3tears-epoch

Generation-stamped configuration epochs with NATS broadcast and per-message echo for cross-pod cache-reload coherence.

Why

Multiple in-memory configuration caches across the platform need to stay coherent across pods on admin writes:

  • a model capabilities registry (registered at startup from the models table)
  • a catalog cache (gateway_models + gateway_providers + gateway_credit_rates)
  • per-tool MCP RBAC grants

Pure NATS broadcast (push) ships with a missed-message hole: a pod that didn't receive the broadcast (subscriber blip, pod just started during the window, JetStream redelivery edge) stays stale. Pure polling (pull) is correct but expensive on hot paths.

This package combines both: a strictly-monotonic generation number (epoch) per subject, broadcast best-effort via NATS and echoed in every relevant response message so consumers detect staleness on the next read and lazy-pull. Push for speed, pull for correctness.

The counter itself lives in a memory-backed NATS KV bucket for every epoch whose value stays inside the cluster. That is deliberate: an epoch is a coherence signal, not a durable fact, and a restart that loses the counter also loses every cache it was sequencing. The one exception is an epoch whose value escapes -- a tile epoch is the v{n} in a tile URL and reaches browser and CDN caches nothing here can reach -- and that family keeps a durable config_epochs row.

This is the standard pattern from etcd mod_revision + watch, K8s resourceVersion + informer, Envoy xDS version_info + ACK, DNS SOA serial + secondary refresh.

Deployment obligation: the KV grant

Every principal that bumps or reads an epoch must be granted the {ns}-epochs KV bucket (AGENT_POD, HUB, GATEWAY in threetears.nats.subject_permissions). A missing KV grant does not raise. A refused JetStream request is never answered, so the call blocks to its deadline and returns a timeout, indistinguishable by shape from an unreachable broker.

The log tells them apart. threetears.nats reads the server's permissions violation frame (which leaves the connection open, so nothing else reports it), names the bucket, and states the js_resources entry to add; the deadline path and a failed bucket open say the same. tests/enforcement/test_kv_bucket_grant_naming.py pins the grant against the bucket the client actually opens, which catches a wrong name before a deploy rather than in a log.

Consumers also register an on_reset callback and schedule a threetears.epoch.catchup_tick pass. A consumer that subscribes and schedules neither still receives broadcasts, and misses everything a broadcast can lose -- including a counter replaced by a broker restart, which every KV operation survives silently.

Identity

The unit of identity is the NATS subject path. Each consumer:

  1. Defines or uses an existing Subject builder for the configuration domain it owns (e.g. Subjects.capabilities_epoch() -> capabilities.epoch).
  2. Calls EpochClient.bump(subject, payload=...) after committing the row mutation that motivates the reload.
  3. Subscribes via EpochListener.subscribe(subject, on_bump=...) from sibling pods.

For the durable family, the hub's config_epochs row PK is the subject path string and Postgres is the source of truth. For everything else the KV counter is, keyed on the subject path (digested when the path falls outside the KV key grammar). The NATS broadcast is best-effort either way. A subscriber that missed every broadcast still catches up on the next request whose response echoes the higher epoch (per-message echo is consumer-side wiring; the framework supplies the building blocks).

Wire envelope

EpochBumpMessage is a frozen Pydantic v2 model:

  • subject_path: str is the namespaced subject the bump targets (the KV counter key, or the row PK for the durable tile family)
  • epoch: int is the new strictly-monotonic value
  • payload: dict[str, Any] | None is an opaque hint for the consumer's reload callback (e.g. {"model_id": "...", "action": "create"})

The framework never inspects payload. Consumers parse if useful, ignore if not. The hint exists so a domain that only changes one row can avoid reloading the entire derived view.

Postgres

CREATE TABLE IF NOT EXISTS config_epochs (
    subject_path TEXT PRIMARY KEY,
    epoch BIGINT NOT NULL DEFAULT 0,
    payload JSONB,
    date_updated TIMESTAMPTZ NOT NULL DEFAULT now()
);

bump(subject, payload) increments the subject's counter and returns the new value. For an ephemeral subject that is a DistributedCounter CAS loop over NATS KV; for the durable family it is INSERT ... ON CONFLICT (subject_path) DO UPDATE SET epoch = config_epochs.epoch + 1, payload = $2, date_updated = now() RETURNING epoch, serialized on the row lock. Both are atomic and both hand back a per-subject contiguous number, so 0 means "never bumped" and the first bump returns 1.

Migration ships as a PLATFORM-scope PackageMigrations registration so consumers wire it via the canonical MigrationRunner alongside the rest of their platform tables.

Project links

Data verified by PyPI on Sep 14, 2026
Data provided by the project maintainers, verified at the time the release was uploaded to PyPI.

Key dates

PyPI data
Data sourced directly from PyPI's database.
  • Released:
Latest release

1 maintainer

PyPI data
Data sourced directly from PyPI's database.
Avatar for pace from gravatar.com pace

Credits

Author: pace

GitHub Statistics

Data verified by PyPI on Sep 14, 2026
The GitHub source repository was provided by the project maintainers and verified by PyPI at the time of upload. Stars, forks, and open issues/PRs are derived from that repository and have not been independently verified.

