# Debug Logging

WirePlumber is instrumented with log messages in its entire codebase. These messages are categorized based on two heuristics: the log topic and the log level.

The log topic is a string that identifies which component of the code this message is coming from. Well-known topics include:

> - wireplumber: messages from the wireplumber daemon

> - wp-*: messages from libwireplumber

> > - wp-core: messages from WpCore

> > - wp-proxy: messages from WpProxy

> > - ... and so on ...

> - m-*: messages from wireplumber modules

> > - m-standard-event-source: messages from libwireplumber-module-standard-event-source

> > - m-lua-scripting: messages from libwireplumber-module-lua-scripting

> > - m-settings: messages from libwireplumber-module-settings

> > - ... and so on ...

> - s-*: messages from scripts

> > - s-linking: messages from the linking/*.lua scripts

> > - s-default-nodes: messages from the default-nodes/*.lua scripts

> > - s-device: messages from the device/*.lua scripts

> > - s-monitors: messages from the monitors/*.lua scripts

> > - ... and so on ...

> - pw.*: messages from libpipewire

> - spa.*: messages from spa plugins

> - mod.*: messages from libpipewire modules

> - conn.*: messages to debug the pipewire socket connection

The log level is a value that designates the importance of the message. The levels that exist in WirePlumber are the following:

> - `F`: Fatal errors. These messages represent situations where execution of the program cannot continue. In the extremely unlikely case that they appear, these messages also cause the process to be terminated.

> - `E`: Critical warnings (or "errors" in the PipeWire terminology). These messages represent situations where something unexpected has happened and someone with understanding of the code should probably take a look at it. These situations are usually programming mistakes or omissions. This does not necessarily mean that the program is not functioning correctly. It may mean, though, that the specific part of the program that logged the message (the plugin, subsystem, ...) may not work optimally.

> - `W`: Warnings. These messages represent situations where something has gone unintentionally wrong, but it was not totally unexpected. The situation is recovered and the program can continue. In many cases, this warning may mean that there is something wrong with the configuration or the environment and may need attention from the user.

> - `N`: Notices. These are important messages that the user should notice, like warnings, but they do not necessarily mean a bad situation.

> - `I`: Informational messages. These messages provide information about the internal operations of the program.

> - `D`: Debug messages. These messages provide details about the internal operations of the program, which can be useful for debugging.

> - `T`: Traces. These messages provide very verbose printouts of internal operations and data that affects these operations. These can be useful for debugging as well, but it may be best to be enabled only for the topic(s) that are intended to be debugged, as they can be very big in volume.

By default, WirePlumber logs only messages from levels `F`, `E`, `W` and `N`. These messages are printed on the standard error (`stderr`) stream, or they are logged to the systemd journal, if WirePlumber was started as a systemd service.

The `WIREPLUMBER_DEBUG` environment variable can be used to change which topics and levels are enabled. The generic syntax is:

    WIREPLUMBER_DEBUG=[<topic pattern>:]<level>,...,

This is a comma-separated list of topics to enable, paired with a level for each topic.

`<level>` can be one of `FEWNIDT` or a numerical log level as listed below.

> 0. fatal errors (`F`)

> 1. critical warnings (`E`)

> 2. warnings and notices (`W` & `N`)

> 3. informational messages (`I`)

> 4. debug messages (`D`)

> 5. trace messages (`T`)

Each level always includes messages from the previous levels, so for instance enabling level `3` (or `I`) will also enable messages from levels `2` and `1` (`N`, `W`, `E` and `F`)

`<topic pattern>` is an optional description of one or more topics. This supports glob style patterns containing `*` and `?`.

If a `<topic pattern>` is not specified, then the given `<level>` is considered to be the global log level, which applies to all topics that have no explicit level specified.

