Welcome!

@DevOpsSummit Authors: Elizabeth White, Zakia Bouachraoui, Liz McMillan, Pat Romanski, Roger Strukhoff

Related Topics: @DevOpsSummit

@DevOpsSummit: Blog Post

Proxy Models in Container Environments | @DevOpsSummit #CloudNative #Serverless #DevOps

Today, containers use some of the same terminology, but are introducing new ones

Inline, side-arm, reverse, and forward. These used to be the terms we used to describe the architectural placement of proxies in the network.

Today, containers use some of the same terminology, but are introducing new ones. That's an opportunity for me to extemporaneously expound* on my favorite of all topics: the proxy.

One of the primary drivers of cloud (once we all got past the pipedream of cost containment) has been scalability. Scale has challenged agility (and sometimes won) in various surveys over the past five years as the number one benefit organizations seek by deploying apps in cloud computing environments. 

unavailable is closed

That's in part because in a digital economy (in which we now operate), apps have become the digital equivalent of brick-and-mortar "open/closed" signs and the manifestation of digital customer assistance. Slow, unresponsive apps have the same effect as turning out the lights or understaffing the store.

Apps need to be available and responsive to meet demand. Scale is the technical response to achieving that business goal. Cloud not only provides the ability to scale, but offers the ability to scale automatically. To do that requires a load balancer. Because that's how we scale apps - with proxies that load balance traffic/requests.

Containers are no different with respect to expectations around scale. Containers must scale - and scale automatically - and that means the use of load balancers (proxies).

If you're using native capabilities, you're doing primitive load balancing based on TCP/UDP. Generally speaking, container-based proxy implementations aren't fluent in HTTP or other application layer protocols and don't offer capabilities beyond plain old load balancing (POLB). That's often good enough, as container scale operates on a cloned, horizontal premise - to scale an app, add another copy and distribute requests across it. Layer 7 (HTTP) routing capabilities are found at the ingress (in ingress controllers and API gateways) and are used as much (or more) for app routing as they are to scale applications.

In some cases, however, this is not enough. If you want (or need) more application-centric scale or the ability to insert additional services, you'll graduate to more robust offerings that can provide programmability or application-centric scalability or both.

To do that means plugging-in proxies. The container orchestration environment you're working in largely determines the deployment model of the proxy in terms of whether it's a reverse proxy or a forward proxy. Just to keep things interesting, there's also a third model - sidecar - that is the foundation of scalability supported by emerging service mesh implementations.

per-app reverse proxy

Reverse Proxy

A reverse proxy is closest to a traditional model in which a virtual server accepts all incoming requests and distributes them across a pool (farm, cluster) of resources.

There is one proxy per ‘application'. Any client that wants to connect to the application is instead connected to the proxy, which then chooses and forwards the request to an appropriate instance. If the green app wants to communicate with the blue app, it sends a request to the blue proxy, which determines which of the two instances of the blue app should respond to the request.

In this model, the proxy is only concerned with the app it is managing. The blue proxy doesn't care about the instances associated with the orange proxy, and vice-versa.

Forward Proxy per-node forward proxy

This mode more closely models that of an traditional outbound firewall.

In this model, each container node has an associated proxy. If a client wants to connect to a particular application or service, it is instead connected to the proxy local to the container node where the client is running. The proxy then chooses an appropriate instance of that application and forwards the client's request.

Both the orange and the blue app connect to the same proxy associated with its node. The proxy then determines which instance of the requested app instance should respond.

In this model, every proxy must know about every application to ensure it can forward requests to the appropriate instance.

per-pod sidecar proxy

Sidecar Proxy

This mode is also referred to as a service mesh router. In this model, each container has its own proxy.

If a client wants to connect to an application, it instead connects to the sidecar proxy, which chooses an appropriate instance of that application and forwards the client's request. This behavior is the same as a forward proxy model. 

