How to run ping & pong

Running ping<->pong is a nice way to test that you can run some basic code and shows how messaging can work between two nodes

Set up real-time niceties:

1. Add the following lines to /etc/security/limits.d/rt.conf, replacing "USERNAME" with the username you're running under. You'll probably need to do this as root, e.g., sudo nano /etc/security/limits.d/rt.conf

USERNAME - nice -20
USERNAME - rtprio 95
USERNAME - memlock unlimited

2. Reboot your machine to pick up the changes

Compile and run the code

1. Compile the code for ping and pong, as well as aos_dump for looking at the messages. We'll assume throughout that you're running from the top level directory of the 971 code.

bazel build -c opt //aos/events:ping //aos/events:pong //aos:aos_dump

2. In 2 separate windows, run the ping and pong commands using the pingpong_config.json config file: 1. bazel-bin/aos/events/ping --config bazel-bin/aos/events/pingpong_config.json 2. bazel-bin/aos/events/pong --config bazel-bin/aos/events/pingpong_config.json

3. In a third window, explore the message stream using aos_dump. Some things you can do: 1. List the channels: bazel-bin/aos/aos_dump --config bazel-bin/aos/events/pingpong_config.json 2. Listen to a specific topic on a channel-- copy one of the channels listed in the first step and put it at the end of the aos_dump command (e.g., "/test aos.examples.Ping") bazel-bin/aos/aos_dump --config bazel-bin/aos/events/pingpong_config.json /test aos.examples.Ping 3. Listen to multiple topics on a channel (e.g., all the topics published on "/test") bazel-bin/aos/aos_dump --config bazel-bin/aos/events/pingpong_config.json /test

NOTE: To make life easier, you can alias aos_dump to include the path and the config file (you may want to specify the full path to the aos_dump executable so it can be run from anywhere)

alias aos_dump='bazel-bin/aos/aos_dump --config bazel-bin/aos/events/pingpong_config.json'

Logging

In addition to running ping and pong, this is a good example to explore event logging.

1. Start by compiling the code:

bazel build -c opt //aos/events/logging:logger_main

2. Create a folder for the log files, e.g.,

mkdir /tmp/log_folder

3. Run the command to log the data:

bazel-bin/aos/events/logging/logger_main --config bazel-bin/aos/events/pingpong_config.json --logging_folder /tmp/log_folder/

A log file should be created in /tmp/log_folder, with a name something like fbs_log-001.bfbs.

If you're running ping and pong at the same time, you should be able to watch the log file grow in size as events are being logged. For example, running ls -lh /tmp/log_folder/* will list the files and their sizes. Doing this periodically (e.g., every 15-30 seconds) should show the new log file growing in size.

4. View the contents of the log file (using log_cat functionality found in the logging sub-directory):

   1. Compile log_cat:

   bazel build -c opt //aos/events/logging:log_cat
   

   2. Run the binary pointed at the recorded event log (this assumes you're running from the base directory of the repository and that the file is named fbs_log-001.bfbs):

   bazel-bin/aos/events/logging/log_cat /tmp/log_folder/fbs_log-001.bfbs
   

EXERCISE:

1. Modify code in ping and pong to see a difference in their behavior, e.g., increment the counter by 2's instead of 1