Začíname s Kubernetes na CentOS 7

Kubernetes je platforma s otvoreným zdrojom vyvinutá spoločnosťou Google na správu kontajnerových aplikácií naprieč klastrom serverov. Stavia na desať a polročných skúsenostiach, ktoré má Google s prevádzkovaním klastrov kontajnerov vo veľkom meradle a poskytuje vývojárom infraštruktúru v štýle Google využívajúcu najlepšie projekty s otvoreným zdrojom, ako sú:

• Docker : technológia aplikačného kontajnera.
• Etcd : distribuované úložisko údajov typu kľúč – hodnota, ktoré spravuje informácie o celom klastri a poskytuje zisťovanie služieb.
• Flannel : prekryvná sieťová štruktúra umožňujúca kontajnerovú konektivitu naprieč viacerými servermi.

Kubernetes umožňuje vývojárom deklaratívne definovať svoju aplikačnú infraštruktúru prostredníctvom súborov YAML a abstrakcií, ako sú moduly, RC a služby (viac o tom neskôr) a zaisťuje, že základný klaster vždy zodpovedá stavu definovanému používateľom.

Niektoré z jeho funkcií zahŕňajú:

• Automatické plánovanie systémových prostriedkov a automatické umiestňovanie aplikačných kontajnerov v rámci klastra.
• Škálovanie aplikácií za chodu jediným príkazom.
• Priebežné aktualizácie s nulovými prestojmi.
• Samoliečenie: automatické preplánovanie aplikácie v prípade zlyhania servera, automatické reštartovanie kontajnerov, kontroly stavu.

Preskočte na inštaláciu , ak ste už oboznámení s Kubernetes.

Základné pojmy

Kubernetes ponúka vývojárom nasledujúce abstrakcie (logické jednotky):

• Pods.
• Kontroléry replikácie.
• Štítky.
• služby.

Pods

Je to základná jednotka pracovných úloh Kubernetes. Modul modeluje „logického hostiteľa“ špecifického pre aplikáciu v kontajnerovom prostredí. Laicky povedané, modeluje skupinu aplikácií alebo služieb, ktoré predtým bežali na rovnakom serveri vo svete pred kontajnermi. Kontajnery vo vnútri modulu zdieľajú rovnaký sieťový menný priestor a môžu zdieľať aj objemy údajov.

Kontroléry replikácie

Pody sú skvelé na zoskupovanie viacerých kontajnerov do logických aplikačných jednotiek, ale neponúkajú replikáciu ani preplánovanie v prípade zlyhania servera.

Tu sa hodí ovládač replikácie alebo RC. RC zaisťuje, že v klastri vždy beží určitý počet modulov danej služby.

Štítky

Sú to metadáta kľúč – hodnota, ktoré možno pripojiť k akémukoľvek zdroju Kubernetes (pody, RC, služby, uzly, ...).

služby

Moduly a ovládače replikácie sú skvelé na nasadenie a distribúciu aplikácií v rámci klastra, ale moduly majú dočasné adresy IP, ktoré sa menia po preplánovaní alebo reštartovaní kontajnera.

Služba Kubernetes poskytuje stabilný koncový bod (pevná virtuálna IP + väzba portu na hostiteľské servery) pre skupinu modulov spravovaných kontrolérom replikácie.

Klaster Kubernetes

Vo svojej najjednoduchšej forme sa klaster Kubernetes skladá z dvoch typov uzlov:

• 1 majster Kubernetes.
• N uzly Kubernetes.

Majster Kubernetes

Kubernetes master je riadiaca jednotka celého klastra.

Hlavné zložky majstra sú:

• Etcd: globálne dostupné úložisko údajov, ktoré ukladá informácie o klastri a službách a aplikáciách spustených v klastri.
• Kube API server: toto je hlavné centrum správy klastra Kubernetes a odhaľuje RESTful rozhranie.
• Controller manager: stará sa o replikáciu aplikácií riadených replikačnými radičmi.
• Plánovač: sleduje využitie prostriedkov v rámci klastra a podľa toho priraďuje pracovné zaťaženie.

Uzol Kubernetes

Uzol Kubernetes sú pracovné servery, ktoré sú zodpovedné za spúšťanie modulov.

