Suggestion: Use some defaults when linking containers

[bompi88]

For the simplicity, when linking containers, use env variables like below if no other env variable is set.

• MONGO_PORT_27017_TCP_ADDR and MONGO_PORT_27017_TCP_PORT
• ELASTICSEARCH_PORT_9200_TCP_ADDR and ELASTICSEARCH_PORT_9200_TCP_PORT

[Alino]

could you please describe with some example, how would you use those variables when linking docker containers? It's not clear to me yet :)

[bompi88]

I'm kind of new to the whole docker thingy, but I think those variables are set if you link the elasticsearch and mongodb container with the --link option. A typical setup could be as follows, where the containers are linked to the mongo2es container at the bottom.

# Run data-only container

docker run \
  --volume=/data/db/ \
  --volume=/usr/share/elasticsearch/data \
  --name=data-only \
  --entrypoint=/bin/echo \
  ubuntu 'Data-only container'

# Run mongodb container

docker run \
  --publish=27017:27017 \
  --volumes-from data-only \
  --volume="$PWD/.mongodb.conf":/mongodb.conf \
  --name=mongodb \
  -d \
  mongo mongod -f /mongodb.conf

# Run Elasticsearch

docker run \
  --publish=9200:9200 \
  --publish=9300:9300 \
  --volumes-from data-only \
  --name=elasticsearch \
  -d \
  elasticsearch

# Build mongoose container within .mongo2es dir
# docker build -t mongo2es .mongo2es

echo "Waiting for Elasticsearch to start"
docker-machine inspect --format '{{ .Driver.IPAddress }}:9200' dev | xargs wget --retry-connrefused --tries=5 -q --waitretry=3 --spider
sleep 1

# Run mongo2es container

docker run \
  -e ROOT_URL=http://localhost:3001 \ # This could have a default value as well?
  --link=mongodb \
  --link=elasticsearch \
  -p 3001:80 \
  --name mongo2es \
  -d \
  mongo2es

In the mongo2es container, those variables are accessible, I think. If those are available you could set the MONGO_URL and so on, based on those? Just a suggestion, and I don't know if this option would be helpful or just misleading? What do you think about the matter?

[Alino]

so if I understand, docker automatically creates those env variables for you if you --link the containers. That's cool, I didn't know that.
You are right, we should make such a 'convention over configuration' that if you link the containers, all required env variables in mongo2es should get set based on those docker auto-generated env variables if they are not explicitly set to something else.
I will look into this issue later someday (I will be probably linking containers when I get my project which is using mongo2es into production).
Pull requests are welcome btw :)

[bompi88]

Awesome :) maybe I'll investigate further next week, which kind of other variables being set and so on. My hands are quite tightened this week while working on my master thesis.

[bompi88]

@Alino I looked into this anyway. Created a two PR's for you to take a look at :)

[Alino]

Good job, I just merged your PRs, but I am not sure about this one, I haven't tested it yet. Did you try it, or are you using this approach? is everything ok with it? Maybe I should keep it opened, and test it later

[bompi88]

Haven't got the time to test it thoroughly yet, sorry.