Change container port in docker compose - docker

Question

I am trying to get a docker-compose file working with both airflow and spark. Airflow typically runs on 8080:8080 which is needed by spark as well. I have the following docker-compose file:
version: '3.7'
services:
master:
image: gettyimages/spark
command: bin/spark-class org.apache.spark.deploy.master.Master -h master
hostname: master
environment:
MASTER: spark://master:7077
SPARK_CONF_DIR: /conf
SPARK_PUBLIC_DNS: localhost
expose:
- 7001
- 7002
- 7003
- 7004
- 7005
- 7077
- 6066
ports:
- 4040:4040
- 6066:6066
- 7077:7077
- 8080:8080
volumes:
- ./conf/master:/conf
- ./data:/tmp/data
worker:
image: gettyimages/spark
command: bin/spark-class org.apache.spark.deploy.worker.Worker spark://master:7077
hostname: worker
environment:
SPARK_CONF_DIR: /conf
SPARK_WORKER_CORES: 2
SPARK_WORKER_MEMORY: 1g
SPARK_WORKER_PORT: 8881
SPARK_WORKER_WEBUI_PORT: 8081
SPARK_PUBLIC_DNS: localhost
links:
- master
expose:
- 7012
- 7013
- 7014
- 7015
- 8881
ports:
- 8081:8081
volumes:
- ./conf/worker:/conf
- ./data:/tmp/data
postgres:
image: postgres:9.6
environment:
- POSTGRES_USER=airflow
- POSTGRES_PASSWORD=airflow
- POSTGRES_DB=airflow
logging:
options:
max-size: 10m
max-file: "3"
webserver:
image: puckel/docker-airflow:1.10.9
restart: always
depends_on:
- postgres
environment:
- LOAD_EX=y
- EXECUTOR=Local
logging:
options:
max-size: 10m
max-file: "3"
volumes:
- ./dags:/usr/local/airflow/dags
# Add this to have third party packages
- ./requirements.txt:/requirements.txt
# - ./plugins:/usr/local/airflow/plugins
ports:
- "8082:8080" # NEED TO CHANGE THIS LINE
command: webserver
healthcheck:
test: ["CMD-SHELL", "[ -f /usr/local/airflow/airflow-webserver.pid ]"]
interval: 30s
timeout: 30s
retries: 3
but specifically need to change the line:
ports:
- "8082:8080" # NEED TO CHANGE THIS LINE
under web server so there's no port conflict. However when I change the container port to something other than 8080:8080 it doesnt work (cannot connect/find server). How do I change the container port successfully?

Answer 1

When you specified port mapping in docker you are giving 2 ports, for instance: 8082:8080.
The right port is the one that is listening within the container.
You can have several containers that listening internally to the same port. They are still not available in your localhost - that's why we use the ports section for.
Now, in your localhost you cannot bind the same port more than once. That's why docker failed when you try to set on the left side 8080 more than one time.
In your current compose file, the spark service port is mapped to 8080 (left side of 8080:8080) and the webserver service is mapped to 8082 (left side of 8082:8080).
if you want to access spark, goto: http://localhost:8080 and for the web server, go to http://localhost:8082