Replace getaddrinfo resolver with trust-dns-resolver

Cargo.toml

@@ -27,7 +27,10 @@ serde = "1.0"
 serde_json = "1.0"
 serde_urlencoded = "0.5"
 tokio = "0.1.7"
+tokio-executor = "0.1.4" # a minimum version so trust-dns-resolver compiles
 tokio-io = "0.1"
+tokio-timer = "0.2.6" # a minimum version so trust-dns-resolver compiles
+trust-dns-resolver = "0.10"
 url = "1.2"
 uuid = { version = "0.7", features = ["v4"] }
 hyper-rustls = { version = "0.15", optional = true }

src/async_impl/client.rs

@@ -60,7 +60,6 @@ struct Config {
     identity: Option<Identity>,
     #[cfg(feature = "tls")]
     tls: TLSBackend,
-    dns_threads: usize,
 }
 
 impl ClientBuilder {
@@ -88,7 +87,6 @@ impl ClientBuilder {
                 identity: None,
                 #[cfg(feature = "tls")]
                 tls: TLSBackend::default(),
-                dns_threads: 4,
             },
         }
     }
@@ -131,7 +129,7 @@ impl ClientBuilder {
                         tls.identity(id);
                     }
 
-                    Connector::new_default_tls(config.dns_threads, tls, proxies.clone())?
+                    Connector::new_default_tls(tls, proxies.clone())?
                 },
                 #[cfg(feature = "rustls-tls")]
                 TLSBackend::Rustls => {
@@ -188,12 +186,12 @@ impl ClientBuilder {
                         tls.set_single_client_cert(certs, key);
                     }
 
-                    Connector::new_rustls_tls(config.dns_threads, tls, proxies.clone())?
+                    Connector::new_rustls_tls(tls, proxies.clone())?
                 }
             }
 
             #[cfg(not(feature = "tls"))]
-            Connector::new(config.dns_threads, proxies.clone())
+            Connector::new(proxies.clone())
         };
 
         let hyper_client = ::hyper::Client::builder()
@@ -327,9 +325,9 @@ impl ClientBuilder {
         self
     }
 
-    /// Set number of DNS threads.
-    pub fn dns_threads(mut self, threads: usize) -> ClientBuilder {
-        self.config.dns_threads = threads;
+    #[doc(hidden)]
+    #[deprecated(note = "DNS no longer uses blocking threads")]
+    pub fn dns_threads(self, _threads: usize) -> ClientBuilder {
         self
     }
 }

src/client.rs

@@ -281,13 +281,6 @@ impl ClientBuilder {
         self
     }
 
-    /// Set the number of threads to use for DNS
-    ///
-    /// Default is 4
-    pub fn dns_threads(self, threads: usize) -> ClientBuilder {
-        self.with_inner(|inner| inner.dns_threads(threads))
-    }
-
     fn with_inner<F>(mut self, func: F) -> ClientBuilder
     where
         F: FnOnce(async_impl::ClientBuilder) -> async_impl::ClientBuilder,

src/connect.rs

@@ -1,6 +1,5 @@
 use futures::Future;
 use http::uri::Scheme;
-use hyper::client::{HttpConnector};
 use hyper::client::connect::{Connect, Connected, Destination};
 use tokio_io::{AsyncRead, AsyncWrite};
 
@@ -14,8 +13,11 @@ use bytes::BufMut;
 use std::io;
 use std::sync::Arc;
 
+use dns::TrustDnsResolver;
 use Proxy;
 
+type HttpConnector = ::hyper::client::HttpConnector<TrustDnsResolver>;
+
 
 pub(crate) struct Connector {
     proxies: Arc<Vec<Proxy>>,
@@ -33,8 +35,8 @@ enum Inner {
 
 impl Connector {
     #[cfg(not(feature = "tls"))]
-    pub(crate) fn new(threads: usize, proxies: Arc<Vec<Proxy>>) -> Connector {
-        let http = HttpConnector::new(threads);
+    pub(crate) fn new(proxies: Arc<Vec<Proxy>>) -> Connector {
+        let http = http_connector();
         Connector {
             proxies,
             inner: Inner::Http(http)
@@ -42,10 +44,10 @@ impl Connector {
     }
 
     #[cfg(feature = "default-tls")]
-    pub(crate) fn new_default_tls(threads: usize, tls: TlsConnectorBuilder, proxies: Arc<Vec<Proxy>>) -> ::Result<Connector> {
+    pub(crate) fn new_default_tls(tls: TlsConnectorBuilder, proxies: Arc<Vec<Proxy>>) -> ::Result<Connector> {
         let tls = try_!(tls.build());
 
