Microservices in the real world

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Questions and Answers

What is a significant drawback of a monolithic application when updating a feature?

Only the feature being updated needs to be taken down.

Patching can be done without affecting user experience.

Features can be updated independently without any downtime.

The entire application may need to be temporarily taken offline. (correct)

How does scaling a feature in a monolithic application typically work?

Scaling depends on user demand for individual parts of the application.

The entire monolithic application must be scaled to scale a single feature. (correct)

Only the specific feature can be scaled independently.

Features can be dynamically allocated more resources as needed.

What term describes the individual small applications that comprise a microservice architecture?

Containers

Monoliths

Legacy systems

Microservices (correct)

What is a common characteristic of the features within a monolithic application?

They depend on each other to operate as a single unit. Signup and view all the answers

What allows microservices to operate independently from one another?

They each run as a separate application or service. Signup and view all the answers

During which circumstance is a monolithic application patch likely to be applied?

Over a weekend when business is slower. Signup and view all the answers

What is the primary advantage of using containers for microservices?

They allow each microservice to be updated independently. Signup and view all the answers

What does the term 'microservice' specifically refer to in cloud native architecture?

A standalone, independent service that performs a specific function. Signup and view all the answers

What should the worker nodes do if they suspect they do not have a majority in a swarm?

Switch to read-only mode and wait for resolution. Signup and view all the answers

When building a swarm, how many managers are recommended for control plane high availability?

Three or five managers are recommended. Signup and view all the answers

Which of the following statements about Docker Desktop is true?

It spins up a VM running Docker in the background. Signup and view all the answers

What environment does Multipass primarily create for running Docker?

Cloud-based Ubuntu virtual machines. Signup and view all the answers

What is the main purpose of setting an advertise address during swarm initialization?

To identify the interface for cluster communications. Signup and view all the answers

When initializing a swarm with Multipass, what command is first used to set up the cluster?

docker swarm init Signup and view all the answers

What is a necessary step when using Docker with Windows Home?

Ensure the network is private. Signup and view all the answers

What happens to a node in a swarm once it is initialized and becomes the first manager?

It is designated as the leader of the swarm. Signup and view all the answers

Which is true regarding the number of VMs launched for a swarm setup?

A total of five VMs should be launched for a robust setup. Signup and view all the answers

What can occur if the manager nodes are not spread across multiple availability zones?

Increased risk of total cluster failure. Signup and view all the answers

What is the significance of the asterisk next to the node in the Docker node list?

It marks the leader node in the cluster. Signup and view all the answers

What command is used to join additional manager nodes to a swarm?

docker swarm join Signup and view all the answers

If you decide to use Play with Docker, what must you do to set up the nodes?

Add new instances five times. Signup and view all the answers

What is the primary role of the worker nodes in a Docker Swarm?

To run the actual application containers and services Signup and view all the answers

Which command is used to create a service in Docker Swarm mode?

docker service create Signup and view all the answers

What does the 'replicas' option specify when creating a Docker service?

The number of identical containers to deploy and manage Signup and view all the answers

What happens when you run 'docker container ls' on a manager-only node?

It only shows the containers running on that specific manager node Signup and view all the answers

Why might you want to prevent business applications from being scheduled on manager nodes?

To keep the manager nodes available for orchestration tasks Signup and view all the answers

How does Docker Swarm handle load balancing for services?

By cycling through worker nodes based on their health status Signup and view all the answers

What command provides information about the tasks running under a specific service in a Docker Swarm?

docker service ps Signup and view all the answers

Which of the following statements is true regarding Docker services?

Docker services enable features like scaling and rolling updates Signup and view all the answers

If running Docker Desktop with a single node, what will happen if you prevent scheduling business apps on managers?

The only node will become overloaded Signup and view all the answers

Which behavior is expected when containers are created with identical configurations in Docker Swarm?

They will load balance requests among themselves Signup and view all the answers

What essential feature does a service object provide in a Docker Swarm that individual containers do not?

Rolling updates and automatic rollbacks Signup and view all the answers

Which command reveals the status of all replicas of a service, including their corresponding nodes?

docker service ps Signup and view all the answers

Why is it essential to keep the worker join token safe when adding nodes to a Docker Swarm?

To prevent unauthorized nodes from joining the swarm Signup and view all the answers

What is the role of the node1 in the described Docker Swarm setup?

It is the leader manager coordinating the swarm Signup and view all the answers

What is the purpose of the 'deploy: replicas 10' directive in the Compose file?

To indicate the number of identical containers to create. Signup and view all the answers

What command is used to deploy a stack using a Compose file?

docker stack deploy -c Signup and view all the answers

What does Docker use as the build context when building an image?

The local directory specified by the period. Signup and view all the answers

How can you scale down the number of replicas in Docker Swarm?

By editing the Compose file and redeploying it. Signup and view all the answers

What is the significance of having a registry for Docker images?

