Bold prediction: docker app will be an alternative to docker compose

Keywords: Docker Nginx JSON git

Docker 19.03 introduces an experimental feature: app, which is an instruction of docker, such as image, run, exec, swarm

Official documents: https://docs.docker.com/engine/reference/commandline/app/

Docker app arranges the docker container as a bundle, named application application. You want to package a set of docker containers as an application for distribution.

Enable app plug-in

app is an experience feature, which will not be enabled by default. The minimum version is 19.03, so first make sure the docker engine is not lower than this version.

Edit ~ /. docker/config.json, and add:

{
  "experimental": "enabled",
  "debug": true
}

Inspection:

docker
...
app*        Docker Application (Docker Inc., v0.8.0)
builder     Manage builds
buildx*     Build with BuildKit (Docker Inc., v0.3.1-tp-docker)
checkpoint  Manage checkpoints
...

The instructions marked with * are experience feature instructions.

# docker app version
Version:               v0.8.0
Git commit:            7eea32b
Built:                 Wed Nov 13 07:28:05 2019
OS/Arch:               linux/amd64
Experimental:          off
Renderers:             none
Invocation Base Image: docker/cnab-app-base:v0.8.0

Create app

Initialize a docker application in the current working directory.

# docker app init myapp
# tree .
.
└── myapp.dockerapp
    ├── docker-compose.yml
    ├── metadata.yml
    └── parameters.yml

1 directory, 3 files

By default, a project directory is created in the working directory, which contains three files:

Choreography file of docker-compose.yml service
 Basic configuration file for metadata.yml project
 Variables referenced by parameters.yml service compose

Creating a single file project: as everyone knows, it is more difficult to distribute a directory than a single file. Therefore, docker app supports the integration of project files of an application into a single file.

# docker app init demo --single-file
# ll
-rw-r--r--. 1 root root 508 Dec  2 07:13 demo.dockerapp

The project file cannot be changed after creation. You can convert the application in directory format to a single file at any time:

docker app merge myapp

In turn, the single file project is converted to directory format:

docker app split myapp

Editorial services

vi myapp.dockerapp/docker-compose.yml

version: "3.6"
services: {
  "nginx": {
    "image": "nginx"
  }
}

Install app

app needs to run in swarm environment. The simplest test environment is to run in a stand-alone environment: docker swarm init -- advertisement addr = your IP address

# docker app install myapp

# docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
i2ceu8f82bsh        myapp_nginx         replicated          1/1                 nginx:latest

# docker app ls
INSTALLATION APPLICATION   LAST ACTION RESULT  CREATED   MODIFIED  REFERENCE
myapp        myapp (0.1.0) install     success 6 seconds 4 seconds

View service

Use the render subcommand to view the service choreography of the docker application:

# docker app render myapp
version: "3.6"
services:
  nginx:
    deploy:
      replicas: 2
    image: nginx

If the myapp project file is not in the current directory, like the image, the docker engine will first pull it from the central warehouse.

Using parameters

Modify the parameters.json file:

"DEPLOY_REPLICAS": 5

Modify docker compose to reference this variable:

version: "3.6"
services: {
  "nginx": {
    "image": "nginx",
    "deploy": {
      "replicas": "${DEPLOY_REPLICAS}"
    }
  }
}

View services:

# docker app render myapp
version: "3.6"
services:
  nginx:
    deploy:
      replicas: 5
    image: nginx

Multi level variables: the parameter configuration file is in yaml format, which is easy to think of - you can use multi-level parameter names, so you can group different variables.

deploy:
  replicas: 2

In the corresponding compose:

"replicas": "${deploy.replicas}"

Variables are not allowed in image.

Update app

upgrade can only update values in variables.
upgrade does not reload the app's configuration file, it can only pass in the key value of the variable through -- set or - S.

Perform update:

# docker app upgrade myapp -s DEPLOY_REPLICAS=2
Updating service myapp_nginx (id: t9n7hcic2ek42qhn35kyfh2lj)
Application "myapp" upgraded on context "default"

# docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
ud4sms7cx9yx        myapp_nginx         replicated          2/2                 nginx:latest

Delete application

docker app uninstall myapp

Publishing application

docker login 192.168.33.10:5000
docker app push myapp

login success
Modified name in metadata: 192.168.33.10:5000 / library / myapp
The secure registers are already configured

But it failed:

# docker app push myapp
192.168.33.10:5000/library/myapp:0.1.0-invoc
fixing up "192.168.33.10:5000/library/myapp:0.1.0" for push: failed to resolve "192.168.33.10:5000/library/myapp:0.1.0-invoc", push the image to the registry before pushing the bundle: failed to do request: Head https://192.168.33.10:5000/v2/library/myapp/manifests/0.1.0-invoc: http: server gave HTTP response to HTTPS client

It seems that it's better to find https instead of secure registers.

Try not to modify the name in metadata, and use the tag parameter on the command line:

# docker app push myapp -t 192.168.33.10:5000/library/myapp
192.168.33.10:5000/library/myapp:latest-invoc
fixing up "192.168.33.10:5000/library/myapp:latest" for push: failed to resolve "192.168.33.10:5000/library/myapp:latest-invoc", push the image to the registry before pushing the bundle: failed to do request: Head https://192.168.33.10:5000/v2/library/myapp/manifests/latest-invoc: http: server gave HTTP response to HTTPS client

-You can see the image of the specified tag in docker images, but push still fails

The warehouse using https protocol still fails.

For private servers, there is no way to solve it for the time being. There are not many documents on the official website.

It is usually pushed to the central warehouse through:

docker app push myapp -t pollyduan/myapp

The red and blue logs are flashing. They look normal. But the end was brutal:

fixing up "docker.io/pollyduan/myapp:latest" for push: failed commit on ref "manifest-sha256:f5dc44557f1d666381791c3d01300d64899ba7b74dc26f4d681bd1827caf61ca": no response

Looking back at the harbor private server, the image also exists, but the error is speechless.

Go back to find more documents and come back to supplement.

Bold prediction: docker app will be an alternative to docker compose, just like swarm is to docker swarm, with the word as proof.

Posted by harinath on Sat, 07 Dec 2019 15:06:18 -0800

Programmer Group