I am trying to run an executable file from another docker container while already inside a docker container. Is this possible?
version: '3.7'
services:
py:
build: .
tty: true
networks:
- dataload
volumes:
- './src:/app'
- '~/.ssh:/ssh'
winexe:
build:
context: ./winexe
dockerfile: Dockerfile
networks:
- dataload
ports:
- '8001:8001'
volumes:
- '~/path/to/winexe:/usr/bin/winexe'
- '~/.ssh:/ssh'
depends_on:
- py
networks:
dataload:
driver: bridge
I am trying to access Winexe from 'py'
Assuming you mean running another Docker container from inside a container, this can be done in several ways:
Install the docker command inside your container and:
Contact the hosting Docker instance over TCP/IP. For this you will have to have exposed the Docker host to the network, which is neither default nor recommended.
Map the docker socket (usually /var/run/docker.sock) in to your container using a volume. This will allow the docker command inside the container to contact the host instance directly.
Be aware this essentially gives the container root level access to the host! I'm sure there are many more ways to do the same, but approach number 2 is the one I see most often.
If you mean to run another executable inside another - already running - Docker container, you can do that in the above way as well by using docker exec or run some kind of daemon in the second container that accepts commands and runs the required command for you.
So you need to think of your containers as if they were two separate computers, or servers, and they can interact accordingly.
Happily, docker-compose gives you a url you can use to communicate between the containers. In the case of your docker-compose file, you could access the winexe container from your py container like so:
http://winexe:8001 // or ws://winexe:8001 or postgres://winexe:8001 (you get the idea)
(I've used port 8001 here because that's the port you've made available for winexe – I have no idea if it could be used for this).
So now what you need is something in your winexe container than listens to that signal and sends a useful reply (like a browser sending an ajax call to a server)
Learn more here:
https://docs.docker.com/compose/networking/
Related
I have two Docker containers—redis (running a Redis database) and node (running a Node.js application). My Node.js application needs to communicate with the Redis database, but I'm not sure how I should arrange this. Here are some ways I've thought of so far:
Put the two containers on one network, expose (but do not publish) port 6379 (or wherever the Redis server is listening) of the redis container, and connect to the exposed port from the node container.
Have the Redis server listen on a UNIX socket that is mounted to some location on the host (i.e., outside of the redis container) that is also mounted into the node container (willl that even work?).
Ditch the separate containers idea altogether and put the Redis server and Node app in the same container (I really do not want to do this).
Which option is the best, or is there something else that you would suggest? I want to maximize performance and security, but I also need to use container(s).
P.S. There are some similar questions to this one out there, but none of them seem to answer my question. That being said, if you find an existing answer that might help, please do link to it.
Presumably, the second approach has a higher performance. There are some comparisons here and here.
In order to implement this approach, you can simply create a docker volume and mount it in both containers. e.g. you can create a Dockerfile based on redis image:
FROM redis:7-alpine
RUN mkdir -p /run/redis-socket
RUN chmod 777 /run/redis-socket
COPY ./etc/redis.conf /etc/redis.conf
ENTRYPOINT ["docker-entrypoint.sh", "/etc/redis.conf"]
and write such config to ./etc/redis.conf:
unixsocket /run/redis-socket/redis.sock
unixsocketperm 777
port 0
Then mount a docker volume to /run/redis-socket/ of redis container. Don't forget to mount that volume to an arbitrary path in your node container.
If you use docker-compose, a sample docker-compose.yml would be like this:
version: "2.3"
services:
redis:
image: my-altered-redis-image
container_name: my-redis
volumes:
- redis-socket:/run/redis-socket
mynode:
image: my-node-image
container_name: my-node
depends_on:
- "redis"
volumes:
- redis-socket:/run/redis-socket
volumes:
redis-socket:
I am writing a docker compose file for my web app.If I use 'link' to connect services with each other do I also need to include 'port'? And is 'depends on' an alternate option of 'links'? What will be best for connection services in a compose file with one another?
The core setup for this is described in Networking in Compose. If you do absolutely nothing, then one service can call another using its name in the docker-compose.yml file as a host name, using the port the process inside the container is listening on.
Up to startup-order issues, here's a minimal docker-compose.yml that demonstrates this:
version: '3'
services:
server:
image: nginx
client:
image: busybox
command: wget -O- http://server/
# Hack to make the example actually work:
# command: sh -c 'sleep 1; wget -O- http://server/'
You shouldn't use links: at all. It was an important part of first-generation Docker networking, but it's not useful on modern Docker. (Similarly, there's no reason to put expose: in a Docker Compose file.)
