Docker and theFuture of Containers in Production

CTO

bryan@joyent.com

Bryan Cantrill

@bcantrill

Prehistory: Virtualization as cloud catalyst

• In the 1960s — shortly after the dawn of computing! — pundits foresaw a compute utility that would be public and multi-tenant

• The vision was four decades too early: it took the internet + commodity computing + virtualization to yield cloud computing

• Virtualization is the essential ingredient for multi-tenant operation — but where in the stack to virtualize?

• Choices around virtualization capture tensions between elasticity, tenancy, and performance

• tl;dr: Virtualization choices drive economic tradeoffs

• The historical answer — since the 1960s — has been to virtualize at the level of the hardware:

• A virtual machine is presented upon which each tenant runs an operating system of their choosing

• There are as many operating systems as tenants

• The singular advantage of hardware virtualization: it can run entire legacy stacks unmodified

• However, hardware virtualization exacts a heavy price: operating systems are not designed to share resources like DRAM, CPU, I/O devices or the network

• Hardware virtualization limits tenancy, elasticity and performance

Hardware-level virtualization?

• Virtualizing at the application platform layer addresses the tenancy challenges of hardware virtualization

• Added advantage of a much more nimble (& developer-friendly!) abstraction…

• ...but at the cost of dictating abstraction to the developer

• This creates the “Google App Engine problem”: developers are in a straightjacket where toy programs are easy — but sophisticated apps are impossible

• Virtualizing at the application platform layer poses many other challenges with respect to security, containment and scalability

Platform-level virtualization?

• Virtualizing at the OS level hits the sweet spot:

• Single OS (i.e., single kernel) allows for efficient use of hardware resources, maximizing tenancy and performance

• Disjoint instances are securely compartmentalized by the operating system

• Gives users what appears to be a virtual machine (albeit a very fast one) on which to run higher-level software

• The ease of a PaaS with the generality of IaaS

• Model was pioneered by FreeBSD jails and taken to their logical extreme by Solaris zones — and then aped by Linux containers

OS-level virtualization!

OS-level virtualization in the cloud

• Joyent runs OS containers in the cloud via SmartOS (our illumos derivative) — and we have run containers in multi-tenant production since ~2006

• Core SmartOS facilities are container-aware and optimized: Zones, ZFS, DTrace, Crossbow, SMF, etc.

• SmartOS also supports hardware-level virtualization — but we have long advocated OS-level virtualization for new build out

• 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 — build their PaaS on OS containers

• Hearing that many were interested in their container orchestration layer (but not their PaaS), dotCloud 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 dependencies and deployment practices into an image

• Images can be layered, allowing for swift development

• Images can be quickly deployed — and re-deployed

• Docker will do to apt what apt did to tar

Docker’s challenges

• The Docker model is the future of containers

• Docker’s challenges are largely around production deployment: security, network virtualization, persistence

• Security concerns are real enough that for multi-tenancy, OS containers are currently running in hardware VMs (!!)

• SmartOS, we have spent a decade addressing these concerns — and are proven in production…

• Could we combine the best of both worlds?

• Could we somehow deploy Docker containers as SmartOS zones?

Docker + SmartOS: Linux binaries?

• First (obvious) problem: while it has been designed to be cross-platform, Docker is Linux-centric

• While Docker could be ported, the encyclopedia of Docker images will likely forever remain Linux binaries

• SmartOS is Unix — but it isn’t Linux…

• Could we somehow natively emulate Linux — and run Linux binaries directly on the SmartOS kernel?

OS emulation: An old idea

• Operating systems have long employed system call emulation to allow binaries from one operating system run on another on the same instruction set architecture

• Combines the binary footprint of the emulated system with the operational advantages of the emulating system

• Sun first did this with SunOS 4.x binaries on Solaris 2.x

• In mid-2000s, Sun developed zone-based OS emulation for Solaris: branded zones

• Several brands were developed — notably including an LX brand that allowed for Linux emulation

LX-branded zones: Life and death

• The LX-branded zone worked for RHEL 3 (!): glibc 2.3.2 + Linux 2.4

• Remarkable amount of work was done to handle device pathing, signal handling, /proc — and arcana like TTY ioctls, ptrace, etc.

