Docker

Question 1

Docker containerisation process

code

Answer 1

Docker file
$docker build
Docker image
$docker run
Docker container

Question 2

docker architecture

Answer 2

( docker client + docker host + registry ) on network protocol stack

Question 3

downsides of containerisation (4)

Answer 3

• performance overhead: every machine that needs to run the microservice needs to have Docker installed
• upfront investment is higher: images/containers take space
• images/containers can get damaged/lost
• easier to package inappropriate/illegal/malicious content into images/containers without being detected

Question 4

Docker Compose

Answer 4

Docker Management tool
- defines and runs multi-containers
- use YAML files to define the configurations of containers
use “docker-compose” to run containers and related operations according to the configurations in the YAML file

Question 5

YAML

Answer 5

• describe software configurations in a human-readable way

Question 6

container networking

Answer 6

each container running on a docker host is in an internal subnetwork set up by the docker engine (acts as a gateway for the containers, providing networking capabilities)

• docker engine sets up an internal network on the docker host, assigns dynamic IP addresses to each container in the internal network (only available in internal network)

Question 7

communication among networking

Answer 7

• container and the host in the same internal network use IP addresses
• container can be assigned a name => communicate in same subnetwork ( act like host names )
• containers in external networks need NAT through the docker engine and docker host

Question 8

accessing a microservice inside a container

Answer 8

• internal IPs are invalid externally => intermediary to translate between external and internal IPs (eg. docker engine)
• port mapping
  *external client may access host IPs (docker host) in external network

Question 9

Network Address Translation

Answer 9

• map one network address to another by modifying the address information in network communication data
• allow data to be rerouted by the network to a different receiver or can appear to come from a different sender

Question 10

port mapping

Answer 10

• redirecting communication data from IP:port number to another IP:port number
• docker engine maps an (external) port of the docker host (a.k.a. host port) to an (internal) port of the container (a.k.a. container port); after that, all incoming request data going to the host port is forwarded to the container port of a particular container; the data replied from the container is forwarded by the docker engine and host back to the original client.
• different container different port number