Adds a buffer that has a tolerance.

include/boost/redis/detail/buffer.hpp

@@ -0,0 +1,99 @@
+#ifndef BOOST_REDIS_BUFFER_HPP
+#define BOOST_REDIS_BUFFER_HPP
+
+#include <limits>
+#include <string>
+#include <algorithm>
+
+#include <boost/asio/buffer.hpp>
+#include <boost/throw_exception.hpp>
+
+namespace boost::redis::detail
+{
+
+template <class Elem, class Traits, class Allocator>
+class dynamic_string_buffer {
+public:
+   using const_buffers_type = asio::const_buffer;
+   using mutable_buffers_type = asio::mutable_buffer;
+
+   explicit
+   dynamic_string_buffer(
+      std::basic_string<Elem, Traits, Allocator>& s,
+      std::size_t maximum_size) noexcept
+   : string_(s)
+   , max_size_(maximum_size)
+   {
+   }
+
+   void clear()
+   {
+      consumed_ = 0;
+   }
+
+   std::size_t size() const noexcept
+   {
+      return (std::min)(string_.size() - consumed_, max_size_);
+   }
+
+   bool empty() const noexcept
+   {
+      return size() == 0;
+   }
+
+   std::size_t max_size() const noexcept
+   {
+      return max_size_;
+   }
+
+   char const& front() const noexcept
+   {
+      return string_.at(consumed_);
+   }
+
+   std::size_t capacity() const noexcept
+   {
+      return (std::min)(string_.capacity(), max_size());
+   }
+
+   mutable_buffers_type data(std::size_t pos, std::size_t n) noexcept
+   {
+      return mutable_buffers_type(asio::buffer(asio::buffer(string_, max_size_) + pos + consumed_, n));
+   }
+
+   const_buffers_type data(std::size_t pos, std::size_t n) const noexcept
+   {
+      return const_buffers_type(asio::buffer(asio::buffer(string_, max_size_) + pos + consumed_, n));
+   }
+
+   void grow(std::size_t n)
+   {
+      if (string_.size() > max_size_ || (string_.size() + n) > max_size_)
+         BOOST_THROW_EXCEPTION(std::length_error{"dynamic_string_buffer too long"});
+
+      string_.resize(string_.size() + n);
+   }
+
+   void shrink(std::size_t n)
+   {
+      string_.resize(n > (string_.size() - consumed_) ? consumed_ : string_.size() - n);
+   }
+
+   void consume(std::size_t n, std::size_t tolerance = 100'000)
+   {
+      consumed_ += n;
+      if (consumed_ > tolerance) {
+         string_.erase(0, consumed_);
+         consumed_ = 0;
+      }
+   }
+
+private:
+   std::basic_string<Elem, Traits, Allocator>& string_;
+   std::size_t consumed_ = 0;
+   std::size_t const max_size_;
+};
+
+}
+
+#endif // BOOST_REDIS_BUFFER_HPP

include/boost/redis/detail/connection_base.hpp

@@ -16,6 +16,7 @@
 #include <boost/redis/resp3/type.hpp>
 #include <boost/redis/config.hpp>
 #include <boost/redis/detail/runner.hpp>
+#include <boost/redis/detail/buffer.hpp>
 
 #include <boost/system.hpp>
 #include <boost/asio/basic_stream_socket.hpp>
@@ -111,7 +112,7 @@ class read_next_op {
             // If we detect a push in the middle of a request we have
             // to hand it to the push consumer. To do that we need
             // some data in the read bufer.
-            if (conn_->read_buffer_.empty()) {
+            if (std::empty(conn_->dbuf_)) {
 
                if (conn_->use_ssl()) {
                   BOOST_ASIO_CORO_YIELD
@@ -130,7 +131,7 @@ class read_next_op {
 
             // If the next request is a push we have to handle it to
             // the receive_op wait for it to be done and continue.
-            if (resp3::to_type(conn_->read_buffer_.front()) == resp3::type::push) {
+            if (resp3::to_type(conn_->dbuf_.front()) == resp3::type::push) {
                BOOST_ASIO_CORO_YIELD
                conn_->async_wait_receive(std::move(self));
                BOOST_REDIS_CHECK_OP1(conn_->cancel(operation::run););
@@ -154,7 +155,7 @@ class read_next_op {
                return;
             }
 
-            conn_->dbuf_.consume(n);
+            conn_->consume(n);
             read_size_ += n;
 
             BOOST_ASSERT(cmds_ != 0);
@@ -204,7 +205,7 @@ struct receive_op {
             return;
          }
 
-         conn_->dbuf_.consume(n);
+         conn_->consume(n);
 
          if (!conn_->is_next_push()) {
             conn_->read_op_timer_.cancel();
@@ -329,6 +330,7 @@ struct run_op {
       {
          conn->write_buffer_.clear();
          conn->read_buffer_.clear();
+         conn->dbuf_.clear();
 
          BOOST_ASIO_CORO_YIELD
          asio::experimental::make_parallel_group(
@@ -408,7 +410,7 @@ struct reader_op {
    bool as_push() const
    {
       return
-         (resp3::to_type(conn->read_buffer_.front()) == resp3::type::push)
+         (resp3::to_type(conn->dbuf_.front()) == resp3::type::push)
           || conn->reqs_.empty()
           || (!conn->reqs_.empty() && conn->reqs_.front()->get_number_of_commands() == 0)
           || !conn->is_waiting_response(); // Added to deal with MONITOR.
@@ -457,7 +459,7 @@ struct reader_op {
          // - https://github.com/redis/redis/issues/11784
          // - https://github.com/redis/redis/issues/6426
          //
-         BOOST_ASSERT(!conn->read_buffer_.empty());
+         BOOST_ASSERT(!conn->dbuf_.empty());
          if (as_push()) {
             BOOST_ASIO_CORO_YIELD
             conn->async_wait_receive(std::move(self));
@@ -890,12 +892,17 @@ class connection_base {
 
    bool is_next_push() const noexcept
    {
-      return !read_buffer_.empty() && (resp3::to_type(read_buffer_.front()) == resp3::type::push);
+      return !dbuf_.empty() && (resp3::to_type(dbuf_.front()) == resp3::type::push);
    }
 
    auto is_open() const noexcept { return stream_->next_layer().is_open(); }
    auto& lowest_layer() noexcept { return stream_->lowest_layer(); }
 
+   void consume(std::size_t n)
+   {
+      dbuf_.consume(n, 1'000'000);
+   }
+
    asio::ssl::context ctx_;
    std::unique_ptr<next_layer_type> stream_;
 
@@ -907,8 +914,9 @@ class connection_base {
    timer_type read_op_timer_;
    runner_type runner_;
 
-   using dyn_buffer_type = asio::dynamic_string_buffer<char, std::char_traits<char>, std::allocator<char>>;
+   using dyn_buffer_type = redis::detail::dynamic_string_buffer<char, std::char_traits<char>, std::allocator<char>>;
 
+   std::size_t const read_buffer_consume_tolerance_ = 1'000'000; // 1Mb
    std::string read_buffer_;
    dyn_buffer_type dbuf_;
    std::string write_buffer_;

tests/test_conn_echo_stress.cpp

@@ -89,7 +89,7 @@ auto async_echo_stress() -> net::awaitable<void>
    int const sessions = 500;
 
    // The number of pings that will be sent by each session.
-   int const msgs = 1000;
+   int const msgs = 1'000;
 
    // The number of publishes that will be sent by each session with
    // each message.