问TransportError: TransportError(503，'search_phase_execution_exception')

EN

from elasticsearch import Elasticsearch
from pandasticsearch import Select

# Connection to ElasticSearch
es = Elasticsearch(['http://localhost:9200'],timeout=600)

# Retrieving all documents in index (no query given)
documents = es.search(index='myindex',body={"query": {"match_all": {}}})

# Convert the result to Pandas Dataframe
pandas_df = Select.from_dict(documents).to_pandas()

GET http://localhost:9200/myindex/_search [status:503 request:0.062s]
GET http://localhost:9200/myindex/_search [status:503 request:0.027s]
GET http://localhost:9200/myindex/_search [status:503 request:0.030s]
GET http://localhost:9200/myindex/_search [status:503 request:0.017s]
Traceback (most recent call last):

File "<ipython-input-6-68e07be7c100>", line 1, in <module>
documents = es.search(index='myindex',body={"query": {"match_all": {}}})

File "C:\Users\XXXXXX\AppData\Local\Continuum\anaconda3\lib\site- 
packages\elasticsearch\client\utils.py", line 76, in _wrapped
return func(*args, params=params, **kwargs)

File "C:\Users\XXXXXX\AppData\Local\Continuum\anaconda3\lib\site- 
packages\elasticsearch\client\__init__.py", line 655, in search
doc_type, '_search'), params=params, body=body)

File "C:\Users\XXXXXX\AppData\Local\Continuum\anaconda3\lib\site- 
packages\elasticsearch\transport.py", line 318, in perform_request
status, headers_response, data = connection.perform_request(method, url, 
params, body, headers=headers, ignore=ignore, timeout=timeout)

File "C:\Users\XXXXXX\AppData\Local\Continuum\anaconda3\lib\site- 
packages\elasticsearch\connection\http_urllib3.py", line 185, in 
perform_request
self._raise_error(response.status, raw_data)

File "C:\Users\XXXXXX\AppData\Local\Continuum\anaconda3\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)

TransportError: TransportError(503, 'search_phase_execution_exception')