67 lines
3.2 KiB
XML
67 lines
3.2 KiB
XML
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== Contextual Routing
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This issue has previously been adressed as "dynamic routing".
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Problem can be split in two, // TODO
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In Axum, routers can be configured using a fluid-like API #footnote[Term borrowed from C\# and OOP].
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#box[```rs
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#[tokio::main]
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async fn main() {
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let app = Router::new()
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.route("/", get(root))
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// .route("/posts", get(get_posts))
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.route("/posts/:post_id", get(get_post_by_id))
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.route("/posts/:post_id/discussions/+thread_ids", get(get_posts_threads));
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todo!("Actually listen")
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}
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async fn root() {
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todo!()
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}
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async fn get_post_by_id(Path(post_id): Path<String>) -> impl IntoResponse {
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todo!()
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}
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async fn get_posts_threads(Path(post_id): Path<String>, Path(discussion_thread_ids): Path<String>) -> impl IntoResponse {
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let discussion_thread_ids = discussion_thread_ids.split("/");
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todo!()
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}
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```]
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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.
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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.
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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.
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This can be used to obtain the remaining path of the request.
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=== Problem Description
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+ The API to implement e.g. has the concept of mount points (similar to how filesystems can be mounted on UNIX-like systems).
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Mount points can contain multiple slashes.
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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
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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.
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This implies a significant problem:
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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).
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+ Another problem is that based on the mount point, the request must be processed by the applicable secret engine.
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Based on context, stored on the DBMS, the request must be passed to the secret engine along with the determinated mount point.
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=== Solution
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Secret Engines have their dedicated router.
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The main router has an instance of these routers along with the database pool wrapped within a struct in its state.
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The router instances have a reference to the database pool, which is internally wrapped by an Atomic Reference Counter (`Arc`).
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Upon a requst, the remaining path is obtained (via `/+mount_path`).
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Then, the path is looked up at the database, also requsting the engine type.
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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".
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If found, the router is called with the request and mount path is given to the router as an "Extension".
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The `call` #link("https://docs.rs/tower/0.4.13/tower/trait.Service.html#tymethod.call")[(link)]
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function which Axum routers inherit from the Tower crate, allows to hand the request over to engine's router.
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