Configurable fetch depth.

doc/rippled-example.cfg

@@ -494,6 +494,20 @@
 #
 #
 #
+# [fetch_depth]
+#
+#   The number of past ledgers to serve to other peers that request historical
+#   ledger data (or "full" for no limit).
+#
+#   Servers that require low latency and high local performance may wish to
+#   restrict the historical ledgers they are willing to serve. Setting this
+#   below 32 can harm network stability as servers require easy access to
+#   recent history to stay in sync. Values below 128 are not recommended.
+#
+#   The default is: full
+#
+#
+#
 # [validation_seed]
 #
 #   To perform validation, this section should contain either a validation seed

src/ripple_app/consensus/LedgerConsensus.cpp

@@ -1445,6 +1445,13 @@ private:
             uMin = 0;
             uMax = 0;
         }
+        else
+        {
+            // Don't advertise ledgers we're not willing to serve
+            uint32 early = getApp().getLedgerMaster().getEarliestFetch ();
+            if (uMin < early)
+               uMin = early;
+        }
         s.set_firstseq (uMin);
         s.set_lastseq (uMax);
         getApp ().getPeers ().foreach (send_always (

src/ripple_app/ledger/LedgerMaster.cpp

@@ -424,6 +424,14 @@ public:
         return true;
     }
 
+    uint32 getEarliestFetch ()
+    {
+        uint32 e = getClosedLedger()->getLedgerSeq();
+        if (e > getConfig().FETCH_DEPTH)
+            e -= getConfig().FETCH_DEPTH;
+        return e;
+    }
+
     void tryFill (Job& job, Ledger::pointer ledger)
     {
         uint32 seq = ledger->getLedgerSeq ();

src/ripple_app/ledger/LedgerMaster.h

@@ -73,6 +73,8 @@ public:
 
     virtual void setMinValidations (int v) = 0;
 
+    virtual uint32 getEarliestFetch () = 0;
+
     virtual void pushLedger (Ledger::pointer newLedger) = 0;
     virtual void pushLedger (Ledger::pointer newLCL, Ledger::pointer newOL) = 0;
     virtual void storeLedger (Ledger::pointer) = 0;

src/ripple_core/functional/Config.cpp

@@ -130,6 +130,7 @@ Config::Config ()
     FEE_CONTRACT_OPERATION  = DEFAULT_FEE_OPERATION;
 
     LEDGER_HISTORY          = 256;
+    FETCH_DEPTH             = 1000000000;
 
     PATH_SEARCH_OLD         = DEFAULT_PATH_SEARCH_OLD;
     PATH_SEARCH             = DEFAULT_PATH_SEARCH;
@@ -533,13 +534,25 @@ void Config::load ()
             {
                 boost::to_lower (strTemp);
 
-                if (strTemp == "none")
+                if (strTemp == "full")
-                    LEDGER_HISTORY = 0;
-                else if (strTemp == "full")
                     LEDGER_HISTORY = 1000000000u;
                 else
                     LEDGER_HISTORY = lexicalCastThrow <uint32> (strTemp);
             }
+            if (SectionSingleB (secConfig, SECTION_FETCH_DEPTH, strTemp))
+            {
+                boost::to_lower (strTemp);
+
+                if (strTemp == "none")
+                    FETCH_DEPTH = 0;
+                else if (strTemp == "full")
+                    FETCH_DEPTH = 1000000000u;
+                else
+                    FETCH_DEPTH = lexicalCastThrow <uint32> (strTemp);
+
+                if (FETCH_DEPTH < 10)
+                    FETCH_DEPTH = 10;
+            }
 
             if (SectionSingleB (secConfig, SECTION_PATH_SEARCH_OLD, strTemp))
                 PATH_SEARCH_OLD     = lexicalCastThrow <int> (strTemp);

src/ripple_core/functional/Config.h

@@ -446,6 +446,7 @@ public:
 
     // Node storage configuration
     uint32                      LEDGER_HISTORY;
+    uint32                      FETCH_DEPTH;
     int                         NODE_SIZE;
 
     // Client behavior

src/ripple_core/functional/ConfigSections.h

@@ -46,6 +46,7 @@ struct ConfigSection
 #define SECTION_FEE_OPERATION           "fee_operation"
 #define SECTION_FEE_ACCOUNT_RESERVE     "fee_account_reserve"
 #define SECTION_FEE_OWNER_RESERVE       "fee_owner_reserve"
+#define SECTION_FETCH_DEPTH             "fetch_depth"
 #define SECTION_LEDGER_HISTORY          "ledger_history"
 #define SECTION_INSIGHT                 "insight"
 #define SECTION_IPS                     "ips"

src/ripple_overlay/impl/PeerImp.h

@@ -2327,6 +2327,11 @@ private:
 	        }
 	        else if (packet.has_ledgerseq ())
 	        {
+	            if (packet.ledgerseq() < getApp().getLedgerMaster().getEarliestFetch())
+	            {
+	                m_journal.debug << "Peer requests early ledger";
+	                return;
+	            }
 	            ledger = getApp().getLedgerMaster ().getLedgerBySeq (packet.ledgerseq ());
 	            if (m_journal.debug)
 	            	m_journal.debug << "Don't have ledger " << packet.ledgerseq ();
@@ -2359,6 +2364,12 @@ private:
 	            return;
 	        }
 
+                if (!packet.has_ledgerseq() && (ledger->getLedgerSeq() < getApp().getLedgerMaster().getEarliestFetch()))
+                {
+                    m_journal.debug << "Peer requests early ledger";
+                    return;
+                }
+
 	        // Fill out the reply
 	        uint256 lHash = ledger->getHash ();
 	        reply.set_ledgerhash (lHash.begin (), lHash.size ());
@@ -2545,6 +2556,13 @@ private:
             return;
         }
 
+        if (haveLedger->getLedgerSeq() < getApp().getLedgerMaster().getEarliestFetch())
+        {
+            m_journal.debug << "Peer requests fetch pack that is too early";
+            charge (Resource::feeInvalidRequest);
+            return;
+        }
+
         Ledger::pointer wantLedger = getApp().getOPs ().getLedgerByHash (haveLedger->getParentHash ());
 
         if (!wantLedger)