ZZX-docker-ls-1.sh

I have three file in my directory named 'flask' :
➜  flask

── app.py
── Dockerfile
── requirement.txt

#----------------------------------------------

$ cat app.py

from flask import Flask
#from flask import render_template, request
import json

app = Flask(__name__)

@app.route("/")
def hello():
    return "Welcome to Python Flask!\n"

if __name__ == "__main__":
    app.run(host='0.0.0.0', port='5009')

#----------------------------------------------

$ cat requirement.txt

Flask==0.10.1

#----------------------------------------------

$ cat Dockerfile

FROM frolvlad/alpine-python2

RUN mkdir /etc/flask

ADD app.py /etc/flask/app.py
ADD requirement.txt /etc/flask/requirement.txt


CMD ["python", "/etc/flask/app.py"]

#----------------------------------------------

> Lets build our docker image with name **flask-v1**


➜  docker build -t flask-v1 .

Sending build context to Docker daemon 4.096 kB

Step 1/5 : FROM frolvlad/alpine-python2
latest: Pulling from frolvlad/alpine-python2
627beaf3eaaf: Pull complete
79d39e719c2e: Pull complete
Digest: sha256:47e3f85dadf401d51c6f74a18d4f693c2157692292e6dae0a078f37499a183ee
Status: Downloaded newer image for frolvlad/alpine-python2:latest
 ---> 603e17608203

Step 2/5 : RUN mkdir /etc/flask
 ---> Running in 0d97b7a8986b
 ---> 9b2a858914e2
Removing intermediate container 0d97b7a8986b

Step 3/5 : ADD app.py /etc/flask/app.py
 ---> 1a4938be7722
Removing intermediate container f4d11b837e26

Step 4/5 : ADD requirement.txt /etc/flask/requirement.txt
 ---> 5d058851dd81
Removing intermediate container 08eef72a4051

Step 5/5 : CMD python /etc/flask/app.py
 ---> Running in 96490917e533
 ---> a081e6cbcf3c
Removing intermediate container 96490917e533

Successfully built a081e6cbcf3c

#----------------------------------------------

> Now, we have made some modification in app.py

$ cat app.py

from flask import Flask
#from flask import render_template, request
import json

app = Flask(__name__)

@app.route("/")
def hello():
    return "Welcome to Python Flask!\n"

#Added utility
def utility():
    return "something"

if __name__ == "__main__":
    app.run(host='0.0.0.0', port='5009')

#----------------------------------------------

> Lets build our docker image with name **flask-v2**


➜  docker build -t flask-v2 .

Sending build context to Docker daemon 4.096 kB

Step 1/5 : FROM frolvlad/alpine-python2
 ---> 603e17608203

Step 2/5 : RUN mkdir /etc/flask
 ---> Using cache
 ---> 9b2a858914e2

Step 3/5 : ADD app.py /etc/flask/app.py
 ---> a7565514aab3
Removing intermediate container 360eb266a458

Step 4/5 : ADD requirement.txt /etc/flask/requirement.txt
 ---> 8441bca383f0
Removing intermediate container 15ebbb15d67d

Step 5/5 : CMD python /etc/flask/app.py
 ---> Running in 73e4bbcbe512
 ---> 0f4a5754f0d0
Removing intermediate container 73e4bbcbe512

Successfully built 0f4a5754f0d0


> You will see only step-2 was taken from cache, rest of the instructions \
ran again because change has been detected by Docker on \
step-3 command ie, ADD app.py , so all subsequent commands \
ran again to build layer on top of previous layer.

#----------------------------------------------

> Now we have made changes in Dockerfile, some reorder of commands.


$ cat Dockerfile

FROM frolvlad/alpine-python2

RUN mkdir /etc/flask

# add requirement file first, then commands which contains some changes.
ADD requirement.txt /etc/flask/requirement.txt
ADD app.py /etc/flask/app.py

CMD ["python", "/etc/flask/app.py"]

#----------------------------------------------

> Lets build our docker image with name flask-v3 and lets see build console.


➜  flask docker build -t flask-v3 .

Sending build context to Docker daemon 4.096 kB

Step 1/5 : FROM frolvlad/alpine-python2
 ---> 603e17608203

Step 2/5 : RUN mkdir /etc/flask
 ---> Using cache
 ---> 9b2a858914e2

Step 3/5 : ADD requirement.txt /etc/flask/requirement.txt
 ---> Using cache
 ---> db8fc95cebff

Step 4/5 : ADD app.py /etc/flask/app.py
 ---> 9fb8351616e1
Removing intermediate container 4e98534d5339

Step 5/5 : CMD python /etc/flask/app.py
 ---> Running in 139f8c4282d8
 ---> e3fae9852d94
Removing intermediate container 139f8c4282d8

Successfully built e3fae9852d94


> Now, you can see only step-2,3 was taken from cache, step-4 command ie, ADD app.py \
build new layer because of change detected in app.py file, and this build \
saved little bit of our time. This is really important in building big Docker images \
where we have bigger chain of command to build an app.

I guess, there is one typo in line 164; It should be docker build -t flask-v3 .