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Hello everyone, I'm Jo, and I work at Guild. Before that, I was working at Amazon. I started using Docker at work at the end of June and was excited about it from the very first day because I used to work with Git before when I was at AEV.
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Docker has proven to be a really beneficial tool, and I believe it's something that everyone should utilize. So, let's dive into what's wrong with your development environment.
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To be honest, nothing is particularly broken. Everyone has their own workflow, and every company has its own approach. However, often we hear 'it worked on my machine,' and this can cause issues.
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The problem is that your development environment probably resembles a snowflake: unique and particular to each user. It often happens that something works on my desktop but fails on my laptop or my coworker's laptop due to differences in operating system versions or library variations. So, the idea here is to standardize as much as possible to ensure that we are on the same page when we run things.
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So, what is Docker? Docker is an open-source platform that has been around since its inception. It originated from the company dotCloud, which later pivoted to create Docker, Inc.
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Docker consists of several components: the Docker Engine, which is the container management runtime that actually runs the containers; a set of tools to package and share images; and the Docker Hub, which is akin to GitHub but for Docker images. It’s the platform where we share images.
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One significant aspect of Docker is its widespread acceptance. Many people utilize Docker, and a lot of images are published on Docker Hub. It reminds me of the Ruby gems ecosystem all over again. Containers utilize operating system-level virtualization, but it’s essential to realize that containers are not VMs.
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Unlike virtual machines (VMs), containers share the Linux kernel, ensuring isolation while maintaining efficiency. Each container can operate as an isolated Linux system without unnecessary overhead. This system employs features of the Linux kernel, such as cgroups and namespaces, which allows for the management of resources and the prioritization of processes.
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A Docker image is essentially a stack of layers packaged together. Each layer depends on its parent, and these layers are managed through a union file system. The file system for the running process appears writable, but the layers themselves are read-only, with only the topmost layer being writable. Any changes made to the application are contained in the top layer, thus avoiding alterations to the original image.
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This innovative approach significantly enhances the efficiency of storage. Consequently, if you have multiple containers running the same base image, you won’t need multiple versions of the same image, since Docker employs a copy-on-write strategy.
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Let's consider an example using Ruby. If we want to build a Ruby environment, we typically start with a base image, such as Ubuntu, and then specify our Ruby version. The Dockerfile will include instructions for building the image, and when we build it, Docker pulls the relevant base image from the repository.
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The Dockerfile starts with the instructions needed to create our Ruby environment. For example, we specify the base image, set the maintainer, and define commands to install Ruby and other dependencies. Each instruction in the Dockerfile corresponds to a layer in the final image.
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After building the image successfully, we can run commands inside our newly-created Ruby environment. Furthermore, if we want to keep our images efficient, we can reduce the size of the final image by cleverly combining and ordering commands within our Dockerfile to take advantage of Docker’s caching mechanism.
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Utilizing proper practices and careful ordering of commands can ensure that we don’t inadvertently increase the size of our images due to unnecessary duplication of data.
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Eventually, we aim to have a well-structured, efficient Ruby application that runs smoothly on Docker. Notably, it's essential to remember that Docker itself provides a plethora of features that streamline the development process.
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For example, we can build an application with PostgreSQL as a backend. In this case, we define one container for the Ruby application and another for PostgreSQL, allowing every developer in the team to utilize the same development environment.
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To connect both containers, we utilize Docker's linking feature, which provides an effective way to set environment variables. When we link containers, Docker automatically injects necessary connection details into the environment, allowing us to seamlessly connect to the PostgreSQL database from our Ruby application.
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After properly setting up our Docker containers, we can run our Ruby on Rails application alongside PostgreSQL. Docker simplifies this process, reducing the setup time and enhancing consistency.
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As projects grow, managing the Docker setup can become complex. Fortunately, tools like Docker Compose help streamline the process by allowing us to define multi-container applications in a simple YAML file. This way, everyone can easily spin up the required services for development, without needing to micromanage each container.
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Furthermore, Docker Compose automates much of the setup and ensures that all developers have a consistent environment without requiring intricate command-line instructions.
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Adopting Docker and tools like Docker Compose can truly transform the developer experience by vastly simplifying the management and execution of complex applications.
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In conclusion, using Docker can provide immense benefits in streamlining the development process and creating a consistent environment across developers' workplaces. By embracing these tools and standards, developers can focus more on building applications and less on configuring environments.
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Remember, while using Docker, always tag your images, try to leverage caching wisely, and avoid unnecessary bloat by thinking strategically about how and when to update your Dockerfiles.
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Leveraging Docker optimally will enhance your productivity and ensure that your development processes are both flexible and reliable.
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I hope today’s session has given you valuable insights into Docker, how it works, and why it can benefit your development workflow. Thank you for your time and attention!
