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Ignacy Kowalczyk
Kubernetes is a system for managing containerized applications across multiple machines that was inspired by Google's internal Borg system but is designed to be portable, scalable, and self-healing. Some key concepts in Kubernetes include pods (groups of tightly coupled containers), labels and selectors (for grouping objects), replication controllers (to maintain availability), and services (for exposing pods). Kubernetes handles tasks like scheduling, health checking, and orchestrating updates seamlessly through its declarative API and control loops.
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Ignacy Kowalczyk
- 1. Kubernetes: lessons learnt fromcluster management at Google Ignacy Kowalczyk Engineering Manager Google
- 2. Image by Connie Zhou Forthe past 15 years, Google has been building out the world’s fastest, most powerful, highest quality cloud infrastructure on the planet.
- 3. job hello_world ={ runtime = { cell = 'ic' } // Cell (data center) to run in binary = '.../hello_world_webserver' // Program to run args = { port = '%port%' } // Command line parameters requirements = { // Resource requirements (optional) ram = 100M disk = 100M cpu = 0.1 } replicas = 10000 // Number of tasks } User view
- 4. Google Cloud Platform Imagesby Connie Zhou Google has been developing and using containers to manage our applications for over 10 years.
- 5. Google Cloud Platform Everythingat Google runs in containers: • Gmail, Web Search, Maps, ... • MapReduce, batch, ... • GFS, Colossus, ... • Even Google’s Cloud Platform: our VMs run in containers! We launch over 2 billion containers per week
- 6. What just happened? web browsers BorgMaster linkshard UI shardBorgMaster link shard UI shardBorgMaster link shard UI shardBorgMaster link shard UI shard Cell Scheduler borgcfg web browsers scheduler Borglet Borglet Borglet Borglet BorgMaster link shard read/UI shard Config file persistent store (Paxos) Binary User view
- 7. What just happened? web browsers BorgMaster linkshard UI shardBorgMaster link shard UI shardBorgMaster link shard UI shardBorgMaster link shard UI shard Cell Scheduler borgcfg web browsers scheduler Borglet Borglet Borglet Borglet BorgMaster link shard read/UI shard Config file persistent store (Paxos) Binary User view
- 8. What just happened? web browsers BorgMaster linkshard UI shardBorgMaster link shard UI shardBorgMaster link shard UI shardBorgMaster link shard UI shard Cell Scheduler borgcfg web browsers scheduler Borglet Borglet Borglet Borglet BorgMaster link shard read/UI shard Config file persistent store (Paxos) Binary User view
- 9. What just happened? web browsers BorgMaster linkshard UI shardBorgMaster link shard UI shardBorgMaster link shard UI shardBorgMaster link shard UI shard Cell Scheduler borgcfg web browsers scheduler Borglet Borglet Borglet Borglet BorgMaster link shard read/UI shard Config file persistent store (Paxos) Binary User view
- 10. What just happened? web browsers BorgMaster linkshard UI shardBorgMaster link shard UI shardBorgMaster link shard UI shardBorgMaster link shard UI shard Cell Scheduler borgcfg web browsers scheduler Borglet Borglet Borglet Borglet BorgMaster link shard read/UI shard Config file persistent store (Paxos) Binary User view
- 11. What just happened? web browsers BorgMaster linkshard UI shardBorgMaster link shard UI shardBorgMaster link shard UI shardBorgMaster link shard UI shard Cell Scheduler borgcfg web browsers scheduler Borglet Borglet Borglet Borglet BorgMaster link shard read/UI shard Config file persistent store (Paxos) Binary User view
- 12. Hello world! Hello world! Hello world! Hello world!Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world!Hello world! Hello world! Hello world! Hello world! Hello world! Hello world!Hello world! Hello world! Hello world! Hello world! Image by Connie Zhou User view Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world! Hello world!
- 13.
