Dapr, or Distributed Application Runtime, is a portable, event-driven runtime that makes it easy for developers to build resilient, microservice stateless and stateful applications that run on the cloud and edge. It aims to enable developers to focus on writing business logic, not solving distributed system challenges, thereby significantly improving their productivity, and reducing development time. With Dapr, you can build microservices that leverage the full benefits of the cloud and edge, without worrying about the challenges associated with distributed systems.
Dapr encapsulates the best practices for building microservice applications into open, independent, building blocks that enable you to build portable applications with the language and framework of your choice. Each building block is completely independent and you can use one, some, or all of them in your application.
Definition and Explanation
Dapr is a runtime that abstracts away the complexity of building a distributed system, so you can focus on your code and not the plumbing. It provides a number of building blocks, each of which is an abstraction for a distributed system capability that can be used independently or together. These building blocks include service invocation, state management, pub/sub messaging, bindings, and observability.
The Dapr runtime can be hosted in multiple environments, including Kubernetes, Azure Service Fabric, and your own hardware. This makes it easy to build and test applications on a local machine, and then deploy them to the cloud without any changes in the code.
Service Invocation
Service invocation is a building block that provides a method for services to call one another directly in a secure and reliable way. This is done using a combination of HTTP and gRPC protocols. The service invocation building block also provides features such as retries, error handling, and circuit breaking, which are essential for creating resilient microservices.
Dapr provides a simple and consistent way to communicate between microservices, regardless of whether they are written in different languages or run in different environments. This is done by providing a standard interface that abstracts away the underlying protocol.
State Management
State management is another building block provided by Dapr. It provides a key/value store API to enable stateful microservices, long running workflows, and short term storage for stateless services. Dapr supports a variety of state stores, including Azure Cosmos DB, AWS DynamoDB, GCP Firestore, and more.
With Dapr's state management, developers can leverage the benefits of stateful services without the complexities of dealing with various state store solutions. Dapr provides a consistent API that abstracts the specific state store implementation, allowing developers to switch the underlying state store without changing any code.
History
Dapr was announced by Microsoft in October 2019 as an open-source project. The goal of Dapr is to make it easier for developers to build distributed applications, especially those that need to run in the cloud. Since its announcement, Dapr has gained a lot of attention in the cloud-native community due to its simplicity and versatility.
Despite being a relatively new project, Dapr has already seen significant adoption. Many organizations are using Dapr to build and run their microservices applications, both in the cloud and on the edge. The project is also seeing significant contributions from the community, with many new features and improvements being added regularly.
Versioning
As an open-source project, Dapr uses semantic versioning. This means that version numbers are assigned in the format of MAJOR.MINOR.PATCH, where MAJOR version indicates incompatible API changes, MINOR version adds functionality in a backwards-compatible manner, and PATCH version makes backwards-compatible bug fixes.
The first stable version of Dapr, version 1.0, was released in February 2021. Since then, there have been several minor and patch releases, each bringing new features, improvements, and bug fixes. The Dapr project maintains a detailed changelog on GitHub, where you can see the history of all releases and the changes made in each one.
Use Cases
Dapr can be used in a variety of scenarios, ranging from simple stateless services to complex stateful applications. It is especially useful in scenarios where you need to build microservices that run on different platforms, as it provides a consistent, platform-agnostic API for common distributed system capabilities.
Some common use cases for Dapr include building microservices architectures, creating event-driven architectures, managing state for long-running workflows, and building real-time, edge-based applications. In each of these scenarios, Dapr provides a set of building blocks that abstract away the complexities of dealing with distributed systems, allowing developers to focus on their business logic.
Microservices Architectures
Microservices architectures are a popular approach for building scalable, resilient applications. However, they also introduce a number of challenges, such as service discovery, communication, and coordination. Dapr provides a set of building blocks that address these challenges, making it easier to build and run microservices applications.
With Dapr, you can easily implement patterns like service invocation, publish/subscribe messaging, and distributed transactions. Dapr also provides a consistent, platform-agnostic API, so you can run your microservices on any platform, whether it's Kubernetes, Azure Service Fabric, or your own hardware.
Event-Driven Architectures
Event-driven architectures are another common use case for Dapr. These architectures are based on the concept of producing, detecting, consuming, and reacting to events. Dapr provides several building blocks that make it easy to build event-driven applications, such as the publish/subscribe messaging building block and the bindings building block.
The publish/subscribe messaging building block provides a simple API for sending and receiving messages. It supports a variety of message brokers, including RabbitMQ, Azure Service Bus, and AWS SNS/SQS. The bindings building block provides a way to trigger your code with events from external systems, or to send events to those systems.
Examples
Let's take a look at some specific examples of how Dapr can be used. These examples will demonstrate how Dapr's building blocks can be used to build a variety of applications, from simple stateless services to complex stateful applications.
Consider a microservices application that consists of several services. Each service is written in a different language and runs in a different environment. Without Dapr, each service would need to implement its own logic for service discovery, communication, and coordination. With Dapr, however, all of these capabilities are provided out of the box. Each service simply interacts with the Dapr runtime, which handles all of the complexities of distributed systems.
Service Invocation Example
Let's start with a simple example of service invocation. In this example, we have a service A that needs to call a method on service B. Without Dapr, service A would need to know the location of service B, and it would need to handle all of the complexities of making a remote method call, such as retries, error handling, and circuit breaking.
With Dapr, however, service A simply makes a local call to the Dapr runtime, which then handles the remote method invocation. The Dapr runtime takes care of finding the location of service B, making the remote method call, and handling any errors that might occur. This greatly simplifies the code in service A, and it makes the service more resilient and scalable.
State Management Example
Now let's consider a more complex example involving state management. In this example, we have a service that needs to maintain some state, such as the current status of a long-running workflow. Without Dapr, the service would need to interact directly with a state store, which could be complex and error-prone.
With Dapr, however, the service simply interacts with the Dapr runtime, which handles all of the complexities of state management. The service can use the Dapr API to save state, retrieve state, and delete state. The Dapr runtime takes care of interacting with the state store, providing a consistent and reliable way to manage state.
Conclusion
In conclusion, Dapr is a powerful tool for building distributed applications. It provides a set of building blocks that abstract away the complexities of distributed systems, allowing developers to focus on their business logic. With Dapr, you can build microservices that run on any platform, using the language and framework of your choice.
Whether you're building a simple stateless service, a complex stateful application, or anything in between, Dapr can help you get there faster and with less code. So why not give it a try? You might just find that it's the tool you've been looking for to take your distributed applications to the next level.