What is the difference between docker run --config vs docker compose config? - docker

Question

So what I am looking at is a docker run command being used in to create a docker container for open telemetry that passes in a config command, and the code looks like...
$ git clone git#github.com:open-telemetry/opentelemetry-collector.git; \
cd opentelemetry-collector/examples; \
go build main.go; ./main & pid1="$!";
docker run --rm -p 13133:13133 -p 14250:14250 -p 14268:14268 \
-p 55678-55679:55678-55679 -p 4317:4317 -p 8888:8888 -p 9411:9411 \
-v "${PWD}/local/otel-config.yaml":/otel-local-config.yaml \
--name otelcol otel/opentelemetry-collector \
--config otel-local-config.yaml; \
kill $pid1; docker stop otelcol
(https://opentelemetry.io/docs/collector/getting-started/#docker)
What I don't understand is how a non-docker related config file(open telemetry config) fits into the "docker run --config" or "docker compose config" commands. Below is the open telemetry config file that seems to be non-docker related
extensions:
memory_ballast:
size_mib: 512
zpages:
endpoint: 0.0.0.0:55679
receivers:
otlp:
protocols:
grpc:
http:
processors:
batch:
memory_limiter:
# 75% of maximum memory up to 4G
limit_mib: 1536
# 25% of limit up to 2G
spike_limit_mib: 512
check_interval: 5s
exporters:
logging:
logLevel: debug
service:
pipelines:
traces:
receivers: [otlp]
processors: [memory_limiter, batch]
exporters: [logging]
metrics:
receivers: [otlp]
processors: [memory_limiter, batch]
exporters: [logging]
extensions: [memory_ballast, zpages]
https://github.com/open-telemetry/opentelemetry-collector/blob/main/examples/local/otel-config.yaml
Now I have looked at these Docker links
https://docs.docker.com/engine/swarm/configs/#how-docker-manages-configs
https://nickjanetakis.com/blog/docker-tip-43-using-the-docker-compose-config-command
but I couldn't figure out how to get the docker run --config command in the open telemetry example to start working in docker compose with docker compose config. Here is my docker compose
version: "3.9"
services:
opentelemetry:
container_name: otel
image: otel/opentelemetry-collector:latest
volumes:
- ~/source/repos/CritterTrackerProject/DockerServices/OpenTelemetry/otel-collector-config.yml:/otel-local-config.yml
config:
- otel-local-config.yml
ports:
- 13133:13133
- 14250:14250
- 14268:14268
- 55678-55679:55678-55679
- 4317:4317
- 8888:8888
- 9411:9411
extra_hosts:
- "host.docker.internal:host-gateway"
networks:
- my-network
jaeger:
# restart: unless-stopped
container_name: jaeger
image: jaegertracing/all-in-one:latest
ports:
- 16686:16686
# - 14250:14250
# - 14268:14268
# - 5775:5775/udp
- 6831:6831/udp
# - 6832:6832/udp
# - 5778:5778
# - 9411:9411
extra_hosts:
- "host.docker.internal:host-gateway"
networks:
- my-network
postgres:
restart: always
container_name: postgres
image: postgres:latest
environment:
- POSTGRES_USER=code
- POSTGRES_PASSWORD=code
ports:
- 5432:5432
volumes:
- postgres:/var/lib/postgresql/data
extra_hosts:
- "host.docker.internal:host-gateway"
networks:
- my-network
nginx:
restart: always
container_name: webserver
image: nginx:latest
build:
context: ~/source/repos/CritterTrackerProject
dockerfile: DockerServices/Nginx/Dockerfile
ports:
- 80:80
- 443:443
extra_hosts:
- "host.docker.internal:host-gateway"
networks:
- my-network
volumes:
postgres:
networks:
my-network:
external: true
name: my-network
Here is my error after running docker compose up in a Git Bash terminal
$ docker compose -f ./DockerServices/docker-compose.yml up -d
services.opentelemetry Additional property config is not allowed

Answer 1

The general form of docker run is
docker run [docker options] image [command]
And if you look at your original command it matches this pattern
docker run \
--rm -p ... -v ... --name ... \ # Docker options
otel/opentelemetry-collector \ # Image
--config otel-local-config.yaml # Command
So what looks like a --config option is really the command part of the container setup; it overrides the Dockerfile CMD, and it is passed as additional arguments to the image's ENTRYPOINT.
In a Compose setup, then, this would be the container's command:.
services:
opentelemetry:
image: otel/opentelemetry-collector:latest
command: --config otel-local-config.yaml
Since this is an application-specific command string, it's unrelated to the docker-compose config command, which is a diagnostic tool that just dumps out parts of your Compose configuration.

Answer 2

What you're doing in the docker run command is the following mounting:
${PWD}/local/otel-config.yaml on the local host to /otel-local-config.yaml from inside the docker
You can achieve same behavior with volumes option from docker compose:
volumes:
"${PWD}/local/otel-config.yaml":/otel-local-config.yaml