Hlavné komponenty uzla sú:

• Docker: démon, ktorý spúšťa aplikačné kontajnery definované v moduloch.
• Kubelet: riadiaca jednotka pre moduly v lokálnom systéme.
• Kube-proxy: sieťový proxy, ktorý zabezpečuje správne smerovanie pre služby Kubernetes.

Inštalácia

V tejto príručke vytvoríme klaster s 3 uzlami pomocou serverov CentOS 7:

• 1 Kubernetes master (kube-master)
• 2 uzly Kubernetes (kube-node1, kube-node2)

Neskôr môžete pridať toľko ďalších uzlov, koľko chcete, podľa rovnakého postupu inštalácie pre uzly Kubernetes.

Všetky uzly

Nakonfigurujte názvy hostiteľov a /etc/hosts:

# /etc/hostname
kube-master
# or kube-node1, kube-node2

# append to /etc/hosts
replace-with-master-server-ip kube-master
replace-with-node1-ip kube-node1
replace-with-node2-ip kube-node2

Zakázať firewall:

systemctl disable firewalld
systemctl stop firewalld

Majster Kubernetes

Nainštalujte hlavné balíčky Kubernetes:

yum install etcd kubernetes-master

Konfigurácia:

# /etc/etcd/etcd.conf
# leave rest of the lines unchanged
ETCD_LISTEN_CLIENT_URLS="http://0.0.0.0:2379"
ETCD_LISTEN_PEER_URLS="http://localhost:2380"
ETCD_ADVERTISE_CLIENT_URLS="http://0.0.0.0:2379"

# /etc/kubernetes/config
# leave rest of the lines unchanged
KUBE_MASTER="--master=http://kube-master:8080"

# /etc/kubernetes/apiserver
# leave rest of the lines unchanged
KUBE_API_ADDRESS="--address=0.0.0.0"
KUBE_ETCD_SERVERS="--etcd_servers=http://kube-master:2379"

Štart atď:

systemctl start etcd

Nainštalujte a nakonfigurujte sieťovú štruktúru Flannel overlay (je to potrebné, aby sa kontajnery bežiace na rôznych serveroch navzájom videli):

yum install flannel

Vytvorte konfiguračný súbor Flanel ( flannel-config.json):

{
  "Network": "10.20.0.0/16",
  "SubnetLen": 24,
  "Backend": {
    "Type": "vxlan",
    "VNI": 1
  }  
}

Nastavte konfiguráciu Flanelu na serveri Etcd:

etcdctl set coreos.com/network/config < flannel-config.json

Nasmerujte Flannel na server Etcd:

# /etc/sysconfig/flanneld
FLANNEL_ETCD="http://kube-master:2379"

Povoľte služby, aby sa spúšťali pri štarte:

systemctl enable etcd
systemctl enable kube-apiserver
systemctl enable kube-controller-manager
systemctl enable kube-scheduler
systemctl enable flanneld

Reštartujte server.

Uzol Kubernetes

Nainštalujte balíky uzlov Kubernetes:

yum install docker kubernetes-node

Nasledujúce dva kroky nakonfigurujú Docker tak, aby používal prekrytia pre lepší výkon. Pre viac informácií navštívte tento blogový príspevok :

Odstrániť aktuálny adresár ukladacieho priestoru docker:

systemctl stop docker
rm -rf /var/lib/docker

Change configuration files:

# /etc/sysconfig/docker
# leave rest of lines unchanged
OPTIONS='--selinux-enabled=false'

# /etc/sysconfig/docker
# leave rest of lines unchanged
DOCKER_STORAGE_OPTIONS=-s overlay

Configure kube-node1 to use our previously configured master:

# /etc/kubernetes/config
# leave rest of lines unchanged
KUBE_MASTER="--master=http://kube-master:8080"

# /etc/kubernetes/kubelet
# leave rest of the lines unchanged
KUBELET_ADDRESS="--address=0.0.0.0"
# comment this line, so that the actual hostname is used to register the node
# KUBELET_HOSTNAME="--hostname_override=127.0.0.1"
KUBELET_API_SERVER="--api_servers=http://kube-master:8080"

Install and configure Flannel overlay network fabric (again - this is needed so that containers running on different servers can see each other):

yum install flannel

Point Flannel to the Etcd server:

# /etc/sysconfig/flanneld
FLANNEL_ETCD="http://kube-master:2379"

Enable services:

systemctl enable docker
systemctl enable flanneld
systemctl enable kubelet
systemctl enable kube-proxy

Reboot the server.

