collectd exit after running

[FS1360472174]

confuse about the readme page,not clear about which steps is necessary.
so just run the Minimal command:
docker run -d -v /var/run/docker.sock:/var/run/docker.sock
-e GRAPHITE_HOST= -e COLLECTD_HOST=
bobrik/collectd-docker

container run then exit,exit code is (6).
search answer from existing issue,found that environment variables should be set.

from page,basicly these variables have default value ,but not COLLECTD_DOCKER_APP and COLLECTD_DOCKER_TASK.

Environment variables
COLLECTD_HOST - host to use in metric name, defaults to MESOS_HOST if defined.
COLLECTD_INTERVAL - metric update interval in seconds, defaults to 10.
GRAPHITE_HOST - host where carbon is listening for data.
GRAPHITE_PORT - port where carbon is listening for data, 2003 by default.
GRAPHITE_PREFIX - prefix for metrics in graphite, collectd. by default.
APP_LABEL_KEY - container label to use for app name, collectd_docker_app by default.
APP_ENV_KEY - container environment variable to use for app name, COLLECTD_DOCKER_APP by default.
TASK_LABEL_KEY - container label to use for task name, collectd_docker_task by default.
TASK_ENV_KEY - container environment variable to use for task name, COLLECTD_DOCKER_TASK by default.

so I add COLLECTD_DOCKER_APP ,COLLECTD_DOCKER_TASK environment variables
but it still exit after running.
any idea about this？
thanks in advance