Sf bay area Kubernetes meetup dec8 2016 - deployment models

Copyright © 2015 Mirantis, Inc. All rights reserved
www.mirantis.com
Kubernetes deployment models
(modelling complex applications in K8S)
Dec8 2016
Piotr Siwczak
(https://www.linkedin.com/in/psiwczak)

Agenda
● Challenges in managing complex microservice architectures
● What’s missing in K8S to manage complex microservice architectures
efficiently
● K8S AppController as an enhancement to handle complex architectures
● Demo of AppController
● Q&A about AppController

Challenges in managing
microservice architectures

Linux as a microservice apps platform
Collection of small, independent programs acting together to
form larger systems.
Programs communicate over standardized protocols/API-s
Abstracts computing resources (kernel)

Unix/Linux simplified architecture
Kernel
Libraries
Init system Interactive shell
Userspace apps
Resource access
Orchestration
User functionality

The role of init system
SysVInit … Upstart … Systemd
Init makes sure that apps start in proper order and deps for
them are handled
e.g.
Network subsystem -> Iptables -> ssh

Apps - combined K8S resources
Kubernetes clients (kubectl...)
Kubernetes resources (pod, service…)
Unix/Linux vs K8S
Kernel
Libraries
Init system Interactive shell
Userspace apps
?

Do we have init equivalent in k8s?
Original photo by https://www.flickr.com/people/waferboard/ License: CC BY v2.0, Title: “wholesome stirfry”
“Containers start in
parallel after volumes are
mounted, leaving no
opportunity for
coordination between
containers...”
https://github.com/kubernetes/kubernetes/blob/master/
docs/proposals/container-init.md

...to make a good dish one needs to follow steps
Original photo by https://www.flickr.com/people/waferboard/ License: CC BY v2.0, Title: “wholesome stirfry”
● heat oil
● add garlic
● add veggies and sauce
● add meat

K8S challenge for complex apps
(T3) wordpress depl/service
(T2) mysql depl/service
(T1) mysql password
password
db dns name
& password
kubectl create -f mysql-pass.yaml
kubectl create -f mysql-deployment.yaml
kubectl create -f wordpress-deplyment.yaml

Is lack of deps really a problem for K8S?
We all know microservices are supposed to orchestrate
themselves and tolerate failures
...but…

...deps seem to be needed
https://blog.xebialabs.com/2015/04/13/before-you-go-over-the-container-cliff-with-docker-mesos-etc-po
ints-to-consider/
“"A common definition for a microservice we often hear mentioned is an
“independently-deployable unit”, and indeed it is good practice to design your
microservices so they can start up successfully without requiring all kinds of other
components to be available. But in the vast majority of cases, “no microservice is an
island”...

Docker-compose and Mesos application groups are here and being used:
https://docs.docker.com/compose/gettingstarted/
https://mesosphere.github.io/marathon/docs/application-groups.html

https://github.com/vishnubob/wait-for-it

https://github.com/mesosphere/kubernetes-mesos/issues/119
http://stackoverflow.com/questions/27701994/specify-order-dockers-run-on-kube
rnetes-pod
https://github.com/kubernetes/kubernetes/issues/29804

https://github.com/Mirantis/k8s-AppController
AppController

● way to express dependencies between K8S objects,
● thus allowing to deploy complex, multi-tier applications
in fully automated fashion
● k8s object dependency graph:
● definitions (nodes)
● dependencies (edges)
AppController - really short summary...

Before…
● kubectl create -f t1.yaml
● check status…
● check status…
● ….
After…
● kubectl create -f
graph.yaml
● k8s-appcontroller ac-run

AppController architecture
Kubernetes
k8s-appcontroller pod
kubeac binary k8s API
extensions
3rd party resources:
dependency
definition

workflow
AppController

AppController workflow - definitions
Definition
Standard K8S
resource
(deployment, pod,
service…)
Definition
Standard K8S
resource
(deployment, pod,
service…)
Definition
Standard K8S
resource
(deployment, pod,
service…)
Definition
Standard K8S
resource
(deployment, pod,
service…)
kubectl create -f definitions.yaml

AppController workflow - definitions
apiVersion: appcontroller.k8s/v1alpha1
kind: Definition
metadata:
name: secret-mysql-pass
secret:
apiVersion: v1
data:
password.txt: cXdxd3F3
kind: Secret
metadata:
creationTimestamp: 2016-12-06T16:56:02Z
name: mysql-pass
namespace: default
secret/mysql-pass
Standard K8S
resource
(secret)
Objects are not created in k8s until triggered by
AppController!

