How do you run a worker with AWS Elastic Beanstalk?

As @chris-wheadon suggested in his comment, you should try to run celery as a deamon in the background. AWS Elastic Beanstalk uses supervisord already to run some deamon processes. So you can leverage that to run celeryd and avoid creating a custom AMI for this. It works nicely for me.

What I do is to programatically add a celeryd config file to the instance after the app is deployed to it by EB. The tricky part is that the file needs to set the required environmental variables for the deamon (such as AWS access keys if you use S3 or other services in your app).

Below there is a copy of the script that I use, add this script to your .ebextensions folder that configures your EB environment.

The setup script creates a file in the /opt/elasticbeanstalk/hooks/appdeploy/post/ folder (documentation) that lives on all EB instances. Any shell script in there will be executed post deployment. The shell script that is placed there works as follows:

1. In the celeryenv variable, the virutalenv environment is stored in
   a format that follows the supervisord notation. This is a comma
   separated list of env variables.
2. Then the script creates a variable celeryconf that contains the
   configuration file as a string, which includes the previously parsed
   env variables.
3. This variable is then piped into a file called celeryd.conf, a
   supervisord configuration file for the celery daemon.
4. Finally, the path to the newly created config file is added to the
   main supervisord.conf file, if it is not already there.

Here is a copy of the script:

files:
  "/opt/elasticbeanstalk/hooks/appdeploy/post/run_supervised_celeryd.sh":
    mode: "000755"
    owner: root
    group: root
    content: |
      #!/usr/bin/env bash

      # Get django environment variables
      celeryenv=`cat /opt/python/current/env | tr '\n' ',' | sed 's/export //g' | sed 's/$PATH/%(ENV_PATH)s/g' | sed 's/$PYTHONPATH//g' | sed 's/$LD_LIBRARY_PATH//g'`
      celeryenv=${celeryenv%?}

      # Create celery configuraiton script
      celeryconf="[program:celeryd]
      ; Set full path to celery program if using virtualenv
      command=/opt/python/run/venv/bin/celery worker -A myappname --loglevel=INFO

      directory=/opt/python/current/app
      user=nobody
      numprocs=1
      stdout_logfile=/var/log/celery-worker.log
      stderr_logfile=/var/log/celery-worker.log
      autostart=true
      autorestart=true
      startsecs=10

      ; Need to wait for currently executing tasks to finish at shutdown.
      ; Increase this if you have very long running tasks.
      stopwaitsecs = 600

      ; When resorting to send SIGKILL to the program to terminate it
      ; send SIGKILL to its whole process group instead,
      ; taking care of its children as well.
      killasgroup=true

      ; if rabbitmq is supervised, set its priority higher
      ; so it starts first
      priority=998

      environment=$celeryenv"

      # Create the celery supervisord conf script
      echo "$celeryconf" | tee /opt/python/etc/celery.conf

      # Add configuration script to supervisord conf (if not there already)
      if ! grep -Fxq "[include]" /opt/python/etc/supervisord.conf
          then
          echo "[include]" | tee -a /opt/python/etc/supervisord.conf
          echo "files: celery.conf" | tee -a /opt/python/etc/supervisord.conf
      fi

      # Reread the supervisord config
      supervisorctl -c /opt/python/etc/supervisord.conf reread

      # Update supervisord in cache without restarting all services
      supervisorctl -c /opt/python/etc/supervisord.conf update

      # Start/Restart celeryd through supervisord
      supervisorctl -c /opt/python/etc/supervisord.conf restart celeryd