Defunct connection instead of using assertion (#485)

* Defunct connection instead of using assertion

Bad data could catch an existing stream in an invalid request state.
It's not the best choice to have an assertion triggered by bad data from
the server-side.

Author: mpenick

src/connection.cpp

@@ -220,7 +220,9 @@ void Connection::on_write(int status, RequestCallback* request) {
       break;
 
     default:
-      assert(false && "Invalid request state after write finished");
+      LOG_ERROR("Invalid request state %s for stream ID %d", callback->state_string(),
+                callback->stream());
+      defunct();
       break;
   }
 }
@@ -284,7 +286,9 @@ void Connection::on_read(const char* buf, size_t size) {
               break;
 
             default:
-              assert(false && "Invalid request state after receiving response");
+              LOG_ERROR("Invalid request state %s for stream ID %d", callback->state_string(),
+                        response->stream());
+              defunct();
               break;
           }
         } else {

src/request_callback.cpp

@@ -172,6 +172,22 @@ void RequestCallback::set_state(RequestCallback::State next_state) {
   }
 }
 
+const char* RequestCallback::state_string() const {
+  switch (state_) {
+    case REQUEST_STATE_NEW:
+      return "NEW";
+    case REQUEST_STATE_WRITING:
+      return "WRITING";
+    case REQUEST_STATE_READING:
+      return "READING";
+    case REQUEST_STATE_READ_BEFORE_WRITE:
+      return "READ_BEFORE_WRITE";
+    case REQUEST_STATE_FINISHED:
+      return "FINISHED";
+  }
+  return "INVALID";
+}
+
 SimpleRequestCallback::SimpleRequestCallback(const String& query, uint64_t request_timeout_ms)
     : RequestCallback(
           RequestWrapper(Request::ConstPtr(new QueryRequest(query)), request_timeout_ms)) {}

src/request_callback.hpp

@@ -189,6 +189,8 @@ class RequestCallback
   State state() const { return state_; }
   void set_state(State next_state);
 
+  const char* state_string() const;
+
   ResponseMessage* read_before_write_response() const { return read_before_write_response_.get(); }
 
   void set_read_before_write_response(ResponseMessage* response) {