This feature is in preview for Linux and Windows Server 2016.
Azure Service Fabric is an orchestrator of services across a cluster of machines, with years of usage and optimization in massive scale services at Microsoft. Services can be developed in many ways, from using the Service Fabric programming models to deploying guest executables. By default, Service Fabric deploys and activates these services as processes. Processes provide the fastest activation and highest density usage of the resources in a cluster. Service Fabric can also deploy services in container images. Importantly, you can mix services in processes and services in containers in the same application.
Containers and Service Fabric roadmap
Over the next few releases, Service Fabric will continue to add extensive support for containers on both Windows and Linux including improvements to networking, resources constraints, security, diagnostics, volume drivers, and tooling support especially in Visual Studio, so that the experience of using container images to deploy services is first class. This provides you with the choice of using either containers to package existing code (for example IIS MVC apps) or the Service Fabric programming models and, because Service Fabric treats these all the same, you can mix them in your applications providing you the flexibility of how to deploy your code. You get the best of both worlds, depending on your scenario.
What are containers?
Containers are encapsulated, individually deployable components that run as isolated instances on the same kernel to take advantage of virtualization that an operating system provides. This means that each application and its runtime, dependencies, and system libraries run inside a container with full, private access to the container's own isolated view of operating system constructs. Along with portability, this degree of security and resource isolation is the main benefit for using containers with Service Fabric, which otherwise runs services in processes.
Containers are a virtualization technology that virtualizes the underlying operating system from applications. Containers provide an immutable environment for applications to run with varying degrees of isolation. Containers run directly on top of the kernel and have an isolated view of the file system and other resources. Compared to virtual machines, containers have the following advantages:
- Small in size: Containers use a single storage space and smaller deltas for each layer to increase efficiency.
- Fast boot-up time: Containers don’t have to boot an operating system, so they can be up and available much faster, typically in seconds, than virtual machines.
- Portability: A containerized application image can be ported to run in the cloud, on premises, inside virtual machines, or directly on physical machines.
- Resource governance: A container can limit the physical resources that it can consume on its host.
Service Fabric supports the following types of containers.
Docker containers on Linux
Docker provides high-level APIs to create and manage containers on top of Linux kernel containers. Docker Hub is a central repository to store and retrieve container images.
For a walkthrough about how to do this, read Deploy a Docker container to Service Fabric.
Windows Server containers
Windows Server 2016 provides two different types of containers that differ in the level of provided isolation. Windows Server containers and Docker containers are similar because both have namespace and file system isolation but share the kernel with the host they are running on. On Linux, this isolation has traditionally been provided by cgroups and namespaces, and Windows Server containers behave similarly.
Windows Hyper-V containers provide more isolation and security because each container does not share the operating system kernel with other containers or with the host. With this higher level of security isolation, Hyper-V containers are targeted at hostile, multitenant scenarios.
For a walkthrough about how to do this, read Deploy a Windows container to Service Fabric.
The following figure shows the different types of virtualization and isolation levels available in the operating system.
Scenarios for using containers
Here are typical examples where a container is a good choice:
- IIS lift and shift: If you have existing ASP.NET MVC apps that you want to continue to use, put them in a container instead of migrating them to ASP.NET Core. These ASP.NET MVC apps are dependent on Internet Information Services (IIS). You can package these into container images from the precreated IIS image and deploy them with Service Fabric. See Container Images on Windows Server for information about how to create IIS images.
- Mix containers and Service Fabric microservices: Use an existing container image for part of your application. For example, you might use the NGINX container for the web front end of your application and stateful services for the more intensive back-end computation.
- Reduce impact of "noisy neighbors" services: You can use the resource governance ability of containers to restrict the resources that a service uses on a host. If services might consume many resources and affect the performance of others (such as a long-running, query-like operation), consider putting these services into containers that have resource governance.
Service Fabric support for containers
Service Fabric currently supports deployment of Docker containers on Linux and Windows Server containers on Windows Server 2016. Support for Hyper-V containers will be added in a future release.
In the Service Fabric application model, a container represents an application host in which multiple service replicas are placed. The following scenarios are supported for containers:
- Stateless services inside containers: These are stateless services that use the Reliable Services and the Reliable Actors programming models. This is currently only supported on Linux. Support for stateless services in Windows containers will be added in future release.
- Stateful services inside containers: These are stateful services that use the Reliable Actors programming model on Linux. Reliable Services are not currently supported on Linux. Support for stateful services in Windows containers will be added in future release.
Service Fabric has several container capabilities that help you build applications that are composed of microservices that are containerized. These are called containerized services. The capabilities include:
- Container image deployment and activation.
- Resource governance.
- Repository authentication.
- Container port to host port mapping.
- Container-to-container discovery and communication.
- Ability to configure and set environment variables.
In this article, you learned about containers, that Service Fabric is a container orchestrator, and that Service Fabric has features that support containers. As a next step, we will go over examples of each of the features to show you how to use them.