Test your Kubernetes server

After all of the servers have rebooted, check if your Kubernetes cluster is operational:

[root@kube-master ~]# kubectl get nodes
NAME         LABELS                              STATUS
kube-node1   kubernetes.io/hostname=kube-node1   Ready
kube-node2   kubernetes.io/hostname=kube-node2   Ready

Example: Deploying a Selenium grid using Kubernetes

Selenium is a framework for automating browsers for testing purposes. It's a powerful tool of the arsenal of any web developer.

Selenium grid enables scalable and parallel remote execution of tests across a cluster of Selenium nodes that are connected to a central Selenium hub.

Since Selenium nodes are stateless themselves and the amount of nodes we run is flexible, depending on our testing workloads, this is a perfect candidate application to be deployed on a Kubernetes cluster.

In the next section, we'll deploy a grid consisting of 5 application containers:

• 1 central Selenium hub that will be the remote endpoint to which our tests will connect.
• 2 Selenium nodes running Firefox.
• 2 Selenium nodes running Chrome.

Deployment strategy

To automatically manage replication and self-healing, we'll create a Kubernetes replication controller for each type of application container we listed above.

To provide developers who are running tests with a stable Selenium hub endpoint, we'll create a Kubernetes service connected to the hub replication controller.

Selenium hub

Replication controller

# selenium-hub-rc.yaml
apiVersion: v1
kind: ReplicationController
metadata:
  name: selenium-hub
spec:
  replicas: 1
  selector:
    name: selenium-hub
  template:
    metadata:
      labels:
        name: selenium-hub
    spec:
      containers:
        - name: selenium-hub
          image: selenium/hub
          ports:
            - containerPort: 4444

Deployment:

[root@kube-master ~]# kubectl create -f selenium-hub-rc.yaml
replicationcontrollers/selenium-hub
[root@kube-master ~]# kubectl get rc
CONTROLLER     CONTAINER(S)   IMAGE(S)       SELECTOR            REPLICAS
selenium-hub   selenium-hub   selenium/hub   name=selenium-hub   1
[root@kube-master ~]# kubectl get pods
NAME                 READY     STATUS    RESTARTS   AGE
selenium-hub-pilc8   1/1       Running   0          50s
[root@kube-master ~]# kubectl describe pod selenium-hub-pilc8
Name:               selenium-hub-pilc8
Namespace:          default
Image(s):           selenium/hub
Node:               kube-node2/45.63.16.92
Labels:             name=selenium-hub
Status:             Running
Reason:             
Message:            
IP:             10.20.101.2
Replication Controllers:    selenium-hub (1/1 replicas created)
Containers:
  selenium-hub:
    Image:      selenium/hub
    State:      Running
      Started:      Sat, 24 Oct 2015 16:01:39 +0000
    Ready:      True
    Restart Count:  0
Conditions:
  Type      Status
  Ready     True
Events:
  FirstSeen             LastSeen            Count   From            SubobjectPath               Reason      Message
  Sat, 24 Oct 2015 16:01:02 +0000   Sat, 24 Oct 2015 16:01:02 +0000 1   {scheduler }                            scheduled   Successfully assigned selenium-hub-pilc8 to kube-node2
  Sat, 24 Oct 2015 16:01:05 +0000   Sat, 24 Oct 2015 16:01:05 +0000 1   {kubelet kube-node2}    implicitly required container POD   pulled      Successfully pulled Pod container image "gcr.io/google_containers/pause:0.8.0"
  Sat, 24 Oct 2015 16:01:05 +0000   Sat, 24 Oct 2015 16:01:05 +0000 1   {kubelet kube-node2}    implicitly required container POD   created     Created with docker id 6de00106b19c
  Sat, 24 Oct 2015 16:01:05 +0000   Sat, 24 Oct 2015 16:01:05 +0000 1   {kubelet kube-node2}    implicitly required container POD   started     Started with docker id 6de00106b19c
  Sat, 24 Oct 2015 16:01:39 +0000   Sat, 24 Oct 2015 16:01:39 +0000 1   {kubelet kube-node2}    spec.containers     pulled      Successfully pulled image "selenium/hub"
  Sat, 24 Oct 2015 16:01:39 +0000   Sat, 24 Oct 2015 16:01:39 +0000 1   {kubelet kube-node2}    spec.containers     created     Created with docker id 7583cc09268c
  Sat, 24 Oct 2015 16:01:39 +0000   Sat, 24 Oct 2015 16:01:39 +0000 1   {kubelet kube-node2}    spec.containers     started     Started with docker id 7583cc09268c