You always connect to the port the process inside the container is running on. ports: are optional; if you have ports:, cross-container calls always connect to the second port number and the remapping doesn't have any effect. In the example above, the client container always connects to the default HTTP port 80, even if you add ports: ['12345:80'] to the server container to make it externally accessible on a different port.
depends_on: affects two things. Try adding depends_on: [server] to the client container to the example. If you look at the "Starting..." messages that Compose prints out when it starts, this will force server to start starting before client starts starting, but this is not a guarantee that server is up and running and ready to serve requests (this is a very common problem with database containers). If you start only part of the stack with docker-compose up client, this also causes server to start with it.
A more complete typical example might look like:
version: '3'
services:
server:
# The Dockerfile COPYs static content into the image
build: ./server-based-on-nginx
ports:
- '12345:80'
client:
# The Dockerfile installs
# https://github.com/vishnubob/wait-for-it
build: ./client-based-on-busybox
# ENTRYPOINT and CMD will usually be in the Dockerfile
entrypoint: wait-for-it.sh server:80 --
command: wget -O- http://server/
depends_on:
- server
SO questions in this space seem to have a number of other unnecessary options. container_name: explicitly sets the name of the container for non-Compose docker commands, rather than letting Compose choose it, and it provides an alternate name for networking purposes, but you don't really need it. hostname: affects the container's internal host name (what you might see in a shell prompt for example) but it has no effect on other containers. You can manually create networks:, but Compose provides a default network for you and there's no reason to not use it.
Hi I am finding it very confusing how I can create a docker file that would run a rabbitmq container, where I can expose the port so I can navigate to the management console via localhost and a port number.
I see someone has provided this dockerfile example, but unsure how to run it?
version: "3"
services:
rabbitmq:
image: "rabbitmq:3-management"
ports:
- "5672:5672"
- "15672:15672"
volumes:
- "rabbitmq_data:/data"
volumes:
rabbitmq_data:
I have got rabbit working locally fine, but everyone tells me docker is the future, at this rate I dont get it.
Does the above look like a valid way to run a rabbitmq container? where can I find a full understandable example?
Do I need a docker file or am I misunderstanding it?
How can I specify the port? in the example above what are first numbers 5672:5672 and what are the last ones?
How can I be sure that when I run the container again, say after a machine restart that I get the same container?
Many thanks
Andrew
Docker-compose
What you posted is not a Dockerfile. It is a docker-compose file.
To run that, you need to
1) Create a file called docker-compose.yml and paste the following inside:
version: "3"
services:
rabbitmq:
image: "rabbitmq:3-management"
ports:
- "5672:5672"
- "15672:15672"
volumes:
- "rabbitmq_data:/data"
volumes:
rabbitmq_data:
2) Download docker-compose (https://docs.docker.com/compose/install/)
3) (Re-)start Docker.
4) On a console run:
cd <location of docker-compose.yml>
docker-compose up
Do I need a docker file or am I misunderstanding it?
You have a docker-compose file. The rabbitmq:3-management is the Docker image built using the RabbitMQ Dockerfile (which you don't need. The image will be downloaded the first time you run docker-compose up.
How can I specify the port? In the example above what are the first numbers 5672:5672 and what are the last ones?
"5672:5672" specifies the port of the queue.
"15672:15672" specifies the port of the management plugin.
The numbers on the left-hand-side are the ports you can access from outside of the container. So, if you want to work with different ports, change the ones on the left. The right ones are defined internally.
This means you can access the management plugin after at http:\\localhost:15672 (or more generically http:\\<host-ip>:<port exposed linked to 15672>).
You can see more info on the RabbitMQ Image on the Docker Hub.
How can I be sure that when I rerun the container, say after a machine restart that I get the same container?
I assume you want the same container because you want to persist the data. You can use docker-compose stop restart your machine, then run docker-compose start. Then the same container is used. However, if the container is ever deleted you lose the data inside it.
That is why you are using Volumes. The data collected in your container gets also stored in your host machine. So, if you remove your container and start a new one, the data is still there because it was stored in the host machine.
I have two Docker containers
A Web API
A Console Application that calls Web API
Now, on my local web api is local host and Console application has no problem calling the API.However, I have no idea when these two things are Dockerized, how can I possibly make the Url of Dockerized API available to Dockerized Console application?
i don't think i need a Docker Compose because I am passing the Url of API as an argument of the API so its just the matter of making sure that the Dockerized API's url is accessible by Dockerized Console
Any ideas?
The idea is not to pass the url, but the hostname of the other container you want to call.
