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 10, 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:
Newer release available (0.41.4)

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 10, 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-0.37.0.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-0.37.0-py3-none-any.whl (28.5 kB view details)

Uploaded Python 3

File details

Details for the file 3tears_epoch-0.37.0.tar.gz.

File metadata

  • Download URL: 3tears_epoch-0.37.0.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-0.37.0.tar.gz
Algorithm Hash digest
SHA256 1ea2b8a6d030206b7ffcb1b1622b532802d53be7a3a9665bbf1d297e215f9865
MD5 26f546d51bf91f58bb21a7f4385971b9
BLAKE2b-256 30daaea8c432de151a446becd647ee6059274f7366aca31b8bb377f8f7e02fa3

See more details on using hashes here.

Provenance

The following attestation bundles were made for 3tears_epoch-0.37.0.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-0.37.0-py3-none-any.whl.

File metadata

  • Download URL: 3tears_epoch-0.37.0-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-0.37.0-py3-none-any.whl
Algorithm Hash digest
SHA256 9bc2336e529f8460ce72c58d409626c5e5be6c421c10f7e0cb3ee87b6b34966f
MD5 f40c45331398a863af2e4ca5db35d2ab
BLAKE2b-256 d62d00853b0154504a72568496071185bfefbcd6b009f227c8d364269d77c4d0

See more details on using hashes here.

Provenance

The following attestation bundles were made for 3tears_epoch-0.37.0-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

0.41.4

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

This release

0.37.0 This release

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