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// Copyright 2020 Oxide Computer Company /*! * Dropshot is a general-purpose crate for exposing REST APIs from a Rust * program. Planned highlights include: * * * Suitability for production use on a largely untrusted network. * Dropshot-based systems should be high-performing, reliable, debuggable, and * secure against basic denial of service attacks (intentional or otherwise). * * * First-class OpenAPI support, in the form of precise OpenAPI specs generated * directly from code. This works because the functions that serve HTTP * resources consume arguments and return values of specific types from which * a schema can be statically generated. * * * Ease of integrating into a diverse team. An important use case for * Dropshot consumers is to have a team of engineers where individuals might * add a few endpoints at a time to a complex server, and it should be * relatively easy to do this. Part of this means an emphasis on the * principle of least surprise: like Rust itself, we may choose abstractions * that require more time to learn up front in order to make it harder to * accidentally build systems that will not perform, will crash in corner * cases, etc. * * By "REST API", we primarily mean an API built atop existing HTTP primitives, * organized into hierarchical resources, and providing consistent, idempotent * mechanisms to create, update, list, and delete those resources. "REST" can * mean a range of things depending on who you talk to, and some people are * dogmatic about what is or isn't RESTy. We find such dogma not only * unhelpful, but poorly defined. (Consider such a simple case as trying to * update a resource in a REST API. Popular APIs sometimes use `PUT`, `PATCH`, * or `POST` for the verb; and JSON Merge Patch or JSON Patch as the format. * (sometimes without even knowing it!). There's hardly a clear standard, yet * this is a really basic operation for any REST API.) * * For a discussion of alternative crates considered, see Oxide RFD 10. * * We hope Dropshot will be fairly general-purpose, but it's primarily intended * to address the needs of the Oxide control plane. * * * ## Usage * * The bare minimum might look like this: * * ```no_run * use dropshot::ApiDescription; * use dropshot::ConfigDropshot; * use dropshot::ConfigLogging; * use dropshot::ConfigLoggingLevel; * use dropshot::HttpServer; * use std::sync::Arc; * * #[tokio::main] * async fn main() -> Result<(), String> { * // Set up a logger. * let log = * ConfigLogging::StderrTerminal { * level: ConfigLoggingLevel::Info, * } * .to_logger("minimal-example") * .map_err(|e| e.to_string())?; * * // Describe the API. * let mut api = ApiDescription::new(); * // Register API functions -- see detailed example or ApiDescription docs. * * // Start the server. * let mut server = * HttpServer::new( * &ConfigDropshot { * bind_address: "127.0.0.1:0".parse().unwrap(), * request_body_max_bytes: 1024, * }, * api, * Arc::new(()), * &log, * ) * .map_err(|error| format!("failed to start server: {}", error))?; * * let server_task = server.run(); * server.wait_for_shutdown(server_task).await * } * ``` * * This server returns a 404 for all resources because no API functions were * registered. See `examples/basic.rs` for a simple, documented example that * provides a few resources using shared state. * * For a given `ApiDescription`, you can also print out an OpenAPI spec * describing the API. See [`ApiDescription::openapi`]. * * * ## API Handler Functions * * HTTP talks about **resources**. For a REST API, we often talk about * **endpoints** or **operations**, which are identified by a combination of the * HTTP method and the URI path. * * Example endpoints for a resource called a "project" might include: * * * `GET /projects` (list projects) * * `POST /projects` (one way to create a project) * * `GET /projects/my_project` (fetch one project) * * `PUT /projects/my_project` (update (or possibly create) a project) * * `DELETE /projects/my_project` (delete a project) * * With Dropshot, an incoming request for a given API endpoint is handled by a * particular Rust function. That function is called an **entrypoint**, an * **endpoint handler**, or a **handler function**. When you set up a Dropshot * server, you configure the set of available API endpoints and which functions * will handle each one by setting up an [`ApiDescription`]. * * Typically, you define an endpoint with a handler function by using the * [`endpoint`] macro. Here's an example of a single endpoint that lists * a hardcoded project: * * ``` * use dropshot::endpoint; * use dropshot::ApiDescription; * use dropshot::HttpError; * use dropshot::HttpResponseOk; * use dropshot::RequestContext; * use http::Method; * use schemars::JsonSchema; * use serde::Serialize; * use std::sync::Arc; * * /** Represents a project in our API */ * #[derive(Serialize, JsonSchema)] * struct Project { * /** name of the project */ * name: String, * } * * /** Fetch a project. */ * #[endpoint { * method = GET, * path = "/projects/project1", * }] * async fn myapi_projects_get_project( * rqctx: