Elasticsearch Zero Downtime Reindexing using elasticsearch-dsl-py ref: https://www.elastic.co/blog/changing-mapping-with-zero-downtime

zero_downtime_reindexing.py

from datetime import datetime
from elasticsearch_dsl import (
    DocType,
    String,
    Integer,
    Float
)


def _suffix():
    return datetime.now().strftime("%Y%m%d%H%M%S%f")


class Company(DocType):
    name = String(analyzer='kuromoji')
    alias = String(analyzer='2gram')
    languages = String(multi=True)
    pref = Integer()
    point = Float()

    class Meta:
        index = 'company'


def reindex():
    """
    Elasticsearch Zero Downtime Reindexing using elasticsearch-dsl-py
    """
    c = Company().connection
    alias = Company._doc_type.index

    # If alias does not exists, As first create new index.
    if not c.indices.exists_alias(alias):
        index = '%s_%s' % (alias, _suffix())
        Company.init(index)
        c.indices.put_alias(alias, index)

    old_index = list(c.indices.get_alias(alias).keys())[0]
    new_index = '%s_%s' % (alias, _suffix())

    # Create new index to ES
    Company.init(new_index)

    # Put document to new index from Django model's records
    dosomething(new_index)

    # Change index through alias.
    c.indices.put_alias(alias, new_index)
    c.indices.update_aliases({
        "actions": [
            {"remove": {"index": old_index, "alias": alias}},
            {"add": {"index": new_index, "alias": alias}}
        ]
    })