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//! Holds Engine related logic
use hyper;
use hyper::client::*;
use hyper::Uri;
use hyper::Body;
use hyper::Method;
use hyper::header::{Authorization, Bearer, ContentLength};
use std::str::FromStr;
use futures::future::Future;
use futures::{future, Stream};
use time::*;
use std::sync::{RwLock, Arc};
use cogs::*;
use std::convert::From;
const TOKEN_EXPIRES_IN_MINS: i64 = 9;
lazy_static! {
static ref ISSUE_TOKEN_URI: Uri = {
Uri::from_str("https://api.cognitive.microsoft.com/sts/v1.0/issueToken").unwrap()
};
}
header! {
(SubscriptionKeyHeader, "Ocp-Apim-Subscription-Key") => [String]
}
/// Struct for holding Engine data
///
/// Instantiate one using Engine::new
pub struct Engine<Connector>
where Connector: Connect + Service
{
credentials: Arc<RwLock<Credentials>>,
client: Arc<Client<Connector>>,
}
impl<Connector> Engine<Connector>
where Connector: Connect,
Connector: Service
{
/// Returns a new Engine
///
/// ```
/// # extern crate hyper;
/// # extern crate hyper_tls;
/// # extern crate tokio_core;
/// # extern crate cogs;
/// # fn main() {
/// # let core = tokio_core::reactor::Core::new().unwrap();
/// # let handle = core.handle();
/// # use cogs::engine::*;
/// # use hyper_tls;
/// let client = hyper::Client::configure()
/// .connector(hyper_tls::HttpsConnector::new(4, &handle).unwrap())
/// .keep_alive(true)
/// .build(&handle);
/// let credentials = Credentials::new(SubscriptionKey::new("abc123"));
/// Engine::new(credentials, client);
/// # }
/// ```
pub fn new(credentials: Credentials, client: Client<Connector>) -> Self {
Engine {
credentials: Arc::new(RwLock::new(credentials)),
client: Arc::new(client),
}
}
/// Runs a Cog and returns its Output
pub fn run<A>(&self, cog: A) -> Box<Future<Item = <A as Cog>::Item, Error = <A as Cog>::Error>>
where A: Cog
{
let mut req: Request = cog.into();
let client_ref = self.client.clone();
// TODO see if we can get rid of boxing with RFC 1522 is finished
let f = self.renew_token().then(move |engine_result| {
// TODO see if we can simplify the awkward match dance here for the sake of error types
let inner_f: Box<Future<Item = <A as Cog>::Item, Error = <A as Cog>::Error>> =
match engine_result {
Ok(AccessToken { token, .. }) => {
{
let mut headers = req.headers_mut();
headers.set(Authorization(Bearer { token: token.clone() }));
}
Box::new(client_ref.request(req)
.map_err(|e| Error::HyperError(e))
.then(|r| <A as Cog>::Output::from(r)))
}
Err(e) => Box::new(<A as Cog>::Output::from(Err(e))),
};
inner_f
});
Box::new(f)
}
/// Conditionally renews the token and returns a valid value in a Future.
///
/// Note, using Box<Future<_,_>> because heck, even Hyper does this (See FutureResponse).
/// Optimise later.
fn renew_token(&self) -> Box<Future<Item = AccessToken, Error = Error>> {
// First, try to retrieve the token using just a read lock.
let retrieve_token_sync: Option<AccessToken> = {
let read_lock = self.credentials.read();
match read_lock {
Ok(ref creds) => {
if creds.should_renew_token() {
None
} else {
creds.access_token.clone()
}
}
_ => None, // ignore the error for now. Maybe we can work with it.
}
};
match retrieve_token_sync {
// Success. Just wrap it in a future
Some(t) => future::ok(t).boxed(),
// Nope
None => {
// Grab a write lock.
let write_lock_sync = self.credentials.write();
match write_lock_sync {
Ok(mut creds) => {
/* Check again now that we're inside a write lock
* It's possible that the token was renewed already by another thread
* by the time we get here
*/
if creds.should_renew_token() {
if creds.renewing_token {
/* Someone is already working on this (likely in another thread),
* so just loop.