License expression

MIT
View SPDX License List

Requires

Python >=3.14

Classifiers

Report project as malware

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

3tears_epoch-0.41.4.tar.gz (49.1 kB view details)

Uploaded Source

Built Distribution

If you're not sure about the file name format, learn more about wheel file names.

3tears_epoch-0.41.4-py3-none-any.whl (28.5 kB view details)

Uploaded Python 3

File details

Details for the file 3tears_epoch-0.41.4.tar.gz.

File metadata

  • Download URL: 3tears_epoch-0.41.4.tar.gz
  • Upload date:
  • Size: 49.1 kB
  • Tags: Source
  • Uploaded using Trusted Publishing? Yes
  • Uploaded via: twine/7.0.0 CPython/3.13.14

File hashes

Hashes for 3tears_epoch-0.41.4.tar.gz
Algorithm Hash digest
SHA256 a48888489d7ca78979f9036204424d4b5c0e0cc69620f2dc011b88dc5aeb2c7b
MD5 9bde452cd2a8a05b6adba5a879454981
BLAKE2b-256 1bfd40f9421258e48029b056cdcdb81013e2519100edb57bb1f80ee01e7a0708

See more details on using hashes here.

Provenance

The following attestation bundles were made for 3tears_epoch-0.41.4.tar.gz:

Publisher: release.yml on pacepace/3tears

Attestations: Values shown here reflect the state when the release was signed and may no longer be current.

File details

Details for the file 3tears_epoch-0.41.4-py3-none-any.whl.

File metadata

  • Download URL: 3tears_epoch-0.41.4-py3-none-any.whl
  • Upload date:
  • Size: 28.5 kB
  • Tags: Python 3
  • Uploaded using Trusted Publishing? Yes
  • Uploaded via: twine/7.0.0 CPython/3.13.14

File hashes

Hashes for 3tears_epoch-0.41.4-py3-none-any.whl
Algorithm Hash digest
SHA256 ea998b8b0b980128ca3499a2382308abfd28c098ca803f28da8708cfd4db1e58
MD5 7c31ca97605a1a0c6e34339ba80a14f7
BLAKE2b-256 f850554ef04d730a14928192ce8dee29514d61c2b36af2a4757fda5cab2b4053

See more details on using hashes here.

Provenance

The following attestation bundles were made for 3tears_epoch-0.41.4-py3-none-any.whl:

Publisher: release.yml on pacepace/3tears

Attestations: Values shown here reflect the state when the release was signed and may no longer be current.

Release history Release notifications | RSS feed

This release

0.41.4 This release

2 files

0.41.3

2 files

0.41.2

2 files

0.41.1

2 files

0.41.0

2 files

0.40.0

2 files

0.39.0

2 files

0.38.0

2 files

0.37.0

2 files

0.36.0

2 files

0.35.1

2 files

0.35.0

2 files

0.34.0

2 files

0.33.0

2 files

0.32.1

2 files

0.32.0

2 files

0.31.0

2 files

0.30.1

2 files

0.30.0

2 files

0.29.0

2 files

0.28.0

2 files

0.27.0

2 files

0.26.1

2 files

0.26.0

2 files

0.25.0

2 files

0.24.7

2 files

0.24.6

2 files

0.24.5

2 files

0.24.4

2 files

0.24.3

2 files

0.24.2

2 files

0.24.1

2 files

0.24.0

2 files

0.23.11

2 files

0.23.10

2 files

0.23.9

2 files

0.23.8

2 files

0.23.7

2 files

0.23.6

2 files

0.23.5

2 files

0.23.3

2 files

0.23.2

2 files

0.23.1

2 files

0.23.0

2 files

0.22.5

2 files

0.22.4

2 files

0.22.3

2 files

0.22.2

2 files

0.22.1

2 files

0.22.0

2 files

0.21.0

2 files

0.20.0

2 files

0.19.4

2 files

0.19.3

2 files

0.19.2

2 files

0.19.1

2 files

0.19.0

2 files

0.18.0

2 files

0.17.9

2 files

0.17.8

2 files

0.17.7

2 files

0.17.6

2 files

0.17.5

2 files

0.17.4

2 files

0.17.3

2 files

0.17.2

2 files

0.17.1

2 files

0.17.0

2 files

0.16.1

2 files

0.16.0

2 files

0.15.0

2 files

0.14.1

2 files

0.14.0

2 files

Anthropic, PBC Visionary sponsor Bloomberg Visionary sponsor Hudson River Trading Visionary sponsor Meta Visionary sponsor NVIDIA Visionary sponsor Microsoft Sustainability sponsor Depot Continuous Integration AWS Cloud computing and Security Sponsor Datadog Monitoring Fastly CDN Google Download Analytics Sentry Error logging StatusPage Status page