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1 .containerd intro
Kubecon Shanghai 2018
Derek McGowan (Docker)
Mike Brown (IBM)
2 .History of containerd
containerd to CNCF
containerd 0.2 - Goal of being a stable runtime
- Integrated in Docker 1.11 with OCI image support
- Simple runtime manager - CRI implementation started
on top of runc - Plugin architecture built
Early 2016 Early 2017
Late 2016
Container Runtime Interface (CRI)
- Containerd scope increased to match
needs of Kubernetes runtime
3 .History of containerd
containerd 1.0 containerd 1.2
- Released in December - Released in October
- API stabilized - Runtime shim API stabilized
- CRI implementation goes - Focus on stability and
alpha in November extensibility
Late 2017 Late 2018
Early 2018
Containerd 1.1
- Released in April
- CRI implementation goes BETA
- CRI added to containerd as
built-in plugin
4 .Why containerd?
● Docker
○ Scope has increased over time
○ Resource footprint not optimal for certain use cases where 3rd parties wish to replace/replicate
certain higher level features that Docker provides
● Common runtime for multiple platforms
○ Kubernetes’ CRI interface
○ Pouch
○ Garden
● Cloud provider integration
○ Less opinionated, more extensible for specialized cloud environments
● Owned by CNCF
● Support for OCI runtime and image specifications
5 .Design Goals
● Loosely coupled components
○ Use any component on its own or all together
● Stable GRPC interface
● Extensibility
○ Use any runtime
○ Support any custom requirements
● Unopinionated
○ All defaults can be overwritten
○ Plugins define their configuration
● Smart client
○ Bring together decoupled components into usable toolset
7 . Smart Client Design
Smart client
- Higher level interface provided by client library
- Responsible for push and pull
- Direct access to low level resources (e.g. snapshots)
- Creates container OCI configuration
8 .GRPC API
GRPC API
- Low level access to components
- Mirrors internal component interfaces
- Snapshots, Content, Containers, Task, Events, etc
9 . Metrics
Metric API
- Metrics exposed through Prometheus API
- Exposes metrics for containerd process AND container
level metrics
- Enabled in containerd config `/etc/containerd/config.toml`
[metrics]
address = "localhost:9090"
10 .Kubernetes Support
Kubernetes Runtime Support
- CRI GRPC API exposed from containerd
- Kubelet can be configured to use containerd as runtime
12 .Plugins (CRI)
CRI Plugin
- Built-in by default
- GRPC service plugin
13 .Plugins (Snapshotter)
Snapshotter Plugin
- Built-in (overlay, btrfs, aufs)
- Supports custom plugins over GRPC in 1.2
14 .Plugins (Runtime)
Runtime plugin
- Support for custom shims in 1.2
- Binary which implements runtime API
- Useful for VM runtimes
- Support for OCI runtimes
- Install through `ctr install`
15 . More Extensibility
- Smart client model (Golang)
- Resolver interface allows custom pull flow
- Direct access to containerd interfaces
- Server plugin architecture
- All services are self registered
- Custom GRPC services
- CRI is a GRPC plugin
- Direct access to internal services
16 .Architecture - Intro to containerd CRI
daemon shims
Kubelet
CRI API
CRI Plugin runc
containerd client
containerd
Services Pod
Container
runtime Container
images Container
Container
network
17 .CRI plugin - (Networking)
All Networking is handled by CNI
- Support for all CNI plugins
- CRI plugin creates a network namespace
for the pod via CNI
- CNI config(s) configure the CNI plugins
which are used to apply the desired
networking features for the pod...
Pod
Container
network
Container
Container
Container
18 . Container Runtime Interface - CRI
● PodSandbox
○ Run, Stop, Remove, List, PortForward (via stream), and Status
● Containers
○ Create, Start, Stop, Remove, List, Status, Update (config), and Stats
○ ExecSync - run a command in a container, return response
○ Exec - run a command in a container asynchronously and stream the io
○ Attach - to a container - returns a stream to io of a running container
● Images
○ List, Status, Pull, Remove, FsInfo (file system information, bytes used... )
● Runtime
○ Version, Config, Status… of the Container Runtime
More: https://godoc.org/k8s.io/kubernetes/pkg/kubelet/apis/cri/runtime/v1alpha2
INFO[2018-10-03T20:03:38.913423245-05:00] starting containerd revision= version=
INFO[2018-10-03T20:03:38.914989294-05:00] serving... address="/run/containerd/containerd.sock"
19 . Tools
● ctr
○ Development tool ships with containerd, unstable (commands may change)
○ Lower level commands (directly managing snapshots, images, containers)
● crictl
○ CLI for any CRI runtime, more stable (commands less likely to change)
○ Higher level operations (pull, run, pod management)
INFO[2018-10-03T20:03:38.913423245-05:00] starting containerd revision= version=
INFO[2018-10-03T20:03:38.914989294-05:00] serving... address="/run/containerd/containerd.sock"
20 . Getting Started
Installing kubeadm:
https://kubernetes.io/docs/setup/independent/install-kubeadm/
To configure Kubernetes with containerd:
https://kubernetes.io/docs/setup/cri/#containerd
https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm/
INFO[2018-10-03T20:03:38.913423245-05:00] starting containerd revision= version=
INFO[2018-10-03T20:03:38.914989294-05:00] serving... address="/run/containerd/containerd.sock"
21 . Demo
● Bring up kubernetes cluster on containred with kubeadm
● Contrast kubectl with crictl - just a bit
● Use crictl to inspect the parts of a default cluster
● Show stats with crictl
● Do a kube 101 nginx example
● Run a browser..
● Find the IP of your nginx server with crictl inspectp
● Load the page..
● Use crictl to show the nginx container log
● Bring the cluster down
● Maybe show the pods are gone but containerd is still up via crictl pods
INFO[2018-10-03T20:03:38.913423245-05:00] starting containerd revision= version=
INFO[2018-10-03T20:03:38.914989294-05:00] serving... address="/run/containerd/containerd.sock"
22 . containerd in the Cloud(s)
● Kelsey Hightower’s “Kubernetes the Hard Way” deploys containerd as the
kubelet runtime
● GKE beta: containerd-based K8s clusters
● IBM Cloud: containerd-based clusters for 1.11+
● Azure: OSS acs-engine includes containerd; AKS moving to containerd
● Amazon: still reviewing runtime options for EKS
● CloudFoundry: moving to containerd from runc
23 .Build on a solid foundation
Build on containerd
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