It enables worker nodes to pull images needed for deployment. Signup and view all the answers

What happens when you decrease the number of replicas in the Compose file from 10 to 4?

The system automatically removes the excess containers. Signup and view all the answers

In case of a node failure, what behavior does Docker swarm demonstrate?

It automatically distributes all tasks evenly across remaining nodes. Signup and view all the answers

What is the primary role of a Git repository in this context?

To provide access to the Dockerfile and application code. Signup and view all the answers

What is described as 'crude' in the context of Docker's load balancing?

The ingress routing mesh at layer 3. Signup and view all the answers

When a Docker service is successfully updated with a reduced number of replicas, what command verifies the change?

docker stack services Signup and view all the answers

What does the reconciliation loop in Docker Swarm do?

It ensures the current observed state matches the desired state. Signup and view all the answers

What is a necessary condition for the worker nodes to deploy replicas?

The image must be available in a container registry. Signup and view all the answers

What is the purpose of using a version control system for configuration files?

To synchronize config files with production environments. Signup and view all the answers

Why is the command 'multipass purge' mentioned in the context?

To permanently remove virtual nodes. Signup and view all the answers

What happens to the number of running containers when a node fails but the desired state is still defined?

Docker will attempt to maintain the desired state by restarting the required containers. Signup and view all the answers

What does the command 'docker service scale' accomplish?

It adjusts the number of replicas for a defined service. Signup and view all the answers

Which of the following is true about services in Docker Swarm?

A service defines a single container template that can be replicated. Signup and view all the answers

Why is it important for declarative configuration files to be accurate?

Incorrect files can lead to potential application failures. Signup and view all the answers

In the context of Docker, what does self-healing or reconciliation refer to?

The automatic adjustment of running containers to match the desired state. Signup and view all the answers

When using multi-container applications with Docker Swarm, what is a stack?

A configuration that describes a multi-container application. Signup and view all the answers

How does Docker differ in handling services compared to normal containers?

Docker services automatically manage the scaling of containers. Signup and view all the answers

What happens if an image is not created before deploying a stack in Docker Swarm?

The deployment will fail since stacks do not support building images on the fly. Signup and view all the answers

Why might newer versions of some containers appear after manually removing existing containers?

Docker attempts to fulfill the desired state by redeploying new containers. Signup and view all the answers

What is the primary function of using Docker Compose files for a project?

To simplify the process of defining and running multi-container applications. Signup and view all the answers

Which command is used to remove running services in Docker Swarm?

docker service rm Signup and view all the answers

What is generally not supported by stacks in Docker Swarm?

Building images from a local Dockerfile on deployment. Signup and view all the answers

What is the benefit of having a declarative configuration file?

It acts as a living documentation for current deployments. Signup and view all the answers

What key feature distinguishes Docker from traditional container management?

Docker offers self-healing capabilities for services. Signup and view all the answers

What is the key benefit of using microservices in application development?

They enable independent scaling and updates of individual components. Signup and view all the answers

Which statement best describes the declarative model in deploying containerized applications?

It simplifies deployment through configuration files. Signup and view all the answers

What is the primary purpose of a 'compose.yaml' file in a multi-container application?

It defines infrastructure and services for the application. Signup and view all the answers

In the context of cloud-native design patterns, what does self-healing refer to?

Automatic recovery and adjustment of services without manual intervention. Signup and view all the answers

What does the term 'auto scaling' imply in a microservice architecture?

Automatically adjusting the number of containers based on traffic needs. Signup and view all the answers

What role does Redis play in the described application architecture?

It acts as a data cache for storing page view counts. Signup and view all the answers

Which of the following best defines 'cloud-native' as discussed in the content?

A set of practices that enhance the build and management of applications. Signup and view all the answers

What is meant by the term 'multi-container app'?

An application comprising multiple microservices in separate containers. Signup and view all the answers

Why is it beneficial to define both networks and volumes in the `compose.yaml` file?

To simplify the interaction between various containers. Signup and view all the answers

When using Docker Swarm, what is the role of the network block in the configuration file?

It creates a network for containers to communicate. Signup and view all the answers

What does the term 'patching' refer to in the context of microservices?

Updating individual components without disrupting the entire application. Signup and view all the answers

Which command is implied to be used by Docker when it processes the configuration in the compose file?

docker build Signup and view all the answers

How does the declarative approach compare to traditional command-line methods in application deployment?

It is simpler, allowing for a holistic view of the application setup. Signup and view all the answers

What functionality does the 'build field' in a microservice definition specify?

The source for building the container image. Signup and view all the answers

What functionality does swarm mode provide in Docker?

Connects multiple Docker hosts into a secure, highly available cluster. Signup and view all the answers

In a Docker swarm, what is the primary role of a manager node?

Hosts the control plane which manages the cluster's operations. Signup and view all the answers

What command is used to bring down a Docker application along with its volumes?

docker compose down --volumes Signup and view all the answers

Why is it important to have an odd number of manager nodes in a Docker swarm?