Here we can see that Kubernetes has placed my selenium-hub container on kube-node2.

Service

# selenium-hub-service.yaml
apiVersion: v1
kind: Service
metadata:
  name: selenium-hub
spec:
  type: NodePort
  ports:
  - port: 4444
    protocol: TCP
    nodePort: 30000
  selector:
    name: selenium-hub

Deployment:

[root@kube-master ~]# kubectl create -f selenium-hub-service.yaml
You have exposed your service on an external port on all nodes in your
cluster.  If you want to expose this service to the external internet, you may
need to set up firewall rules for the service port(s) (tcp:30000) to serve traffic.

See http://releases.k8s.io/HEAD/docs/user-guide/services-firewalls.md for more details.
services/selenium-hub
[root@kube-master ~]# kubectl get services
NAME           LABELS                                    SELECTOR            IP(S)           PORT(S)
kubernetes     component=apiserver,provider=kubernetes   <none>              10.254.0.1      443/TCP
selenium-hub   <none>                                    name=selenium-hub   10.254.124.73   4444/TCP

After deploying the service, it'll be reachable from:

• Any Kubernetes node, via the virtual IP 10.254.124.73 and the port 4444.
• External networks, via any Kubernetes nodes' public IPs, on the port 30000.

(using the public IP of another Kubernetes node)

Selenium nodes

Firefox node replication controller:

# selenium-node-firefox-rc.yaml
apiVersion: v1
kind: ReplicationController
metadata:
  name: selenium-node-firefox
spec:
  replicas: 2
  selector:
    name: selenium-node-firefox
  template:
    metadata:
      labels:
        name: selenium-node-firefox
    spec:
      containers:
        - name: selenium-node-firefox
          image: selenium/node-firefox
          ports:
            - containerPort: 5900
          env:
            - name: HUB_PORT_4444_TCP_ADDR
              value: "replace_with_service_ip"
            - name: HUB_PORT_4444_TCP_PORT
              value: "4444"

Deployment:

Replace replace_with_service_ip in selenium-node-firefox-rc.yaml with the actual Selenium hub service IP, in this case 10.254.124.73.

[root@kube-master ~]# kubectl create -f selenium-node-firefox-rc.yaml
replicationcontrollers/selenium-node-firefox

[root@kube-master ~]# kubectl get rc
CONTROLLER              CONTAINER(S)            IMAGE(S)                SELECTOR                     REPLICAS
selenium-hub            selenium-hub            selenium/hub            name=selenium-hub            1
selenium-node-firefox   selenium-node-firefox   selenium/node-firefox   name=selenium-node-firefox   2

[root@kube-master ~]# kubectl get pods
NAME                          READY     STATUS    RESTARTS   AGE
selenium-hub-pilc8            1/1       Running   1          1h
selenium-node-firefox-lc6qt   1/1       Running   0          2m
selenium-node-firefox-y9qjp   1/1       Running   0          2m

