Merge pull request #6357

42a7a4d daemon: auto public nodes - cache and prioritize most stable nodes (xiphon)

src/rpc/CMakeLists.txt

@@ -35,6 +35,7 @@ set(rpc_base_sources
 
 set(rpc_sources
   bootstrap_daemon.cpp
+  bootstrap_node_selector.cpp
   core_rpc_server.cpp
   rpc_payment.cpp
   rpc_version_str.cpp

src/rpc/bootstrap_daemon.cpp

@@ -2,6 +2,8 @@
 
 #include <stdexcept>
 
+#include <boost/thread/locks.hpp>
+
 #include "crypto/crypto.h"
 #include "cryptonote_core/cryptonote_core.h"
 #include "misc_log_ex.h"
@@ -12,15 +14,22 @@
 namespace cryptonote
 {
 
-  bootstrap_daemon::bootstrap_daemon(std::function<boost::optional<std::string>()> get_next_public_node)
-    : m_get_next_public_node(get_next_public_node)
+  bootstrap_daemon::bootstrap_daemon(
+    std::function<std::map<std::string, bool>()> get_public_nodes,
+    bool rpc_payment_enabled)
+    : m_selector(new bootstrap_node::selector_auto(std::move(get_public_nodes)))
+    , m_rpc_payment_enabled(rpc_payment_enabled)
   {
   }
 
-  bootstrap_daemon::bootstrap_daemon(const std::string &address, const boost::optional<epee::net_utils::http::login> &credentials)
-    : bootstrap_daemon(nullptr)
+  bootstrap_daemon::bootstrap_daemon(
+    const std::string &address,
+    boost::optional<epee::net_utils::http::login> credentials,
+    bool rpc_payment_enabled)
+    : m_selector(nullptr)
+    , m_rpc_payment_enabled(rpc_payment_enabled)
   {
-    if (!set_server(address, credentials))
+    if (!set_server(address, std::move(credentials)))
     {
       throw std::runtime_error("invalid bootstrap daemon address or credentials");
     }
@@ -54,11 +63,16 @@ namespace cryptonote
     return res.height;
   }
 
-  bool bootstrap_daemon::handle_result(bool success)
+  bool bootstrap_daemon::handle_result(bool success, const std::string &status)
   {
-    if (!success && m_get_next_public_node)
+    const bool failed = !success || (!m_rpc_payment_enabled && status == CORE_RPC_STATUS_PAYMENT_REQUIRED);
+    if (failed && m_selector)
     {
+      const std::string current_address = address();
       m_http_client.disconnect();
+
+      const boost::unique_lock<boost::mutex> lock(m_selector_mutex);
+      m_selector->handle_result(current_address, !failed);
     }
 
     return success;
@@ -79,14 +93,18 @@ namespace cryptonote
 
   bool bootstrap_daemon::switch_server_if_needed()
   {
-    if (!m_get_next_public_node || m_http_client.is_connected())
+    if (m_http_client.is_connected() || !m_selector)
     {
       return true;
     }
 
-    const boost::optional<std::string> address = m_get_next_public_node();
-    if (address) {
-      return set_server(*address);
+    boost::optional<bootstrap_node::node_info> node;
+    {
+      const boost::unique_lock<boost::mutex> lock(m_selector_mutex);
+      node = m_selector->next_node();
+    }
+    if (node) {
+      return set_server(node->address, node->credentials);
     }
 
     return false;

src/rpc/bootstrap_daemon.h

@@ -1,26 +1,34 @@
 #pragma  once
 
 #include <functional>
-#include <vector>
+#include <map>
 
 #include <boost/optional/optional.hpp>
+#include <boost/thread/mutex.hpp>
 #include <boost/utility/string_ref.hpp>
 
 #include "net/http_client.h"
 #include "storages/http_abstract_invoke.h"
 
