maybe is a stupid question...but it's possibile to put variable into docker labels of docker-compose.yml file?
my .env file:
HOST_1=www.example.com
HOST_2=www.site.com
into my docker-compose.yml file can you write like this?
services:
site_01:
...
labels:
- "traefik.http.routers.site_01.rule=Host(`${HOST_1}`)"
- "traefik.http.services.site_01.loadbalancer.server.port=80"
site_02:
...
labels:
- "traefik.http.routers.site_02.rule=Host(`${HOST_2}`)"
- "traefik.http.services.site_02.loadbalancer.server.port=80"
Thanks
Yes it is possible and your snippet seem correct. You can check if the labels are there with docker inspect <container_name_or_id>.
It is also possible to add labels at the build stage. The syntax is the same but labels: key must be under build: key.
Related
I have a simple image (mdw:1.0.0) with some content in it:
FROM alpine:3.9
COPY /role /mdw
WORKDIR /mdw
I was expecting that my container 'nginx' would see the content of /mdw folder, but there is no file.
apiVersion: v1
kind: Pod
metadata:
name: init-demo
spec:
initContainers:
- name: install
image: mdw:1.0.0
imagePullPolicy: Never
volumeMounts:
- name: workdir
mountPath: "/mdw"
containers:
- name: nginx
image: nginx
volumeMounts:
- name: workdir
mountPath: /mdw
command: ["ls", "-l", "/mdw"]
volumes:
- name: workdir
emptyDir: {}
Do you know what is the reason and how to fix it ?
Thank you very much
When mounting volume if directory already exists will get wiped. It's intentional and no fix really.
Only way would be to populate the directory after mounting is done.
Your init container doesn't do anything: the Dockerfile doesn't have a CMD and the Kubernetes deployment spec doesn't set a command: either. It starts and immediately exits. (The base Linux distribution images generally have a default command to launch an interactive shell, but absent a tty this will also immediately exit.)
Meanwhile, your Kubernetes setup is also mounting an empty directory over the only content you've put into the image, which prevents the init container from having an effect.
You can build a custom nginx image that directly copies the content in:
FROM nginx
COPY /role /usr/share/nginx/html
Don't use initContainers:, and use that image as the main containers: image.
There is a Docker-specific feature, using Docker named volumes, that can populate a named volume on first use, and you're probably thinking of this feature. This comes with a couple of important caveats (it only takes effect the very first time you run a container, and ignores updates to the image; it doesn't work with bind mounts). This is a plain-Docker-specific feature: Kubernetes will never auto-populate a volume for you.
For example I want to place an application configuration file inside:
/opt/webserver/my_application/config/my_config_file.xml
I create a ConfigMap from file and then place it in a volume like:
/opt/persistentData/
The idea is to run afterwards an script that does something like:
cp /opt/persistentData/my_config_file.xml /opt/webserver/my_application/config/
But it could be any startup.sh script that does needed actions.
How do I run this command/script? (during Pod initialization before Tomcat startup).
I would first try if this works.
spec:
containers:
- volumeMounts:
- mountPath: /opt/webserver/my_application/config/my_config_file.xml
name: config
subPath: my_config_file.xml
volumes:
- configMap:
items:
- key: KEY_OF_THE_CONFIG
path: my_config_file.xml
name: config
name: YOUR_CONFIGMAP_NAME
If not, add an init container to copy the file.
spec:
initContainers:
- name: copy-config
image: busybox
command: ['sh', '-c', '/bin/cp /opt/persistentData/my_config_file.xml /opt/webserver/my_application/config/']
How about mounting the ConfigMap where you actually want it instead of copying over?
update:
The init container #ccshih mentioned should do, but one can try other options too:
Build a custom image modyfying the base one, using a Docker recipe. The example below takes a java+tomcat7 openshift image, adds an additional folder to the app classpath, so you can mount your ConfigMap to /mnt/config without overwriting anything, keeping both folders available.
.
FROM openshift/webserver31-tomcat7-openshift:1.2-6
# add classpaths to config
RUN sed -i 's/shared.loader=/shared.loader=\/mnt\/config/'
/opt/webserver/conf/catalina.properties
Change the ENTRYPOINT of the application, either by modifying the image, or by the DeploymentConfig hooks, see: https://docs.okd.io/latest/dev_guide/deployments/deployment_strategies.html#pod-based-lifecycle-hook
With the hooks one just needs to remember to call the original entrypoint or launch script after all the custom stuff is done.
.
spec:
containers:
-
name: my-app
image: 'image'
command:
- /bin/sh
args:
- '-c'
- cp /wherever/you/have/your-config.xml /wherever/you/want/it/ && /opt/webserver/bin/launch.sh
Currently i have the configuration similar to below -
services:
gunicorn:
build:
context: .
dockerfile: Dockerfile.gunicorn
restart: always
ports:
- 8001
command: "something"
nginx:
build:
context: .
dockerfile: Dockerfile.nginx
ports:
- 80:80
command: "/usr/sbin/nginx"
We want our gunicorn containers to scale dynamically & the configuration gets dynamically updated for new nodes in the nginx service .
