Pushing the Image, Deploying the Stack, and Cleanup

2. Check that the app is running with `docker compose ps`: ```console $ docker compose ps Name Command State Ports ----------------------------------------------------------------------------------- stackdemo_redis_1 docker-entrypoint.sh redis ... Up 6379/tcp stackdemo_web_1 python app.py Up 0.0.0.0:8000->8000/tcp ``` You can test the app with `curl`: ```console $ curl http://localhost:8000 Hello World! I have been seen 1 times. $ curl http://localhost:8000 Hello World! I have been seen 2 times. $ curl http://localhost:8000 Hello World! I have been seen 3 times. ``` 3. Bring the app down: ```console $ docker compose down --volumes Stopping stackdemo_web_1 ... done Stopping stackdemo_redis_1 ... done Removing stackdemo_web_1 ... done Removing stackdemo_redis_1 ... done Removing network stackdemo_default ``` ## Push the generated image to the registry To distribute the web app's image across the swarm, it needs to be pushed to the registry you set up earlier. With Compose, this is very simple: ```console $ docker compose push Pushing web (127.0.0.1:5000/stackdemo:latest)... The push refers to a repository [127.0.0.1:5000/stackdemo] 5b5a49501a76: Pushed be44185ce609: Pushed bd7330a79bcf: Pushed c9fc143a069a: Pushed 011b303988d2: Pushed latest: digest: sha256:a81840ebf5ac24b42c1c676cbda3b2cb144580ee347c07e1bc80e35e5ca76507 size: 1372 ``` The stack is now ready to be deployed. ## Deploy the stack to the swarm 1. Create the stack with `docker stack deploy`: ```console $ docker stack deploy --compose-file compose.yaml stackdemo Ignoring unsupported options: build Creating network stackdemo_default Creating service stackdemo_web Creating service stackdemo_redis ``` The last argument is a name for the stack. Each network, volume and service name is prefixed with the stack name. 2. Check that it's running with `docker stack services stackdemo`: ```console $ docker stack services stackdemo ID NAME MODE REPLICAS IMAGE orvjk2263y1p stackdemo_redis replicated 1/1 redis:3.2-alpine@sha256:f1ed3708f538b537eb9c2a7dd50dc90a706f7debd7e1196c9264edeea521a86d s1nf0xy8t1un stackdemo_web replicated 1/1 127.0.0.1:5000/stackdemo@sha256:adb070e0805d04ba2f92c724298370b7a4eb19860222120d43e0f6351ddbc26f ``` Once it's running, you should see `1/1` under `REPLICAS` for both services. This might take some time if you have a multi-node swarm, as images need to be pulled. As before, you can test the app with `curl`: ```console $ curl http://localhost:8000 Hello World! I have been seen 1 times. $ curl http://localhost:8000 Hello World! I have been seen 2 times. $ curl http://localhost:8000 Hello World! I have been seen 3 times. ``` With Docker's built-in routing mesh, you can access any node in the swarm on port `8000` and get routed to the app: ```console $ curl http://address-of-other-node:8000 Hello World! I have been seen 4 times. ``` 3. Bring the stack down with `docker stack rm`: ```console $ docker stack rm stackdemo Removing service stackdemo_web Removing service stackdemo_redis Removing network stackdemo_default ``` 4. Bring the registry down with `docker service rm`: ```console $ docker service rm registry ``` 5. If you're just testing things out on a local machine and want to bring your Docker Engine out of Swarm mode, use `docker swarm leave`: ```console $ docker swarm leave --force Node left the swarm. ```

This section covers the process of pushing the built web application image to the local registry, deploying the application stack to a Docker swarm, and cleaning up resources after testing. It outlines the steps to push the image using `docker compose push`, which distributes the image to the registry, making it accessible to all nodes in the swarm. Next, it guides you through deploying the stack using `docker stack deploy`, which creates the necessary networks and services for the application, and verifies the deployment by checking the service status with `docker stack services`. The application is then tested using `curl` to ensure that it is accessible and functioning correctly across the swarm nodes. Finally, the section details how to remove the deployed stack, remove the local registry service, and leave the swarm mode if testing is being done on a local machine, using commands like `docker stack rm`, `docker service rm`, and `docker swarm leave`.