Arc<RequestContext>, * ) -> Result<HttpResponseOk<Project>, HttpError> * { * let project = Project { name: String::from("project1") }; * Ok(HttpResponseOk(project)) * } * * fn main() { * let mut api = ApiDescription::new(); * * /* * * Register our endpoint and its handler function. The "endpoint" macro * * specifies the HTTP method and URI path that identify the endpoint, * * allowing this metadata to live right alongside the handler function. * */ * api.register(myapi_projects_get_project).unwrap(); * * /* ... (use `api` to set up an `HttpServer` ) */ * } * * ``` * * There's quite a lot going on here: * * * The `endpoint` macro specifies the HTTP method and URI path. When we * invoke `ApiDescription::register()`, this information is used to register * the endpoint that will be handled by our function. * * The signature of our function indicates that on success, it returns a * `HttpResponseOk<Project>`. This means that the function will * return an HTTP 200 status code ("OK") with an object of type `Project`. * * The function itself has a Rustdoc comment that will be used to document * this _endpoint_ in the OpenAPI schema. * * From this information, Dropshot can generate an OpenAPI specification for * this API that describes the endpoint (which OpenAPI calls an "operation"), * its documentation, the possible responses that it can return, and the schema * for each type of response (which can also include documentation). This is * largely known statically, though generated at runtime. * * * ### `#[endpoint { ... }]` attribute parameters * * The `endpoint` attribute accepts parameters the affect the operation of * the endpoint as well as metadata that appears in the OpenAPI description * of it. * * ```ignore * #[endpoint { * // Required fields * method = { DELETE | GET | PATCH | POST | PUT }, * path = "/path/name/with/{named}/{variables}", * * // Optional fields * tags = [ "all", "your", "OpenAPI", "tags" ], * }] * ``` * * This is where you specify the HTTP method and path (including path variables) * for the API endpoint. These are used as part of endpoint registration and * appear in the OpenAPI spec output. * * The tags field is used to categorize API endpoints and only impacts the * OpenAPI spec output. * * * ### Function parameters * * In general, a handler function looks like this: * * ```ignore * async fn f( * rqctx: Arc<RequestContext>, * [query_params: Query<Q>,] * [path_params: Path<P>,] * [body_param: TypedBody<J>,] * ) -> Result<HttpResponse*, HttpError> * ``` * * Other than the RequestContext, parameters may appear in any order. The types * `Query`, `Path`, and `TypedBody` are called **Extractors** because they cause * information to be pulled out of the request and made available to the handler * function. * * * [`Query`]`<Q>` extracts parameters from a query string, deserializing them * into an instance of type `Q`. `Q` must implement `serde::Deserialize` and * `schemars::JsonSchema`. * * [`Path`]`<P>` extracts parameters from HTTP path, deserializing them into * an instance of type `P`. `P` must implement `serde::Deserialize` and * `schemars::JsonSchema`. * * [`TypedBody`]`<J>` extracts content from the request body by parsing the * body as JSON and deserializing it into an instance of type `J`. `J` must * implement `serde::Deserialize` and `schemars::JsonSchema`. * * If the handler takes a `Query<Q>`, `Path<P>`, or a `TypedBody<J>` and the * corresponding extraction cannot be completed, the request fails with status * code 400 and an error message reflecting a validation error. * * As with any serde-deserializable type, you can make fields optional by having * the corresponding property of the type be an `Option`. Here's an example of * an endpoint that takes two arguments via query parameters: "limit", a * required u32, and "marker", an optional string: * * ``` * use http::StatusCode; * use dropshot::HttpError; * use dropshot::TypedBody; * use dropshot::Query; * use dropshot::RequestContext; * use hyper::Body; * use hyper::Response; * use schemars::JsonSchema; * use serde::Deserialize; * use std::sync::Arc; * * #[derive(Deserialize, JsonSchema)] * struct MyQueryArgs { * limit: u32, * marker: Option<String> * } * * async fn myapi_projects_get( * _: Arc<RequestContext>, * query: Query<MyQueryArgs>) * -> Result<Response<Body>, HttpError> * { * let query_args = query.into_inner(); * let limit: u32 = query_args.limit; * let marker: Option<String> = query_args.marker; * Ok(Response::builder() * .status(StatusCode::OK) * .body(format!("limit = {}, marker = {:?