Ideally if i scale using below command, configurations should get added automatically in nginx -
docker-compose scale gunicorn=2
I read about https://github.com/jwilder/nginx-proxy for docker-compose , but i guess it needs to have the container configuration & VIRTUAL_HOST env passed for them to add dynamically in nginx config .
Please suggest .
You might be better off trying to use a tool designed for this purpose. https://github.com/containous/traefik is one example.
i am trying to pass a configuration file(which is located on master) on nginx container at the time of replication controller creation through kubernetes.. ex. as we are using ADD command in Dockerfile...
There isn't a way to dynamically add file to a pod specification when instantiating it in Kubernetes.
Here are a couple of alternatives (that may solve your problem):
Build the configuration file into your container (using the docker ADD command). This has the advantage that it works in the way which you are already familiar but the disadvantage that you can no longer parameterize your container without rebuilding it.
Use environment variables instead of a configuration file. This may require some refactoring of your code (or creating a side-car container to turn environment variables into the configuration file that your application expects).
Put the configuration file into a volume. Mount this volume into your pod and read the configuration file from the volume.
Use a secret. This isn't the intended use for secrets, but secrets manifest themselves as files inside your container, so you can base64 encode your configuration file, store it as a secret in the apiserver, and then point your application to the location of the secret file that is created inside your pod.
I believe you can also download config during container initialization.
See example below, you may download config instead index.html but I would not use it for sensetive info like passwords.
apiVersion: v1
kind: Pod
metadata:
name: init-demo
spec:
containers:
- name: nginx
image: nginx
ports:
- containerPort: 80
volumeMounts:
- name: workdir
mountPath: /usr/share/nginx/html
# These containers are run during pod initialization
initContainers:
- name: install
image: busybox
command:
- wget
- "-O"
- "/work-dir/index.html"
- http://kubernetes.io
volumeMounts:
- name: workdir
mountPath: "/work-dir"
dnsPolicy: Default
volumes:
- name: workdir
emptyDir: {}
Using fleet I can specify a command to be run inside the container when it is started. It seems like this should be easily possible with Kubernetes as well, but I can't seem to find anything that says how. It seems like you have to create the container specifically to launch with a certain command.
Having a general purpose container and launching it with different arguments is far simpler than creating many different containers for specific cases, or setting and getting environment variables.
Is it possible to specify the command a kubernetes pod runs within the Docker image at startup?
I spend 45 minutes looking for this. Then I post a question about it and find the solution 9 minutes later.
There is an hint at what I wanted inside the Cassandra example. The command line below the image:
id: cassandra
kind: Pod
apiVersion: v1beta1
desiredState:
manifest:
version: v1beta1
id: cassandra
containers:
- name: cassandra
image: kubernetes/cassandra
command:
- /run.sh
cpu: 1000
ports:
- name: cql
containerPort: 9042
- name: thrift
containerPort: 9160
env:
- key: MAX_HEAP_SIZE
value: 512M
- key: HEAP_NEWSIZE
value: 100M
labels:
name: cassandra
Despite finding the solution, it would be nice if there was somewhere obvious in the Kubernetes project where I could see all of the possible options for the various configuration files (pod, service, replication controller).
for those looking to use a command with parameters, you need to provide an array
for example
command: [ "bin/bash", "-c", "mycommand" ]
or also
command:
- "bin/bash"
- "-c"
- "mycommand"
To answer Derek Mahar's question in the comments above:
What is the purpose of args if one could specify all arguments using command?
Dockerfiles can have an Entrypoint only or a CMD only or both of them together.
If used together then whatever is in CMD is passed to the command in ENTRYPOINT as arguments i.e.
ENTRYPOINT ["print"]
CMD ["hello", "world"]
So in Kubernetes when you specify a command i.e.
command: ["print"]
It will override the value of Entrypoint in the container's Dockerfile.
If you only specify arguments then those arguments will be passed to whatever command is in the container's Entrypoint.
In order to specify the command a kubernetes pod runs within the Docker image at startup we need to include the command and args fields inside the yaml file for command and arguments to be passed. For example,
apiVersion: v1
kind: Pod
metadata:
name: command-demo
labels:
purpose: demo-command
spec:
containers:
- name: command-demo-container
image: ubuntu
command: ["/bin/sh"]
args: ["-c", "while true; do echo hello; sleep 10;done"]
Additionally to the accepted answer, you can use variables with values from secrets in the commands as follows:
command: ["/some_command","-instances=$(<VARIABLE_NAME>)"]
env:
- name: <VARIABLE_NAME>
valueFrom:
secretKeyRef:
name: <secret_name>
key: <secret_key>