+#include "bootstrap_node_selector.h"
+
 namespace cryptonote
 {
 
   class bootstrap_daemon
   {
   public:
-    bootstrap_daemon(std::function<boost::optional<std::string>()> get_next_public_node);
-    bootstrap_daemon(const std::string &address, const boost::optional<epee::net_utils::http::login> &credentials);
+    bootstrap_daemon(
+      std::function<std::map<std::string, bool>()> get_public_nodes,
+      bool rpc_payment_enabled);
+    bootstrap_daemon(
+      const std::string &address,
+      boost::optional<epee::net_utils::http::login> credentials,
+      bool rpc_payment_enabled);
 
     std::string address() const noexcept;
     boost::optional<uint64_t> get_height();
-    bool handle_result(bool success);
+    bool handle_result(bool success, const std::string &status);
 
     template <class t_request, class t_response>
     bool invoke_http_json(const boost::string_ref uri, const t_request &out_struct, t_response &result_struct)
@@ -30,7 +38,8 @@ namespace cryptonote
         return false;
       }
 
-      return handle_result(epee::net_utils::invoke_http_json(uri, out_struct, result_struct, m_http_client));
+      const bool result = epee::net_utils::invoke_http_json(uri, out_struct, result_struct, m_http_client);
+      return handle_result(result, result_struct.status);
     }
 
     template <class t_request, class t_response>
@@ -41,7 +50,8 @@ namespace cryptonote
         return false;
       }
 
-      return handle_result(epee::net_utils::invoke_http_bin(uri, out_struct, result_struct, m_http_client));
+      const bool result = epee::net_utils::invoke_http_bin(uri, out_struct, result_struct, m_http_client);
+      return handle_result(result, result_struct.status);
     }
 
     template <class t_request, class t_response>
@@ -52,7 +62,13 @@ namespace cryptonote
         return false;
       }
 
-      return handle_result(epee::net_utils::invoke_http_json_rpc("/json_rpc", std::string(command_name.begin(), command_name.end()), out_struct, result_struct, m_http_client));
+      const bool result = epee::net_utils::invoke_http_json_rpc(
+        "/json_rpc",
+        std::string(command_name.begin(), command_name.end()),
+        out_struct,
+        result_struct,
+        m_http_client);
+      return handle_result(result, result_struct.status);
     }
 
   private:
@@ -61,7 +77,9 @@ namespace cryptonote
 
   private:
     epee::net_utils::http::http_simple_client m_http_client;
-    std::function<boost::optional<std::string>()> m_get_next_public_node;
+    const bool m_rpc_payment_enabled;
+    const std::unique_ptr<bootstrap_node::selector> m_selector;
+    boost::mutex m_selector_mutex;
   };
 
 }

src/rpc/bootstrap_node_selector.cpp

@@ -0,0 +1,117 @@
+// Copyright (c) 2020, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "bootstrap_node_selector.h"
+
+#include "crypto/crypto.h"
+
+namespace cryptonote
+{
+namespace bootstrap_node
+{
+
+  void selector_auto::node::handle_result(bool success)
+  {
+    if (!success)
+    {
+      fails = std::min(std::numeric_limits<size_t>::max() - 2, fails) + 2;
+    }
+    else
+    {
+      fails = std::max(std::numeric_limits<size_t>::min() + 2, fails) - 2;
+    }
+  }
+
+  void selector_auto::handle_result(const std::string &address, bool success)
+  {
+    auto &nodes_by_address = m_nodes.get<by_address>();
+    const auto it = nodes_by_address.find(address);
+    if (it != nodes_by_address.end())
+    {
+      nodes_by_address.modify(it, [success](node &entry) {
+        entry.handle_result(success);
+      });
+    }
+  }
+
+  boost::optional<node_info> selector_auto::next_node()
+  {
+    if (!has_at_least_one_good_node())
+    {
+      append_new_nodes();
+    }
+
+    if (m_nodes.empty())
+    {
+      return {};
+    }
+
+    auto node = m_nodes.get<by_fails>().begin();
+    const size_t count = std::distance(node, m_nodes.get<by_fails>().upper_bound(node->fails));
+    std::advance(node, crypto::rand_idx(count));
+
+    return {{node->address, {}}};
+  }
+
+  bool selector_auto::has_at_least_one_good_node() const
+  {
+    return !m_nodes.empty() && m_nodes.get<by_fails>().begin()->fails == 0;
+  }
+
+  void selector_auto::append_new_nodes()
+  {
+    bool updated = false;
+
+    for (const auto &node : m_get_nodes())
+    {
+      const auto &address = node.first;
+      const auto &white = node.second;
+      const size_t initial_score = white ? 0 : 1;
+      updated |= m_nodes.get<by_address>().insert({address, initial_score}).second;
+    }
+
+    if (updated)
+    {
+      truncate();
+    }
+  }
+
+  void selector_auto::truncate()
+  {
+    const size_t total = m_nodes.size();
+    if (total > m_max_nodes)
+    {
+      auto &nodes_by_fails = m_nodes.get<by_fails>();
+      auto from = nodes_by_fails.rbegin();
+      std::advance(from, total - m_max_nodes);
+      nodes_by_fails.erase(from.base(), nodes_by_fails.end());
+    }
+  }
+
+}
+}

