Meridian Storage S3

meridian-storage-s3 is the S3-compatible Object Adapter for Meridian V1. It implements the released meridian-storage-object-common==1.0.2 contract behind the s3 adapter id. Consumers continue to use mapping-first object Catalog Expressions; bucket names, keys, endpoints, credentials, SDK objects, retention controls, and migration state remain private to deployment composition and this adapter.

Contract and guarantees

The adapter implements all eight V1 Object operation contracts:

• publish_schema and create_resource for adapter-owned Object registry metadata;
• streaming put and get with SHA-256 verification and bounded memory;
• inclusive read_range with per-chunk integrity verification;
• stat, maintenance-only bounded-prefix list, and exact-version delete;
• S3 multipart upload above a validated threshold;
• portable user metadata and immutability/retention intent;
• optional S3 Object Lock enforcement when the IaC-owned bucket enables it;
• deterministic capabilities, authenticated health probes, physical verification, and externally orchestrated migration hooks.

The adapter never provisions a bucket, changes bucket policy, enables versioning/Object Lock, creates identities, manages ACLs, configures lifecycle/replication/recovery, or returns a pre-signed URL. Those authorities remain with Platform or Vangu IaC.

Installation

python -m pip install meridian-storage-s3==1.0.2

Python 3.12 or newer is required. The package pins the released Object Common contract, resolving with Core 1.0.1 and Semantics 2.0.0. It is discovered through the meridian_storage.adapters entry-point group.

Deployment configuration

S3AdapterFactory consumes a closed Meridian BindingConfig. The physical namespace is bucket or bucket/prefix; the binding endpoint, opaque identity/credential secret values, TLS policy, and validated settings are translated privately to the S3 SDK. Supported settings are listed below; unknown settings fail closed.

• identity resolves to the UTF-8 S3 access-key id.
• credential resolves either to the UTF-8 secret access key or to {"secretAccessKey":"...","sessionToken":"..."} for temporary credentials.
• endpoint must already be resolved by IaC. HTTP is accepted only with disabled TLS and allowInsecureHttp: true; authenticated server TLS requires HTTPS plus resolved CA material. Mutual TLS is rejected because the boto3 transport cannot safely consume the Core client identity contract.
• region defaults to us-east-1; addressingStyle is auto, path, or virtual.
• multipartThresholdBytes, multipartPartBytes, spoolMemoryBytes, integrityChunkBytes, maxObjectBytes, maxRangeBytes, and maxAttempts are bounded before an SDK client or transfer is created.
• verifyAfterWrite defaults to true. checksumHeaders enables provider SHA-256 headers in addition to Meridian's mandatory end-to-end digest verification.
• serverSideEncryption is AES256 or aws:kms; kmsKeyId is required only for aws:kms.
• requireVersioning fails authenticated startup unless versioning is verified.
• objectLockMode is GOVERNANCE or COMPLIANCE and requires an IaC-created Object-Lock bucket.

Development-only HTTP endpoints require allowInsecureHttp: true. Production bindings should use authenticated TLS. Enforced retention is advertised only when objectLockMode is configured and the authenticated probe verifies Object Lock on the bucket. This is enforcement evidence, not a WORM compliance or certification claim.

S3MigrationHooks exposes a deterministic forward-only metadata plan and idempotent apply hook. It validates access and records the adapter metadata revision; the external IaC migration job still owns scheduling, rollback/recovery decisions, bucket changes, and lifecycle policy.

Failure and data handling

Payloads are spooled with bounded memory, hashed before publication, uploaded with conditional metadata records, and read back for verification by default. Multipart sessions are aborted on every incomplete path. Range reads fetch and verify every complete integrity chunk covering the requested inclusive range. Logical ids, bucket names, endpoints, credentials, physical keys, and provider response text are absent from consumer references and normalized failures.

The adapter maps authenticated provider failures to the released Object error taxonomy, including conditional conflicts, not-found, range, throttling, quota, corruption, authorization, retention, and unavailable outcomes. Maintenance listing scans a bounded number of pages and uses an opaque logical cursor.

Verification

python -m pytest
python -m mypy src
python -m ruff check .
python -m build

The integration suite targets a disposable real MinIO server and runs the released Object Common conformance runner plus provider-specific multipart, range, metadata, retention, and normalized failure checks. The engine image is pinned by immutable multi-platform digest. CI regenerates and byte-compares the committed conformance report; the locked design/contract inputs and released Object Common wheel hash are recorded in the design baseline.

License

Apache License 2.0. See LICENSE and NOTICE.

Payload composition (1.0.1)

Installed S3 discovery uses Object Common’s default_payload_registry(). An Object consumer using that same default can upload and read through Meridian without registering a second S3 factory. Core intentionally rejects injecting s3 again when its installed entry point is present. Explicit SPI compositions may still pass S3AdapterFactory(payloads=registry); an empty registry is preserved by identity.