## Changing log level at runtime

The debug log level can be changed at runtime using `wpctl`:

    wpctl set-log-level D     # enable debug logging for WirePlumber
    wpctl set-log-level -     # restore default logging for WirePlumber

    wpctl set-log-level 0 4   # enable debug logging for PipeWire daemon
    wpctl set-log-level 0 -   # restore default logging for PipeWire daemon

Equivalently, it is also possible to adjust the logging by setting `log.level` in the `settings` metadata:

    pw-metadata -n settings <ID> log.level "D"   # WirePlumber logging

    pw-metadata -n settings 0 log.level 4        # PipeWire daemon logging

Above, `<ID>` should be replaced by the WirePlumber daemon client ID.

Note that PipeWire daemon log levels must be specified by numbers, not letter codes.

## Changing log level via static configuration

If you need to capture logs from WirePlumber at startup or in other circumstances where changing the level at runtime or setting an environment variable is not feasible, then you may also set the log level in the configuration file.

The log level changes via the `log.level` key in the `context.properties` section:

    context.properties = {
      log.level = "D"
    }

You may use the same syntax as in `WIREPLUMBER_DEBUG` to describe the exact logging you want to achieve. For instance, to log debug messages from all scripts and informational messages from everywhere else:

    context.properties = {
      log.level = "I,s-*:D"
    }

The easiest way to configure this is to drop a fragment file that contains just this.

    $ mkdir -p ~/.config/wireplumber/wireplumber.conf.d
    $ echo 'context.properties = { log.level = "D" }' > ~/.config/wireplumber/wireplumber.conf.d/log.conf

See also Modifying configuration

## Examples

Show all messages:

    WIREPLUMBER_DEBUG=T

Show all messages up to the debug level (F, E, W, N, I & D), excluding trace:

    WIREPLUMBER_DEBUG=D

Show all messages up to the notice level (F, E, W & N), excluding info, debug & trace (this is also the default when `WIREPLUMBER_DEBUG` is omitted):

    WIREPLUMBER_DEBUG=2

Show all messages from the wireplumber library (including traces), but only up to informational messages from other topics:

    WIREPLUMBER_DEBUG=I,wp-*:T

Show debug messages from `wp-registry`, libpipewire and all modules, keeping all other topics up to the notice level.

    WIREPLUMBER_DEBUG=2,wp-registry:4,pw.*:4,m-*:4

## Relationship with the GLib log handler & G_MESSAGES_DEBUG

Older versions of WirePlumber used to use `G_MESSAGES_DEBUG` to control their log output, which is the environment variable that affects GLib's default log handler.

As of WirePlumber 0.3, `G_MESSAGES_DEBUG` is no longer used, since libwireplumber replaces the default log handler.

If you are writing your own application based on libwireplumber, you can choose if you want to replace this log handler using the flags passed to `wp_init()`.

## Relationship with the PipeWire log handler & PIPEWIRE_DEBUG

libpipewire uses the `PIPEWIRE_DEBUG` environment variable, with a similar syntax. WirePlumber replaces the log handler of libpipewire with its own, rendering `PIPEWIRE_DEBUG` useless. Instead, you should use `WIREPLUMBER_DEBUG`. All the log topics that apply to libpipewire and its modules / plugins work the same in `WIREPLUMBER_DEBUG`.

If you are writing your own application based on libwireplumber, you can choose if you want to replace this log handler using the flags passed to `wp_init()`.

### Mapping of PipeWire debug levels to WirePlumber

PipeWire supports 5 levels of debug logging. WirePlumber, on the other hand, supports 7 levels. Some levels seem common, but the terminology and the semantics are slightly different. The following table shows how the various levels are mapped:

Numeric Level | PipeWire | WirePlumber
--- | --- | ---
0 | no log | `F` - Fatal Error
1 | `E` - Error | `E` - Critical Warning
2 | `W` - Warning | `W` - Warning, `N` - Notice
3 | `I` - Info | `I` - Info
4 | `D` - Debug | `D` - Debug
5 | `T` - Trace | `T` - Trace