Local DynamoDB: Unable to execute HTTP request — Connection refused - docker

Question

I run local DynamoDB and an app via docker-compose. Unfortunately I encounter an error when querying DynamoDB from the app:
Unable to execute HTTP request: Connect to dynamodb:80 [dynamodb/172.18.0.2] failed: Connection refused (Connection refused)
Here is how the docker-compose looks like:
version: "3"
services:
dynamodb:
image: "dynamodb-local:latest"
container_name: app-dynamodb
ports:
- "80:8000"
api:
image: "app-backend:latest"
container_name: app-api
ports:
- "5000:5000"
- "5100:5100"
environment:
- DYNAMO_HOST=dynamodb:80
Here is how a Dockerfile for DynamoDB:
FROM openjdk:8-jre
ENV DYNAMODB_VERSION=latest
COPY .aws/ root/.aws/
COPY setup.sh setup.sh
COPY setup-stats.sh setup-stats.sh
RUN apt-get update && \
apt-get install -y python python-pip && \
pip --no-cache-dir install awscli && \
apt-get clean all && \
curl -O https://s3-us-west-2.amazonaws.com/dynamodb-local/dynamodb_local_${DYNAMODB_VERSION}.tar.gz && \
tar zxvf dynamodb_local_${DYNAMODB_VERSION}.tar.gz && \
rm dynamodb_local_${DYNAMODB_VERSION}.tar.gz
EXPOSE 8000
ENTRYPOINT java -Djava.library.path=. -jar DynamoDBLocal.jar --sharedDb -inMemory
UPDATE:
I'm able to connect to dynamoDB JS shell from the host by http://localhost/shell
I'm NOT able to connect to dynamoDB from the app container:
wget dynamodb/shell
Connecting to dynamodb (172.18.0.2:80)
wget: can't connect to remote host (172.18.0.2): Connection refused
The app is written on Scala and uses Scanamo for interaction with DynamoDB

Answer 1

The problem was in missed DYNAMO_ACCESS_KEY and DYNAMO_SECRET_KEY
Despite the dyanmoDB is local and runs in-memory, it requires access_key and secret_key values any way
Furthermore, these values should NOT be empty! So set there anything you want, like "foo" or "bar".

Answer 2

I can see that there is no communication between the DB and the API container. There is a Docker Links Key-Value pair which will help. Please find the updated docker-compose file.
version: "3"
services:
dynamodb:
image: "dynamodb-local:latest"
container_name: app-dynamodb
ports:
- "80:8000"
api:
image: "app-backend:latest"
container_name: app-api
ports:
- "5000:5000"
- "5100:5100"
links:
- dynamodb
environment:
- DYNAMO_HOST=dynamodb:80
This may be the solution Please let me know the Status.