How To Communicate Between Docker Containers Via “Hostname”?

In dealing with containers, Docker easily gets the place of a universal tool for both handling and development of applications. Docker containers are equivalent to isolated environments, therefore, the application of microservices architecture demands no further effort. Among the microservices principles, establishing the proper interaction between containers is a key container and Docker offers multiple tools to support communication between the containers. This article will focus on using hostnames from the host machine to facilitate communication between Docker containers. This will make it easier for users to communicate with various containers.

Understanding Of Primary Terminologies

• Docker: Docker is a framework that takes the load from creating, delivering, and operating apps on geographically dispersed hardware. It employs containerization technologies which let the programmers have the apps and all their dependent components required for their execution packed together and run in individual self-contained environments known as containers. Docker creates a uniform format for constructing, distributing, and managing applications and allows the systems distributed around different environments in the same way. This approach speeds up the software development cycle.
• Container: A container is an entry-level, easily transferred, and independent unit that includes an app along with its dependencies and a complete runtime environment. Containers offer a steady and same platform for applications to run in dissimilar environments, ranging from development, and testing, to production.
• Hostname: A hostname is a designation given to a device that is connected to a personal network and identifies all kinds of different modes of interaction. In Docker container working domain, hostnames are given to individual containers to have the ID that is unique to the Docker network. Hostnames make it possible for containers to communicate with each other by using meaningful identifier names, hence eliminating dependence on IP addresses and making everything simpler to set up and manage.
• Docker Network: Docker Network is a networking feature of Docker and the means to enable communication between containers discarded by the Docker container within the particular Docker host. It is what passes a lot of containers the ability to communicate over a virtual network just like they are doing so locally, they can achieve interaction among services running in the containers. Docker containers can be instantaneously deployed into Docker networks which can be created and dictated by Docker Commands or Docker Compose, enabling flexible networking configurations to match application’s demands.
• Docker Compose: Docker Compose refers to a utility for Docker containers that works well in multi-container applications. Through this it makes it possible the user to specify the kind of services or networks and create volumes through a simple YAML file, known as docker-compose.yml. With Docker Compose, you can declare and run multi-container applications using yaml or json files. This would enable you to easily manage and scale your complex Docker deployments. It controls the initiating and keeping up the images of tiniest containers, networks and disk volumes, which consequently makes this multi-container application be distributed and scales with ease.
• Using Hostnames For Communication: The default containers of the Docker platform can send messages to each other using the IP addresses assigned to them. Although this method is okay, it may result in problems, as it is especially tricky in rapidly fluctuating environments where IP addresses may be changing or with distributed applications when you have to deal with scaling containers. It ensures the system’s ease of contentment and helps the user to organize and assign names for containers instead of IPs.

Establishing Communication Between Docker Containers Via Hostname: Step-By-Step Guide

Step 1: Create A Docker network

• Firstly start with creating a Docker network with the following commands, If you need customization you do with using options.

docker network create my-network

Step 2: Run Two Containers On Created Network

• Created the two network with docker run command on providing network name, port numbers, Docker images and other options as follows:

docker run -d --name webserver -p 80 --network my-network nginx
docker run -d --name database -p 3306:3306 --network mysql

Step 3: Configuring The DNS In Docker Internals

• In the webserver container, add the docker.internal DNS to the list of known hosts.
• For making this use the following command:

echo "127.0.0.1 docker.internal" >> /etc/hosts

Step 4: Ping To Database Container

• In the webserver container, try to ping the database container.
• For ping to database container use the following command:

ping database

Step 5: Status Of Ping Command

• You should see that the ping is successful in the following screenshot.

Step 6: Communicating One Container With Other

• You can now communicate between the two containers using the hostname database.

Container Communication With Docker Compose File

Step 1: Create Docker Network

• In a Docker network, containers that are interlinked may use their own containers as hosts and service call using container names as hostnames.
• Create a Docker network using the following command:

Step 2: Docker Compose

• Use Docker Compose to define the services and networks in a specifically Docker Compose YAML file. For example:

After executing This docker compose, The two containers will be in same network, as this above procedure of communication after once containers in running state can be done for this also.

Conclusion

Using hostnames in Docker with its affordances for the communication across containers make it simpler and easier to realize microservices architecture that is both durable and resilient. Developers can make work with container easier by giving them meaningful hostnames and using Docker’s networks or Docker Compose. They can achieve configuration simplicity, scalability, and portability by doing this. Hostname make it possible to avoid the complexity of IP addresses, eventually containers can easily access to each other without any trouble. Using the method is also not only about the smoother processes inside of containers but also about the improvement in maintainability and the comfort managing. As containerized deployments require configurations for loads of containers so only hostnames matter. Therefore developers can focus on developing solid application which will prove useful for agility and efficiency of containerized deployment.

Docker Containers And Hostname – FAQ’s

Isn’t There Any Way For Hostnames To Ease Containers Communication?

Hostnames map containers to a higher level abstraction and performance structure than IP addresses, and provide better configuration and scalability improvements.

Are There Any Containers That Share Common Name-Shortening Methods, Like Hostnames?

Container names don’t require an assignment with the –name flag or they might need to be retrieved from the same Docker Compose configuration file in order to exchange information using hostnames.

What Happens If Two Containers Have The Same Hostname?

Docker uniquely maps container naming via the host Docker environment. If the two containers would be trying to access the same hostname, Docker could show an error.

Can Hostnames Be Used For Inter-Container Communication Across Different Docker Hosts?

The hostname refers to the entire Docker host meaning that they cannot be used outside of it. The use of another approach involving DNS or service discovery mechanisms is essential in particular cases when hosts are communicated.

How Can I Troubleshoot Hostname Resolution Issues Between Docker Containers?

The network connection between containers which are part of the same Docker network as well as making sure that the proper hostname is associated with each container should be confirmed to ensure smooth operation. Additional check should include whether DNS configuration is supported or not in the Docker environment.