Start trust-dns default resolver on first use

actix-connect/src/lib.rs

@@ -8,6 +8,8 @@
 #[macro_use]
 extern crate log;
 
+use std::cell::RefCell;
+
 mod connect;
 mod connector;
 mod error;
@@ -46,18 +48,34 @@ pub fn start_resolver(cfg: ResolverConfig, opts: ResolverOpts) -> AsyncResolver
     resolver
 }
 
-pub fn start_default_resolver() -> AsyncResolver {
-    let (cfg, opts) = match read_system_conf() {
-        Ok((cfg, opts)) => (cfg, opts),
-        Err(e) => {
-            log::error!("TRust-DNS can not load system config: {}", e);
-            (ResolverConfig::default(), ResolverOpts::default())
-        }
-    };
+thread_local! {
+    static DEFAULT_RESOLVER: RefCell<Option<AsyncResolver>> = RefCell::new(None);
+}
 
-    let (resolver, bg) = AsyncResolver::new(cfg, opts);
-    tokio_current_thread::spawn(bg);
-    resolver
+pub(crate) fn get_default_resolver() -> AsyncResolver {
+    DEFAULT_RESOLVER.with(|cell| {
+        if let Some(ref resolver) = *cell.borrow() {
+            return resolver.clone();
+        }
+
+        let (cfg, opts) = match read_system_conf() {
+            Ok((cfg, opts)) => (cfg, opts),
+            Err(e) => {
+                log::error!("TRust-DNS can not load system config: {}", e);
+                (ResolverConfig::default(), ResolverOpts::default())
+            }
+        };
+
+        let (resolver, bg) = AsyncResolver::new(cfg, opts);
+        tokio_current_thread::spawn(bg);
+
+        *cell.borrow_mut() = Some(resolver.clone());
+        resolver
+    })
+}
+
+pub fn start_default_resolver() -> AsyncResolver {
+    get_default_resolver()
 }
 
 /// Create tcp connector service

actix-connect/src/resolver.rs

@@ -10,10 +10,11 @@ use trust_dns_resolver::{AsyncResolver, Background};
 
 use crate::connect::{Address, Connect};
 use crate::error::ConnectError;
+use crate::get_default_resolver;
 
 /// DNS Resolver Service factory
 pub struct ResolverFactory<T> {
-    resolver: AsyncResolver,
+    resolver: Option<AsyncResolver>,
     _t: PhantomData<T>,
 }
 
@@ -21,13 +22,18 @@ impl<T> ResolverFactory<T> {
     /// Create new resolver instance with custom configuration and options.
     pub fn new(resolver: AsyncResolver) -> Self {
         ResolverFactory {
-            resolver,
+            resolver: Some(resolver),
             _t: PhantomData,
         }
     }
+}
 
-    pub fn resolver(&self) -> &AsyncResolver {
-        &self.resolver
+impl<T> Default for ResolverFactory<T> {
+    fn default() -> Self {
+        ResolverFactory {
+            resolver: None,
+            _t: PhantomData,
+        }
     }
 }
 
@@ -58,7 +64,7 @@ impl<T: Address> NewService for ResolverFactory<T> {
 
 /// DNS Resolver Service
 pub struct Resolver<T> {
-    resolver: AsyncResolver,
+    resolver: Option<AsyncResolver>,
     _t: PhantomData<T>,
 }
 
@@ -66,7 +72,16 @@ impl<T> Resolver<T> {
     /// Create new resolver instance with custom configuration and options.
     pub fn new(resolver: AsyncResolver) -> Self {
         Resolver {
-            resolver,
+            resolver: Some(resolver),
+            _t: PhantomData,
+        }
+    }
+}
+
+impl<T> Default for Resolver<T> {
+    fn default() -> Self {
+        Resolver {
+            resolver: None,
             _t: PhantomData,
         }
     }
@@ -100,7 +115,10 @@ impl<T: Address> Service for Resolver<T> {
                 Either::B(ok(req))
             } else {
                 trace!("DNS resolver: resolving host {:?}", req.host());
-                Either::A(ResolverFuture::new(req, &self.resolver))
+                if self.resolver.is_none() {
+                    self.resolver = Some(get_default_resolver());
+                }
+                Either::A(ResolverFuture::new(req, self.resolver.as_ref().unwrap()))
             }
         }
     }