Before we dive into a discussion of Docker orchestration, let's first take a look at Docker technology itself, an open source platform designed to help developers automate the deployment, scaling, and management of applications. Since its launch in 2013, Docker has rapidly evolved into an essential tool for modern software development and operations.
Docker uses container technology to encapsulate applications and all of their dependencies, thus ensuring that they can run consistently across different environments. Docker's containers are lighter and have significantly shorter startup times than traditional virtualization technologies such as virtual machines. This advantage enables developers to develop and test applications more efficiently, especially in rapid iteration and frequent release scenarios.
With the rise of the DevOps mindset, the line between development and operations is blurring, and Docker provides a powerful technology to support this shift. However, as projects grow in size and complexity, the number of Docker containers grows as well, creating a need for Docker orchestration.
Docker orchestration refers to the tools and techniques for managing and orchestrating multiple Docker containers, with the primary goal of simplifying the process of deploying, scaling, and managing containers. Orchestration makes it easier for users to manage complex application architectures and ensure that components work together efficiently.
Therefore, this article will provide readers with a practical guide to deploying a Docker orchestration project from scratch, helping you to master this key technology and improve the efficiency and flexibility of your application management.
Project preparation
In this section, we will use a Java project as an example, assuming you already have a project with a microservice architecture. The overall project structure might look like the following:
Next, we'll start building Docker containers step-by-step and follow a series of systematic steps to get there.
Core concepts
We will start with a detailed explanation of some basic concepts, including Dockerfile, Docker build commands, and an introduction to the basic concepts of files. After understanding these concepts, we will move on to the hands-on session, where we will deepen our understanding of these tools through practice.
Dockerfile
A Dockerfile is a text file that contains a set of directives required to build a Docker image. These directives not only define the image's base environment, but also describe in detail the application installation steps, required dependencies, configured environment variables, and other necessary settings. Example:
# Use a base image
FROM maven:3.8.3-openjdk-17 AS builder
# Set the working directory
WORKDIR /app
# Copy and source code
COPY .
COPY src . /src
# Build the project
RUN mvn clean package
# Run the application with a lightweight base image
FROM openjdk:17-jdk-slim
# Set the working directory
WORKDIR /app
# Copy the JAR file from the build stage
COPY --from=builder /app/target/demo-0.0. . /
# Set the command to be executed when the container starts
ENTRYPOINT ["java", "-jar", ""]
Next, we need to apply this configuration to our project. For the sake of demonstration, we have used a customized file name to start the project, so that we can show the exact process of each step more clearly. Of course, you can also choose to use the default file name, which is much simpler and more straightforward. No matter which way you choose, the final result is the same. As shown in the figure below:
Build command
docker build is the core command for building Docker images, which is used to convert the instructions defined in the Dockerfile into an executable image. When executing this command, you can use a series of optional parameters to better customize the build process.
docker build [OPTIONS] PATH | URL | -
PATH: Specifies the path to the context containing the Dockerfile. Typically the current directory (.) or a specific directory path.
URL: can be the URL of the Git repository from which Docker will fetch the Dockerfile.
-: Indicates that the Dockerfile is read from standard input.
Commonly used options are these:
- -t, --tag: Specify a name and tag for the image. For example: -t myapp:latest.
- -f, --file: Specify the path to the Dockerfile.
- --no-cache: does not use cache at build time, ensuring that each step is run from scratch.
- --target: If a multi-stage build is defined in the Dockerfile, you can specify the target stage to build to with this option.
file
file is a configuration file for defining and running multiple Docker containers, which makes it easier and more efficient to manage your application's services, network, and data volumes. With this simple YAML file, you can describe the architecture of your entire application in a unified configuration, making it easy to start, stop, and manage containers at a glance. In our sample program, we include the MySQL service.
Although we already have a standalone MySQL instance locally, we chose to start MySQL as a Docker container in order to better demonstrate how to run multiple Docker containers at the same time. It's also worth noting that MySQL already has an officially available pre-built image, which means that we don't need to go through the extra effort of building and configuring the database, we can just use the ready-made image.
