Fix several bugs found in new server scanner code

src/rpc/scanner/server.cpp

@@ -28,6 +28,7 @@
 #include "server.h"
 
 #include <boost/asio/coroutine.hpp>
+#include <boost/asio/dispatch.hpp>
 #include <boost/lexical_cast.hpp>
 #include <boost/numeric/conversion/cast.hpp>
 #include <sodium/utils.h>
@@ -163,12 +164,16 @@ namespace lws { namespace rpc { namespace scanner
 
     void operator()(const boost::system::error_code& error = {})
     {
-      if (!self_ || error)
+      if (error)
       {
         if (error == boost::asio::error::operation_aborted)
           return; // exiting
         MONERO_THROW(error, "server acceptor failed");
       }
+
+      if (!self_ || self_->stop_)
+        return;
+
       assert(self_->strand_.running_in_this_thread());
       BOOST_ASIO_CORO_REENTER(*this)
       {
@@ -192,7 +197,7 @@ namespace lws { namespace rpc { namespace scanner
 
     void operator()(const boost::system::error_code& error = {}) const
     {
-      if (!self_ || error == boost::asio::error::operation_aborted)
+      if (!self_ || self_->stop_ || error == boost::asio::error::operation_aborted)
         return;
 
       assert(self_->strand_.running_in_this_thread());
@@ -223,7 +228,7 @@ namespace lws { namespace rpc { namespace scanner
         return;
       }
 
-      auto reader = self_->disk_.start_read(std::move(self_->read_txn_));
+      auto reader = self_->disk_.start_read();
       if (!reader)
       {
         if (reader.matches(std::errc::no_lock_available))
@@ -240,6 +245,8 @@ namespace lws { namespace rpc { namespace scanner
       if (current_users.count() < self_->active_.size())
       {
         // a shrinking user base, re-shuffle
+        reader->finish_read();
+        self_->accounts_cur_ = current_users.give_cursor();
         self_->do_replace_users();
         return;
       }
@@ -254,6 +261,8 @@ namespace lws { namespace rpc { namespace scanner
           new_accounts.push_back(MONERO_UNWRAP(reader->get_full_account(user.get_value<db::account>())));
           if (replace_threshold < new_accounts.size())
           {
+            reader->finish_read();
+            self_->accounts_cur_ = current_users.give_cursor();
             self_->do_replace_users();
             return;
           }
@@ -268,6 +277,8 @@ namespace lws { namespace rpc { namespace scanner
 
       if (!active_copy.empty())
       {
+        reader->finish_read();
+        self_->accounts_cur_ = current_users.give_cursor();
         self_->do_replace_users();
         return;
       }
@@ -306,7 +317,7 @@ namespace lws { namespace rpc { namespace scanner
 
         self_->next_thread_ %= total_threads;
       }
-      self_->read_txn_ = reader->finish_read();
+      reader->finish_read();
       self_->accounts_cur_ = current_users.give_cursor();
     }
   };
@@ -401,6 +412,28 @@ namespace lws { namespace rpc { namespace scanner
     active_ = std::move(active);
   }
 
+  void server::do_stop()
+  {
+    assert(strand_.running_in_this_thread());
+    if (stop_)
+      return;
+
+    MDEBUG("Stopping rpc::scanner::server async operations");
+    boost::system::error_code error{};
+    check_timer_.cancel(error);
+    acceptor_.cancel(error);
+    acceptor_.close(error);
+
+    for (auto& remote : remote_)
+    {
+      const auto conn = remote.lock();
+      if (conn)
+        boost::asio::dispatch(conn->strand_, [conn] () { conn->cleanup(); });
+    }
+
+    stop_ = true;
+  }
+
   boost::asio::ip::tcp::endpoint server::get_endpoint(const std::string& address)
   {
     std::string host;
@@ -432,12 +465,12 @@ namespace lws { namespace rpc { namespace scanner
       active_(std::move(active)),
       disk_(std::move(disk)),
       zclient_(std::move(zclient)),
-      read_txn_{},
       accounts_cur_{},
       next_thread_(0),
       pass_hashed_(),
       pass_salt_(),
-      webhook_verify_(webhook_verify)
+      webhook_verify_(webhook_verify),
+      stop_(false)
   {
     std::sort(active_.begin(), active_.end());
     for (const auto& local : local_)
@@ -488,6 +521,9 @@ namespace lws { namespace rpc { namespace scanner
       {
         self->acceptor_.close();
         self->acceptor_.open(endpoint.protocol());
+#if !defined(_WIN32)
+        self->acceptor_.set_option(boost::asio::ip::tcp::acceptor::reuse_address(true));
+#endif
         self->acceptor_.bind(endpoint);
         self->acceptor_.listen();
 
