Reading System Logs with DLT¶
PELUX uses a component from GENIVI called DLT (for Diagnostic Log and Trace) which enables distant computers to access the system logs of a machine running PELUX.
DLT is split into two parts:
dlt-daemon: running on PELUX, collecting logs and distributing them on a network
dlt-viewer: running on a developer machine, accessing distant logs from dlt-daemon
Since dlt-daemon is already present on PELUX, you only need to compile dlt-viewer on your development machine. For that, you need to have installed: - git - cmake - the Qt SDK.
Clone the dlt-viewer repository:
git clone https://github.com/GENIVI/dlt-viewer
Compile it with cmake:
cmake -H. -Bbuild cmake --build build
You can now run dlt-viewer from its build directory
Configuring dlt-viewer for your target¶
dlt-viewer must be configured to point to your PELUX machine. You can do that from "Config -> ECU Add". On the first tab, named "ECU", feel free to use an Id and Description that describe your target but make sure the "Interface Type" is set to TCP. On the second tab, named "IP", use the IP address of your target and and make sure the port is set to 3490. You can then hit the "OK" button and your machine should appear in the "Project" part of the main window.
If you don't know the IP address of your target, the Raspberry Pi documentation describes how to find a new device on the network. This can be used for any target, not just Raspberry Pi
Select your target in the dlt-viewer's main window and connect to it using "Config -> ECU Connect". You should now have DLT logs shown on the right pane of dlt-viewer. Be careful though that the actual payload of those logs might be out of your screen, far at the right of the screen.
System logs are usually long and tedious to read. Fortunately, dlt-viewer comes with a filtering capability that can search patterns in logs.
You can use the line edit in the top action bar to search for words such as "set_default". You can also, enable regular expression search and filter with requests such as "set_.*_trace_status"
From a shell¶
On PELUX, DLT comes with a couple of tools that make life easier. One of those tools is called dlt-adaptor-stdin and it can be used to log data from the command line. It reads strings from its standard input so you can use it with UNIX pipes. For example:
echo "PELUX rocks!" | dlt-adaptor-stdin
Should append "PELUX rocks!" to the system logs you can read from dlt-viewer.
From a service¶
DLT provides a library to services so that they can log information. You can get started with a simple service example in the dlt-daemon repository.
For a detailed tutorial on how to get started, follow the DLT cheatsheet.