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This patch adds a `remote` backend for `ext/kv`. This supports connection to Deno Deploy and potentially other services compatible with the KV Connect protocol.
81 lines
3.2 KiB
Markdown
81 lines
3.2 KiB
Markdown
# deno_kv
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This crate provides a key/value store for Deno. For an overview of Deno KV,
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please read the [manual](https://deno.land/manual/runtime/kv).
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## Storage Backends
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Deno KV has a pluggable storage interface that supports multiple backends:
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- SQLite - backed by a local SQLite database. This backend is suitable for
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development and is the default when running locally.
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- Remote - backed by a remote service that implements the
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[KV Connect](#kv-connect) protocol, for example
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[Deno Deploy](https://deno.com/deploy).
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Additional backends can be added by implementing the `DatabaseHandler` trait.
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## KV Connect
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The KV Connect protocol has separate control and data planes to maximize
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throughput and minimize latency. _Metadata Exchange_ and _Data Path_ are the two
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sub-protocols that are used when talking to a KV Connect-compatible service.
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### Metadata Exchange
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To connect to a KV Connect service, the user provides an HTTP or HTTPS URL to
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`Deno.openKv`. A background task is then spawned to periodically make HTTP POST
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requests to the provided URL to refresh database metadata.
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The HTTP `Authorization` header is included and have the format
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`Bearer <access-token>`. The `<access-token>` is a static token issued by the
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service provider. For Deno Deploy, this is the personal access token generated
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from the dashboard. You can specify the access token with the environment
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variable `DENO_KV_ACCESS_TOKEN`.
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Request body is currently unused. The response is a JSON message that satisfies
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the [JSON Schema](https://json-schema.org/) definition in
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`cli/schemas/kv-metadata-exchange-response.v1.json`.
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Semantics of the response fields:
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- `version`: Protocol version. The only supported value is `1`.
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- `databaseId`: UUID of the database.
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- `endpoints`: Data plane endpoints that can serve requests to the database,
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along with their consistency levels.
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- `token`: An ephemeral authentication token that must be included in all
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requests to the data plane. This value is an opaque string and the client
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should not depend on its format.
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- `expiresAt`: The time at which the token expires. Encoded as an ISO 8601
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string.
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### Data Path
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After the first metadata exchange has completed, the client can talk to the data
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plane endpoints listed in the `endpoints` field using a Protobuf-over-HTTP
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protocol called the _Data Path_. The Protobuf messages are defined in
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`proto/datapath.proto`.
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Two sub-endpoints are available under a data plane endpoint URL:
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- `POST /snapshot_read`: Used for read operations: `kv.get()` and
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`kv.getMany()`.
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- **Request type**: `SnapshotRead`
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- **Response type**: `SnapshotReadOutput`
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- `POST /atomic_write`: Used for write operations: `kv.set()` and
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`kv.atomic().commit()`.
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- **Request type**: `AtomicWrite`
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- **Response type**: `AtomicWriteOutput`
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An HTTP `Authorization` header in the format `Bearer <ephemeral-token>` must be
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included in all requests to the data plane. The value of `<ephemeral-token>` is
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the `token` field from the metadata exchange response.
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### Error handling
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All non-client errors (i.e. network errors and HTTP 5xx status codes) are
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handled by retrying the request. Randomized exponential backoff is applied to
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each retry.
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Client errors cannot be recovered by retrying. A JavaScript exception is
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generated for each of those errors.
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