DarylsCorner

Today, in part 2 of this series, I wanted to continue down the path of exploring Azure Service Fabric by presenting an overview of Azure Service Fabric. In part 1 of this series we talked about why you would want to use something like Service Fabric. That led us to a primer discussion around microservices which just so happen to run on the Service Fabric platform. If you haven’t done so already, you may want to read part 1 of this series first as it will help you build a better understanding.

• Exploring Azure Service Fabric (Part 1)
• Deploying Service Fabric Cluster (Part 3)

My Journey to Service Fabric

Recently I was working on a project where the customer had an application that was hosted in Azure. They were utilizing the Cloud Services platform but soon came to terms that it may not be the best option for their application. With Cloud Services there are some limitations around being able to scale an application, primarily dependent upon how the application was architected. They soon realized that they needed a solution where their application workload would be scalable, reliable, and manageable. They had already begun to start working on a microservices approach for the application so it was only fitting that they explore Service Fabric. Hence, why I decided to write this blog series. I figured I could help others down the Service Fabric road to becoming DevOps Unicorns. So let’s see what Service fabric is all about.

What is Service Fabric

Service Fabric in its most simplest form is a platform for running microservices. It can’t be that simple right? Well, it is quite simplistic but there is much more to it than that. Service Fabric is a distributed systems platform that simplifies the packaging, deployment, and manageability of scalable and reliable microservices. This platform significantly changes how developers and administrators approach the deployment and management of mission-critical workloads. No longer do they have to deal with building and managing complex infrastructures. Instead they can focus their efforts on their application, increasing productivity and customer satisfaction.

Service Fabric itself is a shared pool of servers known as the Service Fabric Cluster. The cluster is made up of multiple nodes that host distributed microservices, those being stateful or stateless. By using microservices we have the ability to scale services independently of each other which allows developers to push out updates and fixes more frequently, not to mention reducing the chances of a broken service affecting the entire application. In addition, Service Fabric provides application management capabilities for provisioning, deploying, monitoring, upgrading, patching, and deleting of services. From a natural progression of application hosting we have gone from a physical server, to a virtual machine, to a container, to microservices. So whats next? Nanoservices? There is a concept of an application being too fine-grained and requiring more effort to stitch the services together but we won’t worry about that now. The image below shows a good representation of Service Fabric with many microservices deployed on top. Not only can Service Fabric be deployed in Azure, but it can be deployed in other clouds as well as on-premises.

Traditionally stateless applications required a database of some sort to maintain the state along with caches and queues to address latency. One of the problems with this is that it required more components to manage that didn’t scale really well together. In addition, each additional connection added to the latency. By using stateful microservices we remove the need for those additional components and can maintain high-availability and low-latency by keeping the application code close to the data.

Within Service Fabric there is support for application lifecycle management (ALM) from development, through deployment, during management, and decommissioning. By utilizing packaged microservices, multiple instances can be deployed and upgraded independently. Rolling upgrades can be performed to ensure the application is always available. In the event an upgrade fails, automatic rollback will kick in.

Additional Capabilities

• self-healing applications
• run Service Fabric on your laptop as a dev environment; same code runs in Azure
• services can be built using framework of your choice
• applications deploy in seconds
• write once, deploy anywhere
• deploy on Windows Server or Linux (coming soon)
• deploy hundreds or thousands of applications per machine
• manage using .NET APIs, PowerShell, or REST
• monitor and diagnose the health state
• scale up or down the cluster, capable of scaling to thousands of machines
• redistribute and optimize load after failure

How Service Fabric Works

Briefly let’s discuss how Service Fabric works. Refer to the Azure Service Fabric documentation for a deeper dive.

In Service Fabric you have a cluster of nodes running a Windows service called FabricHost.exe that auto-starts upon boot. This service starts Fabric.exe and FabricGateway.exe which make up the node. Note: When running on your laptop as a dev environment you essentially just run multiple instances of these executables which show up as multiple nodes. An application package that references the service packages for each service type are copied to the image store. Once the package has been copied you can create an instance of the application within the cluster by specifying the type. The application type instance is then assigned a URI name of “fabric:/MyNamedApp“. Within the cluster you can create multiple named applications, each of which are managed and versioned independently. Named services instances are created under its named application which looks like “fabric:/MyNamedApp/MyNamedService“. During the named service creation you specify a partition scheme which spreads across cluster nodes allowing for scale. Within a partition stateless named services have instances while stateful named services have replicas which are kept in sync. Should a replica fail, Service Fabric builds a new replica from existing replicas. In addition, during named service creation, code, data and configuration packages are copied to the node(s) running the service where they can be used. You can create two types of service:

• Stateless: use when persistent state is not required or using external storage
• Stateful: use when persistent state is required. Uses Reliable Collections or Reliable Actors programming models.