}\n", limit, marker).into())?) * } * ``` * * ### Endpoint function return types * * Endpoint handler functions are async, so they always return a `Future`. When * we say "return type" below, we use that as shorthand for the output of the * future. * * An endpoint function must return a type that implements `HttpResponse`. * Typically this should be a type that implements `HttpTypedResponse` (either * one of the Dropshot-provided ones or one of your own creation). * * The more specific a type returned by the handler function, the more can be * validated at build-time, and the more specific an OpenAPI schema can be * generated from the source code. For example, a POST to an endpoint * "/projects" might return `Result<HttpResponseCreated<Project>, HttpError>`. * As you might expect, on success, this turns into an HTTP 201 "Created" * response whose body is constructed by serializing the `Project`. In this * example, OpenAPI tooling can identify at build time that this function * produces a 201 "Created" response on success with a body whose schema matches * `Project` (which we already said implements `Serialize`), and there would be * no way to violate this contract at runtime. * * These are the implementations of `HttpTypedResponse` with their associated * HTTP response code * on the HTTP method: * * | Return Type | HTTP status code | * | ----------- | ---------------- | * | [`HttpResponseOk`] | 200 | * | [`HttpResponseCreated`] | 201 | * | [`HttpResponseAccepted`] | 202 | * | [`HttpResponseDeleted`] | 204 | * | [`HttpResponseUpdatedNoContent`] | 204 | * * In situations where the response schema is not fixed, the endpoint should * return `Response<Body>`, which also implements `HttpResponse`. Note that * the OpenAPI spec will not include any status code or type information in * this case. * * ## What about generic handlers that run on all requests? * * There's no mechanism in Dropshot for this. Instead, it's recommended that * users commonize code using regular Rust functions and calling them. See the * design notes in the README for more on this. * * * ## Support for paginated resources * * "Pagination" here refers to the interface pattern where HTTP resources (or * API endpoints) that provide a list of the items in a collection return a * relatively small maximum number of items per request, often called a "page" * of results. Each page includes some metadata that the client can use to make * another request for the next page of results. The client can repeat this * until they've gotten all the results. Limiting the number of results * returned per request helps bound the resource utilization and time required * for any request, which in turn facilities horizontal scalability, high * availability, and protection against some denial of service attacks * (intentional or otherwise). For more background, see the comments in * dropshot/src/pagination.rs. * * Pagination support in Dropshot implements this common pattern: * * * This server exposes an **API endpoint** that returns the **items** * contained within a **collection**. * * The client is not allowed to list the entire collection in one request. * Instead, they list the collection using a sequence of requests to the one * endpoint. We call this sequence of requests a **scan** of the collection, * and we sometimes say that the client **pages through** the collection. * * The initial request in the scan may specify the **scan parameters**, which * typically specify how the results are to be sorted (i.e., by which * field(s) and whether the sort is ascending or descending), any filters to * apply, etc. * * Each request returns a **page** of results at a time, along with a **page * token** that's provided with the next request as a query parameter. * * The scan parameters cannot change between requests that are part of the * same scan. * * With all requests: there's a default limit (e.g., 100 items returned at a * time). Clients can request a higher limit using a query parameter (e.g., * `limit=1000`). This limit is capped by a hard limit on the server. If the * client asks for more than the hard limit, the server can use the hard limit * or reject the request. * * As an example, imagine that we have an API endpoint called `"/animals"`. Each * item returned is an `Animal` object that might look like this: * * ```json * { * "name": "aardvark", * "class": "mammal", * "max_weight": "80", /* kilograms, typical */ * } * ``` * * There are at least 1.5 million known species of animal -- too many to return * in one API call! Our API supports paginating them by `"name"`, which we'll * say is a unique field in our data set. * * The first request to the API fetches `"/animals"` (with no querystring * parameters) and returns: * * ```json * { * "page_token": "abc123...", * "items": [ * { * "name": "aardvark", * "class": "mammal", * "max_weight": "80", * }, * ... * { * "name": "badger", * "class": "mammal", * "max_weight": "12", * } * ] * } * ``` * * The subsequent request to the API fetches `"/animals?page_token=abc123..."`. * The page token `"abc123..."