s.py

#!/usr/bin/env python3

from os import getenv
from json import dumps

from elasticsearch import Elasticsearch
from elasticsearch.helpers import scan

from starlette.applications import Starlette
from starlette.requests import Request
from starlette.responses import Response, StreamingResponse
from starlette.routing import Route


es_host = getenv("ES", "es")
es = Elasticsearch(es_host)


def cat_indices(request: Request):
    return Response(es.cat.indices(v=True), media_type='text/plain')


def dump_index(request: Request):
    name = request.path_params["name"]
    if not es.indices.exists(name):
        return Response(status_code=404)

    async def _iter():
        chunk = ""
        for i in scan(es, index=name):
            chunk += dumps(i["_source"], ensure_ascii=False) + "\n"
            if len(chunk) > 4096:
                if await request.is_disconnected():
                    break
                yield chunk
                chunk = ""
        if chunk:
            yield chunk

    return StreamingResponse(_iter(), media_type='text/plain')


app = Starlette(routes=[
    Route('/', cat_indices),
    Route('/{name:path}', dump_index),
])