- 14. Images by Connie Zhou A2000-machine service will have >10 task exits per day This is not a problem: it's normal Failures
- 15. Google Cloud Platform PetsCattle Failures
- 16. Advanced bin- packing algorithms Experimental placement of productionVM workload, July 2014 Efficiency stranded resources available resources one machine
- 17. machine image locked intoa platform Plain IaaS downsides: Not portable & Opaque Hypervisor Guest environment app code libraries guest kernel Efficiency
- 18. Plain IaaS downsides: NoIsolation Hypervisor Guest environment app code libraries guest kernel dependency??? app code Efficiency
- 19. Plain IaaS downsides: LittleReuse Hypervisor Guest environment app code libraries guest kernel Guest environment app code libraries guest kernel Guest environment app code libraries guest kernelredundant Efficiency
- 20. Containers create abetter abstraction layer Hypervisor Guest environment app code libraries guest kernel cut here Efficiency
- 21. Node environment Much better:Portable, isolated, static app environments Hypervisor node kernel app code libraries app code libraries app code libraries container 1 container 2 container 3 Efficiency
- 22. Key observation fromGoogle’s experience:
- 23. A datacenter isnot a collection of computers, a datacenter is a computer.
- 24. Google Cloud Platform Kubernetes Greekfor “Helmsman”; also the root of the words “governor” and “cybernetic” • Runs and manages containers • Inspired by Borg • Runs on VMs and bare metal • 100% Open source, written in Go Run applications on clusters not processes on machines
- 25. Google Cloud Platform Kubernetes Gettingstarted http://kubernetes.io/docs/hellonode/
- 26.
- 27. Google confidential │Do not distribute Docker containers ● Isolation - OS-level virtualization features: ○ cgroups - access to resources (CPU, RAM, I/O ○ namespaces - isolated filesystems, networking ○ Copy-on-Write file systems ● Packaging ○ Repositories of images ○ Overlay file systems
- 28.
- 29. Google Cloud Platform Pods Smallgroup of tightly coupled containers & volumes The atom of scheduling & placement Shared namespaces • shared IP address & localhost • shared IPC, etc. • shared volumes Example: data puller & web server Consumers Content Manager File Puller Web Server Volume Pod
- 30. Google Cloud Platform Labels& Selectors
- 31. Google Cloud Platform Arbitrarymetadata Attached to any API object Generally represent identity Queryable by selectors • think SQL ‘select ... where ...’ Labels
- 32. Google Cloud Platform App:MyApp Phase: prod Role: FE App: MyApp Phase: test Role: FE App: MyApp Phase: prod Role: BE App: MyApp Phase: test Role: BE Selectors
- 33. Google Cloud Platform App:MyApp Phase: prod Role: FE App: MyApp Phase: test Role: FE App: MyApp Phase: prod Role: BE App: MyApp Phase: test Role: BE App = MyApp Selectors
- 34. Google Cloud Platform App:MyApp Phase: prod Role: FE App: MyApp Phase: test Role: FE App: MyApp Phase: prod Role: BE App: MyApp Phase: test Role: BE App = MyApp, Role = FE Selectors
- 35. Google Cloud Platform App:MyApp Phase: prod Role: FE App: MyApp Phase: test Role: FE App: MyApp Phase: prod Role: BE App: MyApp Phase: test Role: BE App = MyApp, Role = BE Selectors
- 36. Google Cloud Platform Selectors App:MyApp Phase: prod Role: FE App: MyApp Phase: test Role: FE App: MyApp Phase: prod Role: BE App: MyApp Phase: test Role: BE App = MyApp, Phase = prod
- 37. Google Cloud Platform App:MyApp Phase: prod Role: FE App: MyApp Phase: test Role: FE App: MyApp Phase: prod Role: BE App: MyApp Phase: test Role: BE App = MyApp, Phase = test Selectors
- 38.
- 39. Google Cloud Platform ReplicationControllers Asimple control loop Has 1 job: ensure N copies of a pod • if too few, start some • if too many, kill some • grouped by a selector Cleanly layered on top of the core • all access is by public APIs Replicated pods are fungible • No implied order or identity ReplicationController - name = “my-rc” - selector = {“App”: “MyApp”} - podTemplate = { ... } - replicas = 4 API Server How many? 3 Start 1 more OK How many? 4
- 40.
- 41. Google Cloud Platform Services Agroup of pods that work together • grouped by a selector Gets a stable virtual IP and port • sometimes called the service portal • also a DNS name Hides complexity Client Virtual IP
- 42.
