Give ledger data requests their own job type:

This gives requests for ledger data (and transaction set data)
from peers a separate job type and prioritizes it appropriately.
Previously it was lumped in with fetch packs which have a low
concurrency limit. This should improve the performance of
retrieving historical information.

src/ripple/core/Job.h

@@ -40,8 +40,8 @@ enum JobType
     jtPACK,          // Make a fetch pack for a peer
     jtPUBOLDLEDGER,  // An old ledger has been accepted
     jtVALIDATION_ut, // A validation from an untrusted source
-    jtPROOFWORK,     // A proof of work demand from another server
     jtTRANSACTION_l, // A local transaction
+    jtLEDGER_REQ,    // Peer request ledger/txnset data
     jtPROPOSAL_ut,   // A proposal from an untrusted source
     jtLEDGER_DATA,   // Received data for a ledger we're acquiring
     jtCLIENT,        // A websocket command from the client

src/ripple/core/JobTypes.h

@@ -33,7 +33,6 @@ public:
     typedef std::map <JobType, JobTypeInfo> Map;
     typedef Map::const_iterator const_iterator;
 
-
     JobTypes ()
         : m_unknown (jtINVALID, "invalid", 0, true, true, 0, 0)
     {
@@ -51,14 +50,14 @@ public:
         add (jtVALIDATION_ut, "untrustedValidation",
             maxLimit, true,   false, 2000,  5000);
 
-        // A proof of work demand from another server
-        add (jtPROOFWORK,     "proofOfWork",
-            maxLimit, true,   false, 2000,  5000);
-
         // A local transaction
         add (jtTRANSACTION_l, "localTransaction",
             maxLimit, true,   false, 100,   500);
 
+        // A request for ledger/txnset data from another server
+        add (jtLEDGER_REQ,    "ledgerRequest",
+            2,        true,   false,    0,     0);
+
         // A proposal from an untrusted source
         add (jtPROPOSAL_ut,   "untrustedProposal",
             maxLimit, true,   false, 500,   1250);
@@ -67,10 +66,6 @@ public:
         add (jtLEDGER_DATA,   "ledgerData",
             2,        true,   false, 0,     0);
 
-        // Update pathfinding requests
-        add (jtUPDATE_PF,     "updatePaths",
-            maxLimit, true,   false, 0,     0);
-
         // A websocket command from the client
         add (jtCLIENT,        "clientCommand",
             maxLimit, true,   false, 2000,  5000);
@@ -79,6 +74,10 @@ public:
         add (jtRPC,           "RPC",
             maxLimit, false,  false, 0,     0);
 
+        // Update pathfinding requests
+        add (jtUPDATE_PF,     "updatePaths",
+            maxLimit, true,   false, 0,     0);
+
         // A transaction received from the network
         add (jtTRANSACTION,   "transaction",
             maxLimit, true,   false, 250,   1000);

src/ripple/overlay/impl/PeerImp.cpp

@@ -943,7 +943,7 @@ void
 PeerImp::onMessage (std::shared_ptr <protocol::TMGetLedger> const& m)
 {
     fee_ = Resource::feeMediumBurdenPeer;
-    getApp().getJobQueue().addJob (jtPACK, "recvGetLedger", std::bind(
+    getApp().getJobQueue().addJob (jtLEDGER_REQ, "recvGetLedger", std::bind(
         beast::weak_fn(&PeerImp::getLedger, shared_from_this()), m));
 }