Remove docker container at the end of each test - docker

Question

I'm using docker to scale the test infrastructure / browsers based on the number of requests received in Jenkins.
Created a python script to identify the total number of spec files and browser type, and spin-up those many docker containers. Python code has the logic to determine how many nodes are currently in use, stale and it determines the required number of containers.
I want to programmatically delete the container / de-register the selenium node at the end of each spec file (Docker --rm flag is not helping me).So that the next test will get a clean browser and environment.
The selenium grid runs on the same box where Jenkins is. Once I invoke protractor protractor.conf.js (Step 3), selenium grid will start distributing the tests to the containers created in Step 1.
When I say '--rm' is not helping, I mean the after step3 the communication is mainly between selenium hub and the nodes. I'm finding it difficult to determine which node / container was used by the selenium grid to execute the test and remove the container even before the grid sends another test to the container.
-- Jenkins Build Stage --
Shell:
# Step 1
python ./create_test_machine.py ${no_of_containers} # This will spin-up selenium nodes
# Step 2
npm install # install node modules
# Step 3
protractor protractor.conf.js # Run the protractor tests
--Python code to spin up containers - create_test_machine.py--
Python Script:
import sys
import docker
import docker.utils
import requests
import json
import time
c = docker.Client(base_url='unix://var/run/docker.sock', version='1.23')
my_envs = {'HUB_PORT_4444_TCP_ADDR' :'172.17.0.1', 'HUB_PORT_4444_TCP_PORT' : 4444}
def check_available_machines(no_of_machines):
t = c.containers()
noof_running_containers = len(t)
if noof_running_containers == 0:
print("0 containers running. Creating " + str(no_of_machines) + "new containers...")
spinup_test_machines(no_of_machines)
else:
out_of_stock = 0
for obj_container in t:
print(obj_container)
container_ip_addr = obj_container['NetworkSettings']['Networks']['bridge']['IPAddress']
container_state = obj_container['State']
res = requests.get('http://' + container_ip_addr + ':5555/wd/hub/sessions')
obj = json.loads(res.content)
node_inuse = len(obj['value'])
if node_inuse != 0:
noof_running_containers -= 1
if noof_running_containers < no_of_machines:
spinup_test_machines(no_of_machines - noof_running_containers)
return
def spinup_test_machines(no_of_machines):
'''
Parameter : Number of test nodes to spin up
'''
print("Creating " + str(no_of_machines) + " new containers...")
# my_envs = docker.utils.parse_env_file('docker.env')
for i in range(0,no_of_machines):
new_container = c.create_container(image='selenium/node-chrome', environment=my_envs)
response = c.start(container=new_container.get('Id'))
print(new_container, response)
return
if len(sys.argv) - 1 == 1:
no_of_machines = int(sys.argv[1]) + 2
check_available_machines(no_of_machines)
time.sleep(30)
else:
print("Invalid number of parameters")

Answer 1

Here the difference can be seen clearly when docker run with -d and --rm
Using -doption
C:\Users\apps>docker run -d --name testso alpine /bin/echo 'Hello World'
5d447b558ae6bf58ff6a2147da8bdf25b526bd1c9f39117498fa017f8f71978b
Check the logs
C:\Users\apps>docker logs testso
'Hello World'
Check the last run containers
C:\Users\apps>docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
5d447b558ae6 alpine "/bin/echo 'Hello Wor" 35 hours ago Exited (0) 11 seconds ago testso
Finally user have to remove it explicity
C:\Users\apps>docker rm -f testso
testso
Using --rm, the container is vanished including its logs as soon as the process that is
run inside the container is completed. No trace of container any more.
C:\Users\apps>docker run --rm --name testso alpine /bin/echo 'Hello World'
'Hello World'
C:\Users\apps>docker logs testso
Error: No such container: testso
C:\Users\apps>docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
I believe that it is clear, how to run the container and leaving no trace after process is finished inside of container.

Answer 2

so to start a container in detached mode, you use -d=true or just -d option. By design, containers started in detached mode exit when the root process used to run the container exits. A container in detached mode cannot be automatically removed when it stops, this means you cannot use the --rm option with -d option.
look at this
https://docs.docker.com/engine/reference/run/

Answer 3

You can use nose test. For every "def test_xxx()", it will call the setup and teardown functions with #with_setup decrator. Below is an example:
from nose.tools import *
c = docker.Client(base_url='unix://var/run/docker.sock', version='1.23')
my_envs = {'HUB_PORT_4444_TCP_ADDR' :'172.17.0.1', 'HUB_PORT_4444_TCP_PORT' : 4444}
my_containers = {}
def setup_docker():
""" Setup Test Environment,
create/start your docker container(s), populate the my_containers dict.
"""
def tear_down_docker():
"""Tear down test environment.
"""
for container in my_containers.itervalues():
try:
c.stop(container=container.get('Id'))
c.remove_container(container=container.get('Id'))
except Exception as e:
print e
#with_setup(setup=setup_docker, teardown=tear_down_docker)
def test_xxx():
# do your test here
# you can call a subprocess to run your selenium
Or, you write a separate python script to detect the containers you set up for your test, and then do something like this:
for container in my_containers.itervalues():
try:
c.stop(container=container.get('Id'))
c.remove_container(container=container.get('Id'))
except Exception as e:
print e