docker-compose.yml
version: '3.3'
services:
hello:
image: dockercloud/hello-world
service_auth:
image: beevelop/nginx-basic-auth
ports:
- 8080:80
links:
- hello:web
environment:
HTPASSWD: 'foo:$apr1$odHl5EJN$KbxMfo86Qdve2FH4owePn.'
docker --version
Docker version 17.09.0-ce, build afdb6d4
docker stack deploy -c docker-compose.yml auth
Ignoring unsupported options: links
Why is links not supported?
The official documentation does list what is not supported for compose and stack, and that includes links.
Links are not required to enable services to communicate - by default, any service can reach any other service at that service’s name. (See also, the Links topic in Networking in Compose.)
Hence that option is ignored when deploying a stack in swarm mode with a (version 3) Compose file.
$ docker stack deploy --compose-file docker-compose.yml vossibility
Ignoring unsupported options: links
So: why the option is not supported?
Because links are not needed in a compose scenario, since all services can already communicate one with another (being in the same network set up by compose).
You don't need links starting with version 2 of Compose files. Before v2, you needed to be explicit on what talked to what. In v2+, all containers on the same overlay or custom bridge network will be able to access all listening ports of other containers via their service name as DNS hostname.
Related
Given compose file
version: '3.8'
services:
whoami1:
image: containous/whoami
depends_on:
- whoami2
whoami2:
image: containous/whoami
when deployed to docker swarm docker stack deploy -c docker-compose.yaml test
services whoami1 and whoami2 seem to start in random order and ignore depends_on condition.
docker stack deploy -c docker-compose.yaml test
Creating network test_default
Creating service test_whoami1
Creating service test_whoami2
Does docker swarm support service startup sequencing via dependencies?
No, at least not built in.
Even with depends_on the whoami2 may not yet be ready to interact with whoami1 because it may need time to boot itself:
However, for startup Compose does not wait until a container is “ready” (whatever that means for your particular application) - only until it’s running. There’s a good reason for this.
https://docs.docker.com/compose/startup-order/
They hint at two possibilites to check if whoami2 is ready.
Use a tool such as wait-for-it, dockerize, or sh-compatible wait-for. These are small wrapper scripts which you can include in your application’s image to poll a given host and port until it’s accepting TCP connections.
And depends_on is indeed ignored for docker swarm:
There are several things to be aware of when using depends_on:
(...)
The depends_on option is ignored when deploying a stack in swarm mode with a version 3 Compose file.
https://docs.docker.com/compose/compose-file/#depends_on
There are a lot of applications which I launch on my workstation using docker-compose up.
Reasons:
They don't have an installer, or I don't want to use it
They require a dedicated storage engine to be present
They require a build process step
They are created by me and I want them to be easily launched on any workstation
e.t.c
So what I usually end up with the following file-structure:
myAppDir
- docker-compose.yml
- Dockerfile (not always)
- someConfigFile
And my docker-compose.yml is something like this:
(It can contain 2 or 3 services, but I provide the simplest form that I use)
version: '3.7'
services:
mysql:
image: mysql:5.7.29
restart: always
volumes:
- ./mysqld.cnf:/etc/mysql/mysql.conf.d/mysqld.cnf
environment:
- MYSQL_ROOT_PASSWORD=xyz
ports:
- 3306:3306
Then when I need to launch the application I just perform:
docker-compose up # (or with --build)
Recently I tried to add:
deploy:
resources:
limits:
cpus: '0.50'
memory: 200M
and got a message:
Some services (mysql) use the 'deploy' key, which will be ignored. Compose does not support 'deploy' configuration - use docker stack deploy to deploy to a swarm.
So I tried:
docker stack deploy mystack --compose-file docker-compose.yml
and got message:
Ignoring unsupported options: restart
this node is not a swarm manager. Use "docker swarm init" or "docker swarm join" to connect this node to swarm and try again
This seems more complex that docker-compose up.
I saw that I can use --compatibility flag e.g.
docker-compose --compatibility up
But the word compatibility means to me that I should soon switch to a new way of launching my apps locally.
My question is: What is the new procedure that I should follow for launching apps on my workstation using a docker and a descriptor file, in order to support options present in Compose file v3?
