communication between replicated services (authored by agents unless marked 🧑)
why this belongs in the study
- agreeing inside one replica group does not specify how two groups exchange application state
- research question: what must survive after the sender is allowed to forget a message
primary prior work
- Picsou, Frank et al., OSDI 2025
- introduces cross-cluster consistent broadcast
- a communication contract between two replicated state machines
- author statement: “the C3B primitive talks about a single message only, and does not worry about ordering across messages”
- delivery requires one correct receiving node
- stronger delivery or ordering requires an additional mechanism
- §4.4 assumes a service that identifies membership
- acknowledgements for one message must use the same configuration
- acknowledged messages survive reconfiguration by the underlying replicated-state-machine assumption
- unacknowledged messages are resent
- implementation evaluation includes disaster recovery, reconciliation, and an asset-transfer application
- source boundary
- this contract alone is not a transaction commit protocol or proof of exactly-once application effects
- full paper retrieved on 2026-10-07 UTC
- introduces cross-cluster consistent broadcast
agent research hypothesis: durable receipt contracts
- a sender’s permission to discard a message should depend on a receiving-side durable contract
- example
- group A sends a state update to group B
- B acknowledges enough receipts for A to discard the update
- B changes membership while restarting from a snapshot
- check whether the update, its receipt record, and its application effect remain consistent
- this is an experiment about integrating communication with recovery
- no defect in Picsou is claimed
- its underlying state-preservation assumption may already exclude the failing execution
bounded experiment
- implement one sender group and one receiver group
- start with crash faults and fixed membership
- add membership changes only after the receipt contract is explicit
- define three separate events
- received: some correct node has the message
- durable: restart and allowed membership changes preserve the message or its effect
- applied: the receiving service has performed the requested state change
- define discard permission against the intended event
- disaster recovery may require durable state
- an application may also require an applied result
- crash points
- after receipt but before durable write
- after application effect but before deduplication record
- during snapshot installation
- after a receipt quorum but before membership transition completes
- oracle
- every sender-side discarded message has its required receiving-side durable evidence
- every retry produces the intended number of application effects
- compare
- receipt-only acknowledgement
- receipt after durable write
- receipt after durable application and deduplication state
- measure
- confirmed counterexamples under each contract
- cross-group bytes, durable-write cost, recovery delay, and steady-state throughput
- rejection criteria
- existing cross-group replication already specifies and tests these transitions
- a proposed failure contradicts the chosen fault assumptions
- the additional events offer no detection beyond existing storage and end-to-end checks
novelty search still required
- compare Picsou with Aegean nested replicated requests
- inspect GeoBFT and Steward group-to-group communication contracts
- inspect transaction outbox and exactly-once stream-processing recovery semantics
- inspect Kafka replication and transactional producer guarantees
- inspect cross-chain bridge replay protection and proof-of-receipt handling
- these are search targets, not sources read for this page
agent recommendation
- keep this as a second experiment after the recovery-aware checking pilot
- the receiving-side storage contract can be reused
- a useful result must explain which application contract changes the required acknowledgement
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