1.
DevOps di applicazioni Python
(e non solo) su OpenShift
Francesco Fiore, System Architect
PyCon Nove, 20 aprile 2018

2.
2
Agenda
• Cos’è OpenShift
• Cenni sull’architettura
• Setup di una semplice applicazione
• OpenShift per applicazioni Python: source-to-image
• Dietro le quinte: API objects
• Parametrizzare il setup di applicazioni usando i Template
• Git, OpenShift e Jenkins: integrazione nativa per la CI/CD
• Application lifecycle management
• Application promotion
• Strategie di deployment

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3
OpenShift overview
• Platform as a Service di Red Hat
• OpenShift Origin è un progetto opensource
• Basato su:
– Kubernetes (CaaS)
– Docker
– Atomic
• Add-on rispetto a k8s
– API objects
– Web console
– Software Defined Network
– Docker registry
– logging centralizzato
• Focus su application lifecycle management e automation
• Red Hat OpenShift Container Platform

4.
4
OpenShift vs Kubernetes
Source to
Image (S2I)
Integrated
Registry
Build
Configuration
Image Stream
Deployment
Configuration
Persistent
Volume Claims
Replication
Controller
Replica Sets Daemon Sets
Persistent
Volumes
Secrets Config Maps Services Routes
Software
Defined
Network (SDN)
Web console
Users and
Groups
Projects Namespaces
OpenShift Kubernetes

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5
OpenShift: architettura

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Setup di una applicazione
oc new-project demo
oc new-app https://github.com/ffiore/devops-on-openshift-demo.git
--context-dir samples/flask
--name flask-sample
• OpenShift rileva automaticamente qual è la strategy di build
– if Jenkinsfile -> Pipeline strategy
– elif Dockerfile -> Docker strategy
– else -> Source strategy
File Linguaggio
requirements.txt, setup.py python
pom.xml jee
app.json, package.json nodejs
Godeps, main.go golang
cpanfile, index.pl perl
composer.json, index.php php
Gemfile, Rakefile, config.ru ruby
build.sbt scala
• Se Source strategy, OpenShift
rileva il linguaggio

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Setup di una applicazione
oc new-app https://github.com/ffiore/devops-on-openshift-demo.git
--context-dir samples/flask
--name flask-sample
--env WELCOME_MESSAGE=‘Hello Pycon9!’
--build-env HTTP_PROXY=‘http://x.y.z.w:8080’
oc new-app python:2.7~https://github.com/ffiore/devops-on-
openshift-demo.git
--context-dir samples/flask
--name flask-sample-python27
--env WELCOME_MESSAGE=‘Hello Pycon9!’
oc expose svc flask-sample
• Per esporre l’applicazione all’esterno (Route)

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Source-to-image: Python
• s2i è la modalità utilizzata con Source strategy
• Nessuna modifica all’applicazione
– sufficiente requirements.txt
• 4 modalità di esecuzione
– Gunicorn
• se in requirements.txt o in setup.py (install_requires)
• entrypoint: wsgi.py (wsgi:application) o APP_MODULE
– Django development server
– Python script
• APP_FILE, default app.py
– Script file
• APP_SCRIPT, default app.sh

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Setup di una applicazione: API objects
• BuildConfig
– Build
• ImageStream
– ImageStreamTag
• DeploymentConfig
– ReplicationController
• Pod
• Service
spec:
output:
to:
kind: ImageStreamTag
name: flask-sample:latest
source:
git:
uri: https://github.com/ffiore/devops-on-
openshift-demo
contextDir: samples/flask
type: Git
strategy:
sourceStrategy:
from:
kind: ImageStreamTag
name: python:3.5
namespace: openshift
type: Source
triggers:
- github:
secret: iopmuY9undV5grr7Z8zV
type: GitHub
- generic:
secret: QOhldIxeE2ciwomAgoY9
type: Generic
- type: ConfigChange
- type: ImageChange
apiVersion: v1
kind: BuildConfig
metadata:
annotations:
openshift.io/generated-by: OpenShiftNewApp
labels:
app: flask-sample
name: flask-sample
namespace: demo
...

