Adjust pathfinding configuration defaults:

The pathfinding engine built into the code has several configurable
parameters to adjust the depth of the paths indexed and explored.

These parameters can dramatically impact the performance and memory
consumption of a server; higher values can result in resource usage
increasing exponentially.

These default values were decided early and somewhat arbitrarily at
a time when the network and the size of the network state were much
smaller.

This commit adjusts the default values to reduce the depth of paths
to more reasonable levels; unless explicitly overriden, the changes
mean that pathfinding operations will return fewer, shallower paths
than previous versions of the software.

src/ripple/core/Config.h

@@ -174,10 +174,10 @@ public:
     //                 Servers operating as validators disable path finding by
     //                 default by setting the `PATH_SEARCH_MAX` option to 0
     //                 unless it is explicitly set in the configuration file.
-    int PATH_SEARCH_OLD = 7;
+    int PATH_SEARCH_OLD = 2;
-    int PATH_SEARCH = 7;
+    int PATH_SEARCH = 2;
     int PATH_SEARCH_FAST = 2;
-    int PATH_SEARCH_MAX = 10;
+    int PATH_SEARCH_MAX = 3;
 
     // Validation
     std::optional<std::size_t>

src/test/app/Path_test.cpp

@@ -35,6 +35,7 @@
 #include <condition_variable>
 #include <mutex>
 #include <test/jtx.h>
+#include <test/jtx/envconfig.h>
 #include <thread>
 
 namespace ripple {
@@ -171,6 +172,21 @@ IPE(Issue const& iss)
 
 class Path_test : public beast::unit_test::suite
 {
+    jtx::Env
+    pathTestEnv()
+    {
+        // These tests were originally written with search parameters that are
+        // different from the current defaults. This function creates an env
+        // with the search parameters that the tests were written for.
+        using namespace jtx;
+        return Env(*this, envconfig([](std::unique_ptr<Config> cfg) {
+            cfg->PATH_SEARCH_OLD = 7;
+            cfg->PATH_SEARCH = 7;
+            cfg->PATH_SEARCH_MAX = 10;
+            return cfg;
+        }));
+    }
+
 public:
     class gate
     {
@@ -314,7 +330,7 @@ public:
         testcase("source currency limits");
         using namespace std::chrono_literals;
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         auto const gw = Account("gateway");
         env.fund(XRP(10000), "alice", "bob", gw);
         env.trust(gw["USD"](100), "alice", "bob");
@@ -396,7 +412,7 @@ public:
     {
         testcase("no direct path no intermediary no alternatives");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         env.fund(XRP(10000), "alice", "bob");
 
         auto const result =
@@ -409,7 +425,7 @@ public:
     {
         testcase("direct path no intermediary");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         env.fund(XRP(10000), "alice", "bob");
         env.trust(Account("alice")["USD"](700), "bob");
 
@@ -426,7 +442,7 @@ public:
     {
         testcase("payment auto path find");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         auto const gw = Account("gateway");
         auto const USD = gw["USD"];
         env.fund(XRP(10000), "alice", "bob", gw);
@@ -445,7 +461,7 @@ public:
     {
         testcase("path find");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         auto const gw = Account("gateway");
         auto const USD = gw["USD"];
         env.fund(XRP(10000), "alice", "bob", gw);
@@ -467,7 +483,7 @@ public:
     {
         using namespace jtx;
         testcase("XRP to XRP");
-        Env env(*this);
+        Env env = pathTestEnv();
         env.fund(XRP(10000), "alice", "bob");
 
         auto const result = find_paths(env, "alice", "bob", XRP(5));
@@ -481,7 +497,7 @@ public:
         using namespace jtx;
 
         {
-            Env env(*this);
+            Env env = pathTestEnv();
             env.fund(XRP(10000), "alice", "bob", "carol", "dan", "edward");
             env.trust(Account("alice")["USD"](10), "bob");
             env.trust(Account("bob")["USD"](10), "carol");
@@ -500,7 +516,7 @@ public:
         }
 