` is an opaque token to the client, but typically * encodes the scan parameters and the value of the last item seen * (`"name=badger"`). The client knows it has completed the scan when it * receives a response with no `page_token` in it. * * Our API endpoint can also support scanning in reverse order. In this case, * when the client makes the first request, it should fetch * `"/animals?sort=name-descending"`. Now the first result might be `"zebra"`. * Again, the page token must include the scan parameters so that in subsequent * requests, the API endpoint knows that we're scanning backwards, not forwards, * from the value we were given. It's not allowed to change directions or sort * order in the middle of a scan. (You can always start a new scan, but you * can't pick up from where you were in the previous scan.) * * It's also possible to support sorting by multiple fields. For example, we * could support `sort=class-name`, which we could define to mean that we'll * sort the results first by the animal's class, then by name. Thus we'd get * all the amphibians in sorted order, then all the mammals, then all the * reptiles. The main requirement is that the combination of fields used for * pagination must be unique. We cannot paginate by the animal's class alone. * (To see why: there are over 6,000 mammals. If the page size is, say, 1000, * then the page_token would say `"mammal"`, but there's not enough information * there to see where we are within the list of mammals. It doesn't matter * whether there are 2 mammals or 6,000 because clients can limit the page size * to just one item if they want and that ought to work.) * * * ### Dropshot interfaces for pagination * * We can think of pagination in two parts: the input (handling the pagination * query parameters) and the output (emitting a page of results, including the * page token). * * For input, a paginated API endpoint's handler function should accept a * [`Query`]`<`[`PaginationParams`]`<ScanParams, PageSelector>>`, where * `ScanParams` is a consumer-defined type specifying the parameters of the scan * (typically including the sort fields, sort order, and filter options) and * `PageSelector` is a consumer-defined type describing the page token. The * PageSelector will be serialized to JSON and base64-encoded to construct the * page token. This will be automatically parsed on the way back in. * * For output, a paginated API endpoint's handler function can return * `Result<`[`HttpResponseOk`]<[`ResultsPage`]`<T>, HttpError>` where `T: * Serialize` is the item listed by the endpoint. You can also use your own * structure that contains a [`ResultsPage`] (possibly using * `#[serde(flatten)]`), if that's the behavior you want. * * There are several complete, documented examples in the "examples" directory. * * * ### Advanced usage notes * * It's possible to accept additional query parameters besides the pagination * parameters by having your API endpoint handler function take two different * arguments using `Query`, like this: * * ``` * use dropshot::HttpError; * use dropshot::HttpResponseOk; * use dropshot::PaginationParams; * use dropshot::Query; * use dropshot::RequestContext; * use dropshot::ResultsPage; * use dropshot::endpoint; * use schemars::JsonSchema; * use serde::Deserialize; * use std::sync::Arc; * # use serde::Serialize; * # #[derive(Debug, Deserialize, JsonSchema)] * # enum MyScanParams { A }; * # #[derive(Debug, Deserialize, JsonSchema, Serialize)] * # enum MyPageSelector { A(String) }; * #[derive(Deserialize, JsonSchema)] * struct MyExtraQueryParams { * do_extra_stuff: bool, * } * * #[endpoint { * method = GET, * path = "/list_stuff" * }] * async fn my_list_api( * rqctx: Arc<RequestContext>, * pag_params: Query<PaginationParams<MyScanParams, MyPageSelector>>, * extra_params: Query<MyExtraQueryParams>, * ) -> Result<HttpResponseOk<ResultsPage<String>>, HttpError> * { * # unimplemented!(); * /* ... */ * } * ``` * * You might expect that instead of doing this, you could define your own * structure that includes a `PaginationParams` using `#[serde(flatten)]`, and * this ought to work, but it currently doesn't due to serde_urlencoded#33, * which is really serde#1183. */ mod api_description; mod config; mod error; mod from_map; mod handler; mod http_util; mod logging; mod pagination; mod router; mod server; pub mod test_util; #[macro_use] extern crate slog; pub use api_description::ApiDescription; pub use api_description::ApiEndpoint; pub use api_description::ApiEndpointParameter; pub use api_description::ApiEndpointParameterLocation; pub use api_description::ApiEndpointResponse; pub use api_description::OpenApiDefinition; pub use config::ConfigDropshot; pub use error::HttpError; pub use error::HttpErrorResponseBody; pub use handler::Extractor; pub use handler::HttpResponse; pub use handler::HttpResponseAccepted; pub use handler::HttpResponseCreated; pub use handler::HttpResponseDeleted; pub use handler::HttpResponseOk; pub use handler::HttpResponseUpdatedNoContent; pub use handler::Path; pub use handler::Query; pub use handler::RequestContext; pub use handler::TypedBody; pub use http_util::CONTENT_TYPE_JSON; pub use http_util::CONTENT_TYPE_NDJSON; pub use http_util::HEADER_REQUEST_ID; pub use logging::ConfigLogging; pub use logging::ConfigLoggingIfExists; pub use logging::ConfigLoggingLevel; pub use pagination::EmptyScanParams; pub use pagination::PaginationOrder; pub use pagination::PaginationParams; pub use pagination::ResultsPage; pub use pagination::WhichPage; pub use server::HttpServer; /* * Users of the `endpoint` macro need `http::Method` available. */ pub use http::Method; extern crate dropshot_endpoint; pub use dropshot_endpoint::endpoint;