[root@kube-master ~]# kubectl describe pod selenium-node-firefox-lc6qt
Name:               selenium-node-firefox-lc6qt
Namespace:          default
Image(s):           selenium/node-firefox
Node:               kube-node2/45.63.16.92
Labels:             name=selenium-node-firefox
Status:             Running
Reason:             
Message:            
IP:             10.20.101.3
Replication Controllers:    selenium-node-firefox (2/2 replicas created)
Containers:
  selenium-node-firefox:
    Image:      selenium/node-firefox
    State:      Running
      Started:      Sat, 24 Oct 2015 17:08:37 +0000
    Ready:      True
    Restart Count:  0
Conditions:
  Type      Status
  Ready     True
Events:
  FirstSeen             LastSeen            Count   From            SubobjectPath               Reason      Message
  Sat, 24 Oct 2015 17:08:13 +0000   Sat, 24 Oct 2015 17:08:13 +0000 1   {scheduler }                            scheduled   Successfully assigned selenium-node-firefox-lc6qt to kube-node2
  Sat, 24 Oct 2015 17:08:13 +0000   Sat, 24 Oct 2015 17:08:13 +0000 1   {kubelet kube-node2}    implicitly required container POD   pulled      Pod container image "gcr.io/google_containers/pause:0.8.0" already present on machine
  Sat, 24 Oct 2015 17:08:13 +0000   Sat, 24 Oct 2015 17:08:13 +0000 1   {kubelet kube-node2}    implicitly required container POD   created     Created with docker id cdcb027c6548
  Sat, 24 Oct 2015 17:08:13 +0000   Sat, 24 Oct 2015 17:08:13 +0000 1   {kubelet kube-node2}    implicitly required container POD   started     Started with docker id cdcb027c6548
  Sat, 24 Oct 2015 17:08:36 +0000   Sat, 24 Oct 2015 17:08:36 +0000 1   {kubelet kube-node2}    spec.containers pulled      Successfully pulled image "selenium/node-firefox"
  Sat, 24 Oct 2015 17:08:36 +0000   Sat, 24 Oct 2015 17:08:36 +0000 1   {kubelet kube-node2}    spec.containers created     Created with docker id 8931b7f7a818
  Sat, 24 Oct 2015 17:08:37 +0000   Sat, 24 Oct 2015 17:08:37 +0000 1   {kubelet kube-node2}    spec.containers started     Started with docker id 8931b7f7a818

[root@kube-master ~]# kubectl describe pod selenium-node-firefox-y9qjp
Name:               selenium-node-firefox-y9qjp
Namespace:          default
Image(s):           selenium/node-firefox
Node:               kube-node1/185.92.221.67
Labels:             name=selenium-node-firefox
Status:             Running
Reason:             
Message:            
IP:             10.20.92.3
Replication Controllers:    selenium-node-firefox (2/2 replicas created)
Containers:
  selenium-node-firefox:
    Image:      selenium/node-firefox
    State:      Running
      Started:      Sat, 24 Oct 2015 17:08:13 +0000
    Ready:      True
    Restart Count:  0
Conditions:
  Type      Status
  Ready     True
Events:
  FirstSeen             LastSeen            Count   From            SubobjectPath               Reason      Message
  Sat, 24 Oct 2015 17:08:13 +0000   Sat, 24 Oct 2015 17:08:13 +0000 1   {scheduler }                            scheduled   Successfully assigned selenium-node-firefox-y9qjp to kube-node1
  Sat, 24 Oct 2015 17:08:13 +0000   Sat, 24 Oct 2015 17:08:13 +0000 1   {kubelet kube-node1}    implicitly required container POD   pulled      Pod container image "gcr.io/google_containers/pause:0.8.0" already present on machine
  Sat, 24 Oct 2015 17:08:13 +0000   Sat, 24 Oct 2015 17:08:13 +0000 1   {kubelet kube-node1}    implicitly required container POD   created     Created with docker id ea272dd36bd5
  Sat, 24 Oct 2015 17:08:13 +0000   Sat, 24 Oct 2015 17:08:13 +0000 1   {kubelet kube-node1}    implicitly required container POD   started     Started with docker id ea272dd36bd5
  Sat, 24 Oct 2015 17:08:13 +0000   Sat, 24 Oct 2015 17:08:13 +0000 1   {kubelet kube-node1}    spec.containers created     Created with docker id 6edbd6b9861d
  Sat, 24 Oct 2015 17:08:13 +0000   Sat, 24 Oct 2015 17:08:13 +0000 1   {kubelet kube-node1}    spec.containers started     Started with docker id 6edbd6b9861d

As we can see, Kubernetes has created 2 replicas of selenium-firefox-node and it has distributed them across the cluster. Pod selenium-node-firefox-lc6qt is on kube-node2, while pod selenium-node-firefox-y9qjp is on kube-node1.

We repeat the same process for our Selenium Chrome nodes.