• Worked for a surprising number of binaries!

• But support was only for 2.4 kernels and only for 32-bit; 2.6 + 64-bit appeared daunting…

• Support was ripped out of the system on June 11, 2010

• Fortunately, this was after the system was open sourced in June 2005 — and the source was out there...

LX-branded zones: Resurrection!

• In January 2014, David Mackay, an illumos community member, announced that he was able to resurrect the LX brand —and that it appeared to work!

Linked below is a webrev which restores LX branded zones support to Illumos:

http://cr.illumos.org/~webrev/DavidJX8P/lx-zones-restoration/

I have been running OpenIndiana, using it daily on my workstation for over a month with the above webrev applied to the illumos-gate and built by myself.

It would definitely raise interest in Illumos. Indeed, I have seen many people who are extremely interested in LX zones.

The LX zones code is minimally invasive on Illumos itself, and is mostly segregated out.

I hope you find this of interest.

LX-branded zones: Revival

• Encouraged that the LX-branded work was salvageable, Joyent engineer Jerry Jelinek reintegrated the LX brand into SmartOS on March 20, 2014...

• ...and started the (substantial) work to modernize it

• Guiding principles for LX-branded zone work:

• Do it all in the open

• Do it all on SmartOS master (illumos-joyent)

• Add base illumos facilities wherever possible

• Aim to upstream to illumos when we’re done

LX-branded zones: Progress

• Working assiduously over the course of 2014, progress was difficult but steady:

• Ubuntu 10.04 booted in April

• Ubuntu 12.04 booted in May

• Ubuntu 14.04 booted in July

• 64-bit Ubuntu 14.04 booted in October (!)

• Going into 2015, it was becoming increasingly difficult to find Linux software that didn’t work...

LX-branded zones: Working well...

...and, um, well received

Docker + SmartOS: Provisioning?

• With the binary problem being tackled, focus turned to the mechanics of integrating Docker with the SmartOS facilities for provisioning

• Provisioning a SmartOS zone operates via the global zone that represents the control plane of the machine

• docker is a single binary that functions as both client and server — and with too much surface area to run in the global zone, especially for a public cloud

• docker has also embedded Go- and Linux-isms that we did not want in the global zone; we needed to find a different approach...

Docker Remote API

• While docker is a single binary that can run on the client or the server, it does not run in both at once…

• docker (the client) communicates with docker (the server) via the Docker Remote API

• The Docker Remote API is expressive, modern and robust (i.e. versioned), allowing for docker to communicate with Docker backends that aren’t docker

• The clear approach was therefore to implement a Docker Remote API endpoint for SmartDataCenter

Aside: SmartDataCenter

• Orchestration software for SmartOS-based clouds

• Unlike other cloud stacks, not designed to run arbitrary hypervisors, sell legacy hardware or get 160 companies to agree on something

• SmartDataCenter is designed to leverage the SmartOS differentiators: ZFS, DTrace and (esp.) zones

• Runs both the Joyent Public Cloud and business-critical on-premises clouds at well-known brands

• Born proprietary — but made entirely open source on November 6, 2014: http://github.com/joyent/sdc

SmartDataCenter: Architecture

Booter

AMQPbroker

PublicAPI

Customerportal

ZFS-based multi-tenant filesystem

Virtu

al N

IC

Virtu

al N

IC

VirtualSmartOS(OS virt.)

. . .

Virtu

al N

IC

Virtu

al N

ICLinuxGuest

(HW virt.)

. . .

Virtu

al N

IC

Virtu

al N

IC

WindowsGuest

(HW virt.)

. . .

Virtu

al N

IC

Virtu

al N

IC

Virtual OSor Machine

. . .

