h2hdb

h2hdb is the database and coordination core for the H2HDB multi-repository system. It owns the SQLite/MariaDB schema, bounded transactional workflows, and backend-neutral application facades. Komga and OPDS use the catalog facade; ingest uses the transaction-owning ingest facade and downloader uses the queue facade.

It deliberately does not scan files, parse galleryinfo.txt, manipulate images, choose filesystem paths, serve HTTP, serialize OPDS documents, or depend on hbrowser. Those responsibilities belong to consumer adapters and sibling packages.

What this package provides

  • One generated epoch-3/schema-v2 schema for SQLite and MariaDB.
  • Safe initialization, full schema auditing, and lightweight readiness probes.
  • Current-catalog discovery with Unicode-normalized search, exact facets, keyset pagination, and fixed recently uploaded/downloaded windows.
  • Single-publication, acquisition, cover, thumbnail, and ordered-page metadata through immutable backend-neutral values.
  • Durable download, ingest, publication, cleanup, lease, and retry coordination through public facades.

Catalog readers only see the current publication head. A caller-supplied revision or cursor is checked against durable database authority and fails closed if the catalog advances or the value was forged.

Compatibility model

The active database identity is epoch=3, schema_version=2. This is a greenfield contract: schema v2 does not upgrade or adopt schema v1 or any older database, provide compatibility views, retain old list APIs, or dual-write old and new shapes. Replace an earlier database with a truly empty database and rebuild it from source through the current ingest integration.

migrate constructs or resumes only this checksum-bound schema. An interrupted matching BUILDING run can resume; a previous, foreign, drifted, or otherwise non-empty database is rejected rather than adopted or repaired in place.

The logical schema sources are verification/schema/catalog.toml and verification/schema/operational.toml. Generated artifacts and executable checks are authoritative for relation and bootstrap details, so this README does not copy counts that can drift.

Installation

h2hdb requires Python 3.14 or later. Install the published package into each core administration or consumer environment:

python -m pip install h2hdb

For development from a source checkout, rebuild the repository-local Python and Markdown tool environments with:

./scripts/rebuild-env.sh

Configuration

{
  "database": {
    "sql_type": "sqlite",
    "database": "/var/lib/h2hdb/catalog.sqlite3",
    "access_mode": "read-write"
  },
  "maintenance": {
    "optimize_enabled": true
  },
  "logger": {
    "level": "INFO",
    "file": null
  }
}

For MariaDB, also set host, port, user, password, and database. The supported MariaDB baseline is 10.11.11, including Synology's 10.11.11-1551 package build. The integration gate pins the upstream mariadb:10.11.11 image and verifies the server version before creating its test database. Read-only consumers should use "access_mode": "read-only" and a database account limited to the metadata/read privileges required by schema validation and application reads.

JSON string values consisting exactly of ${ENV_NAME} are resolved from the process environment before validation. Variable names must match [A-Za-z_][A-Za-z0-9_]*; missing or invalid variables stop startup without including their values in the error. Inline interpolation such as db-${INSTANCE} is deliberately unsupported, and unknown JSON fields are rejected.

Schema administration

The CLI exposes exactly three operations:

python -m h2hdb migrate --config config.json
python -m h2hdb check --config config.json
python -m h2hdb ready --config config.json

Choose the operation from database state:

Database state or caller Operation
Truly empty database Run migrate to construct epoch 3/schema v2
Matching interrupted BUILDING epoch Rerun migrate to resume
Matching READY epoch Run read-only check for the full audit
Consumer startup Run check; never initialize schema
Frequent readiness probe Run the O(1) read-only ready check
Previous, foreign, or drifted schema Create a new empty database and rebuild

The wheel-resident generated provider must resolve every required runtime validator and recurring writer binding before it opens or mutates a database; the public administration API does not accept a substitute provider. check holds a read transaction while validating the complete READY schema; ready validates only the exact epoch/version/manifest marker.

Applications can use the same administration boundary directly:

from h2hdb import VNextDatabaseAdminFacade, load_config

config = load_config("config.json")
admin = VNextDatabaseAdminFacade(config)
admin.initialize()  # deployment init job only
admin.check()  # full read-only audit
admin.check_readiness()  # lightweight probe

Public application API

Consumers should import the public facades and immutable domain values from h2hdb; they must not import connector, repository, generated-schema, or table implementation modules.