- 43. Google Cloud Platform Kubernetesnetworking A: 172.16.1.1 3306 B: 172.16.1.2 80 9376 11878SNAT SNAT C: 172.16.1.1 8000
- 44. Google Cloud Platform Kubernetesnetworking A: 172.16.1.1 3306 B: 172.16.1.2 80 9376 11878SNAT SNAT C: 172.16.1.1 8000 REJECTED
- 45. Google Cloud Platform Kubernetesnetworking 10.1.1.0/24 10.1.1.1 10.1.1.2 10.1.2.0/24 10.1.2.1 10.1.3.0/24 10.1.3.1
- 46. Design principles Declarative >imperative: State your desired results, let the system actuate Control loops: Observe, rectify, repeat Network-centric: IP addresses are cheap Cattle > Pets: Manage your workload in bulk
- 47. Borg contributors Core: AbhishekRai, Abhishek Verma, Andy Zheng, Ashwin Kumar, Ben Smith, Beng-Hong Lim, Bin Zhang, Bolu Szewczyk, Brad Strand, Brian Budge, Brian Grant, Brian Wickman, Chengdu Huang, Chris Colohan, Cliff Stein, Cynthia Wong, Daniel Smith, Dave Bort, David Oppenheimer, David Wall, Divyesh Shah, Dawn Chen, Eric Haugen, Eric Tune, Eric Wilcox, Ethan Solomita, Gaurav Dhiman, Geeta Chaudhry, Greg Roelofs, Grzegorz Czajkowski, James Eady, Jarek Kusmierek, Jaroslaw Przybylowicz, Jason Hickey, Javier Kohen, Jeff Dean, Jeremy Dion, Jeremy Lau, Jerzy Szczepkowski, Joe Hellerstein, John Wilkes, Jonathan Wilson, Joso Eterovic, Jutta Degener, Kai Backman, Kamil Yurtsever, Ken Ashcraft, Kenji Kaneda, Kevan Miller, Kurt Steinkraus, Leo Landa, Liza Fireman, Madhukar Korupolu, Maricia Scott, Mark Logan, Mark Vandevoorde, Markus Gutschke, Matt Sparks, Maya Haridasan, Michael Abd-El-Malek, Michael Kenniston, Ming-Yee Iu, Monika Henzinger, Mukesh Kumar, Nate Calvin, Onufry Wojtaszczyk, Olcan Sercinoglu, Paul Menage, Patrick Johnson, Pavanish Nirula, Pedro Valenzuela, Percy Liang, Piotr Witusowski, Praveen Kallakuri, Rafal Sokolowski, Rajmohan Rajaraman, Richard Gooch, Rishi Gosalia, Rob Radez, Robert Hagmann, Robert Jardine, Robert Kennedy, Rohit Jnagal, Roy Bryant, Rune Dahl, Scott Garriss, Scott Johnson, Sean Howarth, Sheena Madan, Smeeta Jalan, Stan Chesnutt, Temo Arobelidze, Tim Hockin, Todd Wang, Tomasz Blaszczyk, Tomasz Wozniak, Tomek Zielonka, Victor Marmol, Vish Kannan, Vrigo Gokhale, Walfredo Cirne, Walt Drummond, Weiran Liu, Xiaopan Zhang, Xiao Zhang, Ye Zhao, and Zohaib Maya. SRE: Adam Rogoyski, Alex Milivojevic, Anil Das, Cody Smith, Cooper Bethea, Folke Behrens, Matt Liggett, James Sanford, John Millikin, Matt Brown, Miki Habryn, Peter Dahl, Robert van Gent, Seppi Wilhelmi, Seth Hettich, Torsten Marek, and Viraj Alankar. BCL and borgcfg: Marcel van Lohuizen and Robert Griesemer. Reviewers: Christos Kozyrakis, Eric Brewer, Malte Schwarzkopf, and Tom Rodeheffer.
- 48. K8s is helpingyou with ● deployment automation ● utilization optimization Q&A kubernetes.io/ignac@google.com Ignacy Kowalczyk Engineering Manager Google