Observer and Pub/Sub Workshop

Attempt before opening the separate practice feedback. Keep a prediction, observed result, explanation and changed-assumption case.

P06: Registration identity

Subscribe the same callback twice; dispose the first handle twice. Under L02, predict remaining callbacks. Implement independent idempotent handles.

P07: Membership during delivery

A removes B and registers C during event 1. A changes membership only on its first invocation. Predict both publications under snapshot membership and immediate suppression. Identify the policy change.

P08: Nested failures

A publishes recursively without catching its error; B raises ValueError; C records the event. State L02 return value and delivery trace. Then remove A and publish again to check recovery.

P09: Push/pull consistency

An event carries version 4; an earlier listener advances the subject to version 5. Compare an immutable pushed event with a later pull. Explain why passing an in-process reference does not copy the whole payload.

P10: Disposal and capacity

Model three mount/dispose cycles and one persistent subscription. Add three event sources and two derived values. Specify cleanup, stale-result cancellation and a bounded-capacity policy; compare a view update with an accepted-operation ledger. Complete L02.

Submit actual errors and repairs, not a quota. Reuse lab evidence where applicable. See contracts and assessment.