*/
self.renew_token()
} else {
let mut req: Request<Body> = Request::new(Method::Post,
ISSUE_TOKEN_URI.clone());
{
let headers = req.headers_mut();
headers.set(SubscriptionKeyHeader(creds
.subscription_key
.0
.clone()));
headers.set(ContentLength(0));
}
// Set the renewing token flag before hitting any async barriers
creds.renewing_token = true;
let req_f = self.client
.request(req)
.map_err(|e| Error::HyperError(e));
let creds_ref_err = self.credentials.clone();
let creds_ref = self.credentials.clone();
let f = req_f.and_then(|r| {
read_to_string(r).and_then(move |t| {
// These weird brackets help the compiler understand scope
// of the write lock.
let r = {
let creds_write_lock = creds_ref.write();
creds_write_lock
.map_err(|_| Error::LockPoisonedError)
.map(|mut creds| {
let access = AccessToken {
token: t,
expires_at: now() + Duration::minutes(TOKEN_EXPIRES_IN_MINS),
};
creds.renewing_token = false;
creds.update_token(access.clone());
access
})
};
r
})
}).map_err(move |e| {
// We failed somewhere so set the renewing token flag to false
let creds_err_lock = creds_ref_err.write();
match creds_err_lock {
Ok(mut creds) => {
creds.renewing_token = false;
e
}
_ => Error::LockPoisonedError // this is more important at this point
}
});
Box::new(f)
}
} else {
// Another thread did the work for us. Just clone and return.
let t = creds.access_token.clone().unwrap();
future::ok(t).boxed()
}
}
_ => future::err(Error::LockPoisonedError).boxed(),
}
}
}
}
}
/// Consumes the body and reads it into a String.
pub fn read_to_string(resp: Response) -> Box<Future<Item = String, Error = Error>> {
Box::new(read_to_bytes(resp).and_then(|b| {
String::from_utf8(b).map_err(|_| Error::FromUtf8Error)
}))
}
/// Consumes a response, returning the body as a vector of bytes
pub fn read_to_bytes(resp: Response) -> Box<Future<Item = Vec<u8>, Error = Error>> {
let vec = if let Some(len) = resp.headers().get::<ContentLength>() {
Vec::with_capacity(**len as usize)
} else {
vec![]
};
Box::new(resp.body()
// Body is a Stream (-.- " )which effectively uses Hyper::Error as well
.map_err(|e| Error::HyperError(e))
.fold(vec, |mut acc, chunk| {
acc.extend_from_slice(chunk.as_ref());
Ok::<_, Error>(acc)
}))
}
#[derive(Debug)]
pub enum Error {
CouldNotRetrieveToken,
FromUtf8Error,
LockPoisonedError,
HyperError(hyper::Error),
}
/// Holds credential information for accessing Cognitive services
pub struct Credentials {
pub subscription_key: SubscriptionKey,
#[doc(hidden)]
access_token: Option<AccessToken>,
#[doc(hidden)]
renewing_token: bool,
}
impl Credentials {
/// Returns a new, uninitiated set of credentials
pub fn new(key: SubscriptionKey) -> Credentials {
Credentials {
subscription_key: key,
access_token: None,
renewing_token: false,
}
}
/// Convenience method for determining whether we should renew the token
pub fn should_renew_token(&self) -> bool {
let now = now();
match self.token_expires_at() {
Some(expires) => now >= *expires,
_ => true,
}
}
/// Updates the access token when needed
fn update_token(&mut self, token: AccessToken) {
self.access_token = Some(token);
}
/// Exposes the token expires at.
fn token_expires_at(&self) -> Option<&Tm> {
match self.access_token {
Some(ref tm) => Some(&tm.expires_at),
_ => None,
}
}
}
/// Wraps a subscription key
pub struct SubscriptionKey(String);
impl SubscriptionKey {
/// Returns a new Subscription key
pub fn new<S: ToString>(key: S) -> SubscriptionKey {
SubscriptionKey(key.to_string())
}
/// Returns the string value of a SubscriptionKey
pub fn value(&self) -> &str {
&self.0[..]
}
}
/// Holds an Access Token
#[derive(Clone)]
struct AccessToken {
token: String,
expires_at: Tm,
}
#[cfg(test)]
mod tests {
use super::*;
use tokio_core;
use std::env;
use hyper_tls;
fn subscription_key() -> String {
env::var("AZURE_SUBSCRIPTION_KEY").unwrap()
}
#[test]
fn renew_token_test() {
let mut core = tokio_core::reactor::Core::new().unwrap();
let handle = core.handle();
let client = Client::configure()
.connector(hyper_tls::HttpsConnector::new(4, &handle).unwrap())
.build(&handle);
let sub_key = SubscriptionKey::new(subscription_key());
let credentials = Credentials::new(sub_key);
let engine = Engine::new(credentials, client);
let work = engine.renew_token();
assert!(core.run(work).is_ok())
}
}