Current-head catalog reads use open_database, which performs the full manifest-bound READY audit before returning a VNextCatalogFacade. The CatalogRevision returned by get_catalog_revision() can fence subsequent calls and is accepted only while it still equals the current head; a head advance makes an older descriptor fail closed:

from h2hdb import (
    CatalogDiscoveryQuery,
    CatalogFacetKind,
    CatalogRecentOrder,
    load_config,
    open_database,
)

catalog = open_database(load_config("readonly-config.json"))
revision = catalog.get_catalog_revision()
query = CatalogDiscoveryQuery(search="example title")
page = catalog.discover_publications(
    query=query,
    limit=50,
    revision=revision,
)
languages = catalog.list_publication_facets(
    facet=CatalogFacetKind.LANGUAGE,
    query=query,
    limit=50,
    revision=revision,
)
recent = catalog.list_recent_publications(
    order=CatalogRecentOrder.UPLOADED,
    revision=revision,
)
publication_id = "urn:h2h:gallery:42"
publication = catalog.get_publication(publication_id, revision=revision)
presentation = catalog.get_publication_presentation(
    publication_id,
    revision=revision,
)

discover_publications() uses seek cursors and accepts normalized AND search plus exact language, subject, and contributor filters. Search is backed only by the revision-scoped SQL index; it does not hydrate every publication to match in Python. list_publication_facets() exposes exact language, subject, and contributor counts under the other active filters. list_recent_publications() has no caller limit or cursor: it returns the complete fixed window of at most 128 acquisition-bearing publications in uploaded or downloaded order.

Acquisitions and images are exposed as immutable, backend-neutral descriptors. The acquisition descriptor carries a download name, media type, and opaque storage-object identity. Presentation reads expose cover, thumbnail, page count, and individual page descriptors with byte extent, media type, digest, and image dimensions. Consumers resolve those descriptors through their own storage adapter; core neither assumes a CBZ layout nor opens image/archive bytes.

Download request creation, bounded listing, and exact-request completion use VNextDownloadQueueFacade:

from h2hdb import VNextDownloadQueueFacade, load_config

queue = VNextDownloadQueueFacade(load_config("writer-config.json"))
request = queue.request_download(42, "https://example.invalid/gallery/42")
pending = queue.list_download_requests(limit=100)
queue.complete_download_request(request)

Each facade call owns fresh database connections and bounded transactions. Catalog reads use a pinned snapshot and then a fresh current-head fence before returning, so a concurrent head advance fails closed. Repository methods that accept connectors or units of work remain internal coordination surfaces.

VNextIngestFacade.prepare_source() consumes the source adapter once, outside every database transaction, and freezes the exact observation pages in a private disk-backed spool. The manifest preflight and later bounded staging steps therefore read the same immutable bytes even if the live source changes mid-run; closing the prepared-source handle removes the temporary spool.

After complete_ingest() releases its SHARED gate lease, resident integrations call VNextIngestFacade.drain_current_only_maintenance(). Each cleanup transaction selects at most 256 logical cleanup keys/families under a renewable EXCLUSIVE lease; each selected key executes only a schema-fixed bounded set of physical deletes. One public attempt advances at most 16 cleanup batches. The typed result is DONE, PROGRESSED, BLOCKED, or CONTENDED; residents immediately retry PROGRESSED, while blocked/contended attempts use the ordinary poll cadence. Every result retains no caller capability, and durable shard checkpoints make response-loss replay safe. Cleanup retains the prior payload until the new current receipt is fully PUBLISHED and no live publication-candidate or source-build predecessor pins it.

Byte ownership and current limits

The ingest integration owns concrete archive and artwork bytes: it renders, stores, protects, resolves, and eventually releases them through its adapters. Core owns only transactional coordination and sealed neutral descriptors; it does not choose storage paths, mandate CBZ/ZIP, decode artwork, or perform filesystem/object-storage I/O.

The durable contract needed to derive CatalogPublication.redownload_required for the current revision is not closed. Readers therefore do not infer it from transient operational rows.

Deployment

The repositories remain independent packages; they are not a shared uv workspace. See docs/multi-repo-deployment.md for database ownership, clean initialization, credentials, startup order, descriptor resolution, and backup boundaries.

Development and verification

Repository contributors should read AGENTS.md before changing code or schema. The local fast check and complete release check are:

./scripts/check-fast.sh
./scripts/check-full.sh

The full check covers formatting, typing, tests, generated-schema drift, schema surface, formal evidence, the installed distribution, SQLite, and the pinned MariaDB 10.11.11 integration profile. MariaDB tests require Docker and H2HDB_TEST_MARIADB=1.

For an isolated editable-install smoke containing explicit consumer sources, run:

./scripts/rebuild-multirepo-integration.sh

Consumers otherwise resolve from the configured package index. To exercise an unpublished wheel, Git ref, or local project, pass it explicitly by package name:

./scripts/rebuild-multirepo-integration.sh \
  --source h2hdb-ingest=/tmp/h2hdb_ingest.whl \
  --source h2hdb-opds='git+https://github.com/Kuan-Lun/h2hdb-opds.git@ref'

License

GNU General Public License version 3 (GPLv3). See LICENSE for the complete terms.

Project links

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Newer release available (0.31.0)

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Credits

Author: Kuan-Lun Wang

GitHub Statistics

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GPL-3.0-only
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Requires

Python >=3.14

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