If you want to specify memory limits and similar constraints for local containers, you need to use a version 2 Compose file. This is called out in the documentation for the deploy: resources: section. docker/compose#4513 has some reasonably clear statements that Compose file version 2 is more targeted at local setups and version 3 more at Swarm installations, and that Docker intends to keep supporting both file versions.
Docker has put many options and functions specific to their Swarm cluster-installation mode into the core product. Anything that mentions a "stack", for example, is specific to a Swarm setup. One consequence of Swarm and plain-Docker things being combined together is that the deploy: Docker Compose options only have an effect in Swarm mode. The documentation for the deploy: key notes:
This only takes effect when deploying to a swarm with docker stack deploy, and is ignored by docker-compose up and docker-compose run.
My question is: What is the new procedure that I should follow for launching apps on my workstation using a docker and a descriptor file, in order to support options present in Compose file v3?
Docker compose V3 is meant to be used with Docker Swarm deployments, therefore you need to run your Docker in Swarm mode, otherwise just keep using the V2 and it's simpler interface for localhost developments.
For example restart is ignored because that responsibility belongs now to the Docker Swarm, not to Docker itself.
Using the compatibility flag it's kind of converting at runtime your V3 compose file into a V2 compose file.
So in short just use V3 if you want to run Docker in Swarm mode to take advantage of all its new features, aka it's kind of a Kubernetes in Docker land.
Here is compose file with config of container that I wish to connect to from external container (defined in another compose file):
version: '3.5'
services:
service-to-connect-to:
build: .
networks:
- my-external-network
networks:
my-external-network:
external: true
and another compose file that contains config for container from which I wish to connect to service-to-connect-to:
version: "3.5"
services:
service-to-connect-from:
build: .
I tried to connect to service-to-connect-to via this domains:
service-to-connect-to
service-to-connect-to.my-external-network
my_external_network.service-to-connect-to
but nothing of them worked.
Where I'm wrong?
Thanks
First, you have to add both services to same network in order to connect them. So, the latter compose file should be something like
version: "3.5"
services:
service-to-connect-from:
build .
networks:
- my-external-network
networks:
my-external-network:
external: true
Now that both services are on the same network they can find each other using container's name. Container name is by default same as the service name BUT docker compose also prefixes it by project name which is by default the directory name where the compose file exists. You can see this if you first start the services by docker-compose up -d and then see how the containers get named by running docker ps. The container name could be for example project1_service-to-connect-to. With this name you can connect from another service.
If you like to, you can also set the container's name explicitly using container_name option for service. When used, compose doesn't prefix the container name anymore.
This is not possible with compose, because the second docker-compose file will create a different network with the current directory name and then your both the services will be in two different docker network and will not be able talk to each other.
So you can do two things:
1. either use same network for both the services (then its better to have one combined compose file).
2. use docker swarm stacks, where you can connect to other services with <service_name>.<stack_name>
References:
https://docs.docker.com/docker-cloud/apps/service-links/#using-service-and-container-names-as-hostnames
https://docs.docker.com/v17.09/engine/userguide/networking/configure-dns/
Note: Even service links does not help, because compose creates different network while running the second file.
I have a docker-compose.yml file which works with docker-compose up --build. My app works and everything is fine.
version: '3'
services:
myapp:
container_name: myapp
restart: always
build: ./myapp
ports:
- "8000:8000"
command: /usr/local/bin/gunicorn -w 2 -b :8000 flaskplot:app
nginx:
container_name: nginx
restart: always
build: ./nginx
ports:
- "80:80"
depends_on:
- myapp
But when I use docker stack deploy -c docker-compose.yml myapp, I get the following error:
Ignoring unsupported options: build, restart
Ignoring deprecated options:
container_name: Setting the container name is not supported.
Creating network myapp_default
Creating service myapp_myapp
failed to create service myapp_myapp: Error response from daemon: rpc error: code = InvalidArgument desc = ContainerSpec: image reference must be provided
any hints how I should "translate" the docker-compose.yml file to make it compatible with docker stack deploy?
To run containers in swarm mode, you do not build them on each swarm node individually. Instead you build the image once, typically on a CI server, push to a registry server (often locally hosted, or you can use docker hub), and specify the image name inside your compose file with an "image" section for each service.