@@ -522,7 +558,17 @@ namespace lws { namespace rpc { namespace scanner
       {
         const lws::scanner_options opts{self->webhook_verify_, false, false};
         if (!lws::user_data::store(self->disk_, self->zclient_, epee::to_span(blocks), epee::to_span(users), nullptr, opts))
-          GET_IO_SERVICE(self->check_timer_).stop();
+        {
+          self->do_stop();
+          self->strand_.context().stop();
+        }
       });
   }
+
+  void server::stop(const std::shared_ptr<server>& self)
+  {
+    if (!self)
+      MONERO_THROW(common_error::kInvalidArgument, "nullptr self");
+    boost::asio::dispatch(self->strand_, [self] () { self->do_stop(); });
+  }
 }}} // lws // rpc // scanner

src/rpc/scanner/server.h

@@ -65,12 +65,12 @@ namespace lws { namespace rpc { namespace scanner
     std::vector<db::account_id> active_;
     db::storage disk_;
     rpc::client zclient_;
-    lmdb::suspended_txn read_txn_;
     db::cursor::accounts accounts_cur_;
     std::size_t next_thread_;
     std::array<unsigned char, 32> pass_hashed_;
     std::array<unsigned char, crypto_pwhash_SALTBYTES> pass_salt_;
     const ssl_verification_t webhook_verify_;
+    bool stop_;
 
     //! Async acceptor routine
     class acceptor;
@@ -79,6 +79,9 @@ namespace lws { namespace rpc { namespace scanner
     //! Reset `local_` and `remote_` scanners. Must be called in `strand_`.
     void do_replace_users();
 
+    //! Stop all async operations
+    void do_stop();
+
   public:
     static boost::asio::ip::tcp::endpoint get_endpoint(const std::string& address);
 
@@ -105,6 +108,9 @@ namespace lws { namespace rpc { namespace scanner
     static void replace_users(const std::shared_ptr<server>& self);
 
     //! Update `users` information on local DB
-    static void store(const std::shared_ptr<server>& self, std::vector<lws::account> users, std::vector<crypto::hash> blocks); 
+    static void store(const std::shared_ptr<server>& self, std::vector<lws::account> users, std::vector<crypto::hash> blocks);
+
+    //! Stop a running instance of all operations
+    static void stop(const std::shared_ptr<server>& self);
   };
 }}} // lws // rpc // scanner

src/rpc/scanner/write_commands.h

@@ -27,6 +27,7 @@
 #pragma once
 
 #include <boost/asio/coroutine.hpp>
+#include <boost/asio/dispatch.hpp>
 #include <boost/asio/write.hpp>
 #include <chrono>
 #include <memory>
@@ -167,7 +168,7 @@ namespace lws { namespace rpc { namespace scanner
 
     if (msg.empty())
     {
-      self->cleanup();
+      boost::asio::dispatch(self->strand_, [self] () { self->cleanup(); });
       return;
     }
 

src/scanner.cpp

@@ -27,6 +27,7 @@
 #include "scanner.h"
 
 #include <algorithm>
+#include <boost/asio/use_future.hpp>
 #include <boost/numeric/conversion/cast.hpp>
 #include <boost/range/combine.hpp>
 #include <boost/thread/condition_variable.hpp>
@@ -1044,23 +1045,27 @@ namespace lws
       users.clear();
       users.shrink_to_fit();
 
-      {
-        auto server = std::make_shared<rpc::scanner::server>(
-          self.io_,
-          disk.clone(),
-          MONERO_UNWRAP(ctx.connect()),
-          queues,
-          std::move(active),
-          opts.webhook_verify
-        );
+      auto server = std::make_shared<rpc::scanner::server>(
+        self.io_,
+        disk.clone(),
+        MONERO_UNWRAP(ctx.connect()),
+        queues,
+        std::move(active),
+        opts.webhook_verify
+      );
 
-        rpc::scanner::server::start_user_checking(server);
-        if (!lws_server_addr.empty())
-          rpc::scanner::server::start_acceptor(std::move(server), lws_server_addr, std::move(lws_server_pass));
-      }
+      rpc::scanner::server::start_user_checking(server);
+      if (!lws_server_addr.empty())
+        rpc::scanner::server::start_acceptor(std::move(server), lws_server_addr, std::move(lws_server_pass));
 
-      // Blocks until sigint, local scanner issue, or exception
+      // Blocks until sigint, local scanner issue, storage issue, or exception
       self.io_.run();
+      self.io_.restart();
+
+      // Make sure server stops because we could re-start after blockchain sync
+      rpc::scanner::server::stop(server);
+      self.io_.poll();
+      self.io_.restart();
     }
 
     template<typename R, typename Q>
@@ -1396,14 +1401,19 @@ namespace lws
 
         boost::asio::steady_timer poll{sync_.io_};
         poll.expires_from_now(rpc::scanner::account_poll_interval);
-        poll.async_wait([] (boost::system::error_code) {});
+        const auto ready = poll.async_wait(boost::asio::use_future);
 
-        sync_.io_.run_one();
+        /* The exchange rates timer could run while waiting, so ensure that
+          the correct timer was run. */
+        while (!has_shutdown() && ready.wait_for(std::chrono::seconds{0}) == std::future_status::timeout)
+        {
+          sync_.io_.run_one();
+          sync_.io_.restart();
+        }
       }
       else
         check_loop(sync_, disk_.clone(), ctx, thread_count, lws_server_addr, lws_server_pass, std::move(users), std::move(active), opts);
 
-      sync_.io_.reset();
       if (has_shutdown())
         return;