+                    app_.getTxQ().apply(app_, view, it.second, flags, j);
+                if (result.second)
+                    any = true;
+            }
+            return any;
+        });
+    }
 
-    app_.openLedger().modify([&](OpenView& view, beast::Journal j) {
-        bool any = false;
-        for (auto const& it : mHeldTransactions)
-        {
-            ApplyFlags flags = tapNONE;
-            auto const result =
-                app_.getTxQ().apply(app_, view, it.second, flags, j);
-            if (result.second)
-                any = true;
-        }
-        return any;
-    });
-
-    // VFALCO TODO recreate the CanonicalTxSet object instead of resetting
-    // it.
     // VFALCO NOTE The hash for an open ledger is undefined so we use
     // something that is a reasonable substitute.
     mHeldTransactions.reset(app_.openLedger().current()->info().parentHash);

src/ripple/app/main/Application.cpp

@@ -1527,6 +1527,7 @@ ApplicationImp::start(bool withTimers)
     {
         setSweepTimer();
         setEntropyTimer();
+        m_networkOPs->setBatchApplyTimer();
     }
 
     m_io_latency_sampler.start();