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I'm trying to deploy 3 Docker containers, having a dependency relation amongst them (A -> B -> C). Now, each container is supposed to run an Akka-Spray instance, on top of a JVM instance.

The problem is: following usual orchestration approaches, container A has been started but the web server hasn't had time to boot up. If it isn't up and running before container B is operational, container B will never catch up and so forth, with C.

I've been trying the following approach lately: share a data volume between containers; after the web server is ready, a helper script will create an empty file in the volume; run a script (through an Upstart service) that looks for an empty file to show up and fires up the next container.

However, using a service is most likely the cause to this issue: running

sudo docker run -d -it --name=backend -v ~/docker-test/:/docker-test -v ~/aux/:/aux ubuntu /bin/bash -c "</path/to/test/script>"

works fine when done simply in command line, but fails randomly in the script executed by the Upstart service (receive message "/bin/bash </path/to/test/script> : no such file or directory").

Anyone's come across this, as well? I'd gratefully welcome any suggestions to overcome this.

HopelessN00b
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Pedro Almeida
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2 Answers2

1

Why not look at a purpose-built docker orchestrator like flynn, deis, shipyard, etc.?

Quite a list here

Community
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Bryan
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1

One option is to just wait until the remote network port is open, which indicates that the web server has started. Code below is based on this thread on SuperUser

#!/bin/sh
SERVICE_IP=`sudo docker inspect -f \"{{.NetworkSettings.IPAddress}}\" $CONTAINER_NAME`
SERVICE_PORT=80
while ! nc -vz \$SERVICE_IP \$SERVICE_PORT; do sleep 1; done

This can be combined with a container build orchestrator (if that orchestrator doesn't natively support waiting for "container port is up" - I don't know what is available in that direction).

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cr7pt0gr4ph7
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