Beam Echo Server Docker example (java) To support the synchronization between slowly booting Docker nodes (ones that perform a time-consuming initialization in run phase). The basic exercise echo server class can be placed into the JRE-based Docker image and executed from ENTRYPOINT or RUN (WIP, need to add forking to make non blocking) after the lengthy initialization is finished. The dependent node then have its ENTRYPOINT modified to become a shell script checking the port availability across the network. Optionally sending a QUIT message shuts down the beam server. For dependency roles that host slow initializing apps (MySQL, Mongo etc) that appear visible in the cluster and listening to public port by default, the app itself is the beam server.

• run locally

javac EchoServer.java

• test locally

export SERVICE_PORT=8889
java EchoServer

(from the separate console)

nc -z localhost 8889; echo $?

0

echo QUIT| telnet 127.0.0.1 8889

Trying 127.0.0.1...
Connected to 127.0.0.1.
Connection closed by foreign host.

in the first console:

Started server on port 8889
Accepted connection from 127.0.0.1
Received QUIT
Stopping accepting the connections
Closing server

• run in container

docker build -f Dockerfile -t basic-echo .
docker run -e SERVICE_PORT=8085 -p 8085:8085 basic-echo

test dockerized

nc -z localhost 8085
echo HELLO| telnet 127.0.0.1 8085
echo QUIT| telnet 127.0.0.1 8085

Started server on port 8085
Accepted connection from 172.17.0.1
Accepted connection from 172.17.0.1
Received QUIT
Stopping accepting the connections
Closing serve

destroy all started containers and image afterwards

docker container prune -f
docker image prune -f

Serguei Kouzmine