Sometimes exchange_view() raises an IndexError exception

[robzenn92]

The exception is the following:

Internal Server Error: /exchange-view
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/django/core/handlers/exception.py", line 35, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py", line 128, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py", line 126, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.6/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/usr/src/cyclon_project/api/views.py", line 102, in exchange_view
    cyclon.partialView.merge(to_send, received_partial_view)
  File "/usr/src/partialView/partialView.py", line 131, in merge
    self.remove_peer(can_be_replaced[i - how_many])
IndexError: list index out of range
[2017-12-13,17:22:00.424 - ERROR] exception.py:118 | handle_uncaught_exception - Internal Server Error: /exchange-view
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/django/core/handlers/exception.py", line 35, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py", line 128, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py", line 126, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.6/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/usr/src/cyclon_project/api/views.py", line 102, in exchange_view
    cyclon.partialView.merge(to_send, received_partial_view)
  File "/usr/src/partialView/partialView.py", line 131, in merge
    self.remove_peer(can_be_replaced[i - how_many])
IndexError: list index out of range

More info in the following stack trace.

[2017-12-13,17:21:58.446 - INFO] cyclon.py:78 | shuffle_partial_view - My partialView:
{'ip': '172.17.0.6', 'limit': 2, 'peer_list': [{'age': 1, 'ip': '172.17.0.9'}, {'age': 1, 'ip': '172.17.0.5'}], 'shuffle_length': 2, 'size': 2}
[2017-12-13,17:21:58.447 - INFO] cyclon.py:81 | shuffle_partial_view - Selected oldest: 172.17.0.9
[2017-12-13,17:21:58.447 - INFO] cyclon.py:84 | shuffle_partial_view - Selected neighbors:
{'ip': '172.17.0.6', 'limit': 2, 'peer_list': [{'age': 1, 'ip': '172.17.0.5'}], 'shuffle_length': 2, 'size': 1}
[2017-12-13,17:21:58.447 - INFO] cyclon.py:87 | shuffle_partial_view - Selected neighbors + myself (will be sent to 172.17.0.9):
{'ip': '172.17.0.6', 'limit': 2, 'peer_list': [{'age': 1, 'ip': '172.17.0.5'}, {'age': 0, 'ip': '172.17.0.6'}], 'shuffle_length': 2, 'size': 2}
[2017-12-13,17:21:58.447 - INFO] cyclon.py:110 | send_message - I am sending Message:
{'source': 'http://172.17.0.6:5000', 'destination': 'http://172.17.0.9:5000', 'data': {'ip': '172.17.0.6', 'limit': 2, 'peer_list': [{'age': 1, 'ip': '172.17.0.5'}, {'age': 0, 'ip': '172.17.0.6'}], 'shuffle_length': 2, 'size': 2}}
[2017-12-13,17:21:58.452 - INFO] cyclon.py:112 | send_message - I got the following response:
<Response [200]>
[2017-12-13,17:21:58.453 - INFO] cyclon.py:94 | shuffle_partial_view - I received (from 172.17.0.9):
{'ip': '172.17.0.9', 'limit': 1, 'peer_list': [{'age': 1, 'ip': '172.17.0.8'}], 'shuffle_length': 1, 'size': 1}
[2017-12-13,17:21:58.453 - INFO] cyclon.py:98 | shuffle_partial_view - My partialView after removing oldest:
{'ip': '172.17.0.6', 'limit': 2, 'peer_list': [{'age': 1, 'ip': '172.17.0.5'}], 'shuffle_length': 2, 'size': 1}
[2017-12-13,17:21:58.453 - INFO] cyclon.py:102 | shuffle_partial_view - My partialView after merging:
{'ip': '172.17.0.6', 'limit': 2, 'peer_list': [{'age': 1, 'ip': '172.17.0.5'}, {'age': 1, 'ip': '172.17.0.8'}], 'shuffle_length': 2, 'size': 2}
[2017-12-13,17:21:58.453 - INFO] base.py:135 | run_job - Job "Cyclon.shuffle_partial_view (trigger: interval[0:00:15], next run at: 2017-12-13 17:22:13 CET)" executed successfully
[2017-12-13,17:21:59.753 - INFO] views.py:75 | get_k_view - {'ip': '172.17.0.6', 'limit': 2, 'peer_list': [{'age': 1, 'ip': '172.17.0.5'}, {'age': 1, 'ip': '172.17.0.8'}], 'shuffle_length': 2, 'size': 2}
[2017-12-13,17:22:00.424 - INFO] views.py:90 | exchange_view - My view before the exchange is:
{'ip': '172.17.0.6', 'limit': 2, 'peer_list': [{'age': 1, 'ip': '172.17.0.8'}], 'shuffle_length': 2, 'size': 1}
[2017-12-13,17:22:00.424 - INFO] views.py:95 | exchange_view - I got (from http://172.17.0.7:5000) the following:
{'ip': '172.17.0.7', 'limit': 3, 'peer_list': [{'age': 1, 'ip': '172.17.0.2'}, {'age': 2, 'ip': '172.17.0.8'}, {'age': 0, 'ip': '172.17.0.7'}], 'shuffle_length': 3, 'size': 3}
[2017-12-13,17:22:00.424 - INFO] views.py:99 | exchange_view - I will send (to http://172.17.0.7:5000) the following:
{'ip': '172.17.0.6', 'limit': 1, 'peer_list': [{'age': 1, 'ip': '172.17.0.8'}], 'shuffle_length': 1, 'size': 1}.
Internal Server Error: /exchange-view
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/django/core/handlers/exception.py", line 35, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py", line 128, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py", line 126, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.6/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/usr/src/cyclon_project/api/views.py", line 102, in exchange_view
    cyclon.partialView.merge(to_send, received_partial_view)
  File "/usr/src/partialView/partialView.py", line 131, in merge
    self.remove_peer(can_be_replaced[i - how_many])
IndexError: list index out of range
[2017-12-13,17:22:00.424 - ERROR] exception.py:118 | handle_uncaught_exception - Internal Server Error: /exchange-view
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/django/core/handlers/exception.py", line 35, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py", line 128, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py", line 126, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.6/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/usr/src/cyclon_project/api/views.py", line 102, in exchange_view
    cyclon.partialView.merge(to_send, received_partial_view)
  File "/usr/src/partialView/partialView.py", line 131, in merge
    self.remove_peer(can_be_replaced[i - how_many])
IndexError: list index out of range