Reduce outbound connections to node.current_outbound while current.

include/bitcoin/node/sessions/session_outbound.hpp

@@ -24,7 +24,7 @@
 
 namespace libbitcoin {
 namespace node {
-    
+
 class BCN_API session_outbound
   : public session_peer<network::session_outbound>
 {
@@ -33,13 +33,22 @@ class BCN_API session_outbound
     using base = session_peer<network::session_outbound>;
     using base::base;
 
+    /// Start connections, reduced when current (call from network strand).
+    void start(network::result_handler&& handler) NOEXCEPT override;
+
 protected:
     /// Outbound connections require the configured node services.
     uint64_t services_required() const NOEXCEPT override
     {
         return system::bit_or(base::services_required(),
             node_settings().services_required());
     }
+
+private:
+    void handle_started(const code& ec,
+        const network::result_handler& handler) NOEXCEPT;
+    bool handle_chase(const code& ec, event_value value) NOEXCEPT;
+    void update_connections() NOEXCEPT;
 };
 
 } // namespace node

include/bitcoin/node/settings.hpp

@@ -50,6 +50,7 @@ class BCN_API settings
     double minimum_fee_rate;
     double minimum_bump_rate;
     uint64_t batch_signatures;
+    uint16_t current_connections;
     uint16_t announcement_cache;
     uint16_t fee_estimate_horizon;
     uint32_t maximum_height;

src/protocols/protocol_observer.cpp

@@ -197,7 +197,11 @@ bool protocol_observer::handle_broadcast_terminator(const code& ec,
     if (stopped(ec))
         return false;
 
-    if (!message->targets(identifier(), outbound(), opposite()))
+    using target = network::diagnostics::target;
+    const auto slotted = (group() == target::outbound) &&
+        is_terminal(message->slots());
+
+    if (!slotted && !message->targets(identifier(), outbound(), opposite()))
         return true;
 
     message->stopped();

src/sessions/session_outbound.cpp

@@ -18,8 +18,88 @@
  */
 #include <bitcoin/node/sessions/session_outbound.hpp>
 
+#include <bitcoin/node/chase.hpp>
+#include <bitcoin/node/define.hpp>
+
 namespace libbitcoin {
 namespace node {
 
+#define CLASS session_outbound
+
+using namespace system;
+using namespace std::placeholders;
+
+BC_PUSH_WARNING(NO_THROW_IN_NOEXCEPT)
+
+// Start/stop sequence.
+// ----------------------------------------------------------------------------
+
+void session_outbound::start(network::result_handler&& handler) NOEXCEPT
+{
+    BC_ASSERT(stranded());
+
+    update_connections();
+    base::start(BIND(handle_started, _1, std::move(handler)));
+}
+
+void session_outbound::handle_started(const code& ec,
+    const network::result_handler& handler) NOEXCEPT
+{
+    BC_ASSERT(stranded());
+
+    if (ec || stopped() || is_zero(node_settings().current_connections))
+    {
+        handler(ec);
+        return;
+    }
+
+    subscribe_chase(BIND(handle_chase, _1, _2));
+    update_connections();
+    handler(ec);
+}
+
+// Currency.
+// ----------------------------------------------------------------------------
+
+bool session_outbound::handle_chase(const code&, event_value value) NOEXCEPT
+{
+    BC_ASSERT(stranded());
+
+    if (stopped())
+        return false;
+
+    switch (to_chase(value))
+    {
+        case chase::block:
+        case chase::stale:
+        {
+            update_connections();
+            break;
+        }
+        case chase::stop:
+        {
+            return false;
+        }
+        default:
+        {
+            break;
+        }
+    }
+
+    return true;
+}
+
+// Outbound is reduced when current, when inbound is enabled (delay_inbound).
+void session_outbound::update_connections() NOEXCEPT
+{
+    BC_ASSERT(stranded());
+
+    const auto reduced = node_settings().current_connections;
+    const auto configured = network_settings().outbound.connections;
+    set_connections((is_recent() && to_bool(reduced)) ? reduced : configured);
+}
+
+BC_POP_WARNING()
+
 } // namespace node
 } // namespace libbitcoin

src/settings.cpp

@@ -45,6 +45,7 @@ settings::settings() NOEXCEPT
     minimum_fee_rate{ 0.0 },
     minimum_bump_rate{ 0.0 },
     allowed_deviation{ 1.5 },
+    current_connections{ 10 },
     announcement_cache{ 42 },
     fee_estimate_horizon{ 0 },
     ////snapshot_bytes{ 200'000'000'000 },

test/settings.cpp

@@ -47,6 +47,7 @@ BOOST_AUTO_TEST_CASE(settings__node__default_context__expected)
     BOOST_REQUIRE_EQUAL(node.minimum_bump_rate, 0.0);
     BOOST_REQUIRE_EQUAL(node.allowed_deviation, 1.5);
     BOOST_REQUIRE_EQUAL(node.batch_signatures, 0_u64);
+    BOOST_REQUIRE_EQUAL(node.current_connections, 10_u16);
     BOOST_REQUIRE_EQUAL(node.announcement_cache, 42_u16);
     BOOST_REQUIRE_EQUAL(node.fee_estimate_horizon, 0u);
     BOOST_REQUIRE_EQUAL(node.maximum_height, 0_u32);