-        let mut http = HttpConnector::new(threads);
+        let mut http = http_connector();
         http.enforce_http(false);
         let http = ::hyper_tls::HttpsConnector::from((http, tls.clone()));
 
@@ -56,8 +58,8 @@ impl Connector {
     }
 
     #[cfg(feature = "rustls-tls")]
-    pub(crate) fn new_rustls_tls(threads: usize, tls: rustls::ClientConfig, proxies: Arc<Vec<Proxy>>) -> ::Result<Connector> {
-        let mut http = HttpConnector::new(threads);
+    pub(crate) fn new_rustls_tls(tls: rustls::ClientConfig, proxies: Arc<Vec<Proxy>>) -> ::Result<Connector> {
+        let mut http = http_connector();
         http.enforce_http(false);
         let http = ::hyper_rustls::HttpsConnector::from((http, tls.clone()));
 
@@ -68,6 +70,11 @@ impl Connector {
     }
 }
 
+fn http_connector() -> HttpConnector {
+    let http = HttpConnector::new_with_resolver(TrustDnsResolver::new());
+    http
+}
+
 impl Connect for Connector {
     type Transport = Conn;
     type Error = io::Error;

src/dns.rs

@@ -0,0 +1,73 @@
+use std::io;
+use std::sync::{Arc, Mutex};
+
+use futures::{future, Future};
+use hyper::client::connect::dns as hyper_dns;
+use trust_dns_resolver::AsyncResolver;
+
+// If instead the type were just `AsyncResolver`, it breaks the default recursion limit
+// for the compiler to determine if `reqwest::Client` is `Send`. This is because `AsyncResolver`
+// has **a lot** of internal generic types that pushes us over the limit.
+//
+// "Erasing" the internal resolver type saves us from this limit.
+type ErasedResolver = Box<Fn(hyper_dns::Name) -> ::trust_dns_resolver::BackgroundLookupIp + Send + Sync>;
+
+#[derive(Clone)]
+pub(crate) struct TrustDnsResolver {
+    inner: Arc<Mutex<Option<ErasedResolver>>>,
+}
+
+impl TrustDnsResolver {
+    pub(crate) fn new() -> Self {
+        TrustDnsResolver {
+            inner: Arc::new(Mutex::new(None)),
+        }
+    }
+}
+
+impl hyper_dns::Resolve for TrustDnsResolver {
+    type Addrs = ::std::vec::IntoIter<::std::net::IpAddr>;
+    type Future = Box<Future<Item=Self::Addrs, Error=io::Error> + Send>;
+
+    fn resolve(&self, name: hyper_dns::Name) -> Self::Future {
+        let inner = self.inner.clone();
+        Box::new(future::lazy(move || {
+            let mut inner = inner.lock().expect("lock resolver");
+            if inner.is_none() {
+                // The `bg` (background) future needs to be spawned onto an executor,
+                // but a `reqwest::Client` may be constructed before an executor is ready.
+                // So, the `bg` future cannot be spawned *until* the executor starts to
+                // `poll` this future.
+                match AsyncResolver::from_system_conf() {
+                    Ok((resolver, bg)) => {
+                        ::tokio::spawn(bg);
+                        *inner = Some(Box::new(move |name| {
+                            resolver.lookup_ip(name.as_str())
+                        }));
+                    },
+                    Err(err) => {
+                        return future::Either::A(
+                            future::err(io::Error::new(io::ErrorKind::Other, err.to_string()))
+                        );
+                    }
+                }
+            }
+
+            future::Either::B((inner
+                .as_mut()
+                .expect("resolver is set"))(name)
+                //.lookup_ip(name.as_str())
+                .map(|lookup| {
+                    lookup
+                        .iter()
+                        .collect::<Vec<_>>()
+                        .into_iter()
+                })
+                .map_err(|err| {
+                    io::Error::new(io::ErrorKind::Other, err.to_string())
+                }))
+        }))
+    }
+}
+
+

src/lib.rs

@@ -163,6 +163,7 @@ extern crate serde_urlencoded;
 extern crate tokio;
 #[cfg_attr(feature = "default-tls", macro_use)]
 extern crate tokio_io;
+extern crate trust_dns_resolver;
 extern crate url;
 extern crate uuid;
 
@@ -203,6 +204,7 @@ mod connect;
 mod connect_async;
 mod body;
 mod client;
+mod dns;
 mod into_url;
 mod proxy;
 mod redirect;