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Basic example of standalone jbpf operation

This example showcases a basic jbpf usage scenario. It provides a dummy C++ application (example_app), that initializes jbpf in standalone mode, and an example codelet (example_codelet.o). The example demonstrates the following:

  1. How to declare and call hooks.
  2. How to register handler functions for capturing output data from codelets in standalone mode.
  3. How to load and unload codeletsets using the LCM CLI tool (via a Unix socket API).
  4. How to send data back to running codelets.

For more details of the exact behavior of the application and the codelet, check here. You can also check the inline comments in example_app.cpp and example_codelet.c

Usage

This example expects jbpf to be built (see README.md).

To build the example from scratch, we run the following commands:

$ source ../../setup_jbpfp_env.sh
$ make

This should produce these artifacts:

  • example_app
  • example_codelet.o
  • schema:manual_ctrl_event_serializer.so - serializer library for manual_ctrl_event protobuf struct.
  • schema:packet_serializer.so - serializer library for packet protobuf struct.
  • schema.pb - compiled protobuf of schema.proto.
  • schema.pb.c - nanopb generated C file.
  • schema.pb.h - nanopb generated H file.

To bring up the application, we run the following commands:

$ source ../../setup_jbpfp_env.sh
$ ./run_app.sh

To start the local decoder:

$ source ../../setup_jbpfp_env.sh
$ ./run_decoder.sh

If successful, we shoud see the following line printed:

[JBPF_INFO]: Started LCM IPC server

To load the codeletset, we run the following commands on a second terminal window:

$ source ../../setup_jbpfp_env.sh
$ ./load.sh

If the codeletset was loaded successfully, we should see the following output in the example_app window:

[JBPF_INFO]: VM created and loaded successfully: example_codelet

After that, the agent should start printing periodical messages (once per second):

INFO[0008] {"seqNo":5, "value":-5, "name":"instance 5"}  streamUUID=00112233-4455-6677-8899-aabbccddeeff
INFO[0009] {"seqNo":6, "value":-6, "name":"instance 6"}  streamUUID=00112233-4455-6677-8899-aabbccddeeff
INFO[0010] {"seqNo":7, "value":-7, "name":"instance 7"}  streamUUID=00112233-4455-6677-8899-aabbccddeeff

To send a manual control message to the example_app, we run the command:

$ ./send_input_msg.sh 101

This should trigger a message in the example_app:

[JBPF_DEBUG]:  Called 2 times so far and received manual_ctrl_event with value 101

To unload the codeletset, we run the command:

$ ./unload.sh

The example_app should stop printing the periodical messages and should give the following output:

[JBPF_INFO]: VM with vmfd 0 (i = 0) destroyed successfully