To ensure a majority can be reached even during a network failure. Signup and view all the answers

What happens when a network issue isolates two of four manager nodes?

Both sides enter a read-only mode, preventing further changes. Signup and view all the answers

Which of the following statements best approximates the benefits of using Docker Compose?

It simplifies complex orchestration into a single text file format. Signup and view all the answers

What is the purpose of the `docker compose up` command?

To build networks, volumes, and run the application in the background. Signup and view all the answers

What is a likely drawback of keeping persistent volumes in Docker?

They can consume excessive storage space indefinitely. Signup and view all the answers

In the context of microservices, how do microservices relate to Docker containers?

Microservices function independently and map directly to individual containers. Signup and view all the answers

Which of the following best defines 'desired state' in the context of Docker?

The configuration that describes expected outcomes of the deployed system. Signup and view all the answers

How can you access a web application running on Docker at port 5001?

By opening a browser and navigating to the assigned port on localhost. Signup and view all the answers

What is a key advantage of using YAML files in Docker?

They provide a clear and concise method to define application stacks. Signup and view all the answers

Why is it beneficial to run Redis as a microservice alongside a web front-end container?

Microservices can communicate more effectively when isolated in their services. Signup and view all the answers

In a Docker application, what does the command `docker list networks` accomplish?

Shows the network configurations and their connectivity status. Signup and view all the answers

Study Notes

Microservices Architecture

Microservices break down a large application into smaller, independent applications (microservices). Each microservice focuses on a specific feature.
Monolithic applications, in contrast, bundle all features into a single unit. Updating or scaling a single feature requires updating or scaling the entire application, potentially causing downtime.
Microservices run as separate containers, often utilizing different servers. They communicate over a network to provide the overall application experience. This design allows for independent scaling, patching, and updating of individual microservices without affecting others.

Cloud-Native Capabilities

Cloud-native features encompass functionalities like automatic scaling, patching, rolling updates, and self-healing.
Cloud-native applications are not limited to cloud environments; local development environments can utilize Docker Desktop or Play with Docker.

Multi-Container Applications & Declarative Deployment

Multi-container applications consist of multiple containers running different microservices.
The declarative approach simplifies deployment by defining configurations in a YAML file (e.g., compose.yaml). This config file defines the desired state of the application, including networks, services, and volumes, making deployment easier and more manageable than using individual commands.
Docker Compose automatically handles the deployment and management of multi-container applications based on the declarative config file.

Docker Swarm Fundamentals

Docker Swarm allows connecting multiple Docker hosts into a highly available cluster (Swarm).
A Docker Swarm cluster consists of nodes, which can be physical servers, VMs, or cloud instances. Each node is either a manager (hosts the control plane) or a worker (runs application containers).
Running three or more managers ensures high availability. Odd numbers of manager nodes mitigate split-brain scenarios where a network fault could leave the cluster in multiple indecisive states. Manager nodes maintain control of the cluster and handle scheduling tasks.
Workers are nodes that run application containers.
Spreading nodes across availability zones minimizes single point of failure risks.

Building a Swarm Cluster

Creating a swarm cluster typically involves initializing a set of manager nodes on different physical/virtual machines.
docker swarm init is the command to initialize a swarm.
The docker swarm join token worker command produces a unique token required for worker nodes to join the swarm.
Worker nodes join the swarm using the generated unique join tokens.

Working with Docker Swarm Services

Docker services in a Swarm manage application containers, offering functionality like scaling, rolling updates, and self-healing.
docker service create creates a service.
Services are defined by a template, specifying the image, port mappings, and the number of replicas (instances) to deploy.
The docker service ps command lists service instances across all nodes in the swarm, rather than just on the local node as docker container ls would. The command shows the details of each container (like location on which machine) and the status of replicas.
Docker Swarm can automatically scale replicas up or down as needed based on demand. This automatic adjustment is achieved through the internal reconciliation process of Docker Swarm, reacting to the observed state of the cluster compared against the desired state. This self-healing ensures consistency and stability despite outages or changes.

Declarative Deployment with Docker Swarm (Stacks)

A declarative approach using a YAML file is the preferred method for deployment in Swarm (called a stack).
The docker stack deploy command deploys an application stack to the Swarm based on the declarative config file.
The stack config has to contain a pre-built image, pre-built (i.e. built outside of the deploying stack deployment phase). Using Dockerfiles to define the image building processes during the deploy phase, therefore, is not supported.
Configuration files (e.g., docker-compose.yml) define the desired state of the application and its dependencies.
Updates can be made to the config files and re-applied to Swarm using docker stack deploy. This is the recommended way for managing changes in a production setting.

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Description

This quiz explores the fundamental differences between microservices and monolithic applications, focusing on their architecture, advantages, and limitations. It covers key concepts such as scaling, feature updates, and the independence of microservices. Test your knowledge on cloud native architecture with these insightful questions.