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https://github.com/fafhrd91/actix-web
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128 lines
3.6 KiB
Markdown
128 lines
3.6 KiB
Markdown
# Database integration
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## Diesel
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At the moment of 1.0 release Diesel does not support asynchronous operations.
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But it possible to use `actix` synchronous actor system as a db interface api.
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Technically sync actors are worker style actors, multiple of them
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can be run in parallel and process messages from same queue (sync actors work in mpmc mode).
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Let's create simple db api that can insert new user row into sqlite table.
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We have to define sync actor and connection that this actor will use. Same approach
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could be used for other databases.
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```rust,ignore
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use actix::prelude::*;
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struct DbExecutor(SqliteConnection);
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impl Actor for DbExecutor {
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type Context = SyncContext<Self>;
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}
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```
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This is definition of our actor. Now we need to define *create user* message and response.
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```rust,ignore
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struct CreateUser {
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name: String,
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}
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impl Message for CreateUser {
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type Result = Result<User, Error>;
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}
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```
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We can send `CreateUser` message to `DbExecutor` actor, and as result we get
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`User` model. Now we need to define actual handler implementation for this message.
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```rust,ignore
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impl Handler<CreateUser> for DbExecutor {
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type Result = Result<User, Error>;
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fn handle(&mut self, msg: CreateUser, _: &mut Self::Context) -> Self::Result
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{
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use self::schema::users::dsl::*;
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// Create insertion model
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let uuid = format!("{}", uuid::Uuid::new_v4());
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let new_user = models::NewUser {
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id: &uuid,
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name: &msg.name,
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};
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// normal diesl operations
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diesel::insert_into(users)
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.values(&new_user)
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.execute(&self.0)
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.expect("Error inserting person");
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let mut items = users
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.filter(id.eq(&uuid))
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.load::<models::User>(&self.0)
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.expect("Error loading person");
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Ok(items.pop().unwrap())
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}
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}
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```
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That is it. Now we can use *DbExecutor* actor from any http handler or middleware.
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All we need is to start *DbExecutor* actors and store address in a state where http handler
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can access it.
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```rust,ignore
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/// This is state where we will store *DbExecutor* address.
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struct State {
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db: Addr<Syn, DbExecutor>,
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}
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fn main() {
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let sys = actix::System::new("diesel-example");
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// Start 3 parallel db executors
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let addr = SyncArbiter::start(3, || {
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DbExecutor(SqliteConnection::establish("test.db").unwrap())
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});
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// Start http server
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HttpServer::new(move || {
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Application::with_state(State{db: addr.clone()})
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.resource("/{name}", |r| r.method(Method::GET).a(index))})
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.bind("127.0.0.1:8080").unwrap()
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.start().unwrap();
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println!("Started http server: 127.0.0.1:8080");
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let _ = sys.run();
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}
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```
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And finally we can use address in a request handler. We get message response
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asynchronously, so handler needs to return future object, also `Route::a()` needs to be
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used for async handler registration.
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```rust,ignore
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/// Async handler
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fn index(req: HttpRequest<State>) -> Box<Future<Item=HttpResponse, Error=Error>> {
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let name = &req.match_info()["name"];
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// Send message to `DbExecutor` actor
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req.state().db.send(CreateUser{name: name.to_owned()})
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.from_err()
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.and_then(|res| {
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match res {
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Ok(user) => Ok(httpcodes::HttpOk.build().json(user)?),
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Err(_) => Ok(httpcodes::HttpInternalServerError.into())
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}
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})
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.responder()
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}
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```
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Full example is available in
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[examples directory](https://github.com/actix/actix-web/tree/master/examples/diesel/).
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More information on sync actors could be found in
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[actix documentation](https://docs.rs/actix/0.5.0/actix/sync/index.html).
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