Unable to roslaunch a robot and the specified world in gazebo.

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I have been working on a project where I had developed a small robot in gazebo. I have been trying to control the robot with a custom python based ros plugin. When I tried to launch the file using the command "roslaunch spider_gazebo spider_world.launch" where spider_gazebo is the catkin package that contains the world launch file. I have been having several errors like ,

Reading symbols from gzserver...(no debugging symbols found)...done.
[tcsetpgrp failed in terminal_inferior: Inappropriate ioctl for device]
[tcsetpgrp failed in terminal_inferior: Inappropriate ioctl for device]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[ INFO] [1561716326.657107032]: Finished loading Gazebo ROS API Plugin.
[ INFO] [1561716326.658858219]: waitForService: Service [/gazebo/set_physics_properties] has not been advertised, waiting...
[tcsetpgrp failed in terminal_inferior: Inappropriate ioctl for device]
[New Thread 0x7fffccb24700 (LWP 5412)]
[New Thread 0x7fffcc323700 (LWP 5413)]
[New Thread 0x7fffc7b22700 (LWP 5414)]
[New Thread 0x7fffc5321700 (LWP 5415)]
[tcsetpgrp failed in terminal_inferior: Inappropriate ioctl for device]
[tcsetpgrp failed in terminal_inferior: Inappropriate ioctl for device]
[tcsetpgrp failed in terminal_inferior: Inappropriate ioctl for device]
[tcsetpgrp failed in terminal_inferior: Inappropriate ioctl for device]
[New Thread 0x7fffc0a13700 (LWP 5418)]
[New Thread 0x7fffc0212700 (LWP 5419)]
[New Thread 0x7fffbfa11700 (LWP 5422)]
[New Thread 0x7fffb7fff700 (LWP 5423)]
[New Thread 0x7fffbf210700 (LWP 5424)]
[New Thread 0x7fffbea0f700 (LWP 5436)]
[New Thread 0x7fffbe20e700 (LWP 5437)]
[New Thread 0x7fffbda0d700 (LWP 5438)]
[New Thread 0x7fffbd20c700 (LWP 5439)]
[New Thread 0x7fffbca0b700 (LWP 5440)]
[New Thread 0x7fffb77fe700 (LWP 5441)]
[New Thread 0x7fffb6ffd700 (LWP 5442)]

and this keeps continuing. when I checked the terminal, these are the nodes that are created

gazebo (gazebo_ros/debug)
    gazebo_gui (gazebo_ros/gzclient)
    rob_st_pub (robot_state_publisher/robot_state_publisher)
    urdf_spawner (gazebo_ros/spawn_model)
  /spider/
    controller_spawnner (controller_manager/spawner)

along with that all the joint parameters and robot_description were also loaded. But later after that the above error keeps repeating and when i tried to kill the process with ctrl+c, I get the following error before closing the gazebo server.

[urdf_spawner-4] killing on exit
[rob_st_pub-6] killing on exit
[gazebo_gui-3] killing on exit
[gazebo-2] killing on exit
Quit
(gdb) Service call failed: unable to connect to service: [Errno 4] Interrupted system call
[gazebo-2] escalating to SIGTERM
Exception ignored in: <gdb.GdbOutputFile object at 0x7f9b14bd6eb8>
Traceback (most recent call last):
  File "/usr/share/gdb/python/gdb/__init__.py", line 43, in flush
    def flush(self):
KeyboardInterrupt
[rosout-1] killing on exit
[master] killing on exit
shutting down processing monitor...
... shutting down processing monitor complete

can anyone please help me what this gdb service failure is ? as mentioned the plugin i wrote is in python and I haven't even run it. I though first I could launch the robot in gazebo and then in another terminal I can do ROS_MASTER_URI and then launch the control file along with the plugin. but I have been having this error when launching the robot in gazebo itself. can anyone help me point out in the right direction. Thank you

update: I have tried to check the parameter server and all the joints were loaded and i tried to ... (more)