src/rpc/bootstrap_node_selector.h

@@ -0,0 +1,103 @@
+// Copyright (c) 2020, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#pragma  once
+
+#include <functional>
+#include <limits>
+#include <map>
+#include <string>
+#include <utility>
+
+#include <boost/multi_index_container.hpp>
+#include <boost/multi_index/member.hpp>
+#include <boost/multi_index/ordered_index.hpp>
+#include <boost/optional/optional.hpp>
+
+#include "net/http_client.h"
+
+namespace cryptonote
+{
+namespace bootstrap_node
+{
+
+  struct node_info
+  {
+    std::string address;
+    boost::optional<epee::net_utils::http::login> credentials;
+  };
+
+  struct selector
+  {
+    virtual void handle_result(const std::string &address, bool success) = 0;
+    virtual boost::optional<node_info> next_node() = 0;
+  };
+
+  class selector_auto : public selector
+  {
+  public:
+    selector_auto(std::function<std::map<std::string, bool>()> get_nodes, size_t max_nodes = 1000)
+      : m_get_nodes(std::move(get_nodes))
+      , m_max_nodes(max_nodes)
+    {}
+
+    void handle_result(const std::string &address, bool success) final;
+    boost::optional<node_info> next_node() final;
+
+  private:
+    bool has_at_least_one_good_node() const;
+    void append_new_nodes();
+    void truncate();
+
+  private:
+    struct node
+    {
+      std::string address;
+      size_t fails;
+
+      void handle_result(bool success);
+    };
+
+    struct by_address {};
+    struct by_fails {};
+
+    typedef boost::multi_index_container<
+      node,
+      boost::multi_index::indexed_by<
+        boost::multi_index::ordered_unique<boost::multi_index::tag<by_address>, boost::multi_index::member<node, std::string, &node::address>>,
+        boost::multi_index::ordered_non_unique<boost::multi_index::tag<by_fails>, boost::multi_index::member<node, size_t, &node::fails>>
+      >
+    > nodes_list;
+
+    const std::function<std::map<std::string, bool>()> m_get_nodes;
+    const size_t m_max_nodes;
+    nodes_list m_nodes;
+  };
+
+}
+}

src/rpc/core_rpc_server.cpp

@@ -178,7 +178,7 @@ namespace cryptonote
     return set_bootstrap_daemon(address, credentials);
   }
   //------------------------------------------------------------------------------------------------------------------------------
-  boost::optional<std::string> core_rpc_server::get_random_public_node()
+  std::map<std::string, bool> core_rpc_server::get_public_nodes(uint32_t credits_per_hash_threshold/* = 0*/)
   {
     COMMAND_RPC_GET_PUBLIC_NODES::request request;
     COMMAND_RPC_GET_PUBLIC_NODES::response response;
@@ -187,47 +187,51 @@ namespace cryptonote
     request.white = true;
     if (!on_get_public_nodes(request, response) || response.status != CORE_RPC_STATUS_OK)
     {
-      return boost::none;
+      return {};
     }
 
