Python elasticsearch client failing scroll functionality

output.txt

C:\Users\BillyBob\ES_Queries>python scrollTest.py
DXF1ZXJ5QW5kRmV0Y2gBAAAAAAAO-9cWR25VNkxzVjFTSVNubDRCdEoyTnFXQQ==
Traceback (most recent call last):
  File "scrollTest.py", line 54, in main
    getAllDocs2()
  File "scrollTest.py", line 16, in getAllDocs2
    res2 = es.scroll(scroll_id = scroll, scroll = '1m')
  File "C:\Python27\lib\site-packages\elasticsearch\client\utils.py", line 73, in _wrapped
    return func(*args, params=params, **kwargs)
  File "C:\Python27\lib\site-packages\elasticsearch\client\__init__.py", line 1033, in scroll
    params=params, body=body)
  File "C:\Python27\lib\site-packages\elasticsearch\transport.py", line 312, in perform_request
    status, headers, data = connection.perform_request(method, url, params, body, ignore=ignore, timeout=timeout)
  File "C:\Python27\lib\site-packages\elasticsearch\connection\http_urllib3.py", line 129, in perform_request
    self._raise_error(response.status, raw_data)
  File "C:\Python27\lib\site-packages\elasticsearch\connection\base.py", line 125, in _raise_error
    raise HTTP_EXCEPTIONS.get(status_code, TransportError)(status_code, error_message, additional_info)
RequestError: TransportError(400, u'action_request_validation_exception', u'Validation Failed: 1: scrollId is missing;')

{u'_score': 1.0, u'_type': u'logs', u'_id': u'AV8LhQqZyn_BE1UV4cVV', u'_source': {u'host': u'**.**.**.**', u'@timestamp': u'2017-10-11T13:13:15.000Z', ...
{u'_score': 1.0, u'_type': u'logs', u'_id': u'AV8LhQqZyn_BE1UV4cVW', u'_source': {u'host': u'**.**.**.**', u'@timestamp': u'2017-10-11T13:13:15.000Z', ...
FAILED hitCount: 2
Traceback (most recent call last):
  File "scrollTest.py", line 42, in getAllDocs3
    for hit in s:
  File "C:\Python27\lib\site-packages\elasticsearch\helpers\__init__.py", line 379, in scan
    **scroll_kwargs)
  File "C:\Python27\lib\site-packages\elasticsearch\client\utils.py", line 73, in _wrapped
    return func(*args, params=params, **kwargs)
  File "C:\Python27\lib\site-packages\elasticsearch\client\__init__.py", line 1033, in scroll
    params=params, body=body)
  File "C:\Python27\lib\site-packages\elasticsearch\transport.py", line 312, in perform_request
    status, headers, data = connection.perform_request(method, url, params, body, ignore=ignore, timeout=timeout)
  File "C:\Python27\lib\site-packages\elasticsearch\connection\http_urllib3.py", line 129, in perform_request
    self._raise_error(response.status, raw_data)
  File "C:\Python27\lib\site-packages\elasticsearch\connection\base.py", line 125, in _raise_error
    raise HTTP_EXCEPTIONS.get(status_code, TransportError)(status_code, error_message, additional_info)
RequestError: TransportError(400, u'action_request_validation_exception', u'Validation Failed: 1: scrollId is missing;')
Total hits: 2

scrollTest.py

from __future__ import print_function
import elasticsearch as elasticsearch
import elasticsearch.helpers
import traceback

"""
Testing the retrieval of all documents using _search/scroll via
python client wrapper elasticsearch.helpers.scan() and search()/scroll().

Elastic server version: 5.6.4, Lucene 6.6.1
Python elasticsearch module version: VERSION = (5, 5, 2)
"""

def getAllDocs2():
  """
  Trying to retrieve all ~20k documents using search() and scroll()
  methods of elasticsearch.Elasticsearch. This fails with message
  "Validation Failed: scrollId is missing;".
  """
	es = elasticsearch.Elasticsearch(["http://*.*.*.*:80/elasticsearch/"])
	qDict = {'query': {'match_all' : {}}}
	index = "netflow-v5-2017.10.11"
	
	#res = es.search(index=index, doc_type='myType', body=doc,scroll='1m')
	res = es.search(index=index,  body=qDict,scroll='3m')
	scroll = res['_scroll_id']
	print(scroll)
	res2 = es.scroll(scroll_id = scroll, scroll = '1m')
	print(res2['_scroll_id'])

def getAllDocs3():
  """
  Another attempt to retrieve all ~20k documents using the elasticsearch.helpers.scan
  wrapper method. This also fails with "Validation Failed: scrollId is missing;".
  """
  
	es = elasticsearch.Elasticsearch(["http://*.*.*.*:80/elasticsearch/"])
	hitCount = 0
	index = "netflow-v5-2017.10.11"
	qDict = {'query': {'match': {}}}
	
	s = elasticsearch.helpers.scan(es,
				query=qDict,
				index=index,
				size=2,
				preserve_order=True,
				clear_scroll=False,
				scroll='5m'
			)

	try:
		for hit in s:
			hitCount += 1
			print(hit)
		print("SUCCESS hitCount: {}".format(hitCount))
	except:
		print("FAILED hitCount: {}".format(hitCount))
		traceback.print_exc()
	
	print("Total hits: {}".format(hitCount))

def main():
	try:
		getAllDocs2()
	except:
		traceback.print_exc()
		
	try:
		getAllDocs3()
	except:
		traceback.print_exc()

if __name__ == "__main__":
	main()
	

See output.txt exception messages for what happens when getAllDocs2 and then getAllDocs3 are called from main. These are just attempts to dump all documents from an index, using the elasticsearch python clients, one using the helpers.scan() method and the other using search()+scroll(). The elastic version is 5.6.4, client is correct for elastic 5.x.x. I've tested other clients as well, and they all fail with a message about the 'scrollId' missing. However, using wireshark I can observe the clients sending back a b64-encoded scroll_id parameter to the correct '_search/scroll endpoint', but the the server returns a 400 bad request containing 'Validation Failed: 1: scrollId is missing;'. Using the kibana query testing console I am able to iterate documents using the '_search/scroll' endpoint correctly, so I at least know scrolling can succeed. But these python rest clients are failing , despite correctly sending back scroll_id to elastic after the first query.