Logging

Ignition records two types of information to files:

• Console messages
  • From the server process only, not the GUI
  • Logged to a plain-text server_console.log file
  • Always recorded
• Simulation state
  • Entity poses, insertion and deletion
  • Logged to an Ignition Transport state.tlog file
  • Recording must be enabled from the command line or the C++ API
  • Can be played back using the command line or the C++ API

Record

From command line

Run the example world with --record flag. This records data to a default path, i.e. ~/.ignition/gazebo/log/<timestamp>:

ign gazebo -v 4 -r --record pose_publisher.sdf

A custom path can be specified for recorded files through the --record-path flag. When --record-path is specified, --record does not need to be separately specified:

ign gazebo -v 4 -r --record-path ./foo pose_publisher.sdf

Other options for recording:

• --record-resources: Models and textures can be recorded, in addition to states, by specifying this flag. This implicitly enables --record flag.
• --log-overwrite: If the record path already exists, overwrite it. Defaults to false, in which case it's recorded to the given path with a number appended (i.e. /tmp/log(1), /tmp/log(2)...).
• --log-compress: Compress the recorded file.

From C++ API

All features available through the command line are also available through gz::sim::ServerConfig. When instantiating a server programmatically, logging options can be passed to the constructor, for example:

gz::sim::ServerConfig serverConfig;
serverConfig.SetUseLogRecord(true);
serverConfig.SetLogRecordPath("custom_path");
 
gz::sim::Server server(serverConfig);

From plugin in SDF

Recording can be specified in the SDF, under <world> tag:

<world name="default">
    ...
    <plugin
      filename="ignition-gazebo-log-system"
      name="gz::sim::systems::LogRecord">
    </plugin>
    ...
</world>

Currently, it is enforced that only one recording instance is allowed to start during a Gazebo run.

Record path

The final record path will depend on a few options:

• If state recording is not enabled, only the console log is recorded to ~/.ignition/gazebo/log/<timestamp>.
• If only --record, all files are recorded to ~/.ignition/gazebo/log/<timestamp>.
• If --record-path is specified:
  • If the path doesn't exist, logs are recorded there.
  • If the path exists:
    • If no --log-overwrite, logs are recorded to a new path with a number appended, i.e. /tmp/log(1), /tmp/log(2)...
    • If --log-overwrite, the directory is cleared and logs recorded to it.

Playback

From command line

Playback can be triggered by --playback command line flag. <path> is the directory specified to record:

ign gazebo -r -v 4 --playback <path>

From plugin in SDF

Playing back via the SDF tag <path> has been removed. Please use the command line argument.

Known issues

• When using command-line playback there is currently a small caveat. In the case that the recorded file uses ogre2, the playback appears brighter, because the default SDF that is loaded by Server.cc for playback uses ogre.
• Currently, specifying record and playback at the same time is not allowed. We may support this in the future, to support cropping a recording or changing the encoding.