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README

This is a demo project of a PubSub application using ∅mq with Google's Protocol Buffers for serializing data build with Maven.

∅mq

I have a multi account system, so I have to switch to my administrator account.

su admin 

Install ∅mq form source (the latest homebrew version 3.2.1-rc2 had some errors that cause jzmq unit tests to fail)

cd ~/Projects/external
git clone git://github.com/zeromq/libzmq.git
cd libzmq
./autogen.sh
./configure
make
make install

Exit to the normal user

exit

jzmq

Switch to admun user

su admin

Install latest jzmq

cd ~/Projects/external
git clone git://github.com/zeromq/jzmq.git
cd jzmq
./autogen.sh
./configure
make
make install

Test the installation

cd perf
java -Djava.library.path=/usr/local/lib -classpath /usr/local/share/java/zmq.jar:../src/zmq.jar:zmq-perf.jar local_lat tcp://127.0.0.1:5555 1 100

At the first run this fails

...
Library not loaded: /usr/local/lib/libzmq.1.dylib
  Referenced from: /usr/local/lib/libjzmq.0.dylib

And indeed the file does not exist, but libzmq.3.dylib does exist, so

ln -s /usr/local/lib/libzmq.3.dylib /usr/local/lib/libzmq.1.dylib

Rerun the perf test

java -Djava.library.path=/usr/local/lib -classpath /usr/local/share/java/zmq.jar:../src/zmq.jar:zmq-perf.jar local_lat tcp://127.0.0.1:5555 1 100
java -Djava.library.path=/usr/local/lib -classpath /usr/local/share/java/zmq.jar:../src/zmq.jar:zmq-perf.jar remote_lat tcp://127.0.0.1:5555 1 100

Proceed to compile the maven artifact

cd ..
export JAVA_HOME=`/usr/libexec/java_home -v 1.7`
mvn clean install -DskipTests

Exit to the normal user

exit

Maven and jzmq

Although jzmq's official maven.readme advices you to add a dependency to the native artifact, I didn't work. In fact it did only work without the native library.

So just add

<dependency>
	<groupId>org.zeromq</groupId>
	<artifactId>jzmq</artifactId>
	<version>${version.jzmq}</version>
</dependency>

to your dependencies.

Protocol Buffers

I want to use Google's Protocol Buffers as the serializing mechanism

Protocol Buffers are a way of encoding structured data in an efficient yet extensible format. Google uses Protocol Buffers for almost all of its internal RPC protocols and file formats.

brew install protobuf

There is a Maven plugin to build .proto files. It's not released on Maven Central, so you have to add the plugin repository to your $M2_HOME/settings.xml. In this example I added it directly to the pom.xml though.

<pluginRepositories>
    <pluginRepository>
        <id>protoc-plugin</id>
        <url>http://sergei-ivanov.github.com/maven-protoc-plugin/repo/releases/</url>
    </pluginRepository>
</pluginRepositories>

To include the generated source in Eclipse with m2eclipse. You also have to add

<plugin>
	<groupId>org.codehaus.mojo</groupId>
	<artifactId>build-helper-maven-plugin</artifactId>
	<executions>
		<execution>
			<id>add-source</id>
			<phase>generate-sources</phase>
			<goals>
				<goal>add-source</goal>
			</goals>
			<configuration>
				<sources>
					<source>${project.build.directory}/generated-sources/protoc</source>
				</sources>
			</configuration>
		</execution>
	</executions>
</plugin>

to your pom.xml.

Appendix

FAQ

java.lang.UnsatisfiedLinkError

Exception in thread "main" java.lang.UnsatisfiedLinkError: /usr/local/lib/libjzmq.0.dylib: dlopen(/usr/local/lib/libjzmq.0.dylib, 1): Library not loaded: /usr/local/lib/libzmq.1.dylib
  Referenced from: /usr/local/lib/libjzmq.0.dylib
  Reason: image not found
	at java.lang.ClassLoader$NativeLibrary.load(Native Method)
	at java.lang.ClassLoader.loadLibrary1(ClassLoader.java:1939)
	at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1864)
	at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1854)
	at java.lang.Runtime.loadLibrary0(Runtime.java:845)
	at java.lang.System.loadLibrary(System.java:1084)
	at org.zeromq.ZMQ.<clinit>(ZMQ.java:35)
	at local_lat.main(local_lat.java:36)

There is a /usr/local/lib/libzmq.3.dylib but no /usr/local/lib/libzmq.3.dylib.

As a workaround I executed

ln -s /usr/local/lib/libzmq.3.dylib /usr/local/lib/libzmq.1.dylib

dyld: DYLD_ environment variables being ignored

When trying to fix my zeromq installation I got

dyld: DYLD_ environment variables being ignored because main executable (/usr/bin/sudo) is setuid or setgid

Turned out $LD_LIBRARY_PATH was set. Unset it via

unset LD_LIBRARY_PATH 

testDestruction(org.zeromq.ZContextTest): no jzmq in java.library.path

cd ~/Projects/external/jzmq
mvn clean install

fails with

Tests in error: 
  testDestruction(org.zeromq.ZContextTest): no jzmq in java.library.path
  ...

What is java.library.path

java.library.path is used for pointing to native system libraries (dll or so files). It points to a directory and calls to native code that use System.loadLibrary look in that directory for the native libs.

The project dependencies (jar files) should be specified on the application's classpath, not in this location.

from 1

Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin

As I couldn't get the tests to finish I did

mvn clean install -DskipTests

But was greeted with

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:2.7:jar (attach-javadoc) on project jzmq: MavenReportException: Error while creating archive:Unable to find javadoc command: The environment variable JAVA_HOME is not correctly set.

Make sure JAVA_HOME is set. If you have Java 6

export JAVA_HOME=`/usr/libexec/java_home -v 1.6`

or Java 7

export JAVA_HOME=`/usr/libexec/java_home -v 1.7`

junit.framework.AssertionFailedError

Unfortunately the Maven tests for jzmq ddidn't finish (correctly).

singleMessage(org.zeromq.ZDispatcherTest)  Time elapsed: 1.01 sec  <<< FAILURE!
junit.framework.AssertionFailedError: expected:<0> but was:<1>

and even worse Running org.zeromq.ZFrameTest seems to be stuck in an endless loop.

The mailing list suggested to remove homebrews latest version (3.2.1-rc2) and install libzmq from source.

This solved the problems with the tests.

Install zeromq from source

The mailing list suggested to install zeromq from source

brew remove zeromq
git clone git://github.com/zeromq/libzmq.git
cd libzmq/
./autogen.sh
./configure
make
make install

Testing the installation with perf failed at first

cd perf
java -Djava.library.path=/usr/local/lib -classpath /usr/local/share/java/zmq.jar:../src/zmq.jar:zmq-perf.jar local_lat tcp://127.0.0.1:5555 1 100
...
Library not loaded: /usr/local/lib/libzmq.1.dylib
  Referenced from: /usr/local/lib/libjzmq.0.dylib

So, I executed

ln -s /usr/local/lib/libzmq.3.dylib /usr/local/lib/libzmq.1.dylib

Then I recompiled jzmq

cd ../jzmq
make clean
make
make install

Now the tests successfully ran, so installed the artifact

export JAVA_HOME=`/usr/libexec/java_home -v 1.7`
mvn clean install

Resources

The code example for protocol buffers is taken from 2 and the basic pubsub example is taken from ∅mq official java examples 3, and 4

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