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elasticsearch API
cat：https://www.elastic.co/guide/en/elasticsearch/reference/6.3/cat.html
indices：https://www.elastic.co/guide/en/elasticsearch/reference/6.3/indices.html
search：https://www.elastic.co/guide/en/elasticsearch/reference/6.3/search.html
document：https://www.elastic.co/guide/en/elasticsearch/reference/6.3/docs.html
cluster：https://www.elastic.co/guide/en/elasticsearch/reference/6.3/cluster.html