pipewire/doc/pipewire-daemon.dox

/** \page page_daemon PipeWire Daemon

The PipeWire daemon is the central process that manages data exchange between
devices and clients.

Typically general, users run one PipeWire daemon that listens for incoming
connections and manages devices. Clients (including the \ref
page_session_manager) are separate processes that talk to the daemon using the
PipeWire socket (default: `$XDG_RUNTIME_DIR/pipewire-0`). This approach
provides address-space separation between the privileged daemon and
non-privileged clients.

\dot
digraph pw {
  compound=true;
  node [shape="box"];

  subgraph cluster_pw {
	rankdir="TB";
	label="PipeWire daemon";
	style="dashed";

	subgraph cluster_prot_native {
		label="pipewire-module-protocol-native";
		style="solid";
		socket [label="$XDG_RUNTIME_DIR/pipewire-0"];
		mod_impl [label="module implementation"];

		socket -> mod_impl;
	}
	core [label="PipeWire Core"];
	alsa [label="PipeWire ALSA support"];

	mod_impl -> core;
	core -> alsa;
  }

  kernel

  client1 [ label="Media Player" ];
  client2 [ label="Audio Software" ];
  sm [ label="Session Manager", style="dotted" ];

  client1 -> socket;
  client2 -> socket;
  sm -> socket;
  alsa -> kernel;
}
\enddot

As shown above, the protocol is handled by the \ref
page_module_protocol_native. From PipeWire's point-of-view this module is just
another module.

# Configuration Files

On startup, the daemon reads a configuration file to configure itself.
It executes a series of commands listed in the config file. The lookup order
for configuration files are:

- `$XDG_CONFIG_HOME/pipewire/pipewire.conf` (usually `$HOME/.config/pipewire/pipewire.conf`)
- `$sysconfdir/pipewire/pipewire.conf` (usually `/etc/pipewire/pipewire.conf`)
- `$datadir/pipewire/pipewire.conf` (usually `/usr/share/pipewire/pipewire.conf`)

The first configuration file found is loaded as the base configuration.

Next, configuration sections are collected in the directories in this
order:

- `$datadir/pipewire/pipewire.conf.d/` (usually `/usr/share/pipewire/pipewire.conf.d/`)
- `$sysconfdir/pipewire/pipewire.conf.d/` (usually `/etc/pipewire/pipewire.conf.d/`)
- `$XDG_CONFIG_HOME/pipewire/pipewire.conf.d/` (usually `$HOME/.config/pipewire/pipewire.conf.d/`)

They are applied to the global configuration file. Properties are overwritten
and array elements are appended. This makes it possible to make small custom customizations
or additions to the main configuration file.

The environment variables `PIPEWIRE_CONFIG_DIR`, `PIPEWIRE_CONFIG_PREFIX`, 
and `PIPEWIRE_CONFIG_NAME`. Can be used to specify an alternative configuration
directory, subdirectory, and filename respectively.

## Configuration File Format

PipeWire's configuration file format is JSON. In addition to true JSON 
PipeWire also understands a more compact JSON representation. Where
`"` can be omitted around strings, no trailing commas are required and
`:` or `=` can be used to separate object keys from their values.
Also, `#` can be used to start a comment until the end of the line.

The configuration file format is grouped into sections.  A section is
either a dictionary (`{}`) or an array (`[]`). Dictionary and array entries
are separated by whitespace and may be simple value assignment, an array or
a dictionary. For example:

```
# A dictionary section
context.properties = {
       # Keys often have a dot notation
       core.daemon = true
}

# An array section containing three dictionary objects
context.modules = [
    # a dictionary object with one key assigned to a string
    { name = libpipewire-module-protocol-native }
    { name = libpipewire-module-profiler }

    # a dictionary object with two keys, one assigned to a string
    # the other one to an array of strings
    { name = libpipewire-module-portal
      flags = [ ifexists nofail ]
    }
]
```

Allowed configuration file sections are:

- **context.properties**  (dictionary):   These   properties  configure  the
  pipewire instance.
- **context.spa-libs** (dictionary): Maps plugin features with globs to a
  spa library.
- **context.modules** (array): Each entry in the array is a dictionary with
  the name of the module to load, including optional args and flags. Most
  modules support being loaded multiple times.
- **context.objects** (array):  Each entry in the array is a dictionary con‐
  taining the factory to create an object from and optional  extra  argu‐
  ments specific to that factory.
- **context.exec**  (array): Each entry in the array is dictionary containing
  the path of a program to execute on startup and optional args. This ar‐
  ray usually contains an entry to start the session manager.


# Logging

The `PIPEWIRE_DEBUG` environment variable can be used to enable
more debugging. This variable supports one of two formats:

- `PIPEWIRE_DEBUG=<level>` where `<level>` is either a numerical log level or its
   respective key, see below.
- `PIPEWIRE_DEBUG=<glob1>:<level1>,<glob2>:<level2>,...` where the globs are
  shell globs to match on log topics and the levels are the respective
  log level to set for that topic. Globs are applied in order and a matching
  glob overrides an earlier glob for that category. For example,
  `PIPEWIRE_DEBUG=*:E,mod.*:D,mod.foo:X` enables global error messages,
  debugging on all modules but no messages on the foo module.
- `<level>` specifies the log level:

  + `X` or `0`: No logging is enabled.
  + `E` or `1`: Error logging is enabled.
  + `W` or `2`: Warnings are enabled.
  + `I` or `3`: Informational messages are enabled.
  + `D` or `4`: Debug messages are enabled.
  + `T` or `5`: Trace messages are enabled. These messages can be logged
     	from the realtime threads.

PipeWire uses a `category.topic` naming scheme, with the following categories:

- `pw.*`: PipeWire internal topics.
- `mod.*`: Module topics, for example `mod.foo` would usually refer to the
  `foo` module.
- `ms.*`: Media session topics.
- `ms.mod.*`: Media session modules, for example `ms.foo` would usually refer
   to the `media-session-foo` module.
- `conn.*`: Connection specific topics such as printing raw messages sent over
  a communication socket. These are in a separate namespace as they are
  usually vastly more verbose than the normal debugging topics.
  This namespace must be explicitly enabled with a `conn.<glob>` glob.

The behavior of the logging can be further controlled with the following
environment variables:

- `PIPEWIRE_LOG_SYSTEMD=false`: Disable logging to the systemd journal.
- `PIPEWIRE_LOG=<filename>`: Redirect the log to the given filename.
- `PIPEWIRE_LOG_LINE=false`: Don't log filename, function, and source code line.

*/