Chrome node replication controller:

# selenium-node-chrome-rc.yaml
apiVersion: v1
kind: ReplicationController
metadata:
  name: selenium-node-chrome
  labels:
    app: selenium-node-chrome
spec:
  replicas: 2
  selector:
    app: selenium-node-chrome
  template:
    metadata:
      labels:
        app: selenium-node-chrome
    spec:
      containers:
      - name: selenium-node-chrome
        image: selenium/node-chrome
        ports:
          - containerPort: 5900
        env:
          - name: HUB_PORT_4444_TCP_ADDR
            value: "replace_with_service_ip"
          - name: HUB_PORT_4444_TCP_PORT
            value: "4444"

Deployment:

[root@kube-master ~]# kubectl create -f selenium-node-chrome-rc.yaml
replicationcontrollers/selenium-node-chrome
[root@kube-master ~]# kubectl get rc
CONTROLLER              CONTAINER(S)            IMAGE(S)                SELECTOR                     REPLICAS
selenium-hub            selenium-hub            selenium/hub            name=selenium-hub            1
selenium-node-chrome    selenium-node-chrome    selenium/node-chrome    app=selenium-node-chrome     2
selenium-node-firefox   selenium-node-firefox   selenium/node-firefox   name=selenium-node-firefox   2
[root@kube-master ~]# kubectl get pods
NAME                          READY     STATUS    RESTARTS   AGE
selenium-hub-pilc8            1/1       Running   1          1h
selenium-node-chrome-9u1ld    1/1       Running   0          1m
selenium-node-chrome-mgi52    1/1       Running   0          1m
selenium-node-firefox-lc6qt   1/1       Running   0          11m
selenium-node-firefox-y9qjp   1/1       Running   0          11m

Wrapping up

V tejto príručke sme nastavili malý klaster Kubernetes s 3 servermi (1 hlavný radič + 2 pracovníci).

Pomocou modulov, RC a služby sme úspešne nasadili Selenium Grid pozostávajúci z centrálneho rozbočovača a 4 uzlov, čo umožňuje vývojárom spustiť v klastri 4 súbežné testy Selenium naraz.

Kubernetes automaticky naplánoval kontajnery v rámci celého klastra.

Samoliečenie

Kubernetes automaticky preplánuje moduly na zdravé servery, ak jeden alebo viac našich serverov vypadne. V mojom príklade je na kube-node2 momentálne spustený modul Selenium hub a 1 modul uzla Selenium Firefox.

[root@kube-node2 ~]# docker ps
CONTAINER ID        IMAGE                                  COMMAND                CREATED             STATUS              PORTS               NAMES
5617399f146c        selenium/node-firefox                  "/opt/bin/entry_poin   5 minutes ago       Up 5 minutes                            k8s_selenium-node-firefox.46e635d8_selenium-node-firefox-zmj1r_default_31c89517-7a75-11e5-8648-5600001611e0_baae8e00   
185230a3b431        gcr.io/google_containers/pause:0.8.0   "/pause"               5 minutes ago       Up 5 minutes                            k8s_POD.3805e8b7_selenium-node-firefox-zmj1r_default_31c89517-7a75-11e5-8648-5600001611e0_40f809df                     
fdd5834c249d        selenium/hub                           "/opt/bin/entry_poin   About an hour ago   Up About an hour                        k8s_selenium-hub.cb8bf0ed_selenium-hub-pilc8_default_6c98c1ff-7a68-11e5-8648-5600001611e0_5765e2c9                     
00e4ccb0bda8        gcr.io/google_containers/pause:0.8.0   "/pause"               About an hour ago   Up About an hour                        k8s_POD.3b3ee8b9_selenium-hub-pilc8_default_6c98c1ff-7a68-11e5-8648-5600001611e0_8398ac33  

Zlyhanie servera simulujeme vypnutím kube-node2. Po niekoľkých minútach by ste mali vidieť, že kontajnery, ktoré bežali na kube-node2, boli preplánované na kube-node1, čím sa zabezpečilo minimálne prerušenie služby.

