Until now I developed Python applications locally using docker and docker-compose. Now I'd like to change my development workflow to use skaffold with docker as builder, with kubectl as deployer and with minikube for managing the local kubernetes cluster.
Let's say I've this docker based hello world for FastAPI:
project structure:
app/app.py
Dockerfile
app/app.py
from typing import Optional
from fastapi import FastAPI
app = FastAPI()
@app.get("/")
def read_root():
return {"Hello": "World"}
@app.get("/items/{item_id}")
def read_item(item_id: int, q: Optional[str] = None):
return {"item_id": item_id, "q": q}
Dockerfile:
FROM tiangolo/uvicorn-gunicorn-fastapi:python3.7
COPY ./app /app
If I run docker build -t hello-fastapi . and docker run -p 80:80 hello-fastapi I can access the service via 0.0.0.0 or localhost. I skip the docker-compose things here cause it does not matter w.r.t. the skaffold setup.
To use skaffold I have the exact same project structure and content but I added the skaffold + kubectl specific things (skaffold.yaml, deployment.yaml):
project structure:
app/app.py
k8s/deployment.yaml
Dockerfile
skaffold.yaml
k8s/deployment.yaml
apiVersion: v1
kind: Service
metadata:
name: fastapi-service
labels:
app: fastapi-service
spec:
clusterIP: None
ports:
- port: 80
name: fastapi-service
selector:
app: fastapi-service
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: fastapi-service
labels:
app: fastapi-service
spec:
replicas: 1
selector:
matchLabels:
app: fastapi-service
template:
metadata:
labels:
app: fastapi-service
spec:
containers:
- name: fastapi-service
image: fastapi-service
ports:
- containerPort: 80
skaffold.yaml
apiVersion: skaffold/v2beta10
kind: Config
build:
artifacts:
- image: fastapi-image
deploy:
kubectl:
manifests:
- k8s/*
If I run skaffold dev everything seems to be fine:
Listing files to watch...
- fastapi-service
Generating tags...
- fastapi-service -> fastapi-service:latest
Some taggers failed. Rerun with -vdebug for errors.
Checking cache...
- fastapi-service: Found Locally
Tags used in deployment:
- fastapi-service -> fastapi-service:17659a877904d862184d7cc5966596d46b0765f1995f7abc958db4b3f98b8a35
Starting deploy...
- service/fastapi-service created
- deployment.apps/fastapi-service created
Waiting for deployments to stabilize...
- deployment/fastapi-service is ready.
Deployments stabilized in 2.165700782s
Press Ctrl+C to exit
Watching for changes...
[fastapi-service] Checking for script in /app/prestart.sh
[fastapi-service] Running script /app/prestart.sh
[fastapi-service] Running inside /app/prestart.sh, you could add migrations to this file, e.g.:
[fastapi-service]
[fastapi-service] #! /usr/bin/env bash
[fastapi-service]
[fastapi-service] # Let the DB start
[fastapi-service] sleep 10;
[fastapi-service] # Run migrations
[fastapi-service] alembic upgrade head
[fastapi-service]
[fastapi-service] [2020-12-15 19:02:57 +0000] [1] [INFO] Starting gunicorn 20.0.4
[fastapi-service] [2020-12-15 19:02:57 +0000] [1] [INFO] Listening at: http://0.0.0.0:80 (1)
[fastapi-service] [2020-12-15 19:02:57 +0000] [1] [INFO] Using worker: uvicorn.workers.UvicornWorker
[fastapi-service] [2020-12-15 19:02:57 +0000] [8] [INFO] Booting worker with pid: 8
...
However I cannot access the service via my web browser. How can I access the service from my local machine via e.g. the web browser?
EDIT:
According to minikube service list the service fastapi-service exists:
|----------------------|---------------------------|--------------|-----|
| NAMESPACE | NAME | TARGET PORT | URL |
|----------------------|---------------------------|--------------|-----|
| default | fastapi-service | No node port |
| default | kubernetes | No node port |
| kube-system | kube-dns | No node port |
| kubernetes-dashboard | dashboard-metrics-scraper | No node port |
| kubernetes-dashboard | kubernetes-dashboard | No node port |
|----------------------|---------------------------|--------------|-----|
But I cannot access it via curl $(minikube service fastapi-service --url):
curl: (3) Failed to convert to ACE; string contains a disallowed character
curl: (6) Could not resolve host: service
curl: (6) Could not resolve host: default
curl: (6) Could not resolve host: has
curl: (6) Could not resolve host: no
curl: (6) Could not resolve host: node
curl: (6) Could not resolve host: port
Probably this is related to Unable to get ClusterIP service url from minikube . If I change deployment.yaml to
apiVersion: v1
kind: Service
metadata:
name: fastapi-service
labels:
app: fastapi-service
spec:
type: NodePort
ports:
- targetPort: 80
port: 80
selector:
app: fastapi-service
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: fastapi-service
labels:
app: fastapi-service
spec:
replicas: 1
selector:
matchLabels:
app: fastapi-service
template:
metadata:
labels:
app: fastapi-service
spec:
containers:
- name: fastapi-service
image: fastapi-service
ports:
- containerPort: 80
accessing the service via curl $(minikube service fastapi-service --url) is successful:
{"message":"Hello world! From FastAPI running on Uvicorn with Gunicorn. Using Python 3.7"}
However I cannot access the service via the web browser.
Use Skaffold
--port-forwardto enable automatic port fowarding of services and user-defined port-forwards.Skaffold normally tries select a local port that is close to the remote port where possible. But since port 80 is a protected port, Skaffold will choose a different local port. You can explicitly configure a port forward your
skaffold.yamlto specify the local port. Using user-defined port-forwards can help avoid potential confusion should you add other services later on.Instead of running
skaffold devrun withskaffold dev --port-forward. Now you can access the service vialocalhost:9000.You can also use
kubectl port-forwardto manually forward ports; Skaffold uses this same functionality to implement its port forwarding.