Migration Guide#

Session Ownership#

ezmsg-qt now uses EzSession as the only public runtime owner.

Before:

app = QtWidgets.QApplication([])
bridge = EzGuiBridge(app)
widget = MyWidget(bridge)

with bridge:
    app.exec()

After:

app = QtWidgets.QApplication([])
session = EzSession()
widget = MyWidget(session)

with session:
    app.exec()

The public bridge object is gone; EzSession is now the only public runtime owner.

Attach endpoints explicitly:

self.sub = EzSubscriber(MyTopic.OUTPUT, parent=self, session=session)
self.pub = EzPublisher(MyTopic.INPUT, parent=self, session=session)

Runtime Topic Switching#

EzSubscriber can switch topics directly, and EzPublisher now supports the same API.

self.sub = EzSubscriber(MyTopic.A, parent=self, session=session)
self.pub = EzPublisher(MyTopic.B, parent=self, session=session)

self.sub.set_topic(MyTopic.C)
self.pub.set_topic(MyTopic.D)

self.sub.clear_topic()
self.pub.clear_topic()

Notes:

  • set_topic(...) and clear_topic() require a running session

  • both calls block until the session applies the change

  • topic reflects the currently active topic

Processor Pipelines#

ProcessorGraph attaches to a session and always runs off the UI thread.

graph = (
    ProcessorGraph(MyTopic.RAW, parent=self)
    .parallel(Filter)
    .local(DisplayTransform)
    .connect(self.on_data)
    .attach(session)
)

  • .parallel(...) runs a stage group in its own sidecar process

  • .local(...) runs a stage group in the shared sidecar process

Topic Normalization#

Qt session topics follow ezmsg core enum semantics.

  • Enum topics map to Enum.name

  • string topics are used as-is

If your graph previously relied on str(MyEnum.VALUE), update external graph connections to use MyEnum.VALUE.name or the plain string topic name.

Publisher Queueing#

EzPublisher supports configurable queue policies:

  • unbounded

  • block

  • drop_oldest

  • drop_latest

  • coalesce_latest

Example:

self.pub = EzPublisher(
    MyTopic.INPUT,
    parent=self,
    session=session,
    queue_policy="coalesce_latest",
    max_pending=1,
)