Now, let's begin the process!
version: '3.8'
services.
app: /studiousxiaoyu/my-java-app:latest
image: /studiousxiaoyu/my-java-app:latest # Replace it with your Java app image.
ports.
- "18080:18080" # map ports
environment: /studiousxiaoyu/my-java-app:latest
SPRING_DATASOURCE_URL: jdbc:mysql://db:13306/agent?useSSL=false&serverTimezone=UTC&useUnicode=true&characterEncoding= utf-8
SPRING_DATASOURCE_USERNAME: user
SPRING_DATASOURCE_PASSWORD: password
SPRING_DATASOURCE_PASSWORD: password
image: mysql:5.7 # using MySQL 5.7
db: image: mysql:5.7 # Using MySQL 5.7
MYSQL_ROOT_PASSWORD: root_password # Set root user password
MYSQL_DATABASE: agent # Create the database
MYSQL_USER: user # Creating a new user
MYSQL_PASSWORD: password # Create new user password
ports: "13306:13306
- "13306:13306" # Mapping MySQL ports
volumes: db_data:/vb_data:/vb_data
- db_data:/var/lib/mysql # Data persistence
volumes: db_data:/var/lib/mysql # Data persistence
db_data: # define a data volume
You can do this by runningdocker-compose up command to start all the commands in the services defined in the document.
Start building
Assuming we have successfully deployed the code project from the repository to the server, the next step is to do it directly on the server. If you haven't installed Docker yet, you can install it on your own first, the process is not complicated.
After completing the installation, simply go to the project root directory and execute the appropriate commands to get started.
docker build -t my-java-app -f .
The specific steps and flow of the construction process are shown in Fig:
We can be patient and wait for the next steps to be completed, as the process is already very similar to the production environment at this point. Next, we simply push the final build to our private repository for subsequent deployment and management.
mirror (computing)
Of course, the company's private repository address is essential. Here, we take Tencent Cloud's container image service as an example to show how to store and manage images.
Push private libraries
We've already explained in detail how to create a private repository, so we won't repeat the steps here. Now, we can push the built image directly to the repository for subsequent use and management.
Next, we will perform a tagging operation on our image, and after completing the tagging operation, we push the image to a private repository for subsequent deployment and use.
sudo docker tag my-java-app:latest /studiousxiaoyu/my-java-app:latest
sudo docker push /studiousxiaoyu/my-java-app:latest
The final push was successful as follows:
container orchestration
Next, we will use orchestration files to define and manage the required services. In order to do this, we need to create a file in the specified directory named file. The contents of this file will be consistent with the configuration we showed earlier.
After creating the file, we will run the startup command directly to verify that we have configured it correctly and to see if the individual services start successfully.
docker-compose -f up -d
Finally, looking at the logs, we successfully launched:
summarize
With this paper, we delve into the core concepts of Docker and the importance of its orchestration technology. From Docker's lightweight container architecture to its use in modern DevOps environments, Docker not only improves the efficiency of development and deployment, but also makes multi-container management more efficient. We provide a step-by-step introduction to the use of Dockerfile, build commands, and documentation to help readers master how to build and manage microservice architectures.
In the specific operation, we take a Java project as an example and show how to build and deploy Docker containers in the local environment through practical demonstration guides. As your project scales up, it will be especially important to master Docker orchestration, which not only simplifies the container management process, but also enhances the flexibility and scalability of your application. We hope the guidelines provided in this article are helpful.
I'm Rain, a Java server-side coder, studying the mysteries of AI technology. I love technical communication and sharing, and I am passionate about open source community. I am also a Tencent Cloud Creative Star, Ali Cloud Expert Blogger, Huawei Cloud Enjoyment Expert, and Nuggets Excellent Author.
💡 I won't be shy about sharing my personal explorations and experiences on the path of technology, in the hope that I can bring some inspiration and help to your learning and growth.
🌟 Welcome to the effortless drizzle! 🌟