TL;DR

TBD

Example of usage

Ulyp is a Java recording debugger. Usage is relatively simple.

• First, download or build the agent

• Second, use system properties in order to enable the recording. Here is the minimum set of options one will need for recording.

  -javaagent:~/Work/ulyp/ulyp-agent/build/libs/ulyp-agent-0.2.1.0.jar
  -Dulyp.methods=**.HibernateShowcase.save
  -Dulyp.file=/tmp/hibernate-recording.dat
  

All methods with name save and class name HibernateShowcase (regardless of the package) will be recorded including all nested method calls.

• Run your code with system properties set.

  @Transactional
  public void save() throws Exception {
      User user = new User("Test", "User");
      saver.save(user);
  }
  

• Run the UI and open the recording file. Enjoy the view

Build from source

Build with gradle: ./gradlew build

Build without tests: ./gradlew build -x test

Run UI: ./gradlew :ulyp-ui:run

Key details

All instrumentation is done using byte buddy library. All Java objects are recorded by the recorders. Each recorder supports a particular set of Java types and is responsible for serializing object values into bytes. SBE library is used for serializing objects into bytes. Note that Ulyp doesn't fully serialize objects. Let's say, for String the first couple of hundred symbols are only recorded.

All data is written to file in a flat format. UI later uses RocksDB in order to build the index

The agent has functional tests. The agent is built and then used to record Java subprocess execution. The recording is then later analyzed and verified. Here is the example of test.

What's not recorded

Currently, none of java standard library classes are instrumented. This means calls of, let's say, add method of java collections are not recorded. However, Ulyp does record object values of java system library classes like strings, numbers, collections (more on that below) etc.

Type initializers (static blocks) are not recorded and there are no plans to support this.

Constructors are not recorded by default (which may distort the view), but may be recorded by specifying system prop -Dulyp.constructors. The reason why constructors are not recorded by default, is simply that it's not possible to instrument constructors in such fashion that any exception thrown inside the constructor is caught and rethrown. But this is exactly what should be done, but is not possible. Therefore, when such case happens, the corresponding recording file may become invalid. In that case UI will show error, and a user should disable the option and run the code again without constructors recorded.

Collections are not recorded by default but can be with system prop -Dulyp.collections. The available values are JAVA and ALL. When set to ALL all collection values will be recorded (actually only first three items are recorded). This means Ulyp will iterate any object which implements java.util.Collection interface. This may be too much especially for certain programs where there are a lot of proxy collections (like Hibernate or Hazelcast proxy collections when iteration triggers network calls). Hence the JAVA option value which only records Java collections.

Try running some code with additional properties -Dulyp.constructors -Dulyp.collections=JAVA to see the difference:

UI

UI Controls

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