'NoneType' object has no attribute 'uri'

[james beedy]

still hitting this every 1/5

unit-pdl-api-3: 14:04:50 INFO unit.pdl-api/3.juju-log pgsql:68: Invoking reactive handler: reactive/pdl_api.py:98:get_set_postgresql_data
unit-pdl-api-3: 14:04:51 ERROR unit.pdl-api/3.juju-log pgsql:68: Hook error:
Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/charms/reactive/__init__.py", line 97, in main
    bus.dispatch(restricted=restricted_mode)
  File "/usr/local/lib/python3.5/dist-packages/charms/reactive/bus.py", line 375, in dispatch
    _invoke(other_handlers)
  File "/usr/local/lib/python3.5/dist-packages/charms/reactive/bus.py", line 351, in _invoke
    handler.invoke()
  File "/usr/local/lib/python3.5/dist-packages/charms/reactive/bus.py", line 173, in invoke
    self._action(*args)
  File "/var/lib/juju/agents/unit-pdl-api-3/charm/reactive/pdl_api.py", line 106, in get_set_postgresql_data
    kv.set('db_uri', pgsql.master.uri)
AttributeError: 'NoneType' object has no attribute 'uri'

[Stuart Bishop (stub)]

If pgsql.master is None, it means the master is not yet available. Handlers should generally wait for the relname.master.available state, at which point they can expect pgsql.master to be valid and pgsql.master.uri to work.

Is the handler guarded by @when('XXXX.master.available'), or some other state like XXX.connected ?

[james beedy (jamesbeedy)]

https://gist.github.com/jamesbeedy/1c501e4c03a6f183f19f4692cdf10042

[Stuart Bishop (stub)]

This will occur if the .master.available state is already set and the client calls any of the set_* methods. The state will remain set, but the .master property will start returning None because the master database is no longer available, because the requested database properties do not yet match what is being offered by the PostgreSQL master unit.

1) PostgreSQL unit runs its relation-joined and relation-changed hooks, advertising connection details to the client
2) Client runs its relation-joined hook, setting the .master.available state because the master database is available
3) In this or a later hook, client calls set_database. For the remainder of the hook, and all further hooks until the PostgreSQL server has run its relation-changed hook, the .master.available state remains set while the .master property returns None.

Fix is to reset the states in the set_* methods.

[Stuart Bishop (stub)]

The state is already being reset in the set_* methods. The _set_value helper method removes the {relname}.master.available state at the same time it publishes the requested changes on the relation.

I'm at a loss how the example code could end up in such a situation.

[james beedy (jamesbeedy)]

@stub I haven't hit this in quite some time now .... given I haven't been spinning up psql instances as frequently as before. Its fine by me if you want to close this out.

[Stuart Bishop (stub)]

This stuff pretty much got rewritten with an update to use the new Endpoint base from charms.reactive. So calling this fixed released and looking forward to brand new bugs ;)