Doing that will get rid of the hard error. You'll likely remove the build section of the compose file since it no longer applies.
Specifying "container_name" is unsupported because it would break the ability to scale or perform updates (a container name must be unique within the docker engine). Let swarm name the containers and reference your app on the docker network by it's service name.
Specifying "depends_on" is not supported because containers may be started on different nodes, and rolling updates/failure recovery may remove some containers providing a service after the app started. Docker can retry the failing app until the other service starts up, or preferably you configure an entrypoint that waits for the dependencies to become available with some kind of ping for a minute or two.
Without seeing your Dockerfile, I'd also recommend setting up a healthcheck on each image. Swarm mode uses this to control rolling updates and recover from application failures.
Lastly, consider adding a "deploy" section to your compose file. This tells swarm mode how to deploy and update your service, including how many replicas, constraints on where to run, memory and CPU limits and requirements, and how fast to update the service. You can define a restart policy here as well but I recommend against it since I've seen docker engines restarting containers that conflict with swarm mode deploying containers on other nodes, or even a new container on the same node.
You can see the full compose file documentation with all of these options here: https://docs.docker.com/compose/compose-file/
I have project with docker-compose file and want to migrate to V3, but when deploy with
docker stack deploy --compose-file=docker-compose.yml vertx
It does not understand build path, links, container names...
My file locate d here
https://github.com/armdev/vertx-spring/blob/master/docker-compose.yml
version: '3'
services:
eureka-node:
image: eureka-node
build: ./eureka-node
container_name: eureka-node
ports:
- '8761:8761'
networks:
- vertx-network
postgres-node:
image: postgres-node
build: ./postgres-node
container_name: postgres-node
ports:
- '5432:5432'
networks:
- vertx-network
environment:
POSTGRES_USER: postgres
POSTGRES_PASSWORD: socnet
POSTGRES_DB: socnet
vertx-node:
image: vertx-node
build: ./vertx-node
container_name: vertx-node
links:
- postgres-node
- eureka-node
ports:
- '8585:8585'
networks:
- vertx-network
networks:
vertx-network:
driver: overlay
when I run docker-compose up, it is working, but with
stack deploy not.
How to define path for docker file?
docker stack deploy works only on images, not on builds.
This means that you will have to push your images to an image registry (created with the build process), later docker stack deploy will download the images and execute them.
here you have an example of how was it done for a php application.
You have to pay attention to the parts 1, 3 and 4.
The articles are about php, but can easily be applied to any other language.
The swarm mode "docker service" interface has a few fundamental differences in how it manages containers. You are no longer directly running containers like with "docker run", and it is assumed that you will be doing this in a distributed environment more often than not.
I'll break down the answer by these specific things you listed.
It does not understand build path, links, container names...
Links
The link option has been deprecated for quite some time in favor of the network service discovery feature introduced alongside the "docker network" feature. You no longer need to specify specific links to/from containers. Instead, you simply need to ensure that all containers are on the same network and then they can discovery eachother by the container name or "network alias"
docker-compose will put all your containers into the same network by default, and it sets up the compose service name as an alias. That means if you have a service called 'postgres-node', you can reach it via dns by the name 'postgres-node'.
Container Names
The "docker service" interface allows you to declare a desired state. "I want x number of identical services". Since the interface must support x number of instances of a service, it doesn't allow you to choose the specific container name. Instead, you get to choose the service name. In the case of 'docker stack deploy', the service name defined under the services key in your docker-compose.yml file will be used, but it will also prepend the stack name to the service name.
In most cases, I would argue that overriding the container name in a docker-compose.yml file is unnecessary, even when using regular containers via docker-compose up.
If you need a different name for network service discovery purposes, add a different alias or use the service name alias that you get when using docker-compose or docker stack deploy.
build path
Because swarm mode was built to be a distributed system, building an image in place locally isn't something that "docker stack deploy" was meant to do. Instead, you should build and push your image to a registry that all nodes in your cluster can access.
In the case where you are using a single node swarm "cluster", you should be able to use the docker-compose build option to get the images built locally, and then use docker stack deploy.