4. Ping desde entre dos containers de un mismo POD
En este laboratorio se mostrara que se pueden alcanzar containers en un mismo pod. En este laboratorio se usara la imagen santos/flask-hello-world de laboratorios atras, y tambien usara una configuracion sencilla nginx.
-
Crear el archivo de configuracion de nginx nginx-vol/default.conf el el directorio que vamos a enlazar con un volumen al container.
server {
listen 80;
listen [::]:80;
server_name localhost;
location /flask_app {
proxy_pass http://127.0.0.1:5000/;
}
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root /usr/share/nginx/html;
}
}
ngnx crea un proxy_pass de localhost/flask_app a localhost:5000, este es el puerto de escucha de la aplicacion de flask que se usara en este laboratorio.
-
Recordar que kubernetes no tiene comunicacion directa con nuestra maquina, tiene comunicacion directa con la maquina virtual que monta minikube, como se quiere montar un directorio de nuestra maquina como un volumen, primero se debe montar en la maquina virtual de minikube.
minikube mount nginx-vol/:/mynginx/
# 📁 Mounting host path myvol/ into VM as /mynginx/ ...
# ▪ Mount type:
# ▪ User ID: docker
# ▪ Group ID: docker
# ▪ Version: 9p2000.L
# ▪ Message Size: 262144
# ▪ Options: map[]
# ▪ Bind Address: 192.168.39.1:40637
# 🚀 Userspace file server: ufs starting
# ✅ Successfully mounted myvol/ to /mynginx/
# 📌 NOTE: This process must stay alive for the mount to be accessible ...
/mynginx en la VM.
-
Yaml de creacion del Pod
# save as ./spec.yaml
apiVersion: v1
kind: Pod
metadata:
name: two-containers-ping
spec:
restartPolicy: Never
volumes:
- name: shared-data
hostPath:
path: /mynginx/
type: Directory
containers:
- name: nginx-container
image: nginx
volumeMounts:
- name: shared-data
mountPath: /etc/nginx/conf.d
- name: flask-test-app
image: santos/flask-hello-world
imagePullPolicy: Never
# ports:
# - containerPort: 5000
-
Crear el pod usando kubectl
$ kubectl apply -f ./spec.yaml
# pod/two-containers-ping created
-
Revisar el estado del nuevo pod
kubectl get pod two-containers-ping --output=yaml
| output kubectl get pod |
|---|
| apiVersion: v1
kind: Pod
metadata:
annotations:
kubectl.kubernetes.io/last-applied-configuration: |
{"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"name":"two-containers-ping","namespace":"default"},"spec":{"containers":[{"image":"nginx","name":"nginx-container","volumeMounts":[{"mountPath":"/etc/nginx/conf.d","name":"shared-data"}]},{"image":"santos/flask-hello-world","imagePullPolicy":"Never","name":"flask-test-app"}],"restartPolicy":"Never","volumes":[{"hostPath":{"path":"/mynginx/","type":"Directory"},"name":"shared-data"}]}}
creationTimestamp: "2022-06-17T14:38:29Z"
name: two-containers-ping
namespace: default
resourceVersion: "52327"
uid: 6dbb4caa-87b3-498a-8c4a-a7aeb76842af
spec:
containers:
- image: nginx
imagePullPolicy: Always
name: nginx-container
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /etc/nginx/conf.d
name: shared-data
- mountPath: /var/run/secrets/kubernetes.io/serviceaccount
name: kube-api-access-8vpjq
readOnly: true
- image: santos/flask-hello-world
imagePullPolicy: Never
name: flask-test-app
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /var/run/secrets/kubernetes.io/serviceaccount
name: kube-api-access-8vpjq
readOnly: true
dnsPolicy: ClusterFirst
enableServiceLinks: true
nodeName: minikube
preemptionPolicy: PreemptLowerPriority
priority: 0
restartPolicy: Never
schedulerName: default-scheduler
securityContext: {}
serviceAccount: default
serviceAccountName: default
terminationGracePeriodSeconds: 30
tolerations:
- effect: NoExecute
key: node.kubernetes.io/not-ready
operator: Exists
tolerationSeconds: 300
- effect: NoExecute
key: node.kubernetes.io/unreachable
operator: Exists
tolerationSeconds: 300
volumes:
- hostPath:
path: /mynginx/
type: Directory
name: shared-data
- name: kube-api-access-8vpjq
projected:
defaultMode: 420
sources:
- serviceAccountToken:
expirationSeconds: 3607
path: token
- configMap:
items:
- key: ca.crt
path: ca.crt
name: kube-root-ca.crt
- downwardAPI:
items:
- fieldRef:
apiVersion: v1
fieldPath: metadata.namespace
path: namespace
status:
conditions:
- lastProbeTime: null
lastTransitionTime: "2022-06-17T14:38:29Z"
status: "True"
type: Initialized
- lastProbeTime: null
lastTransitionTime: "2022-06-17T14:38:31Z"
status: "True"
type: Ready
- lastProbeTime: null
lastTransitionTime: "2022-06-17T14:38:31Z"
status: "True"
type: ContainersReady
- lastProbeTime: null
lastTransitionTime: "2022-06-17T14:38:29Z"
status: "True"
type: PodScheduled
containerStatuses:
- containerID: docker://0b53b339b7c06b7475739cbde17795ce24f71bc8d7d2e41da07d220162b6475d
image: santos/flask-hello-world:latest
imageID: docker://sha256:105bc09b0a7e87f7344040742f1fa011e00e7a36bac1f1cabc8a5303ceb1db30
lastState: {}
name: flask-test-app
ready: true
restartCount: 0
started: true
state:
running:
startedAt: "2022-06-17T14:38:31Z"
- containerID: docker://8175ac7cd60060159888a723b7a36a93486a38e9b6cd4379d7e86fbb4647375d
image: nginx:latest
imageID: docker-pullable://nginx@sha256:2bcabc23b45489fb0885d69a06ba1d648aeda973fae7bb981bafbb884165e514
lastState: {}
name: nginx-container
ready: true
restartCount: 0
started: true
state:
running:
startedAt: "2022-06-17T14:38:31Z"
hostIP: 192.168.39.232
phase: Running
podIP: 172.17.0.16
podIPs:
- ip: 172.17.0.16
qosClass: BestEffort
startTime: "2022-06-17T14:38:29Z"
|
Ready
-
Entrar al container nginx-container
$ kubectl exec -it two-containers-ping -c nginx-container -- /bin/bash
# root@two-containers-ping:/
-
Hacer un get a http://localhost/flask_app/
$root@two-containers-ping: curl http://localhost/flask_app
# hello word from flask!
Conclusion
Containers within a pod share an IP address and port space, and can find each other via localhost s