-    const auto get_random_node_address = [](const std::vector<public_node>& public_nodes) -> std::string {
-      const auto& random_node = public_nodes[crypto::rand_idx(public_nodes.size())];
-      const auto address = random_node.host + ":" + std::to_string(random_node.rpc_port);
-      return address;
+    std::map<std::string, bool> result;
+
+    const auto append = [&result, &credits_per_hash_threshold](const std::vector<public_node> &nodes, bool white) {
+      for (const auto &node : nodes)
+      {
+        const bool rpc_payment_enabled = credits_per_hash_threshold > 0;
+        const bool node_rpc_payment_enabled = node.rpc_credits_per_hash > 0;
+        if (!node_rpc_payment_enabled ||
+            (rpc_payment_enabled && node.rpc_credits_per_hash >= credits_per_hash_threshold))
+        {
+          result.insert(std::make_pair(node.host + ":" + std::to_string(node.rpc_port), white));
+        }
+      }
     };
 
-    if (!response.white.empty())
-    {
-      return get_random_node_address(response.white);
-    }
+    append(response.white, true);
+    append(response.gray, false);
 
-    MDEBUG("No white public node found, checking gray peers");
-
-    if (!response.gray.empty())
-    {
-      return get_random_node_address(response.gray);
-    }
-
-    MERROR("Failed to find any suitable public node");
-
-    return boost::none;
+    return result;
   }
   //------------------------------------------------------------------------------------------------------------------------------
   bool core_rpc_server::set_bootstrap_daemon(const std::string &address, const boost::optional<epee::net_utils::http::login> &credentials)
   {
     boost::unique_lock<boost::shared_mutex> lock(m_bootstrap_daemon_mutex);
 
+    constexpr const uint32_t credits_per_hash_threshold = 0;
+    constexpr const bool rpc_payment_enabled = credits_per_hash_threshold != 0;
+
     if (address.empty())
     {
       m_bootstrap_daemon.reset(nullptr);
     }
     else if (address == "auto")
     {
-      m_bootstrap_daemon.reset(new bootstrap_daemon([this]{ return get_random_public_node(); }));
+      auto get_nodes = [this, credits_per_hash_threshold]() {
+        return get_public_nodes(credits_per_hash_threshold);
+      };
+      m_bootstrap_daemon.reset(new bootstrap_daemon(std::move(get_nodes), rpc_payment_enabled));
     }
     else
     {
-      m_bootstrap_daemon.reset(new bootstrap_daemon(address, credentials));
+      m_bootstrap_daemon.reset(new bootstrap_daemon(address, credentials, rpc_payment_enabled));
     }
 
     m_should_use_bootstrap_daemon = m_bootstrap_daemon.get() != nullptr;
@@ -1941,7 +1945,7 @@ namespace cryptonote
       if (*bootstrap_daemon_height < target_height)
       {
         MINFO("Bootstrap daemon is out of sync");
-        return m_bootstrap_daemon->handle_result(false);
+        return m_bootstrap_daemon->handle_result(false, {});
       }
 
       uint64_t top_height = m_core.get_current_blockchain_height();

src/rpc/core_rpc_server.h

@@ -267,7 +267,7 @@ private:
     //utils
     uint64_t get_block_reward(const block& blk);
     bool fill_block_header_response(const block& blk, bool orphan_status, uint64_t height, const crypto::hash& hash, block_header_response& response, bool fill_pow_hash);
-    boost::optional<std::string> get_random_public_node();
+    std::map<std::string, bool> get_public_nodes(uint32_t credits_per_hash_threshold = 0);
     bool set_bootstrap_daemon(const std::string &address, const std::string &username_password);
     bool set_bootstrap_daemon(const std::string &address, const boost::optional<epee::net_utils::http::login> &credentials);
     enum invoke_http_mode { JON, BIN, JON_RPC };

tests/unit_tests/CMakeLists.txt

@@ -34,6 +34,7 @@ set(unit_tests_sources
   blockchain_db.cpp
   block_queue.cpp
   block_reward.cpp
+  bootstrap_node_selector.cpp
   bulletproofs.cpp
   canonical_amounts.cpp
   chacha.cpp

