We have a web application of flask framework written in python. The application code is dockerized and deployed in kubernetes.
The application writes to a file in static directory once a user hits an API. I am unable to do so. I know that as when I check the list of files in the static location using another API, it does not show that file. Please help.
YAML file is given below:
apiVersion: v1
kind: ReplicationController
metadata:
name: backend-rc
labels:
type: backend-type
spec:
replicas: 32
template:
metadata:
labels:
type: backend-type
spec:
containers:
- name: backend-container
image: gcr.io/syw-msm/ts-m:pc-v1.0
imagePullPolicy: Always
ports:
- containerPort: 8080
protocol: TCP
env:
- name: POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: POD_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespaceThe dockerfile configuration is given below:
FROM ubuntu:latest
RUN apt-get update -y
RUN apt-get install -y python-pip python-dev build-essential python-tk
COPY . /app
WORKDIR /app
RUN chmod -R 777 /app/static
RUN pip install -r requirements.txt
RUN pip install fbprophet
ENTRYPOINT ["/usr/bin/python"]
CMD ["app.py"]You have 32 replicas in your definition. The API call which makes the app to write the file locally hits one pod (replica), and the call that checks for its existence hits a different one. It is expected that the file is not there.
If you scale the number of replicas to 1, it will work. You can try for testing purposes, but this probably isn't what you want.
If you need storage with r/w access from multiple replicas, you will need to rework your app to use some form of shared file system or database.
In case you care about that file this is a good idea anyway - pods are meant to be ephemeral and are not for storing state.