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1990s/2000s: Architectural big album rock
• The late 1990s saw the rise of three-tier architectures consisting of presentation, application logic and data tiers
• Many names for roughly the same notion: “Service-oriented architecture”, “Model/View/Controller”, etc.
• The AJAX+REST revolution of the mid-2000s gave rise to true web applications in which application logic could live on the edge
• Led to a punk uprising...
Post-AJAX punks
• Why should HTTP be restricted to the web?
• Why should REST be restricted to web apps?
• Why should JavaScript be restricted to the client?
• Instead of having one monolithic architecture, why not have a series of (smaller) services that merely did one thing well?
• In case this sounds vaguely familiar...
Proto-punk: The Unix philosophy
• The Unix philosophy, as articulated by Doug McIlroy:
• Write programs that do one thing and do it well
• Write programs to work together
• Write programs that handle text streams, because that is a universal interface
• The single most important revolution in software systems thinking!
• Applying it to HTTP-based services...
Punk architecture: Microservices
• Microservices do one thing, and strive to do it well
• Replace a small number of monoliths with many services that have well-documented, small HTTP-based APIs
• Larger systems can be composed of these smaller services
• And there is an organizational analogue: microservices can break large organizations into smaller, more effective ones
Punks in prod: Deploying microservices
• Microservices are tautologically small
• One physical machine per service is clearly uneconomical…
• ...but deploying many orthogonal services on a single machine is a well-known operational nightmare (e.g. conflicting dependencies, shared fault domain)
• The key is to virtualize — but at what layer of the stack?
• Virtualization has ramifications with respect to performance and density — which is to say, economics
Hardware-level virtualization?
• The historical answer to virtualization — since the 1960s — has been to virtualize the hardware:
• A virtual machine is presented upon which each tenant runs an operating system that they choose (and must manage)
• There are as many operating systems on a machine as tenants!
• Can run entire legacy stacks unmodified...
• ...but operating systems are heavy and don’t play well with others with respect to resources like DRAM, CPU, I/O devices, etc.
• With microservices, overhead dominates!
Platform-level virtualization?
• Virtualizing at the application platform layer addresses the tenancy challenges of hardware virtualization, and presents a much more nimble (& developer friendly!) abstraction...
• ...but at the cost of dictating abstraction to the developer
• This is the “Google App Engine” problem: developers are in a straightjacket where toy programs are easy — but sophisticated applications are impossible
• Virtualizing at the application platform layer poses many other challenges with respect to security, containment, etc.
OS-level virtualization!
• Virtualizing at the operating system hits a sweet spot:• A single operating system (i.e. a single kernel) allows for efficient use of
hardware resources, maximizing tenancy and performance
• Disjoint instances are securely compartmentalized by the operating system
• Gives tenants what appears to be a virtual machine (albeit a very fast one) on which to run higher-level software: PaaS ease with IaaS generality
• Also: boots like a bandit!
• Model was pioneered by FreeBSD jails and taken to their logical extreme by Solaris zones — and then aped by Linux containers
OS-level virtualization at Joyent
• Joyent runs OS containers in the cloud via SmartOS — and we have run containers in multi-tenant production since ~2006
• Adding support for hardware-based virtualization circa 2011 strengthened our resolve with respect to OS-based virtualization
• This is especially true for microservices: as services get small, overhead and latency become increasingly important — and OS containers become a bigger and bigger win
• We emphasized their operational characteristics — performance, elasticity, tenancy — and for many years, we were a lone voice...
Containers as PaaS foundation?
• Some saw the power of OS containers to facilitate up-stack platform-as-a-service abstractions
• For example, dotCloud — a platform-as-a-service provider — built their PaaS on OS containers
• Struggling as a PaaS, dotCloud pivoted — and open sourced their container-based orchestration layer...
...and Docker was born
Docker revolution
• Docker has used the rapid provisioning + shared underlying filesystem of containers to allow developers to think operationally
• Developers can encode deployment procedures via an image
• Images can be reliably and reproducibly deployed as a container
• Images can be quickly deployed — and re-deployed
• Docker complements the DIY ethos of microservices
• Docker will do to apt what apt did to tar
Broader container revolution
• The Docker model has pointed to the future of containers
• Docker’s challenges today are largely operational: network virtualization, persistence, security, etc.
• Security concerns are not due to Docker per se, but rather to the architectural limitations of the Linux “container” substrate
• For multi-tenancy, state-of-the-art for Docker containers is to run in hardware virtual machines (!!)
• Deploying OS containers in hardware virtual machines negates their economic advantage!
The future of containers in production?
• Can we achieve an ideal world that combines the development model of Docker with the deployment model of SmartOS?
• To facilitate this ideal, we at Joyent have:
• Added the ability to run Linux binaries in a SmartOS container
• Added a Docker API end point to SmartDataCenter, the container-native stack that runs our public cloud
• Open sourced everything
• Here’s to the punk rock revolution of microservices + containers!
