title: Docker for Java Enterprise Architects, Designerns 'n' Coders
Example 1) JBoss, WebSphere
Java Enterprise Application Server runs Java Enterprise Applications packaged in enterprise "containers".
.ear= Enterprise Application Archive (just a zip with zips inside) - or -.war= Web Archive (just a zip)
What's wrong?
What's wrong with Java Enterprise Application Servers (e.g. JBoss, WebSphere, etc.)?
Basically runs only Java, Java, Java. (*)
(*): Might be Ruby for Java (JRuby), Clojure, Scala or any other language compiling to Java byte code running on the Java virtual machine.
Example 2) Docker
Runs ANY application. (*)
PHP, anyone? Yes. Node.js, anyone? Yes. Java, anyone? Yes. COBOL, anyone? Yes. PostgreSQL, anyone? Yes. Redis, anyone? Yes. And Ruby, anyone? Yes!
(*): Remember its all 0 and 1 all the way down (including Java) ;-)
Ok.
What's the docker package format? Any guess?
Use what works - don't reinvent the wheel, the kitchen sink or the toothbrush.
What works for more than 50+ years?
Yes. Scripts. Scripts. Scripts.
What's the docker package format (e.g. Dockerfile)? And the winner is...
Linux Shell Scripts (*)
(*) No zips just plain old vanilla text
Example: Hello world in a container
Dockerfile:
FROM ubuntu
RUN echo 'Hello world'
Proof of the pudding. Let's build it:
$ docker build .
Sending build context to Docker daemon 2.048kB
Step 1/2 : FROM ubuntu
Step 2/2 : RUN echo 'Hello world'
Hello world
Successfully built 09953f45072b
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
<none> <none> 09953f45072b 2 minutes ago 73.9MB
One Container is One Process
Every container is "isolated" - own protected (secure, safe) memory space and own "virtual" server
Virtual Machine (e.g. VMBox, VirtualBox, KVM, etc.)
Not the Java "Virtual Machine" is NOT a virtual machine e.g. you cannot boot any operation system.
Bootup (Startup) Time
How long does it take to bootup (startup) a virtual machine image?
- 10 secs
- 30 secs
- 1 min
- 2 mins
How long does it take to bootup (startup) a container image?
- 0.015 secs
- 0.029 secs
- 0.042 secs
10 000 x Faster! - Yes, ten thousand times faster!
Wow. Wow. Wow. What's the catch? How is this possible?
Is it all Java? ;-)
It is all Linux ;-)
No magic. A container (application) always (re)uses the same (one and only) Linux kernel.
No need to bootup / startup an operating system kernel image.
Uses overlay file system, copy-on-write and much more for the high speed.
Example: Node.js hello world web app in a container
hello.js:
var express = require('express');
var app = express.createServer();
// respond with "hello world" when a GET request is made
app.get('/', function(req, res) {
res.send( 'hello world' );
});
app.listen( 8080 );
package.json:
{
"name": "nodejs-sample",
"version": "1.0.0",
"dependencies": {
"express": "^2.3.0"
}
}
Example: Node.js hello world web app in a container (Cont.)
Dockerfile:
FROM ubuntu
# Install Node.js and npm
RUN apt-get install -y nodejs npm
# Install app dependencies
COPY package.json /src/package.json
RUN cd /src; npm install --production
# Bundle app source
COPY hello.js /src/hello.js
# App binds to port 8080
EXPOSE 8080
# Last but not least, define the command to run your app
CMD ["node", "/src/hello.js"]
Example: Node.js hello world web app in a container (Cont.)
Done. Build the image and run.
$ docker build -t hello_nodejs .
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
hello_nodejs latest 00362d5176e4 2 minutes ago 944MB
$ docker run -p 8080:8080 -d hello_nodejs
Step 1. Try it out.
Works on Windows (requires 64-bit) runs Docker Server in the Windows Subsystem for Linux v2 (WSL2).
Step 2. Use Docker for development and testing.
Step 3. Share Dockerfiles (and images) with your (co-)workers or the world.
Step 4. Use Docker in production?
- Atomic Linux
- Alpine Linux
- CoreOS Linux
- and others
One Server
Example 1) Containers
Sell X Containers
Example 2) Virtual Machines
Sell Y Virtual "Root" Machines
Who will "win" in a (turbo) captialistic system?
Is X or Y bigger?
=> Container are more "efficient" e.g. lets you sell more units (e.g. "virtual" servers) per "physical" server
Twelf-Factor Applications (As Used by Heroku) - see 12factor.net
I. Codebase One codebase tracked in revision control, many deploys
II. Dependencies Explicitly declare and isolate dependencies
III. Config Store config in the environment
IV. Backing Services Treat backing services as attached resources
V. Build, release, run Strictly separate build and run stages
VI. Processes Execute the app as one or more stateless processes
VII. Port binding Export services via port binding
VIII. Concurrency Scale out via the process model
IX. Disposability Maximize robustness with fast startup and graceful shutdown
X. Dev/prod parity Keep development, staging, and production as similar as possible
XI. Logs Treat logs as event streams
XII. Admin processes Run admin/management tasks as one-off processes