Bug#34536576 connection-pool does not release connection closed by server

Issue
=====

With connection-pool enabled, a connection may get stuck in the pool if
it is closed by the server.

1. Start router with

- [DEFAULT] max_idle_server_connections=1
- [routing:*] client_ssl_mode=PREFERRED and server_ssl_mode=PREFERRED
- max_total_connections=1

2. connect to router and close the connection again (adds the connection
   to the pool)
3. connect to the server directly and kill the pooled connection
   - SHOW PROCESSLIST
   - KILL ...
   - (should release the connection)
4. connect to router again: fails

Change
======

The underlying problem is equality between net::stream_errc::eof from
different shared objects failing.

The connection-pool's "net::stream_errc::eof"'s .category() refers to a
differ "static stream_category" then the one that's passed to
connection-pool.

That stems from the stream-category being defined in the header which
leads to multiple instances of the same "static", one per shared-object.

- add a equivalent() method to net::stream_errc's error-category which
  handles the "multiple instances" case.

Change-Id: Iadf74ccbfdee606aff1221740554bcd9dfc04653

Author: weigon

router/src/connection_pool/src/connection_pool.cc

@@ -24,8 +24,6 @@
 
 #include "mysqlrouter/connection_pool.h"
 
-#include <iostream>
-
 #include "mysql/harness/net_ts/buffer.h"
 #include "mysql/harness/net_ts/socket.h"
 
@@ -37,7 +35,7 @@ void PooledConnection::async_recv_message() {
 
   conn_->async_recv(recv_buf_, [this](std::error_code ec, size_t /* recved */) {
     if (ec) {
-      if (ec == net::stream_errc::eof) {
+      if (ec == make_error_condition(net::stream_errc::eof)) {
         // cancel the timer and let that close the connection.
         idle_timer_.cancel();
 

router/src/harness/include/mysql/harness/net_ts/buffer.h

@@ -30,6 +30,7 @@
 #include <limits>     // std::numeric_limits
 #include <stdexcept>  // length_error
 #include <string>
+#include <string_view>
 #include <system_error>
 #include <type_traits>
 #include <utility>
@@ -69,6 +70,28 @@ inline const std::error_category &stream_category() noexcept {
           return "unknown";
       }
     }
+
+    bool equivalent(int mycode,
+                    const std::error_condition &other) const noexcept override {
+      if (*this == other.category() ||
+          std::string_view(name()) ==
+              std::string_view(other.category().name())) {
+        return mycode == other.value();
+      }
+
+      return false;
+    }
+
+    bool equivalent(const std::error_code &other,
+                    int mycode) const noexcept override {
+      if (*this == other.category() ||
+          std::string_view(name()) ==
+              std::string_view(other.category().name())) {
+        return mycode == other.value();
+      }
+
+      return false;
+    }
   };
 
   static stream_category_impl instance;
@@ -79,6 +102,10 @@ inline std::error_code make_error_code(net::stream_errc e) noexcept {
   return {static_cast<int>(e), net::stream_category()};
 }
 
+inline std::error_condition make_error_condition(net::stream_errc e) noexcept {
+  return {static_cast<int>(e), net::stream_category()};
+}
+
 // 16.4 [buffer.mutable]
 
 class mutable_buffer {