Definitions - summary
Definition:
● “node” in the graph
● wrapper over regular k8s resource
● defers the creation of the resource until triggered (in
contrary to “kubectl create -f” which creates the resource
immediately

AppController - dependencies
Definition
Standard K8S
resource
(deployment, pod,
service…)
Definition
Standard K8S
resource
(deployment, pod,
service…)
Definition
Standard K8S
resource
(deployment, pod,
service…)
Definition
Standard K8S
resource
(deployment, pod,
service…)
start end
kubectl create -f deps.yaml

AppController - dependencies
apiVersion: appcontroller.k8s/v1alpha1
kind: Dependency
metadata:
name: mysql-pass--to--mysql-deployment
parent: secret/mysql-pass
child: deployment/mysql
secret/mysql-pass
Standard K8S
resource
(secret)
deployment/mysql
Standard K8S
resource
(deployment)

Dependencies - summary
Dependency:
● “edge” in the graph
● links definitions together
● provides the sense of dependency between definitions

AppController - application rollout
Definition
Standard K8S
resource
(deployment, pod,
service…)
Definition
Standard K8S
resource
(deployment, pod,
service…)
Definition
Standard K8S
resource
(deployment, pod,
service…)
Definition
Standard K8S
resource
(deployment, pod,
service…)
start end
kubectl exec k8s-appcontroller ac-run
kubectl exec k8s-appcontroller kubeac
get-status

AppController workflow - summary
● “wrap” regular k8s resources into definitions > defs.yaml
● load defs.yaml to k8s
● create dependencies between resources > deps.yaml
● load deps.yaml into k8s
● trigger the app deployment from AppController
application (kubectl exec k8s-appcontroller ac-run)

MySQL + Wordpress
Demo

def_db_password
AppController - wordpress deployment
secret:
db_password
def_db_deploymt
deployment:
mysql-deploym
ent
def_db_service
service:
db_service
def_wp_deploymt
deployment:
wordpress-dep
loyment
def_wp_service
service:
wordpress-ser
vice
DB_PASS
DB_HOSTNAME, DB_PASS

Questions/Answers

Q&A
Q:
What if I abort the deployment in the middle - how does AppController recover
from partially provisioned graph?
A:
AppController will check the status of already provisioned resources. Will only
provision the ones which are absent

Q&A
Q:
Can I run multiple AppControllers on a single K8S ?
A:
You can run 1 AppController per namespace

Q&A
Q:
What K8S resources can be currently wrapped into definitions?
A:
- Daemonset
- Job
- Petset
- Pod
- Replicaset
- Service
- ConfigMap
- Secrets
- Deployments

Q&A
Q:
How is provisioning of resources validated?
A:
Status of the k8s resource is checked.
AppController implements also some checks of its own (e.g. for replicasets
readiness probe is based on “success factor” or all resources ready. Success
factor is a part of appcontroller and for services we are checking service selector
and see if the backends are ready - e.g. replica sets)

Q&A
Q:
What’s on the roadmap?
A:
Graph notifications, reactions, error handling
More resources supported
Usability improvements
Better documentation (incl. real-life complex examples)

Q&A
Q:
How AppController is different from Init Containers?
A:
Supports more complex deployments (complex graphs)
Handles deps not only between containers
Checks resource states (no need to implement custom probes in the container)
Keeps debug logs in one place
Can react to changes in the graph

Recording
https://www.youtube.com/watch?v=7GSwSTtBAYo&utm_cont
ent=38600000

Thank you!

Sf bay area Kubernetes meetup dec8 2016 - deployment models

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