I’m learning hadoop using docker compose. I couldn’t access namenode/datanode by using a hostname after I modified the local hosts file, but it works fine when I access 127.0.0.1:9870 or localhost:9864, I don’t know why and how to fix it. Please help me.

Here’s my configurations.
docker-compose.yaml

version: "2"
services:
   namenode:
      image: apache/hadoop:3
      hostname: namenode
      command: ["hdfs", "namenode"]
      ports:
        - 8020:8020
        - 9870:9870
      env_file:
        - ./config
      environment:
          ENSURE_NAMENODE_DIR: "/opt/hadoop/name"
      networks:
        - hadoop
   datanode:
      image: apache/hadoop:3
      hostname: datanode
      depends_on:
        - namenode
      command: ["hdfs", "datanode"]
      ports:
        - 9864:9864
        - 9865:9865
        - 9866:9866
      env_file:
        - ./config
      networks:
        - hadoop
   resourcemanager:
      image: apache/hadoop:3
      hostname: resourcemanager
      command: ["yarn", "resourcemanager"]
      ports:
         - 8088:8088
         - 19888:19888
         - 19890:19890
      env_file:
        - ./config
      volumes:
        - ./test.sh:/opt/test.sh
      networks:
        - hadoop
   nodemanager:
      image: apache/hadoop:3
      command: ["yarn", "nodemanager"]
      env_file:
        - ./config
      ports:
        - 8040:8040    #NodeManager
      networks:
        - hadoop

networks:
  hadoop:
    driver: bridge

hosts

127.0.0.1 namenode
127.0.0.1 datanode

I want to know the reason for this phenomenon， thank you.