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10
Setup di una applicazione: API objects
• BuildConfig
– Build
• ImageStream
– ImageStreamTag
• DeploymentConfig
– ReplicationController
• Pod
• Service
apiVersion: v1
kind: ImageStream
metadata:
annotations:
openshift.io/generated-by: OpenShiftNewApp
labels:
app: flask-sample
name: flask-sample
namespace: demo
spec: {}
status:
dockerImageRepository:
172.30.0.128:5000/demo/flask-sample

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11
Setup di una applicazione: API objects
• BuildConfig
– Build
• ImageStream
– ImageStreamTag
• DeploymentConfig
– ReplicationController
• Pod
• Service
template:
metadata:
...
labels:
app: flask-sample
deploymentconfig: flask-sample
spec:
containers:
- image: flask-sample:latest
imagePullPolicy: Always
name: flask-sample
ports:
- containerPort: 8080
protocol: TCP
dnsPolicy: ClusterFirst
restartPolicy: Always
terminationGracePeriodSeconds: 30
triggers:
- type: ConfigChange
- imageChangeParams:
automatic: true
containerNames:
- flask-sample
from:
kind: ImageStreamTag
name: flask-sample:latest
namespace: demo
type: ImageChange
apiVersion: v1
kind: DeploymentConfig
metadata:
name: flask-sample
namespace: demo
spec:
replicas: 1
strategy:
rollingParams:
...
type: Rolling

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12
Setup di una applicazione: API objects
• BuildConfig
– Build
• ImageStream
– ImageStreamTag
• DeploymentConfig
– ReplicationController
• Pod
• Service
apiVersion: v1
kind: Service
metadata:
annotations:
openshift.io/generated-by: OpenShiftNewApp
labels:
app: flask-sample
name: flask-sample
namespace: demo
spec:
clusterIP: 172.30.82.11
ports:
- name: 8080-tcp
port: 8080
protocol: TCP
targetPort: 8080
selector:
app: flask-sample
deploymentconfig: flask-sample
type: ClusterIP

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Creare un Template
• Aggiungere altri API object
– ConfigMap
– Secret
– PersistentVolumeClaim
– ...
• Personalizzare gli oggetti
– consumare ConfigMap, Secret, PVC, ecc.
– creare legami tra componenti applicativi (es. applicazione + database)
• Parametrizzare gli oggetti
• Riutilizzare il tutto
– su project/ambienti diversi
– per applicazioni diverse

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Usare i Template
oc process –f python-flask-sample-s2i.yaml
-p APPLICATION_NAME=‘welcome-app’
-p SOURCE_REPOSITORY_URL=‘https://github.com/ffiore/devops-on-openshift-
demo’
-p CONTEXT_DIR=‘samples/flask’
-p WELCOME_MESSAGE=‘Hello Pycon9!’ –o yaml | oc create –f -
• Creare l’applicazione usando il Template
• Inserire un Template «a catalogo»
oc –n devops create –f django-postgresql-persistent.yaml
• Usare un Template «a catalogo»
oc –n devops process django-psql-persistent
-p NAME=‘django-app’
-p SOURCE_REPOSITORY_URL=‘https://github.com/sclorg/django-ex’
| oc –n demo create –f -

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Automatizzare con Jenkins
• BuildConfig possono avere strategy jenkinsPipelineStrategy
– jenkinsfile
– webhook per il triggering da Git
• OpenShift si aspetta di trovare una istanza di Jenkins
– creazione della pipeline in Jenkins
– creazione di un Build
• In alternativa, jenkins-ephemeral
• Jenkins
– autoconfigurazione al primo deploy
• puntamenti a Kubernetes
• provisioning pipeline esistenti
– openshift jenkins plugin (deprecato da OpenShift 3.7)
– openshift jenkins client plugin (GA da OpenShift 3.7)
• Parametrizzare usando Template
– automatic setup e CI/CD

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Lifecycle management
• git flow/gitlab
flow/...
• github/generic
webhook
git
push/merge
• build applicazione
• unit test
(postCommit)
• build image
build • setup/update
database (pre)
• deploy applicazione
• integration test
(post)
deploy

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Lifecycle management e software promotion
git
push/merge
•git flow/gitlab flow/...
•github/generic webhook
build
•build applicazione
•unit test (postCommit)
•build image
deploy DEV
•setup/update database (pre)
•deploy applicazione
•functional/integration test (post)
deploy
STAGING
•setup/update database (pre)
•deploy applicazione
•smoke test (post)
deploy
PRODUCTION
•setup/update database (pre)
•deploy applicazione
•smoke test (post)