         {
-            Env env(*this);
+            Env env = pathTestEnv();
             auto const gw = Account("gateway");
             auto const USD = gw["USD"];
             env.fund(XRP(10000), "alice", "bob", "carol", gw);
@@ -534,7 +550,7 @@ public:
     {
         testcase("alternative path consume both");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         auto const gw = Account("gateway");
         auto const USD = gw["USD"];
         auto const gw2 = Account("gateway2");
@@ -563,7 +579,7 @@ public:
     {
         testcase("alternative paths consume best transfer");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         auto const gw = Account("gateway");
         auto const USD = gw["USD"];
         auto const gw2 = Account("gateway2");
@@ -592,7 +608,7 @@ public:
     {
         testcase("alternative paths - consume best transfer first");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         auto const gw = Account("gateway");
         auto const USD = gw["USD"];
         auto const gw2 = Account("gateway2");
@@ -623,7 +639,7 @@ public:
     {
         testcase("alternative paths - limit returned paths to best quality");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         auto const gw = Account("gateway");
         auto const USD = gw["USD"];
         auto const gw2 = Account("gateway2");
@@ -658,7 +674,7 @@ public:
     {
         testcase("path negative: Issue #5");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         env.fund(XRP(10000), "alice", "bob", "carol", "dan");
         env.trust(Account("bob")["USD"](100), "alice", "carol", "dan");
         env.trust(Account("alice")["USD"](100), "dan");
@@ -696,7 +712,7 @@ public:
     {
         testcase("path negative: ripple-client issue #23: smaller");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         env.fund(XRP(10000), "alice", "bob", "carol", "dan");
         env.trust(Account("alice")["USD"](40), "bob");
         env.trust(Account("dan")["USD"](20), "bob");
@@ -715,7 +731,7 @@ public:
     {
         testcase("path negative: ripple-client issue #23: larger");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         env.fund(XRP(10000), "alice", "bob", "carol", "dan", "edward");
         env.trust(Account("alice")["USD"](120), "edward");
         env.trust(Account("edward")["USD"](25), "bob");
@@ -742,7 +758,7 @@ public:
     {
         testcase("via gateway");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         auto const gw = Account("gateway");
         auto const AUD = gw["AUD"];
         env.fund(XRP(10000), "alice", "bob", "carol", gw);
@@ -764,7 +780,7 @@ public:
     {
         testcase("path find");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         env.fund(XRP(10000), "alice", "bob", "carol");
         env.trust(Account("alice")["USD"](1000), "bob");
         env.trust(Account("bob")["USD"](1000), "carol");
@@ -782,7 +798,7 @@ public:
     {
         testcase("quality set and test");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         env.fund(XRP(10000), "alice", "bob");
         env(trust("bob", Account("alice")["USD"](1000)),
             json("{\"" + sfQualityIn.fieldName + "\": 2000}"),
@@ -828,7 +844,7 @@ public:
     {
         testcase("trust normal clear");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         env.fund(XRP(10000), "alice", "bob");
         env.trust(Account("bob")["USD"](1000), "alice");
         env.trust(Account("alice")["USD"](1000), "bob");
@@ -878,7 +894,7 @@ public:
     {
         testcase("trust auto clear");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         env.fund(XRP(10000), "alice", "bob");
         env.trust(Account("bob")["USD"](1000), "alice");
         env(pay("bob", "alice", Account("bob")["USD"](50)));
@@ -931,7 +947,7 @@ public:
     {
         testcase("Path Find: XRP -> XRP and XRP -> IOU");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         Account A1{"A1"};
         Account A2{"A2"};
         Account A3{"A3"};
@@ -1018,7 +1034,7 @@ public:
     {
         testcase("Path Find: non-XRP -> XRP");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         Account A1{"A1"};
         Account A2{"A2"};
         Account G3{"G3"};
@@ -1055,7 +1071,7 @@ public:
     {
         testcase("Path Find: Bitstamp and SnapSwap, liquidity with no offers");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         Account A1{"A1"};
         Account A2{"A2"};
         Account G1BS{"G1BS"};
@@ -1135,7 +1151,7 @@ public:
     {
         testcase("Path Find: non-XRP -> non-XRP, same currency");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         Account A1{"A1"};
         Account A2{"A2"};
         Account A3{"A3"};
@@ -1264,7 +1280,7 @@ public:
     {
         testcase("Path Find: non-XRP -> non-XRP, same currency)");
         using namespace jtx;
-        Env env(*this);
+        Env env = pathTestEnv();
         Account A1{"A1"};
         Account A2{"A2"};
         Account A3{"A3"};
@@ -1315,7 +1331,7 @@ public:
         auto const USD = gw["USD"];
         {
             // XRP -> IOU receive max
-            Env env(*this);
+            Env env = pathTestEnv();
             env.fund(XRP(10000), alice, bob, charlie, gw);
             env.close();
             env.trust(USD(100), alice, bob, charlie);
@@ -1338,7 +1354,7 @@ public:
         }
         {
             // IOU -> XRP receive max
-            Env env(*this);
+            Env env = pathTestEnv();
             env.fund(XRP(10000), alice, bob, charlie, gw);
             env.close();
             env.trust(USD(100), alice, bob, charlie);