See Networking in Compose
By default Compose sets up a single network for your app. Each container for a service joins the default network and is both reachable by other containers on that network, and discoverable by them at a hostname identical to the container name.
This is what replace the deprecated --link option.
And if your containers are not running on a single Docker server node, Docker Swarm Mode would enable that discoverability across multiple nodes.
This is the best way I have found to connect multiple containers in a local machine / single cluster.
Given: data-provider-service, data-consumer-service
Option 1: Using Network
docker network create data-network
docker run --name=data-provider-service --net=data-network -p 8081:8081 data-provider-image
docker run --name=data-consumer-service --net=data-network -p 8080:8080 data-consumer-image
Make sure to use URIs like: http://data-provider-service:8081/ inside your data-consumer-service.
Option 2: Using Docker Compose
You can define both the services in a docker-compose.yml file and use depends_on property in data-provider-service.
e.g.
data-consumer-service:
depends_on:
- data-provider-service
You can see more details here on my Medium post: https://saggu.medium.com/how-to-connect-nultiple-docker-conatiners-17f7ca72e67f
You can use the link option with docker run:
Run the API:
docker run -d --name api api_image
Run the client:
docker run --link api busybox ping api
You should see that api can be resolved by docker.
That said, going with docker-compose is still a better option.
The problem can be solved easily if using compose feature. With compose, you just create one configuration file (docker-compose.yml) like this :
version: '3'
services:
db:
image: postgres
web:
build: .
command: python3 manage.py runserver 0.0.0.0:8000
volumes:
- .:/code
ports:
- "8000:8000"
depends_on:
- db
To make it run, just call up like this :
docker-compose up
This is the best way to run all your stack, so, check this reference :
https://docs.docker.com/compose/
Success!
I have a Node.js web-application that connects to a Neo4j database. I would like to encapsulate these in a single Docker image (using also a Neo4j Docker container), but I'm a docker novice and can't seem to figure this out. What's the recommended way to do it in the latest Docker versions?
My intuition would be to run the Neo4j container nested inside the app container. But from what I've read, I think the supported / recommended approach is to link the containers together. What I need is pretty well illustrated in this image. But the article where the image comes from isn't clear to me. Anyway, it's using the soon-to-be-deprecated legacy container linking, while networking is recommended these days. A tutorial or explanation would be much appreciated.
Also, how does docker-compose fit into all this?
Running a container within another container would imply to run a Docker engine within a Docker container. This is referenced as dind for Docker-in-Docker and I would strongly advise against it. You can search 'dind' online and discover why in most cases it is a bad idea, but as it is not the main object of your question I won't extend this subject any further.
Running both a node.js process and a neo4j process in the same container
While most people will tell you to refrain yourself from running more than one process within a Docker container, nothing prevents you from doing so. If you want to follow this path, take a look at the Using Supervisor with Docker from the Docker documentation website, or at the Phusion baseimage Docker image.
Just be aware that this way of doing things will make your Docker image more and more difficult to maintain over time.
Linking containers
As you found out, keeping Docker images as simple as you can (i.e: running one and only one app within a Docker container) will make your life easier on the long term.
Linking containers together is trivial when both containers run on the same Docker engine. It is just a matter of:
having your neo4j container expose the port its service listens on
running your node.js container with the --link <neo4j container name>:<alias> option
within the node.js application configuration, set the neo4j host to the <alias> hostname, docker will take care of forwarding that connection to the IP it assigned to the neo4j container
When you want to run those two containers on different hosts, things get more difficult.
With Docker Compose, you have to use the link: key to define your links
The new Docker network feature
You also discovered that linking containers won't be supported in the future and that the new way of making multiple Docker containers communicate is to create a virtual network and attach those 2 containers to that network.
Here's how to proceed:
docker network create mynet
docker run --detach --name myneo4j --net mynet neo4j
docker run --detach --name mynodejs --net mynet <your nodejs image>
Your node application configuration should then use myneo4j as the host to connect to.
To tell Docker Compose to use the new network feature, you would have to use the --x-networking option. Also you would not use the links: key.
Using the new networking feature also means that you won't be able to define any alias for the db. As a result you have to use the container name. Beware that unless you use the container_name: key in your docker-compose.yml file, Compose will create container names based on the directory which contains your docker-compose.yml file, the service name as found in the yml file and a number.
For instance, the following docker-compose.yml file, if within a directory named "foo" would create two containers named foo_web_1 and foo_db_1:
web:
build: .
ports:
- "8000:8000"
db:
image: postgres
when started with docker-compose --x-networking up, the web app configuration should then use foo_db_1 as the db hostname.