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Rolling deployment
• Rimpiazzare le istanze della vecchia
versione con la nuova
– readiness check
– canary deployment
– rollback automatico
• builtin in OpenShift
• quando:
– no downtime
– N-1 compatibility
• lifecycle hooks
– pre
– post
pre hook
scale in
old rc
scale out
new rc
repeat
scaling
post hook
git push
build
deploy

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Recreate deployment
• Rimpiazzare tutte le istanze della
vecchia versione con la nuova
– readiness check
– rollback automatico
• builtin in OpenShift
• quando:
– migrazione dati
– no N-1 compatibility
– RWO volume
• downtime
• lifecycle hooks
– pre
– mid
– post
pre hook
scale in
to 0
mid hook
scale out
to N
post hook
git push
build
deploy

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Blue-green deployment
• Obiettivo: testing prima dello switch
del traffico
– smoke test
– integration test
• 2 versioni dell’applicazione
– production
– internal (release candidate)
• ‘internal’ può essere pubblica o
privata
• 2 service
• 2 deployment configuration
• switch gestito da Jenkins
• alternativa, API manager
– <public, staging, private> URL
• N-1 compatibility
git push
build
deploy
test
go live

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21
Blue-green deployment
Pod
Service
Route app
app-blue
app-blue-1-x app-blue-1-y
app-green
app-green-2-z app-green-2-k
app.os.local.int

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Blue-green deployment
Pod
Service
Route app
app-blue
app-blue-1-x app-blue-1-y
app-green
app-green-2-z app-green-2-k
app.os.local.int
oc patch route app –p ‘{“spec”: {“to”: {“name”: “app-green”}}}’

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Canary deployment
• Obiettivo: ridurre il rischio di deploy
di una nuova versione
• come blue/green, ma entrambe
versioni online
• 1 service
• 2 deployment configuration
• molteplici shard
• proxy shard
– scale out/in deployment configs ->
traffic splitter (%)
• N-1 compatibility
• gestito da Jenkins
git push
build
deploy
go live
test
scale
out/in

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Canary deployment
Pod
Service
Route app
app
app1-1-x app1-1-y app1-1-z app2-1-k
app.os.local.int

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25
Canary deployment
Pod
Service
Route app
app
app1-1-x app1-1-y app2-1-k app2-1-t
app.os.local.int
oc scale --replicas=2 dc app2 && oc scale --replicas=2 dc app1

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Canary deployment
Pod
Service
Route app
app
app2-1-k app2-1-t app2-1-j app2-1-w
app.os.local.int
oc scale --replicas=4 dc app2 && oc scale --replicas=0 dc app1

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A/B deployment
• Obiettivi:
– testing di 2 (o più) versioni
contemporaneamente
– 2 (o più) configurazioni, stessa
versione (es. più region)
• come A/B testing, ma codice + config
• 1 service
• 2 (o più) deployment configuration
• molteplici shard
• proxy shard
– scale out/in deployment configs ->
traffic splitter (%)
• N-1 compatibility
• gestito da Jenkins
git push
build
deploy
go live
test
scale
out/in

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A/B deployment
Pod
Service
Route app
app
app-1-x app-1-k app-a-1-y app-b-2-z
app.os.local.int

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A/B deployment
Pod
Service
Route app
app
app-1-x app-a-1-y app-b-2-z app-b-2-k
oc scale --replicas=2 dc app-b && oc scale --replicas=1 dc app
app.os.local.int

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A/B deployment
Pod
Service
Route app
app
app-a-1-y app-a-1-t app-b-2-z app-b-2-k
oc scale --replicas=2 dc app-a && oc scale --replicas=0 dc app
app.os.local.int

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A/B deployment
Pod
Service
Route app
app
app-b-2-z app-b-2-k app-b-2-t app-b-2-w
oc scale --replicas=4 dc app-b && oc scale --replicas=0 dc app-a
app.os.local.int

32.
Sede Legale e Unità Operativa
Via Alfredo Campanini, 6
20124 Milano
Tel: +39 02.66732.1 – Fax: +39 02.66732.300
Unità Operativa
Via Cristoforo Colombo, 163
00147 Roma
Tel: +39 06.9826.9600 – Fax: +39 06.9826.9680
Grazie per l’attenzione!
francesco.fiore@par-tec.it | @ffiore81
https://www.par-tec.it