The difference between a sidecar and forward proxy is that sidecar proxies do not need to modify the container orchestration environment. For example, in order to plug-in a forward proxy to k8s, you need both the proxy and a replacement for kube-proxy. Sidecar proxies do not require this modification because it is the app that automatically connects to its "sidecar" proxy instead of being routed through the proxy.

Each model has its advantages and disadvantages. All three share a reliance on environmental data (telemetry and changes in configuration) as well as the need to integrate into the ecosystem. Some models are pre-determined by the environment you choose, so careful consideration as to future needs - service insertion, security, networking complexity - need to be evaluated before settling on a model.

We're still in early days with respect to containers and their growth in the enterprise. As they continue to stretch into production environments it's important to understand the needs of the applications delivered by containerized environments and how their proxy models differ in implementation.

*It was extemporaneous when I wrote it down. Now, not so much.

Lori MacVittie's blog post originally published here.

More Stories By Lori MacVittie

Lori MacVittie is responsible for education and evangelism of application services available across F5’s entire product suite. Her role includes authorship of technical materials and participation in a number of community-based forums and industry standards organizations, among other efforts. MacVittie has extensive programming experience as an application architect, as well as network and systems development and administration expertise. Prior to joining F5, MacVittie was an award-winning Senior Technology Editor at Network Computing Magazine, where she conducted product research and evaluation focused on integration with application and network architectures, and authored articles on a variety of topics aimed at IT professionals. Her most recent area of focus included SOA-related products and architectures. She holds a B.S. in Information and Computing Science from the University of Wisconsin at Green Bay, and an M.S. in Computer Science from Nova Southeastern University.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@DevOpsSummit Stories
The platform combines the strengths of Singtel's extensive, intelligent network capabilities with Microsoft's cloud expertise to create a unique solution that sets new standards for IoT applications," said Mr Diomedes Kastanis, Head of IoT at Singtel. "Our solution provides speed, transparency and flexibility, paving the way for a more pervasive use of IoT to accelerate enterprises' digitalisation efforts. AI-powered intelligent connectivity over Microsoft Azure will be the fastest connected path for IoT innovators to scale globally, and the smartest path to cross-device synergy in an instrumented, connected world.
There are many examples of disruption in consumer space – Uber disrupting the cab industry, Airbnb disrupting the hospitality industry and so on; but have you wondered who is disrupting support and operations? AISERA helps make businesses and customers successful by offering consumer-like user experience for support and operations. We have built the world’s first AI-driven IT / HR / Cloud / Customer Support and Operations solution.
ScaleMP is presenting at CloudEXPO 2019, held June 24-26 in Santa Clara, and we’d love to see you there. At the conference, we’ll demonstrate how ScaleMP is solving one of the most vexing challenges for cloud — memory cost and limit of scale — and how our innovative vSMP MemoryONE solution provides affordable larger server memory for the private and public cloud. Please visit us at Booth No. 519 to connect with our experts and learn more about vSMP MemoryONE and how it is already serving some of the world’s largest data centers. Click here to schedule a meeting with our experts and executives.
Codete accelerates their clients growth through technological expertise and experience. Codite team works with organizations to meet the challenges that digitalization presents. Their clients include digital start-ups as well as established enterprises in the IT industry. To stay competitive in a highly innovative IT industry, strong R&D departments and bold spin-off initiatives is a must. Codete Data Science and Software Architects teams help corporate clients to stay up to date with the modern business digitalization solutions. Achieve up to 50% early-stage technological process development cost cutdown with science and R&D-driven investment strategy with Codete's support.
As you know, enterprise IT conversation over the past year have often centered upon the open-source Kubernetes container orchestration system. In fact, Kubernetes has emerged as the key technology -- and even primary platform -- of cloud migrations for a wide variety of organizations. Kubernetes is critical to forward-looking enterprises that continue to push their IT infrastructures toward maximum functionality, scalability, and flexibility. As they do so, IT professionals are also embracing the reality of Serverless architectures, which are critical to developing and operating real-time applications and services. Serverless is particularly important as enterprises of all sizes develop and deploy Internet of Things (IoT) initiatives.