tests/unit_tests/bootstrap_node_selector.cpp

@@ -0,0 +1,172 @@
+// Copyright (c) 2020, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//  conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//  of conditions and the following disclaimer in the documentation and/or other
+//  materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//  used to endorse or promote products derived from this software without specific
+//  prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <gtest/gtest.h>
+
+#include "rpc/bootstrap_node_selector.h"
+
+class bootstrap_node_selector : public ::testing::Test
+{
+protected:
+  void SetUp() override
+  {
+    nodes.insert(white_nodes.begin(), white_nodes.end());
+    nodes.insert(gray_nodes.begin(), gray_nodes.end());
+  }
+
+  const std::map<std::string, bool> white_nodes = {
+    {
+      "white_node_1:18089", true
+    },
+    {
+      "white_node_2:18081", true
+    }
+  };
+  const std::map<std::string, bool> gray_nodes = {
+    {
+      "gray_node_1:18081", false
+    },
+    {
+      "gray_node_2:18089", false
+    }
+  };
+
+  std::map<std::string, bool> nodes;
+};
+
+TEST_F(bootstrap_node_selector, selector_auto_empty)
+{
+  cryptonote::bootstrap_node::selector_auto selector([]() {
+    return std::map<std::string, bool>();
+  });
+
+  EXPECT_FALSE(selector.next_node());
+}
+
+TEST_F(bootstrap_node_selector, selector_auto_no_credentials)
+{
+  cryptonote::bootstrap_node::selector_auto selector([this]() {
+    return nodes;
+  });
+
+  for (size_t fails = 0; fails < nodes.size(); ++fails)
+  {
+    const auto current = selector.next_node();
+    EXPECT_FALSE(current->credentials);
+
+    selector.handle_result(current->address, false);
+  }
+}
+
+TEST_F(bootstrap_node_selector, selector_auto_success)
+{
+  cryptonote::bootstrap_node::selector_auto selector([this]() {
+    return nodes;
+  });
+
+  auto current = selector.next_node();
+  for (size_t fails = 0; fails < nodes.size(); ++fails)
+  {
+    selector.handle_result(current->address, true);
+
+    current = selector.next_node();
+    EXPECT_TRUE(white_nodes.count(current->address) > 0);
+  }
+}
+
+TEST_F(bootstrap_node_selector, selector_auto_failure)
+{
+  cryptonote::bootstrap_node::selector_auto selector([this]() {
+    return nodes;
+  });
+
+  auto current = selector.next_node();
+  for (size_t fails = 0; fails < nodes.size(); ++fails)
+  {
+    const auto previous = current;
+
+    selector.handle_result(current->address, false);
+
+    current = selector.next_node();
+    EXPECT_NE(current->address, previous->address);
+  }
+}
+
+TEST_F(bootstrap_node_selector, selector_auto_white_nodes_first)
+{
+  cryptonote::bootstrap_node::selector_auto selector([this]() {
+    return nodes;
+  });
+
+  for (size_t iterations = 0; iterations < 2; ++iterations)
+  {
+    for (size_t fails = 0; fails < white_nodes.size(); ++fails)
+    {
+      const auto current = selector.next_node();
+      EXPECT_TRUE(white_nodes.count(current->address) > 0);
+
+      selector.handle_result(current->address, false);
+    }
+
+    for (size_t fails = 0; fails < gray_nodes.size(); ++fails)
+    {
+      const auto current = selector.next_node();
+      EXPECT_TRUE(gray_nodes.count(current->address) > 0);
+
+      selector.handle_result(current->address, false);
+    }
+  }
+}
+
+TEST_F(bootstrap_node_selector, selector_auto_max_nodes)
+{
+  const size_t max_nodes = nodes.size() / 2;
+
+  bool populated_once = false;
+  cryptonote::bootstrap_node::selector_auto selector([this, &populated_once]() {
+    if (!populated_once)
+    {
+      populated_once = true;
+      return nodes;
+    }
+
+    return std::map<std::string, bool>();
+  }, max_nodes);
+
+  std::set<std::string> unique_nodes;
+
+  for (size_t fails = 0; fails < nodes.size(); ++fails)
+  {
+    const auto current = selector.next_node();
+    unique_nodes.insert(current->address);
+
+    selector.handle_result(current->address, false);
+  }
+
+  EXPECT_EQ(unique_nodes.size(), max_nodes);
+}