When you’re debugging yourself or asking for help, there are some tools built into Mopidy that you should know about.

Getting help

If you get stuck, you can get help at the our Discourse forum or in the #mopidy-users stream on Zulip chat.

If you stumble into a bug or have a feature request, please create an issue in the issue tracker. If you’re unsure if it’s a bug or not, ask for help in the forum or the chat first. The source code may also be of help.

Show effective configuration

The config subcommand will print your full effective configuration the way Mopidy sees it after all defaults and all config files have been merged into a single config document. Any secret values like passwords are masked out, so the output of the command should be safe to share with others for debugging.

If you run Mopidy manually in a terminal, run:

mopidy config

If you run Mopidy as a system service, run:

sudo mopidyctl config

Show installed dependencies

The deps subcommand will list the paths to and versions of any dependency Mopidy or the extensions might need to work. This is very useful data for checking that you’re using the right versions, and that you’re using the right installation if you have multiple installations of a dependency on your system.

If you run Mopidy manually in a terminal, run:

mopidy deps

If you run Mopidy as a system service, run:

sudo mopidyctl deps

Debug logging

If you run mopidy -v or mopidy -vv, mopidy -vvv, or mopidy -vvvv Mopidy will print more and more debug log to stderr. All four options will give you debug level output from Mopidy and extensions, while -vv, -vvv, and -vvvv will give you more log output from their dependencies as well.

To save a debug log to file for sharing with others, you can pipe stdout and stderr to a file:

mopidy -vvvv 2>&1 | tee mopidy.log

If you run Mopidy as a system service, adding arguments on the command line might be complicated. As an alternative, you can set the configuration logging/verbosity to 4 instead of passing -vvvv on the command line:

verbosity = 4

If you run Mopidy as a system service and are using journald, like most modern Linux systems, you can view the Mopidy log by running:

sudo journalctl -u mopidy

To save the output to a file for sharing, run:

sudo journalctl -u mopidy | tee mopidy.log

If you want to reduce the logging for some component, see the docs for the loglevels/* config section.

For example, to only get error log messages from requests, even when running with maximum verbosity, you can add the following to mopidy.conf:

requests = error

Track metadata

If you find missing or incorrect metadata for a track, or are experiencing problems during local scanning, you can manually view track metadata as seen by Mopidy by running:

python3 -m path_to_your_file

It may be useful to compare that output against other music playback software or audio tagging tools. One such tool is GStreamer’s own gst-discoverer-1.0 which can be installed with sudo apt install gstreamer1.0-plugins-base-apps and invoked by running:

gst-discoverer-1.0 path_to_your_file

Mopidy relies on GStreamer library functions to handle audio metadata so if you find gst-discoverer-1.0 is also unable to correctly read the metadata, but other software succeeds, then the problem is likely to be with GStreamer itself. In this situation you will likely find the behaviour is dependent on the version of GStreamer being used and/or the file format.

Debugging deadlocks

If Mopidy hangs without an obvious explanation, you can send the SIGUSR1 signal to the Mopidy process. If Mopidy’s main thread is still responsive, it will log a traceback for each running thread, showing what the threads are currently doing. This is a very useful tool for understanding exactly how the system is deadlocking. If you have the pkill command installed, you can use this by simply running:

pkill -SIGUSR1 mopidy

You can read more about the deadlock debug helper in the Pykka documentation.

Debugging GStreamer

If you really want to dig in and debug GStreamer behaviour, then check out the Debugging section of GStreamer’s documentation for your options. Note that Mopidy does not support the GStreamer command line options, like --gst-debug-level=3, but setting GStreamer environment variables, like GST_DEBUG, works with Mopidy. For example, to run Mopidy with debug logging and GStreamer logging at level 3, you can run:

GST_DEBUG=3 mopidy -v

This will produce a lot of output, but given some GStreamer knowledge this is very useful for debugging GStreamer pipeline issues. Additionally GST_DEBUG_FILE=gstreamer.log can be used to redirect the debug logging to a file instead of stdout.

Lastly GST_DEBUG_DUMP_DOT_DIR can be used to get descriptions of the current pipeline in dot format. Currently we trigger a dump of the pipeline on every completed state change: