Problem running example of locationd

[shaned24]

I ran into the same issue when trying to implement the example from https://docs.ubuntu.com/core/en/stacks/location/location-service/docs/obtain-location

I have defined the plugs

plugs: [ location-observe ]

And then try the prime

snap try prime --jailmode
snap connect location-dbus:location-observe locationd:service-observe

The following error:

ERROR:dbus.proxies:Introspect error on :1.184:/com/ubuntu/location/Service: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.AccessDenied: An AppArmor policy prevents this sender from sending this message to this recipient; type="method_call", sender=":1.238" (uid=0 pid=18915 comm="python3 -m location_dbus.location " label="snap.location-dbus.location (complain)") interface="org.freedesktop.DBus.Introspectable" member="Introspect" error name="(unset)" requested_reply="0" destination=":1.184" (uid=0 pid=23503 comm="/snap/locationd/163/bin/locationd run --bus=system" label="snap.locationd.run (enforce)")
Traceback (most recent call last):
  File "/snap/location-dbus/x12/usr/lib/python3.5/runpy.py", line 184, in _run_module_as_main
    "__main__", mod_spec)
  File "/snap/location-dbus/x12/usr/lib/python3.5/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/shaned24/code/location_dbus/location_dbus/location.py", line 17, in <module>
    session_path = service.CreateSessionForCriteria(requirements)
  File "/snap/location-dbus/x12/usr/lib/python3/dist-packages/dbus/proxies.py", line 70, in __call__
    return self._proxy_method(*args, **keywords)
  File "/snap/location-dbus/x12/usr/lib/python3/dist-packages/dbus/proxies.py", line 145, in __call__
    **keywords)
  File "/snap/location-dbus/x12/usr/lib/python3/dist-packages/dbus/connection.py", line 651, in call_blocking
    message, timeout)
dbus.exceptions.DBusException: org.freedesktop.DBus.Error.InvalidArgs: Type of message, '(a{sb})', does not match expected type '(a{sv})'

Further information:

@lucyllewy

I believe you’ve connected these incorrectly. I think they should be connected to core , though I may be wrong, which happens automatically when you don’t specify a target slot:

Unfortunately there is no core interface slot called “location-observe” I can only connect my location-observe plug to locationd:service-observe

Supported interfaces

Interfaces enable resources from one snap to be shared with another and with the system. The table below lists currently supported interfaces, with links to further details for each interface. The following column names are used: Interface is the syntactical interface name, as used by snaps. Description is a brief overview of what the interface permits. Select the interface name to open the interface-specific page for a more detailed description on each interface. Categories are used t…

Debugging with snappy debug shows:

= AppArmor =
Time: Dec 11 01:58:15
Log: apparmor="DENIED" operation="dbus_method_call"  bus="system" path="/com/ubuntu/location/Service" interface="org.freedesktop.DBus.Introspectable" member="Introspect" name=":1.238" mask="receive" pid=23503 label="snap.locationd.run" peer_pid=18915 peer_label="snap.location-dbus.location"
DBus access
Suggestion:
* try adding 'location-observe' to 'plugs'

My interfaces:

snap interfaces | grep location
:network                                  locationd
:network-manager                           locationd
locationd:service-control                  location-dbus:location-control,locationd:client-control
locationd:service-observe                  location-dbus:location-observe,locationd:client-observe
-                                          locationd:ubx
-                                          locationd:wpa