Service discovery in kubernetes with fabric8

BASEL BERN BRUGG DÜSSELDORF FRANKFURT A.M. FREIBURG I.BR. GENF
HAMBURG KOPENHAGEN LAUSANNE MÜNCHEN STUTTGART WIEN ZÜRICH
Service discovery in Kubernetes with
Fabric8Andy Moncsek
Senior Consultant
Andy.Moncsek@trivadis.com
Twitter: @AndyAHCP

Agenda
2 27.10.2017
1. Why service discovery?
2. Some Kubernetes basics
3. Service discovery in Kubernetes
4. Fabric8 & Service discovery
Service discovery in Kubernetes with Fabric8

Why service discovery ?
Service discovery in Kubernetes with Fabric83 27.10.2017

Why Service discovery ?
Dynamically
assigned
172.178.178.1:56477
172.178.178.2:66467
172.178.178.3:76767
Client /
API
Gatewa
y
?
Dynamically
changing
Loadbalancing?

Client-side discovery
1. register
2. query
3. request
Client knows
specific
service
instance

Server-side discovery
1.
register
2. request
3.
query
4.
Loadbalance
Client does
not know a
specific
service
instance

Some Kubernetes basics

Some Kubernetes basics: What it is....
 Kubernetes is platform designed to automate deploying,
scaling, and operating application containers.
 Deploy your applications quickly and predictably.
 Scale your applications on the fly.
 Roll out new features seamlessly.

Kubernetes Namespaces
”virtual" cluster
Separates DEV, TEST, PROD, ... environments
9 27.10.2017 Service discovery in Kubernetes with Fabric8

Kubernetes Pods
Group of containers
Shares network/namespace/ IP
Shares environmental variables
Shared volumes

Kubernetes Controller
Ensure X pods are running
Pod templates
Rolling update

Kubernetes Services
Pod discovery
IP per service
1-N port numbers
Route to pods
Load balancer

Kubernetes Services (2)

External IP depends on:
Service type = LB
Infrastructure

Cluster IP:
Internal IP address
Accessible by any
component in
namespace

NodePort:
Unique per service
$NODE_IP:$NODEPORT
ClusterIP references a
NodePort on a specific
Node

Endpoints:
1:1 Endpoint – Pod
Represents the IP
address of a Pod
Can be queried by API

Service discovery in Kubernetes

 How you can find your services in Kubernetes?
 Install Consul, Zookeeper, ...  Out of scope ;-)
 Discovery using Environment variables
 Discovery using DNS
 Discovery using Kubernetes master (with Fabric8 API)

 Discovery using Environment variables
 When a Pod starts, a set of env variables for each active service
added
 {SVCNAME}_SERVICE_HOST & {SVCNAME}_SERVICE_PORT
 In case of many port definitions the port name is added:
{SVCNAME}_SERVICE_PORT_{PORTNAME}
 Drawback: the Service must already exist!

 Discovery using DNS
 The DNS Server watches the Kubernetes API for new Services
 Creates a set of DNS records for each
 E.g. Service: “myservice”, Namespace: “default” myservice.default
 You can access the service using: http://myservice/…...
 Drawback:
 DNS must be enabled
 No protocol- & port-information

Fabric8 & service discovery

 What is Fabric8?
Fabric8 is an integrated open source DevOps and Integration
Platform which works out of the box on any Kubernetes or
OpenShift environment and provides Continuous Delivery,
Management, ChatOps and a Chaos Monkey.

 The Fabric8 kubernetes-client (http://goo.gl/17Hbp1)
 provides a Java API for working with the Kubernetes and
OpenShift REST API
 The kubernetes-client API is used by many projects:
 Several discovery plugins (e.g. Hazelcast)
 fabric8-spring-boot (https://goo.gl/JgN721)
 K8sdiscovery (https://goo.gl/Hok1gT)

 Why & When do you want to use fabric8 kubernetes-client?
 Discover Endpoints (Pods) for Client-side LB or monitoring
 Simple discovery of different ports / protocols
 Discovery using labels!

Fabric8 & service discovery - Example
client.
endpoints().
inNamespace(„hazelcast
“).
withLabel(„cluster1“).list
()
client.
endpoints().
inNamespace(„hazelcast
“).
withLabel(„cluster2“).list
()
spec:
replicas: 3
template:
metadata:
labels:
cluster1

Demo

One more thing ;-)

? ?
?
?
??

Discover external Services
 Solution:
 Services without selectors
 Service with ExternalName

Services without selectors
kind: Service
apiVersion: v1
metadata:
name: my-service
spec:
selector:
app: MyApp
ports:
- protocol: TCP
port: 80
targetPort: 9376
kind: Endpoints
apiVersion: v1
metadata:
name: my-service
subsets:
- addresses:
- ip: 1.2.3.4
ports:
- port: 9376
Manually deploy

Service with ExternalName
kind: Service
apiVersion: v1
metadata:
name: my-service
namespace: prod
spec:
type: ExternalName
externalName: my.database.com
my-service.prod.svc.CLUSTER  CNAME =
my.database.com

Summary
 Use discovery by Service name (DNS) in simple cases
 Use env variables for Port discovery
 Use Fabric8 Kubernetes-Client discovery when:
 Endpoint discovery needed (Client-Side discovery)
 Labels are working better for you
 Dealing with different ports
 Metadata is needed (monitoring)

Thank you
Andy Moncsek
Senior Consultant
Andy.Moncsek@trivadis.com
Twitter: @AndyAHCP
27.10.201737 Service discovery in Kubernetes with Fabric8

Links
 https://maven.fabric8.io
 https://github.com/fabric8io/kubernetes-client
 https://github.com/amoAHCP/K8SDiscoveryPresentation

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Service discovery in kubernetes with fabric8

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