Cannot connect to kafka docker container from outside client (wurstmeister images) - docker

Question

There are so many answers for this question that I ended up being totally confused about how I can connect to Kafka docker container from an outside client.
I have created two docker machines, a manager and a worker with these commands:
docker-machine create manager
docker-machine create worker1
I have add these two nodes inside a docker swarm.
docker#manager:~$ docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
6bmovp3hr0j2w5irmexvvjgzq * manager Ready Active Leader 19.03.5
mtgbd9bg8d6q0lk9ycw10bxos worker1 Ready Active 19.03.5
docker-compose.yml:
version: '3.2'
services:
zookeeper:
image: wurstmeister/zookeeper
ports:
- "2181:2181"
kafka:
image: wurstmeister/kafka:latest
ports:
- target: 9094
published: 9094
protocol: tcp
mode: host
environment:
HOSTNAME_COMMAND: "hostname | awk -F'-' '{print $$2}'"
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: INSIDE:PLAINTEXT,OUTSIDE:PLAINTEXT
KAFKA_ADVERTISED_LISTENERS: INSIDE://:9092,OUTSIDE://_{HOSTNAME_COMMAND}:9094
KAFKA_LISTENERS: INSIDE://:9092,OUTSIDE://:9094
KAFKA_INTER_BROKER_LISTENER_NAME: INSIDE
volumes:
- /var/run/docker.sock:/var/run/docker.sock
From inside docker, everything works fine. I can create topics and then produce/consume messages.
I created a python script in order to consume messages from outside docker. The simple code is presented below:
from kafka import KafkaConsumer
import json
try:
print('Welcome to parse engine')
consumer = KafkaConsumer('streams-plaintext-input', bootstrap_servers='manager:9094')
for message in consumer:
print(message)
except Exception as e:
print(e)
# Logs the error appropriately.
pass
But the code is stack forever. The connection is not correct. Can anyone provide any help on how to setup a connection?

Answer 1

Since you are using docker-machine you have to either
Run your code also in a container (using kafka:9092)
Run your code within the VM OS (using vm-host-name:9094)
Add PLAINTEXT://localhost:9096 to the advertised listeners, expose 9096 from the VM to your host, then use localhost:9096 in your code (note: 9096 is some random port)
The gist is that clients must be able to connect to the bootstrap address and the advertised one that is being returned. If it cannot connect to the second, code will timeout.