SmartOS kernel(network booted)

SmartOS kernel(flash booted)

Provisioner

Instrumenter

Heartbeater

DHCP/TFTP

AMQP

AMQP agents

Public HTTP

Head-node

Compute node Tens/hundreds per

head-node

. . .

SDC 7 core services

BinderDNS

Operatorportal

. . .

Firewall

SmartDataCenter: Core Services

Analyticsaggregator

Key/ValueService(Moray)

FirewallAPI

(FWAPI)

VirtualMachine

API(VMAPI)

DirectoryService(UFDS)

DesignationAPI

(DAPI)

WorkflowAPI

NetworkAPI

(NAPI)

Compute-Node API(CNAPI)

ImageAPI

Alerts &Monitoring

(Amon)

PackagingAPI

(PAPI)

ServiceAPI

(SAPI)

DHCP/TFTP

AMQP

DNS

Booter

AMQPbroker

Binder

PublicAPI

Customerportal

Public HTTP

Operatorportal

OperatorServices Manta

Other DCs

Note: Service interdependencies not shown for readability

Head-nodeOther core services

may be provisioned on compute nodes

SDC7 Core Services

SmartDataCenter + Docker

• Implementing an SDC-wide endpoint for the Docker remote API allows us to build in terms of our established core services: UFDS, CNAPI, VMAPI, Image API, etc.

• Has the welcome side-effect of virtualizing the notion of Docker host machine: Docker containers can be placed anywhere within the data center

• From a developer perspective, one less thing to manage

• From an operations perspective, allows for a flexible layer of management and control: Docker API endpoints become a potential administrative nexus

• As such, virtualizing the Docker host is somewhat analogous to the way ZFS virtualized the filesystem...

SmartDataCenter + Docker: Challenges

• Some Docker constructs have (implicitly) encoded co-locality of Docker containers on a physical machine

• Some of these constructs (e.g., --volumes-from) we will discourage but accommodate by co-scheduling

• Others (e.g., host directory-based volumes) we are implementing via NFS backed by Manta, our (open source!) distributed object storage service

• Moving forward, we are working with Docker to help assure that the Docker Remote API doesn’t create new implicit dependencies on physical locality

SmartDataCenter + Docker: Networking

• Parallel to our SmartOS and Docker work, we have been working on next-generation software-defined networking for SmartOS and SmartDataCenter

• Goal was to use standard encapsulation/decapsulation protocols (i.e., VXLAN) for overlay networks

• We have taken a kernel-based (and ARP-inspired) approach to assure scale

• Complements SDC’s existing in-kernel, API-managed firewall facilities

• All done in the open: on the dev-overlay branch of SmartOS (illumos-joyent) and as sdc-portolan

Putting it all together: sdc-docker

• Our Docker engine for SDC, sdc-docker, implements the end points for the Docker Remote API

• Work is young (started in earnest in early fall 2014), but because it takes advantage of a proven orchestration substrate, progress has been very quick…

• We will be deploying it into early access production in the Joyent Public Cloud in Q1CY15

• It’s open source: http://github.com/joyent/sdc-docker; you can install SDC (either on hardware or on VMware) and check it out for yourself!

• A demo is worth a thousand slides...

Future of containers in production

• For nearly a decade, we at Joyent have believed that OS-virtualized containers are the future of computing

• While the efficiency gains are tremendous, they have not alone been enough to propel containers into the mainstream

• We believe that the developer ease of Docker combined with the proven production substrate of SmartOS and SmartDataCenter yields the best of all worlds

• The future of containers is one without compromise: developer efficiency, operational elasticity, multi-tenant security and on-the-metal performance!

Thank you!

• Jerry Jelinek, @pfmooney, @jmclulow and @jperkin for their work on LX branded zones

• @joshwilsdon, @trentmick, @cachafla and @orlandov for their work on sdc-docker

• @rmustacc, @wayfaringrob, @fredfkuo and @notmatt for their work on SDC overlay networking

• The countless engineers who have worked on or with illumos because they believed in OS-based virtualization