Log Generation at Runtime

Whenever a new Syskit instance is started, for instance by executing syskit run, Syskit creates a new log directory. This log directory is named after the date and time - for instance 20211011-1123 for 11:23 on the 11/10/2021 - and optionally an index if more than one Syskit instance was started within the same minute (e.g. 20211011-1123.1). These folders are by default created within the bundle itself, under logs/. The logs of the currently running Syskit instance (or the last instance that was started) is pointed to by a current symlink under the same folder.

Instead of the logs folder, one can choose a different base folder by setting the ROBY_BASE_LOG_DIR environment variable. If it is set, the logs will be created under $ROBY_BASE_LOG_DIR/$APPNAME/$TIME_TAG where $APPNAME is the basename of the Syskit app folder (e.g. $APPNAME is tutorials in bundles/tutorials)

All Syskit-deployed systems should strive to put all runtime-generated data within the log folder. The remainder of this section will describe what type of data is stored there by default, and how that can be controlled. The analysis of these log files will be handled in followup sections.

Component Output Ports

In a Rock system, all output ports may be logged by the system. By default, they are all logged. Logging is the default.

Each deployment - i.e. each process that contains component - has a single log component (the logger::Logger from the tools/logger package) that is configured by Syskit to log the output ports of the components that run within that process.

When using a default deployment, the generated log file has the same name than the component that is being deployed, suffixed with .N.log where N is a sequential number starting at zero. This number is incremented each time the process is restarted. For instance, the logs of

Syskit.use_task_context OroGen.motors_weg_cvw300.Task => "left_motor"

will be named left_motor.0.log, left_motor.1.log and so on.

When using explicit deployments, the generated log file has the same name than the deployment, including the specified prefix if there is one. For instance, the logs of a motor_control deployment declared with

Syskit.use_deployment OroGen::Deployments.motor_control => "left_"

will be stored in left_motor_control.0.log, left_motor_control.1.log

Controlling Which Outputs Ports are Logged

As we just saw, a Rock+Syskit system will log all output ports. This may become a bit much in a production system - especially with sensors like cameras or LIDARs.

Syskit of course has a way to enable and disable ports from being logged. The way to do it is by defining log groups, that declare sets of output ports based on port, component or type names. These log groups can then be enabled or disabled. Ports are not logged if all groups that match them are disabled.

Group declarations are usually done within a robot configuration (in config/robots/):

Syskit.conf.logs.create_group "Images" do |g|

The regexp is matched against the port name, the task name and the type name. For instance, to control logging of Rock's default image type:

Syskit.conf.logs.create_group "Images" do |g|

Groups are enabled on creation. To disable a group on creation instead, do

Syskit.conf.logs.create_group "Images", enabled: false do |g|

The easiest way to control a group is through the Syskit IDE. In the runtime pane, open the Logs tab and enable/disable groups:

TODO: screencast

Component Standard Output and Error

The component's standard output and error streams are streamed to text files. The text files are named with $NAME.$PID.txt, where $NAME follows the same rules than the data logs (above), and $PID is the process ID of the underlying process.

Component Properties

Syskit creates a single properties.0.log file containing all property values from the components. When a process is started, Syskit reads the initial property values and save them. Afterwards, it will save any update it applies to the properties.

Syskit Events

In addition to the component data, text output and properties, Syskit has an extensive system for its own internal events. The corresponding log is named $ROBOTNAME-events.log (e.g. gazebo-events.log for a Syskit instance executed with syskit run -r gazebo). This log can be analyzed to determine the task structure (composition / tasks) as well as event information.


  • Syskit currently does not log any data from the ruby tasks