Kafka reliability / Contract explorer
Kafka Delivery Contract Explorer
Which part of this pipeline has a guarantee, under which assumptions, and what remains unknown?
Baseline: apache-java-4.3.1 · source 26b251a451ce
This deterministic teaching model runs in your browser and never connects to Kafka. It accepts only bounded synthetic controls. Curated scenario and variant IDs may appear in a shareable URL; custom local values, payloads, brokers, credentials, and production identifiers never do. Exports include only what you request.
Deterministic teaching model · apache-java-4.3.1
D01: Local acceptance is not publication evidence
What can a local enqueue or acks 0 establish?
Current outcome · step 0 of 2
The default matrix separates publication, progress, sink effect, identity, retention, and recovery authority.
Default synthetic example loaded.
Contract boundaries
- Application intent
- Untracked local send
- A process crash can erase the only copy before broker dispatch.
- Publication evidence
- idempotent-retry
- The selected acknowledgement capability still depends on effective settings and failure assumptions.
- Same-batch duplicate append
- Conditionally protected
- PID, epoch, partition, and sequence can recognize the same retained batch. A new send remains new work.
- Transactional visibility
- read_committed
- HW, LSO, control records, and aborted ranges remain distinct exclusive boundaries.
- Consumer progress
- after-effect
- Effect order alone does not make progress atomic or prevent gaps.
- Business effect
- Repeated effect possible
- Kafka commit, abort, and ownership movement cannot retract or deduplicate the external effect.
- Protection retention
- UNKNOWN
- Source retention does not preserve sink identity, authority, or schema meaning.
- Recovery authority
- 1 unresolved obligation(s)
- Resolve missing identity, retention, effect, and ownership evidence before effect-capable recovery.
Evidence obligations
- Obligation 1
- unresolved
- Reconcile sink protection and restore-point retention.
Invariant results
Producer settings alone never establish one business effect
holds in model
External effect rows depend on sink identity, retention, and provider/local transaction contracts.
Unknown or expired retention never defaults to holds
holds in model
Unknown and expired retention remain unresolved or counterexamples.
Changing topology removes incompatible ordinary-profile rows
holds in model
Outside-profile selections return only the bounded independent-review result.
Ordered trace
The state table shows model truth. Each observer result says what the current caller can establish at that step.
| Step | Actor | Action | Observer result |
|---|---|---|---|
| 11 ms | reader | Set producerContract to no-broker-confirmation | producerContract changes to no-broker-confirmation; dependent guarantee rows are recomputed and stale rows are removed. |
| 22 ms | reader | Set observation to not-observed | observation changes to not-observed; dependent guarantee rows are recomputed and stale rows are removed. |
Evidence and limits
Assumptions and known limits
- Selections describe declared contracts; they do not inspect a real system.
- Unknown evidence stays unknown instead of inheriting a favorable default.
- Capability projection is not certification, configuration advice, or live verification.
A capability row is not a pipeline certificate
The matrix projects declared contracts across publication, visibility, progress, identity, retention, and sink effects. It removes incompatible rows when the topology changes and keeps missing evidence UNKNOWN. Use the counterexample and evidence obligations to write a review question; do not turn the result into a production-safe score.
Assumptions and limits
- Feature levels, protocol versions, client settings, and binary versions remain separate facts.
- Replication examples use stable committed ISR membership between declared transitions.
- The ordinary transaction profile disables transaction.two.phase.commit.enable.
- Browser traces are deterministic teaching models, not broker observations or production recommendations.