Authoring multipart Ubuntu cloud-init configuration with Java

Canonical's wonderful Amazon EC2 Images come with a powerful configuration tool called cloud-init that lets you pass configuration via user-data. One of the more interesting capabilities is that cloud-init allows a combination of different configuration payloads using MIME as a system for aggregating parts.

Below is an example of how to create a multipart configuration compatible with cloud-init using Java:

import java.util.Properties;

import javax.mail.Session;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;


public class CloudInitMultipart {

    public static void main(String[] args) throws Exception {
        String config = "#cloud-config\n" 
            + "mounts:\n" 
            + " - [ sdf, /mnt/data, \"auto\", \"defaults,nobootwait\", \"0\", \"0\" ]\n\n" 
            + "packages:\n"
            + " - emacs23-nox\n\n";
        MimeMultipart mime = new MimeMultipart();
        MimeBodyPart part1 = new MimeBodyPart();
        part1.setText(config, "us-ascii", "cloud-config");
        part1.setFileName("cloud-config.txt");
        MimeBodyPart part2 = new MimeBodyPart();
        String script = "#!/bin/bash\n\n" 
            + "NOW=`date +%s`\n" 
            + "touch /mnt/$NOW";
        part2.setText(script, "us-ascii", "x-shellscript");
        part2.setFileName("runme.sh");
        mime.addBodyPart(part1);
        mime.addBodyPart(part2);
        MimeMessage msg = new MimeMessage(Session.getDefaultInstance(new Properties()));
        msg.setContent(mime);
        msg.writeTo(System.out);
    }
}

This will create a multipart configuration combining a cloud-config element which installs emacs and creates an fstab entry, and also runs a bash script that creates a file. The output can then be used as user-data for launching an EC2 instance with this configuration.

How to Build Terracotta from Source

It seems that the folks at Terracotta have decided to make it nearly impossible to download any version older than the current version. As is common in real-world applications, sometimes it is desirable to stay on a version a little behind the bleeding edge because you know what you've got works for what you're doing. Terracotta has made things more difficult than usual by holding back a critical fix for a compatibility issue between Java 1.6.0_20 and Terracotta 3.2.0. The fix is available in version 3.2.2, which is only available to customers with a support contract with Terracotta.

So, I'll show you how to build 3.2.2 from source. It's a little trickier than implied in the above-linked thread, and the Terracotta Build Page doesn't explain it all.

First, we need to check out the 3.2.2 source code:

svn co http://svn.terracotta.org/svn/tc/dso/tags/3.2.2

Next, set up some required environment variables. Terracotta needs to know where your JRE, JDK, and Ant live. The following locations worked for me on my Ubuntu 10.04 install with Sun's Java 6, substitute the locations for your OS/Java distro:

export ANT_HOME=/usr/share/ant
export JAVA_HOME=/usr/lib/jvm/java-6-sun/jre
export JAVA_HOME_16=/usr/lib/jvm/java-6-sun

In my case, I only have Java 6, and I don't care about previous versions of Java. So we need to instruct the Terracotta build system to not try to use older releases. Modify the file 3.2.2/code/base/jdk.def.yml to comment out the Java 1.5 stuff:

#
# All content copyright (c) 2003-2006 Terracotta, Inc.,
# except as may otherwise be noted in a separate copyright notice.
# All rights reserved
#

# Defines the various JDKs used by the build system.
#
# Each JDK specification begins with a unique name that uniquely identifies
# the JDK version.  After the name come the following attributes:
#
#   min_version: The minumum JDK version
#   max_version: The maximum JDK version
#   env: A list of names of configuration properties that the build system uses
#        to locate the JDK installation
#   alias: A list of alternative names for the JDK

#J2SE-1.5:
#    min_version: 1.5.0_0
#    max_version: 1.5.999_999
#    env:
#      - J2SE_15
#      - JAVA_HOME_15
#    alias:
#      - tests-1.5
#      - "1.5"

JavaSE-1.6:
    min_version: 1.6.0_0
    max_version: 1.6.999_999
    env:
      - JAVASE_16
      - JAVASE_6
      - JAVA_HOME_16
    alias:
      - tests-1.6
      - "1.6"

Ok, now we're ready to build. Here's what I used to build the core Terracotta distribution using the Sun JDK. You may need to tweak the jdk parameter as needed for the location of your jdk.

cd 3.2.2/code/base
./tcbuild --no-extra dist dso OPENSOURCE jdk=/usr/lib/jvm/java-6-sun

The build will download all its dependencies and compile the Terracotta release. Note that this is the core distribution only, it does not build TIMs or anything like that. Once the build is complete, there will be a new folder

3.2.2/code/base/build/dist

This contains the Terracotta distribution that you would have downloaded.