First of all, I am sorry that the grammar may be incorrect because I used Google Translate.
1.Deploy pods and services in a Kubernetes environment.
apiVersion: v1
kind: Pod
metadata:
name: testml
labels:
app: testml-pod
spec:
containers:
- name: testmlserver
image: test_ml_server:2.8
ports:
- containerPort: 8080
- containerPort: 5100
env:
- name: POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
volumeMounts:
- name: testserver-api
mountPath: /app/test/api
- name: testmlserver-csv
mountPath: /app/test/csv
- name: testmldb
image: test_ml_db:1.4
ports:
- containerPort: 1433
env:
- name: POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
volumeMounts:
- name: estmldb
mountPath: /var/opt/mssql/data
volumes:
- name: testmlserver-api
hostPath:
path: /usr/testhostpath/testmlserver/api
- name: testmlserver-csv
hostPath:
path: /usr/testmlhostpath/testserver/csv
- name: testmldb
hostPath:
path: /usr/testmlhostpath/testmldb
After the server container is deployed, run the python server in the container.
apiVersion: v1
kind: Service
metadata:
name: testml-service
spec:
type: NodePort
ports:
- name: testml-server-port
port: 8080
targetPort: 8080
protocol: TCP
nodePort: 30080
- name: testml-python-port
port: 5100
targetPort: 5100
protocol: TCP
nodePort: 30051
- name: testml-db-port
port: 1433
targetPort: 1433
protocol: TCP
nodePort: 30014
selector:
app: test-pod
In this way, both pods and services have been deployed.
Connect to the server(tomcat) container and run the python server file.
At this time, the address value used when calling the python server from the web is 'http://testml:5100'
I tried to write it and communicate with it.
However, Cross-Origin Read Blocking (CORB) has occurred
I tried also with'http://localhost:5100' because there is another way to communicate in one container, but Connetc refused.
In the docker-compose environment, I checked that the python server is called when communicating with localhost, but I do not know the cause of the error in the kubernets environment.
Checking various things As a result of checking the port in the server (tomcat) container, it is confirmed that 0.0.0.0 does not apply to only the python port.
How can I call the python server normally in the server container?
In web server(tomcat) connect with the db container by pod name as shown below. POD NAME => testml
<property name="url" value="jdbc:log4jdbc:sqlserver://testml:1433;database=test_ml;autoReconnect=true" />
In the same way, I tried to connect the python server with pod name, but it fails.
<api.host.server=http://testml:5100>
I think you can't connect by pod's name unless you have a headless service defined. You can connect via Pod's IP but that is not a recommended approach since the Pod's IP is dynamic and can change across updates.
However, as you have created a Service object as well, you can use that for communication using it's name as http://testml-service:port.
Further, as the Service object is of type NodePort, you can also connect via the IP of the nodes of the cluster.
Related
I would like to run an application in local cluster for development purposes with kind using docker. Based on the description https://kind.sigs.k8s.io/docs/user/quick-start/ I defined the cluster
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
nodes:
- role: control-plane
- role: worker
extraPortMappings:
- containerPort: 30000
hostPort: 5432
protocol: TCP
and the deployment with container:
containers:
- name: postgres
image: postgres:14.0
ports:
- containerPort: 5432
and the service
apiVersion: v1
kind: Service
metadata:
name: database
spec:
selector:
name: app
type: NodePort
ports:
- name: postgres
port: 5432
targetPort: 5432
nodePort: 30000
which I assumed should allow me to connect with dbeaver from my windows 11 host. This looks to be not working so I would like to ask, how should I configure that to being able to access it from host. What I have already tried is: localhost:30000, 127.0.0.1:30000 and also 127.0.0.1:5432, localhost:5432
Also kubectl get services command tells me that:
Type: NodePort, Port(S): 5432:30000/TCP, External-IP: <none>, Cluster-Ip:10.96.211.69, name:something
I found a solution, I turned out to be that I placed extractPortMappings inside worker node instead of control-plane. It's weird that it doesn't fail but after moving this part to correct place it started to work!
So the solution is to change to this:
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
nodes:
- role: control-plane
extraPortMappings:
- containerPort: 30000
hostPort: 5432
protocol: TCP
- role: worker
How to bind multiple ports of a pod to make them visible on the pod IP?
