Elasticsearch post-start script to automatic update indicies settings (example with docker-compose)

elasticsearch-poststart-settings.yaml

version: "3.3"

services:
  elasticsearch:
    container_name: elasticsearch
    image: docker.elastic.co/elasticsearch/elasticsearch-oss:7.3.1
    restart: unless-stopped
    ports:
      - "9200:9200"
    environment:
      ES_JAVA_OPTS: "-Xmx2g -Xms2g"
      bootstrap.memory_lock: "true"
      discovery.type: "single-node"
      http.host: "0.0.0.0"
      action.auto_create_index: "false"
      network.host: "0.0.0.0"
    ulimits:
      nofile:
         soft: 65536
         hard: 65536
      memlock:
        hard: -1
        soft: -1
    volumes:
      - /tmp/elasticsearch/data:/var/lib/elasticsearch/data:Z
  elasticsearch-poststart:
    image: alpine/curl:latest
    depends_on:
      - elasticsearch
    restart: "no"
    command:
      - /bin/sh
      - -c
      - |
        echo "$$(date) - [debug] --------------------"
        echo "$$(date) - [debug] - ES_HOST: $${ES_HOST}"
        echo "$$(date) - [debug] - READ_ONLY_ALLOW_DELETE: $${READ_ONLY_ALLOW_DELETE}"
        echo "$$(date) - [debug] - MAX_RESULT_WINDOWS: $${MAX_RESULT_WINDOWS}"
        while true; do
          if [[ "$$(curl --write-out %{http_code} --silent --output /dev/null $${ES_HOST}/_cat/health?h=st)" -eq 200 ]]; then
            break
          else
            echo "$$(date) - [warning] - waiting for $${ES_HOST} to be ready"
            sleep 5
          fi
        done
        echo ""
        echo "$${READ_ONLY_ALLOW_DELETE}," | while read -d, -r pair; do
          IFS='=' read -r key val <<EOF
        $${pair}
        EOF
          echo "$$(date) - [info] - PUT /$${key}/_settings with index.blocks.read_only_allow_delete=$${val}"
          curl -XPUT -H "Content-Type: application/json" --silent $${ES_HOST}/$${key}/_settings -d "{\"index.blocks.read_only_allow_delete\": $${val}}"
          echo ""
        done
        echo ""
        echo "$${MAX_RESULT_WINDOWS}," | while read -d, -r pair; do
          IFS='=' read -r key val <<EOF
        $${pair}
        EOF
          echo "$$(date) - [info] - PUT /$${key}/_settings with index.max_result_window=$${val}"
          curl -XPUT -H "Content-Type: application/json" --silent $${ES_HOST}/$${key}/_settings -d "{\"index.max_result_window\": $${val}}"
          echo ""
        done
    environment:
      ES_HOST: "elasticsearch:9200"
      READ_ONLY_ALLOW_DELETE: _all=false
      # READ_ONLY_ALLOW_DELETE: my-index=false,other-index=true
      MAX_RESULT_WINDOWS: _all=11000
      # MAX_RESULT_WINDOWS: my-index=13000,other-index=20000