webapp:
    build: .
    ports: ['3000:3000']
    volumes: ['.:/openfarm']
    links: ['mongo','search']
    environment:
        S3_BUCKET_NAME:
        S3_ACCESS_KEY:
        S3_SECRET_KEY:
        SERVER_S3_ACCESS_KEY:
        SERVER_S3_SECRET_KEY:
        ALERTS:
        SECRET_KEY_BASE: '0ccd94b250496de9a5765981b0703279bc4ece38c6213a81a3dd8fe215dc51d4c7eee05f49370b010ecf62109e201f935536496ec661a759118ebb011420060a'
        MONGO_HOST: mongo_1
        ELASTICSEARCH_URL: 'http://search:9200'

mongo:
    image: 'mongo:2.6'

search:
    image: 'elasticsearch:1.4'

webapp:
    build: .
    ports: ['3000:3000']
    volumes: ['.:/openfarm']
    links: ['mongo','search']
    environment:
        S3_BUCKET_NAME:
        S3_ACCESS_KEY:
        S3_SECRET_KEY:
        SERVER_S3_ACCESS_KEY:
        SERVER_S3_SECRET_KEY:
        ALERTS:
        SECRET_KEY_BASE: '0ccd94b250496de9a5765981b0703279bc4ece38c6213a81a3dd8fe215dc51d4c7eee05f49370b010ecf62109e201f935536496ec661a759118ebb011420060a'
        MONGO_HOST: mongo
        ELASTICSEARCH_URL: 'http://search:9200'

mongo:
    image: 'mongo:2.6'

search:
    image: 'elasticsearch:1.4'

Use MONGO_HOST=mongo instead of mongo_1
Use MONGO_HOST=mongo instead of mongo_1