[root@kube-node1 ~]# docker ps
CONTAINER ID        IMAGE                                  COMMAND                CREATED             STATUS              PORTS               NAMES
5bad5f582698        selenium/hub                           "/opt/bin/entry_poin   19 minutes ago      Up 19 minutes                           k8s_selenium-hub.cb8bf0ed_selenium-hub-hycf2_default_fe9057cf-7a76-11e5-8648-5600001611e0_ccaad50a                     
dd1565a94919        selenium/node-firefox                  "/opt/bin/entry_poin   20 minutes ago      Up 20 minutes                           k8s_selenium-node-firefox.46e635d8_selenium-node-firefox-g28z5_default_fe932673-7a76-11e5-8648-5600001611e0_fc79f977   
2be1a316aa47        gcr.io/google_containers/pause:0.8.0   "/pause"               20 minutes ago      Up 20 minutes                           k8s_POD.3805e8b7_selenium-node-firefox-g28z5_default_fe932673-7a76-11e5-8648-5600001611e0_dc204ad2                     
da75a0242a9e        gcr.io/google_containers/pause:0.8.0   "/pause"               20 minutes ago      Up 20 minutes                           k8s_POD.3b3ee8b9_selenium-hub-hycf2_default_fe9057cf-7a76-11e5-8648-5600001611e0_1b10c0e7                              
c611b68330de        selenium/node-firefox                  "/opt/bin/entry_poin   33 minutes ago      Up 33 minutes                           k8s_selenium-node-firefox.46e635d8_selenium-node-firefox-8ylo2_default_31c8a8f3-7a75-11e5-8648-5600001611e0_922af821   
828031da6b3c        gcr.io/google_containers/pause:0.8.0   "/pause"               33 minutes ago      Up 33 minutes                           k8s_POD.3805e8b7_selenium-node-firefox-8ylo2_default_31c8a8f3-7a75-11e5-8648-5600001611e0_289cd555                     
caf4e725512e        selenium/node-chrome                   "/opt/bin/entry_poin   46 minutes ago      Up 46 minutes                           k8s_selenium-node-chrome.362a34ee_selenium-node-chrome-mgi52_default_392a2647-7a73-11e5-8648-5600001611e0_3c6e855a     
409a20770787        selenium/node-chrome                   "/opt/bin/entry_poin   46 minutes ago      Up 46 minutes                           k8s_selenium-node-chrome.362a34ee_selenium-node-chrome-9u1ld_default_392a15a4-7a73-11e5-8648-5600001611e0_ac3f0191     
7e2d942422a5        gcr.io/google_containers/pause:0.8.0   "/pause"               47 minutes ago      Up 47 minutes                           k8s_POD.3805e8b7_selenium-node-chrome-9u1ld_default_392a15a4-7a73-11e5-8648-5600001611e0_f5858b73                      
a3a65ea99a99        gcr.io/google_containers/pause:0.8.0   "/pause"               47 minutes ago      Up 47 minutes                           k8s_POD.3805e8b7_selenium-node-chrome-mgi52_default_392a2647-7a73-11e5-8648-5600001611e0_20a70ab6

Škálovanie vašej Selénovej mriežky

Škálovanie vašej Selenium Grid je s Kubernetes veľmi jednoduché. Predstavte si, že namiesto 2 uzlov Firefoxu by som chcel spustiť 4. Upscaling je možné vykonať jediným príkazom:

[root@kube-master ~]# kubectl scale rc selenium-node-firefox --replicas=4
scaled

[root@kube-master ~]# kubectl get rc
CONTROLLER              CONTAINER(S)            IMAGE(S)                SELECTOR                     REPLICAS
selenium-hub            selenium-hub            selenium/hub            name=selenium-hub            1
selenium-node-chrome    selenium-node-chrome    selenium/node-chrome    app=selenium-node-chrome     2
selenium-node-firefox   selenium-node-firefox   selenium/node-firefox   name=selenium-node-firefox   4

[root@kube-master ~]# kubectl get pods
NAME                          READY     STATUS    RESTARTS   AGE
selenium-hub-pilc8            1/1       Running   1          1h
selenium-node-chrome-9u1ld    1/1       Running   0          14m
selenium-node-chrome-mgi52    1/1       Running   0          14m
selenium-node-firefox-8ylo2   1/1       Running   0          40s
selenium-node-firefox-lc6qt   1/1       Running   0          24m
selenium-node-firefox-y9qjp   1/1       Running   0          24m
selenium-node-firefox-zmj1r   1/1       Running   0          40s