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LTTng-UST Java Agent Test Package

This git tree contains integration tests and benchmarks for the LTTng-UST Java Agent. It requires many additional dependencies compared to the library itself, so it is shipped as a separate package for now.

Prerequisites

For example, on Ubuntu you can use the LTTng PPA, then Maven and OpenJDK from the main repository:

sudo apt-add-repository ppa:lttng/ppa
sudo apt-get update
sudo apt-get install lttng-tools babeltrace2 maven openjdk-8-jre

Also make sure mvn -version reports a Java version: 1.8 or higher. If it does not, you may need to set your JAVA_HOME accordingly.

Usage

First you need to make install the LTTng-UST git branch you want to test. For example:

git clone git://git.lttng.org/lttng-ust.git
cd lttng-ust/
(do some modifications, checkout a different branch, etc.)
./bootstrap
./configure --enable-java-agent-all
make
sudo make install

Then, cd back to the directory where you cloned the present git tree, and issue a

mvn clean verify

This will run all the tests on the UST agent that was make install'ed. Tests will be skipped if they cannot find their required classes or native libraries, so make sure the output mentions succesful tests and not skipped ones.

Please make sure you have no lttng session active prior to or during the tests, or it might interfere with the test runs!

Detailed JUnit test reports will be available under lttng-ust-java-tests-{jul|log4j}/target/failsafe-reports/

Setting library paths

By default, the tests will look for the Java and JNI libraries in the default locations of make install (/usr/local/lib, /usr/local/share/java, etc.)

If for example, you installed into the /usr prefix instead of /usr/local, you can use the following properties to specify different locations for the lttng-ust-agent-java jars:

mvn clean verify \
-Dcommon-jar-location=/usr/share/java/lttng-ust-agent-common.jar \
-Djul-jar-location=/usr/share/java/lttng-ust-agent-jul.jar \
-Dlog4j-jar-location=/usr/share/java/lttng-ust-agent-log4j.jar \
-Dlog4j2-jar-location=/usr/share/java/lttng-ust-agent-log4j2.jar

To specify a different locations for the JNI .so libraries, you can set the -Djava.library.path property on the JVM:

mvn (...) -DargLine=-Djava.library.path=/usr/lib

Note: do not use MAVEN_OPTS to set the library path, since the argLine property defined in the build will overwrite it.

Running a single test

This test suite is comprised of integration tests. We use the failsafe maven plugin [1]. To run a single test, one can use the test class name and the following command:

mvn clean verify -Dit.test=JulAppContextOrderingIT -DfailIfNoTests=false

The -DfailIfNoTests=false argument is necessary otherwise maven will fail on the first test set that is empty. See [2] for more info.

[1] http://maven.apache.org/surefire/maven-failsafe-plugin/index.html [2] http://maven.apache.org/surefire/maven-failsafe-plugin/examples/single-test.html

Running tests by tags

Tests can also be filtered by Junit tags or tag expressions [1], for example to run only the Log4 1.x agent tests:

mvn clean verify -Dgroups='agent:log4j'

Or to exclude the tests of the Log4j2 domain:

mvn clean verify -Dgroups='!domain:log4j2'

[1] https://junit.org/junit5/docs/current/user-guide/#running-tests-tags

Debugging a test

Note that for most tests, the test itself is the traced application. The fastest and "easiest" way of putting a breakpoint is to use eclipse.

Download eclipse (for java dev). Import a maven project that points to this repo:

File -> Import -> Project -> Select Maven folder -> Select Existing Maven Projects
Point the root directory to this repo. Select all projects. Finish

Setup the Debug Configuration:

Run -> Debug Configurations.
Select Remote Java Application.
Press the New Configuration button.
Give it the name "Remote lttng maven".
Select the project and select `lttng-tools-java`
Set the port to 5005
Go in the Source tab.
Click Add -> Java project -> Select all
Click Apply
Click Close

Now let's run a single test with debug:

mvn clean verify -Dit.test=JulAppContextOrderingIT -DfailIfNoTests=false -Dmaven.failsafe.debug

Wait for:

Listening for transport dt_socket at address: 5005

Now go back to eclipse:

Navigate to where you want to put a break point. For example, JulAppContextOrderingIT.registerAgent.
Ctrl + shift + b can be used to set a tracepoint at the desired line.

Then attach to the debugger:

Run -> Debug Configurations.
Select on the right "Remote lttng maven"
Click Debug

You should hit the breakpoint at some point and from there use steps etc.

If you want to debug lttng-ust, you need to insert a breakpoint at a valid point in time for the test and then use gdb to hook yourself to the java process. From there debugging is the same as any C application. You will need to ignore SIGSEV from java under gdb:

handle SIGSEGV nostop noprint pass

Running the benchmarks

By default only the unit/integration tests are run. To also run the benchmarks, run Maven with the benchmark profile, as follows:

mvn clean verify -Pbenchmark

The benchmark results should be part of the standard output.