DKNet

Implement a custom reservation store

Part of DKNet.AspCore.Idempotency. Implement IIdempotencyKeyStore directly; the shared relational classes are internal. This example inspects the contract and constructs the identity your store receives:

using DKNet.AspCore.Idempotency.Filtering;
using DKNet.AspCore.Idempotency.Store;
Console.WriteLine(typeof(IIdempotencyKeyStore).GetMethods().Length); // 2
var info = new IdempotentKeyInfo
{
    Endpoint = "/ORDERS", Method = "POST", IdempotentKey = "order-1"
};
Console.WriteLine(info.CompositeKey); // :POST:/ORDERS:order-1

A custom store must reserve atomically before reporting a new key, then replace that reservation with completion data.

Method	Return type	Required behavior
`IsKeyProcessedAsync(IdempotentKeyInfo)`	`ValueTask<(bool processed, CachedResponse? response)>`	Atomically reserve before returning `(false, null)`. Return `(true, null)` while in flight, or `(true, response)` after completion.
`MarkKeyAsProcessedAsync(IdempotentKeyInfo, CachedResponse)`	`ValueTask`	Replace the reservation with completion data and honor the intended retention window.

Use a bounded in-flight reservation, and make reclaim atomic. All shipped stores use status 102 as the reservation sentinel and SHA-256 over CompositeKey. A separate read followed by an unconditional write admits two winners.

CachedResponse requires StatusCode, nullable Body, ContentType, CreatedAt, and nullable ExpiresAt at construction. Its derived IsExpired compares the non-null expiry against UTC now. IdempotentKeyInfo requires Endpoint and Method; Scope defaults empty and IdempotentKey is nullable. The filter validates the key before handing it to the store.

⚠️ Gotchas & limits

Register your implementation with AddIdempotentKey<TStore>(). It is singleton and must support concurrent calls.
The interface supplies no cancellation token, transaction, release operation, or reservation ownership token.
Hash the full composite identity rather than stripping or truncating it. Never use SafeKey as storage identity.
Retention and duplicate behavior must be tested against the actual backing store; interface conformance alone proves no atomicity.

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