A really simple way to do rapid development with docker/kubernetes.
Prerequisites:
- A kubernetes cluster (tested on minikube)
- Freshpod deployed
- A python3 interpreter locally.
pip install docker-microsync
Lets say you have a development image tagged myimage:latest current deployed and is up to date, this image is running a project thats built from the current directory and this directory is mapped to /opt/src, you would invoke docker-microsync like this:
docker-microsync . /opt/src myimage:latest
And changes in the current directory will be copied to /opt/src in the docker image.
You can tweak the timeout by using the --timeout command line option and you can specify a list of file extensions to pay attention to by supplying a list comma separated to the --file-extensions flag.
Using the "demo" app that is supplied.
➜ demo eval $(minikube docker-env)
➜ demo docker build . -t docker-microsync:latest
Sending build context to Docker daemon 4.608kB
Step 1/2 : from nginx:1.15.7
---> 568c4670fa80
Step 2/2 : COPY message.txt /usr/share/nginx/html
---> 1351305b2ee4
Successfully built 1351305b2ee4
Successfully tagged docker-microsync:latest
➜ demo kubectl apply -f yaml/*
deployment.apps/nginx-deployment created
➜ demo kubectl expose deployment nginx-deployment --type=LoadBalancer --name=my-service
service/my-service exposed
➜ demo kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 3m
my-service LoadBalancer 10.100.46.146 <pending> 80:31010/TCP 39s
➜ demo minikube ip
192.168.99.100
➜ demo kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 3m
my-service LoadBalancer 10.100.46.146 <pending> 80:31010/TCP 39s
➜ demo curl 192.168.99.100:31010/message.txt
My message # this is the old message
➜ demo pip install docker-microsync # install docker-microsync
➜ demo docker-microsync . /usr/share/nginx/html docker-microsync:latest
Starting to watch for changed files - 0.5 second timeout.
<switch terminal>
➜ demo echo "My lovely new message" > message.txt
< 5 second wait>
➜ demo curl 192.168.99.100:31010/message.txt
My lovely new message
This tool runs on your local development environment and watches the filesystem for changes. After a timeout period, (default 0.5 seconds) It proceeds to build a docker image, which is based on the latest image for your app. This is a complementary to "freshpod" (https://github.com/GoogleCloudPlatform/freshpod) which will re-deploy running pods that are using the image.
I seen the need for a tool that is uncomplicated. Similar tools require creating VPNs etc. which seems complicated. This requires no special networking etc and freshpod comes out of the box with tools like Minikube.
This tool is known to work on Linux and OSX, in theory it can work on windows but this is untested.
It's quite simple. It uses the excellent watchdog library to watch for filesystem changes in a platform independent way. It then keeps an in-memory docker context and adds any changed files to that context. After a specific period of timeout it sends the context along with a Dockerfile and this adds the required layers to the current running image and tags it accordingly.
Freshpod then redeploys any running pods using the image as it sees that a new image has been tagged.
It depends how long your app takes to initialise. The new image will be built in 1-3 seconds and it usually takes another 5 seconds for kubernetes to redeploy an application.
It runs in memory so big files that are changing will be slow and memory hungry. Moving files doesnt delete the old file (PRs welcome)
File attributes(like executable) arent copied.