Server: remove CacheKey::PREFIX_CACHE, kv_def!, string_kv_def!

Removes the associated const `PREFIX_CACHE` from the `CacheKey` trait,
and supporting macro APIs.

This diff should be non-breaking in that the key strings should be the
same as before, just without the API confusion.

Formerly it was possible to specify an override for the prefix of cache
keys via an optional 3rd arg to `kv_def!`, and `string_kv_def!`.

The issue is, the override (or the default when omitted) are not
included in the actual string form of the key unless you explicitly
`format!()` it in there.

This is to say, the following are equivalent:

```rust
// specify the override, then manually format it in.
kv_def!(KeyA, ValA, "MY_PREFIX")
impl KeyA {
  pub fn new(x: &str) -> Self {
    Self(format!("{Self::PREFIX_CACHE}_{x}"))
  }
}

// no override, so `Self::PREFIX_CACHE` is whatever the default is, but
// it doesn't matter... it's not included in the key string :(
kv_def!(KeyA, ValA)
impl KeyA {
  pub fn new(x: &str) -> Self {
    // Including the prefix here means this version of KeyA is equiv
    Self(format!("MY_PREFIX_{x}"))
  }
}
```

The problem comes when you omit `Self::PREFIX_CACHE` in the key string itself.
The assumption would be either the default prefix, or an override when
specified, would be included in the string automatically, but it isn't.

Removing the confusing 3rd arg from the macros and eliminating the
associated const should mean moving forward: "wysiwyg." If there's a
prefix in the key string, that's the prefix. There's no need for
defaults or overrides.

Author: svix-onelson

server/svix-server/src/core/cache/mod.rs

@@ -38,10 +38,9 @@ pub enum Error {
 type Result<T> = std::result::Result<T, Error>;
 
 /// A valid key value for the cache -- usually just a wrapper around a [`String`]
-pub trait CacheKey: AsRef<str> + Send + Sync {
-    const PREFIX_CACHE: &'static str = "SVIX_CACHE";
-}
-/// Any (de)serializable structure usuable as a value in the cache -- it is associated with a
+pub trait CacheKey: AsRef<str> + Send + Sync {}
+
+/// Any (de)serializable structure usable as a value in the cache -- it is associated with a
 /// given key type to ensure type checking on creation or reading of values from the cache
 pub trait CacheValue: DeserializeOwned + Serialize + Send + Sync {
     type Key: CacheKey;
@@ -74,14 +73,6 @@ pub(crate) use kv_def_inner;
 /// A macro that creates a [`CacheKey`] and ties it to any value that implements
 /// [`DeserializeOwned`] and [`Serialize`]
 macro_rules! kv_def {
-    ($key_id:ident, $val_struct:ident, $lit_prefix:literal) => {
-        crate::core::cache::kv_def_inner!($key_id, $val_struct);
-
-        impl CacheKey for $key_id {
-            const PREFIX_CACHE: &'static str = $lit_prefix;
-        }
-    };
-
     ($key_id:ident, $val_struct:ident) => {
         crate::core::cache::kv_def_inner!($key_id, $val_struct);
 
@@ -115,14 +106,6 @@ pub(crate) use string_kv_def_inner;
 // Used downstream and for testing:
 #[allow(unused_macros)]
 macro_rules! string_kv_def {
-    ($key_id:ident, $val_struct:ident, $lit_prefix:literal) => {
-        crate::core::cache::string_kv_def_inner!($key_id, $val_struct);
-
-        impl CacheKey for $key_id {
-            const PREFIX_CACHE: &'static str = $lit_prefix;
-        }
-    };
-
     ($key_id:ident, $val_struct:ident) => {
         crate::core::cache::string_kv_def_inner!($key_id, $val_struct);
 

server/svix-server/src/core/idempotency.rs

@@ -52,7 +52,7 @@ enum SerializedResponse {
     },
 }
 
-kv_def!(IdempotencyKey, SerializedResponse, "SVIX_IDEMPOTENCY_CACHE");
+kv_def!(IdempotencyKey, SerializedResponse);
 
 impl IdempotencyKey {
     fn new(auth_token: &str, key: &str, url: &str) -> IdempotencyKey {
@@ -65,6 +65,7 @@ impl IdempotencyKey {
         hasher.update(url);
 
         let res = hasher.finalize();
+        // FIXME: add (previously omitted) prefix: `SVIX_IDEMPOTENCY_CACHE`
         IdempotencyKey(base64::encode(res))
     }
 }

server/svix-server/src/core/message_app.rs

@@ -214,7 +214,7 @@ impl AppEndpointKey {
     // FIXME: Rewrite doc comment when AppEndpointValue members are known
     /// Returns a key for fetching all cached endpoints for a given organization and application.
     pub fn new(org: &OrganizationId, app: &ApplicationId) -> AppEndpointKey {
-        AppEndpointKey(format!("{}_APP_v3_{}_{}", Self::PREFIX_CACHE, org, app))
+        AppEndpointKey(format!("SVIX_CACHE_APP_v3_{}_{}", org, app))
     }
 }
 

server/svix-server/src/worker.rs

@@ -73,7 +73,7 @@ pub struct FailureCacheValue {
     pub first_failure_at: DateTimeUtc,
 }
 
-kv_def!(FailureCacheKey, FailureCacheValue, "SVIX_FAILURE_CACHE");
+kv_def!(FailureCacheKey, FailureCacheValue);
 
 impl FailureCacheKey {
     pub fn new(
@@ -82,11 +82,8 @@ impl FailureCacheKey {
         endp_id: &EndpointId,
     ) -> FailureCacheKey {
         FailureCacheKey(format!(
-            "{}_{}_{}_{}",
-            Self::PREFIX_CACHE,
-            org_id,
-            app_id,
-            endp_id
+            "SVIX_FAILURE_CACHE_{}_{}_{}",
+            org_id, app_id, endp_id
         ))
     }
 }