Service Fabric Architecture

The diagram below shows the major subsystems of Service Fabric with a brief description of each.

• Transport Subsystem – provides secure communication between nodes
• Federation Subsystem – creates cluster of nodes into single entity for detecting failures, perform leader election, and provide consistent routing
• Management Subsystem – manages lifecycle of applications and services
• Testability Subsystem – help devs test services through simulated faults before and after deploying applications and services to production
• Communication Subsystem – resolve service locations
• Reliabilty Subsystem – responsible for reliability through replication, resource management and failover
• Hosting and Activation – manages lifecycle of an application on a single node
• Application Model – enables tooling
• Native and Managed APIs – exposed to devs

In Summary

Service Fabric is being termed the next-gen platform for building and managing cloud-scale applications. If you are interested in seeing how this works or even deploying Service Fabric, stay tuned for the next post in this series where we will Deploy Service Fabric.

This is the first in a series of posts about Exploring Azure Service Fabric. My goal here is to give you an idea of why you may want to use Service Fabric, provide an overview of the service itself, and demo a few deployment options. Below is a list of posts that I plan to include in this series so stay tuned if you find this of any interest..

• Overview of Service Fabric (Part 2)
• Deploying Service Fabric Cluster (Part 3)

In this first part of the series I wanted to talk about some of the driving factors for using something like Service Fabric. If you are reading this you probably are already familiar with the term microservices. If not, Wikipedia defines the term like so. “Microservices is a software architecture style in which complex applications are composed of small, independent processes communicating with each other using language-agnostic APIs. These services are small, highly decoupled and focus on doing a small task, facilitating a modular approach to system-building.”

Over the last few years microservices have emerged to replace the traditional tiered architectures and monolithic applications that are tightly coupled. So why is this? Think back to the days when you needed to update your application with a new feature, or worse, you hit the boundaries of your application and needed to scale up or out. It was no easy task and it caused updates and fixes to build up until a new version of the application was released. As a business, if you weren’t able to evolve your application to better suit your end users, then it slowly faded away as people stopped using it. With today’s technologies, when we talk about building applications, you need to consider the scope. Most conversations lead to the cloud in some form or fashion so we need to ensure that the applications are designed for scale and capacity. With scale and capacity being unpredictable, the cloud becomes an ideal platform for running our applications. If you need to scale it becomes much easier, provided that your application has been designed as a collection of fine-grained autonomous services that have their own lifecycles and collaborate together. This allows you to get feature updates and enhancements to your customers at a much faster pace all while continuing to improve your application based on customer feedback. This is what is known as the lean startup model wherein you start with an idea, build (code), measure (data), and learn (pivot if needed). This in turn creates more reliable releases. Does any of this sound somewhat like the concept of DevOps? Sure it does, after all our goal is to accelerate the flow of work through dev, test, and IT Ops in a way that speeds application delivery and increases efficiencies.

With that said, it isn’t as simple as flipping a switch and you go from a monolithic app design to a microservices app design. In some cases you may need to start with a monolithic approach and slowly move towards a microservices design. This sort of approach would allow you to slowly decompose the app starting with lower tier services that need to be more scalable, all while moving towards a microservices approach. Additional benefits of microservices include language-agnostic, interaction with other microservices, resilient to failures, and self-healing services. The end goal of a microservices approach is to compose your application into smaller, autonomous services running in containers across a cluster of machines.  This allows smaller teams to focus on a service that is independently tested, deployed, scaled, and upgraded. Can you start to see how all of this fits together, the DevOps culture, the lean startup model, and microservices.

Microsoft was used to delivering applications in a monlithic form but soon realized they needed a way to deploy large scale services like Azure SQL databases, DocumentDB, along with other core services, that allowed for independent team development, was scalable and reliable, with low latency. This is where Service Fabric comes in. Essentially it is a platform for running microservices. We will get into more of its capabilities in a part 2 of this series.

An important concept that I want to cover, before we move on, is without a framework of principles and practices to guide your design, it will be quite difficult to deliver and maintain a microservices environment. You and your teams will want to review these and put together a framework covering these principles. Doing so will help you achieve success.

• Strategic Goals: high-level goals defining where the company is going so the technology is aligned to best suit the customer (ie. expand into European and Asian markets)
• Principles: rules defined that align with what you are doing from a strategic goal. Keep it small – no more than 10 so they can be remembered (ie. allow for portability)
• Practices: how to ensure the principles are carried out. Detailed guidance for performing tasks (ie coding and design guidelines)

Note: For smaller teams you may end up combining principles and practices.

Being able to articulate this in the form of a chart  to summarize these concepts will be most useful and readable. This could be something as simple as the below diagram.

For additional information on this topic check out the book  “Building Microservices” by Sam Newman.

Stay tuned for the next post in this series where we will dig deeper into an overview of Service Fabric and its features.