Something analogous to Docker's docker run -p 1234:5555 -p 6789:9999 my_image
The only example of YAML definition I've found in documentation and tutorials uses single port without binding:
spec:
containers:
- name: my_container
image: 'my_image'
ports:
- containerPort: 8080
Could you give a link to the documentation describing the case or a short example of binding multiple ports?
spec.containers.ports is an array, which means you can specify multiple ports like so in your Pod definition:
apiVersion: v1
kind: Pod
metadata:
name: pod-multiple-ports
labels:
app: pod-multiple-ports
spec:
containers:
- name: my-container
image: myexample:latest
ports:
- containerPort: 80
- containerPort: 443
For our CI pipeline I setup a Kubernetes pod config (see below). There is one issue that the php app can't connect to the mysql container because it can't resolve the host "mysql".
Error message:
mysqli_connect(): php_network_getaddresses: getaddrinfo failed: Name or service not known
pod config:
apiVersion: v1
kind: Pod
spec:
containers:
- name: php
image: docker.pkg.github.com/foo-org/bar-php/bar-php:latest
- name: nginx
image: docker.pkg.github.com/foo-org/bar-nginx/bar-nginx:latest
command:
- cat
tty: true
- name: mysql
image: docker.pkg.github.com/foo-org/bar-mysql/bar-mysql:latest
env:
- name: MYSQL_ROOT_PASSWORD
value: bazz
ports:
- containerPort: 3306
readinessProbe:
tcpSocket:
port: 3306
initialDelaySeconds: 5
tty: true
imagePullSecrets:
- name: ci-gh-registry
This runs in GKE but I guess this doesn't make a difference?
Any ideas why and how to fix it?
provide host as 127.0.0.1 or localhost instead of mysql containers in a pod communicate over localhost
First time using Kubernetes. I have an API and a database, and I want the two pods to communicate with each other.
Based on the docs, I should create a service.
I have created a service for each of the two pods, though still not able to connect to the pod using the services IP address.
For example if the MySQL service that is created has an IP address of 11.22.33.44, I can run the following command to try to connect to the pod of that service:
mysql -h11.22.33.44 -uuser -ppassword foo
...and it will hang and eventually the connection will time out.
I create the pod and service like so:
kubectl create -f ./mysql.yaml
mysql.yaml:
apiVersion: v1
kind: Service
metadata:
name: mysql-service
spec:
selector:
app: mysql
ports:
- protocol: TCP
port: 80
targetPort: 3306
---
apiVersion: v1
kind: Pod
metadata:
name: mysql
spec:
containers:
- name: mysql
image: my-custom-mysql-image:latest
ports:
- containerPort: 3306
protocol: TCP
name: mysql
env:
- name: MYSQL_DATABASE
value: "foo"
- name: MYSQL_USER
value: "user"
- name: MYSQL_ROOT_PASSWORD
value: "password"
- name: MYSQL_HOST
value: "127.0.0.1"
your service has a selector defined
selector:
app: mysql
yet your Pod has no labels whatsoever, hence the service can not identify it as its backend and has no endpoint to direct traffic for ClusterIP. You should also stick to standard port number on service as well, so like this :
ports:
- protocol: TCP
port: 3306
targetPort: 3306
I have multiple Kubernetes pods running on a server. One of the pods contains a database application that only accepts connections from a specific subnet (i.e. other Kubernetes pods).
I'm trying to connect to the DB application from the server itself, but the connection is refused because the server's IP is not part of the allowed subnet.
Is there a way to create a simple pod that accepts connections from the server and forwards them to the pod containing the DB app?
Unfortunately, the DB app cannot be reconfigured to accept other connections.
Thank you
The easiest solution is probably to add another container to your pod running socat or something similar and make it listen and connect to your local pod's IP (important: connect to the pod ip, not 127.0.0.1 if your database program is configured to only accept connections from the overlay network).
Then modify the service you have for these pods and add the extra port.
The example below assumes port 2000 is running your program and 2001 will be the port that is forwarded to 2000 inside the pod.
Example (the example is running netcat simulating your database program):
apiVersion: v1
kind: Pod
metadata:
name: database
labels:
app: database
spec:
containers:
- name: alpine
image: alpine
command: ["nc","-v","-n","-l","-p","2000"]
ports:
- containerPort: 2000
- name: socat
image: toughiq/socat
ports:
- containerPort: 2001
env:
- name: LISTEN_PROTO
value: "TCP4"
- name: LISTEN_PORT
value: "2001"
- name: TARGET_PROTO
value: "TCP4"
- name: TARGET_HOST
valueFrom:
fieldRef:
fieldPath: status.podIP
- name: TARGET_PORT
value: "2000"
---
apiVersion: v1
kind: Service
metadata:
name: database
spec:
selector:
app: database
ports:
- name: myport
port: 2000
targetPort: 2000
protocol: TCP
- name: socat
port: 2001
targetPort: 2001
protocol: TCP
externalIPs: [xxxxxx]