feedback plugin: abort sending the report on server shutdown

network timeouts might be rather large and feedback plugin
waits forever for the sender thread to exit.

an alternative could've been to use GNU-specific pthread_timedjoin_np(),
where _np mean "not portable".

plugin/feedback/feedback.cc

@@ -340,6 +340,10 @@ static int free(void *p)
     shutdown_plugin= true;
     mysql_cond_signal(&sleep_condition);
     mysql_mutex_unlock(&sleep_mutex);
+
+    for (uint i= 0; i < url_count; i++)
+      urls[i]->abort();
+
     pthread_join(sender_thread, NULL);
 
     mysql_mutex_destroy(&sleep_mutex);

plugin/feedback/feedback.h

@@ -52,6 +52,7 @@ class Url {
 
   const char *url()   { return full_url.str; }
   size_t url_length() { return full_url.length; }
+  virtual void abort() =  0;
   virtual int send(const char* data, size_t data_length) =  0;
   virtual int set_proxy(const char *proxy, size_t proxy_len)
   {

plugin/feedback/url_http.cc

@@ -37,8 +37,9 @@ static const uint FOR_WRITING= 1;
 class Url_http: public Url {
   protected:
   const LEX_STRING host, port, path;
-  bool ssl;
   LEX_STRING proxy_host, proxy_port;
+  my_socket fd;
+  bool ssl;
 
   bool use_proxy()
   {
@@ -47,7 +48,8 @@ class Url_http: public Url {
 
   Url_http(LEX_STRING &url_arg, LEX_STRING &host_arg,
           LEX_STRING &port_arg, LEX_STRING &path_arg, bool ssl_arg) :
-    Url(url_arg), host(host_arg), port(port_arg), path(path_arg), ssl(ssl_arg)
+    Url(url_arg), host(host_arg), port(port_arg), path(path_arg),
+    fd(INVALID_SOCKET), ssl(ssl_arg)
     {
       proxy_host.length= 0;
     }
@@ -60,6 +62,7 @@ class Url_http: public Url {
   }
 
   public:
+  void abort();
   int send(const char* data, size_t data_length);
   int set_proxy(const char *proxy, size_t proxy_len)
   {
@@ -158,13 +161,18 @@ Url* http_create(const char *url, size_t url_length)
   return new Url_http(full_url, host, port, path, ssl);
 }
 
+void Url_http::abort()
+{
+  if (fd != INVALID_SOCKET)
+    closesocket(fd); // interrupt I/O waits
+}
+
 /* do the vio_write and check that all data were sent ok */
 #define write_check(VIO, DATA, LEN)             \
   (vio_write((VIO), (uchar*)(DATA), (LEN)) != (LEN))
 
 int Url_http::send(const char* data, size_t data_length)
 {
-  my_socket fd= INVALID_SOCKET;
   char buf[1024];
   size_t len= 0;
 
@@ -180,6 +188,7 @@ int Url_http::send(const char* data, size_t data_length)
     return 1;
   }
 
+  DBUG_ASSERT(fd == INVALID_SOCKET);
   for (addr= addrs; addr != NULL; addr= addr->ai_next)
   {
     fd= socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol);
@@ -208,6 +217,7 @@ int Url_http::send(const char* data, size_t data_length)
     sql_print_error("feedback plugin: vio_new failed for url '%s'",
                     full_url.str);
     closesocket(fd);
+    fd= INVALID_SOCKET;
     return 1;
   }
 
@@ -236,6 +246,7 @@ int Url_http::send(const char* data, size_t data_length)
         free_vio_ssl_acceptor_fd(ssl_fd);
       closesocket(fd);
       vio_delete(vio);
+      fd= INVALID_SOCKET;
       return 1;
     }
   }
@@ -334,6 +345,7 @@ int Url_http::send(const char* data, size_t data_length)
   }
 #endif
 
+  fd= INVALID_SOCKET;
   return res;
 }