Patches AWS Elastic Beanstalk's default nginx configuration to support websockets, for use with an Application Load Balancer.

enable-websockets.config

container_commands:
  enable_websockets:
    command: |
      sed -i '/\s*proxy_set_header\s*Connection/c \
              proxy_set_header Upgrade $http_upgrade;\
              proxy_set_header Connection "upgrade";\
              ' /tmp/deployment/config/#etc#nginx#conf.d#00_elastic_beanstalk_proxy.conf

hi , did not work for me , but - I use tomcat8 beanstalk instance ...
any suggestion ...?
error says that it did not find the config file .?

Did anyone get this script working for tomcat8 using the ALB?

Yes, change your proxy server to nginx
http://docs.aws.amazon.com/elasticbeanstalk/latest/dg/java-tomcat-platform.html#java-tomcat-platform-configfiles
I used the "Example .ebextensions/tomcat-settings.config"

option_settings:
  aws:elasticbeanstalk:container:tomcat:jvmoptions:
    Xms: 512m
    Xmx: 512m
    JVM Options: '-Xmn128m'
  aws:elasticbeanstalk:application:environment:
    API_ENDPOINT: mywebapi.zkpexsjtmd.us-west-2.elasticbeanstalk.com
  aws:elasticbeanstalk:environment:proxy:
    GzipCompression: 'true'
    ProxyServer: nginx
  aws:elasticbeanstalk:environment:proxy:staticfiles:
    /pub: public