Docker Internals - Twilio talk November 14th, 2013
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This document summarizes key aspects of Docker internals, including how it provides isolation using namespaces and cgroups, manages images using AUFS and layers, and runs and manages containers via its daemon. It outlines Docker's use of isolation, images, process management, and roadmap for future versions including new backend interfaces and improved service discovery.
Docker Internals - Twilio talk November 14th, 2013
- 1. Docker Internals SF Docker Meetup at Twilio 11/14/2013 Docker version 0.6.6 / 0.7.0-rc5 ##dockermeetup By Guillaume J. Charmes <[email protected]> @charme_g
- 2. This is your last chance 1. 2. 3. 4. Isolation Images Process Management Roadmap
- 3. Isolation • LXC • • • • Cgroups/Namespaces Processes Mounts Network • Network • NAT (DOCKER chain) • Expose / Links • File System • Chroot on steroids
- 4. Isolation • Isolation: Namespaces • Only 1 syscall (setns()). No hypervisor • Mounts, Uts (hostname), Net, Pid, IPC, User • Resource management: Cgroups • Memory Limitation • CPU Shares • Future: blkio
- 5. Isolation • Network • • • • Bridge Veth NAT Expose / Links • File System • Chroot++ • Image management
- 7. Images • AUFS • Image format • • • • Base image Layer + parent id Whiteouts (.wh.) Difference Image vs Container • Registry • Future • Devicemapper • Backend interface
- 8. Images • Why AUFS? • Production usage for years • Layers • Multiple RO layers, 1 RW -> Diff • Limitations • 42 layers • Whiteouts • Deletion management
- 9. Images • Image format • Payload (layer) • Metadata (parent id) • Image vs Container • Differences • Future: Unified format
- 10. Images • Image sharing: Registry • Push/Pull via diffs • Future • Backend interface / Devicemapper • Unified image format: whiteouts (.wh.)
- 12. Process Management • Docker daemon • Transports unix/tcp docker run internals • Attach logic • Logs • Host Integration • Dockerfile • RUN • EXPOSE • What is the Context? • Service Discovery
- 13. Process Management • Docker daemon • Transports: docker –d –H tcp://127.0.0.1:4243 –H unix:///var/run/docker.sock • Holds all containers • Handles the logging • Docker client • Everything uses the Remote API
- 14. Process Management docker run • Create • Start • Attach internals • General Config vs Host Config • Attach protocol • TTY • Non-TTY
- 16. Roadmap • Docker 0.7 • File system backend interface • Docker 0.8 • Isolation backend interface • Full introspection • Future • Ambassador Pattern
- 17. Conclusion • Wide global support with backend interfaces • Service discovery improvement • Road to multi host / orchestration