diff --git a/chapters/04-Architecture.typ b/chapters/04-Architecture.typ index f962f0b..55186be 100644 --- a/chapters/04-Architecture.typ +++ b/chapters/04-Architecture.typ @@ -1,3 +1,4 @@ = Architecture +#include "./architecture/Dynamic-Routing.typ" diff --git a/chapters/architecture/Dynamic-Routing.typ b/chapters/architecture/Dynamic-Routing.typ new file mode 100644 index 0000000..be3cd9d --- /dev/null +++ b/chapters/architecture/Dynamic-Routing.typ @@ -0,0 +1,67 @@ + +== Contextual Routing + +This issue has previously been adressed as "dynamic routing". + +Problem can be split in two, // TODO + +In Axum, routers can be configured using a fluid-like API #footnote[Term borrowed from C\# and OOP]. + +#box[```rs +#[tokio::main] +async fn main() { + let app = Router::new() + .route("/", get(root)) + // .route("/posts", get(get_posts)) + .route("/posts/:post_id", get(get_post_by_id)) + .route("/posts/:post_id/discussions/+thread_ids", get(get_posts_threads)); + + todo!("Actually listen") +} + +async fn root() { + todo!() +} + +async fn get_post_by_id(Path(post_id): Path) -> impl IntoResponse { + todo!() +} + +async fn get_posts_threads(Path(post_id): Path, Path(discussion_thread_ids): Path) -> impl IntoResponse { + let discussion_thread_ids = discussion_thread_ids.split("/"); + + todo!() +} +```] + +As it can be seen, a parameter can be extracted from the URL path by using `/:some_name` and can be placed as any infix of the URL: at the beginning, in the middle, or the end. +However, as the path is split by slash characters (`/`), the extracted part must not contain slashes and hence can only be (up to) one part of the path. + +Longer parts of the request can be obtained using `+some_name` and can only be placed as a postfix of the URL, but not other types of infixes. +This can be used to obtain the remaining path of the request. + +=== Problem Description + ++ The API to implement e.g. has the concept of mount points (similar to how filesystems can be mounted on UNIX-like systems). + Mount points can contain multiple slashes. + For example `/v1/some/mount/point/data/some/path/secret` may consist of a mount point `some/mount/point` and further, following routes of the mapped secret engine. //TODO + In this example, `/data` is related to the Key-Value engine and `/some/path/secret` specifies a path within the secret engine instance mounted at the mount point. + This implies a significant problem: + How to determinate what part of the URL displays a mount point, where it is not certan, what the postfix of the URL will be (this problem follows). + ++ Another problem is that based on the mount point, the request must be processed by the applicable secret engine. + Based on context, stored on the DBMS, the request must be passed to the secret engine along with the determinated mount point. + +=== Solution + +Secret Engines have their dedicated router. +The main router has an instance of these routers along with the database pool wrapped within a struct in its state. +The router instances have a reference to the database pool, which is internally wrapped by an Atomic Reference Counter (`Arc`). + +Upon a requst, the remaining path is obtained (via `/+mount_path`). +Then, the path is looked up at the database, also requsting the engine type. +If not found, the last last slash character and the following string is removed and looked up again. This is repeated, until the path either is found or has a length of zero, rejecting the request as "404 Not Found". + +If found, the router is called with the request and mount path is given to the router as an "Extension". +The `call` #link("https://docs.rs/tower/0.4.13/tower/trait.Service.html#tymethod.call")[(link)] +function which Axum routers inherit from the Tower crate, allows to hand the request over to engine's router.