While if you use container_name:
web:
build: .
ports:
- "8000:8000"
db:
image: postgres
container_name: mydb
when started with docker-compose --x-networking up, the web app configuration should then use mydb as the db hostname.
Example of using Docker Compose to run a web app using nodeJS and neo4j
In this example, I will show how to dockerize the example app from github project aseemk/node-neo4j-template which uses nodejs and neo4j.
I assume you already have Docker 1.9.0+ and Docker Compose 1.5+ installed.
This project will use 2 docker containers, one to run the neo4j database and one to run the nodeJS web app.
Dockerizing the web app
We need to build a Docker image from which Docker compose will run a container. For that, we will write a Dockerfile.
Create a file named Dockerfile (mind the capital D) with the following content:
FROM node
RUN git clone https://github.com/aseemk/node-neo4j-template.git
WORKDIR /node-neo4j-template
RUN npm install
# ugly 20s sleep to wait for neo4j to initialize
CMD sleep 20s && node app.js
This Dockerfile describes the steps the Docker engine will have to follow to build a docker image for our web app. This docker image will:
be based on the official node docker image
clone the nodeJS example project from Github
change the working directory to the directory containing the git clone
run the npm install command to download and install the nodeJS app dependencies
instruct docker which command to use when running a container of that image
A quick review of the nodeJS code reveals that the author allows us to configure the URL to use to connect to the neo4j database using the NEO4J_URL environment variable.
Dockerizing the neo4j database
Well people took care of that for us already. We will use the official Docker image for neo4j which can be found on the Docker Hub.
A quick review of the readme tells us to use the NEO4J_AUTH environment variable to change the neo4j password. And setting this variable to none will disable the authentication all together.
Setting up Docker Compose
In the same directory as the one containing our Dockerfile, create a docker-compose.yml file with the following content:
db:
container_name: my-neo4j-db
image: neo4j
environment:
NEO4J_AUTH: none
web:
build: .
environment:
NEO4J_URL: http://my-neo4j-db:7474
ports:
- 80:3000
This Compose configuration file describes 2 services: db and web.
The db service will produce a container named my-neo4j-db from the official neo4j docker image and will start that container setting up the NEO4J_AUTH environment variable to none.
The web service will produce a container named at docker compose discretion using a docker image built from the Dockerfile found in the current directory (build: .). It will start that container setting up the environment variable NEO4J_URL to http://my-neo4j-db:7474 (note how we use here the name of the neo4j container my-neo4j-db). Furthermore, docker compose will instruct the Docker engine to expose the web container's port 3000 on the docker host port 80.
Firing it up
Make sure you are in the directory that contains the docker-compose.yml file and type: docker-compose --x-networking up.
Docker compose will read the docker-compose.yml file, figure out it has to first build a docker image for the web service, then create and start both containers and finally will provide you with the logs from both containers.
Once the log shows web_1 | Express server listening at: http://localhost:3000/, everything is cooked and you can direct your Internet navigator to http://<ip of the docker host>/.
To stop the application, hit Ctrl+C.
If you want to start the app in the background, use docker-compose --x-networking up -d instead. Then in order to display the logs, run docker-compose logs.
To stop the service: docker-compose stop
To delete the containers: docker-compose rm
Making neo4j storage persistent
The official neo4j docker image readme says the container persists its data on a volume at /data. We then need to instruct Docker Compose to mount that volume to a directory on the docker host.
Change the docker-compose.yml file with the following content:
db:
container_name: my-neo4j-db
image: neo4j
environment:
NEO4J_AUTH: none
volumes:
- ./neo4j-data:/data
web:
build: .
environment:
NEO4J_URL: http://my-neo4j-db:7474
ports:
- 80:3000
With that config file, when you will run docker-compose --x-networking up, docker compose will create a neo4j-data directory and mount it into the container at location /data.
Starting a 2nd instance of the application
Create a new directory and copy over the Dockerfile and docker-compose.yml files.
We then need to edit the docker-compose.yml file to avoid name conflict for the neo4j container and the port conflict on the docker host.
Change its content to:
db:
container_name: my-neo4j-db2
image: neo4j
environment:
NEO4J_AUTH: none
volumes:
- ./neo4j-data:/data
web:
build: .
environment:
NEO4J_URL: http://my-neo4j-db2:7474
ports:
- 81:3000
Now it is ready for the docker-compose --x-networking up command. Note that you must be in the directory with that new docker-compose.yml file to start the 2nd instance up.