Here’s how you can write docker images that you can pipe into:

Dockerfile, here I’m installing the go programs I’m going to run and pipe into:

FROM golang
RUN go get github.com/segmentio/throttle
RUN go get github.com/segmentio/json_to_nsq
COPY entrypoint.sh /entrypoint.sh
CMD ["/bin/sh", "/entrypoint.sh"]

entrypoint.sh, here I’m reading from stdin and piping into the programs I want to run:

rate=${2:-50}
addr=${3:-nsqd:4150}

echo "Sending events to $addr at the rate of $rate/s"

cat - \
    | throttle $rate \
    | json_to_nsq -t events -a "$addr"

And here’s how to run it (assuming the image is called events):

cat events.json | docker run -it events