proxy: Update `dns` module to use new Trust-DNS `AsyncResolver` API (#1032)

Depends on #974.  Closes #859.

This PR updates the proxy's `dns` module to use the new `AsyncResolver` API I
added to `trust-dns-resolver` in bluejekyll/trust-dns#487. This allows us to 
spawn one `Future` that will drive DNS resolution in the background, rather
than having to repeatedly clone a heavyweight `ResolverFuture` for every 
lookup. It also means that we no longer have to clone the name to resolve in
quite as many places.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Cargo.lock

@@ -102,6 +102,14 @@ dependencies = [
  "time 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "cloudabi"
+version = "0.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "bitflags 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "codegen"
 version = "0.1.0"
@@ -153,7 +161,7 @@ dependencies = [
  "tower-reconnect 0.1.0 (git+https://github.com/tower-rs/tower)",
  "tower-service 0.1.0 (git+https://github.com/tower-rs/tower)",
  "tower-util 0.1.0 (git+https://github.com/tower-rs/tower)",
- "trust-dns-resolver 0.9.0 (git+https://github.com/bluejekyll/trust-dns?rev=5c966b86e7d847ad14344e494237e162dc635de0)",
+ "trust-dns-resolver 0.9.0 (git+https://github.com/bluejekyll/trust-dns)",
  "untrusted 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "webpki 0.18.0-alpha3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -766,6 +774,23 @@ dependencies = [
  "winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "rand"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "fuchsia-zircon 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.40 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "redox_syscall"
 version = "0.1.37"
@@ -1222,7 +1247,7 @@ dependencies = [
 [[package]]
 name = "trust-dns-proto"
 version = "0.4.0"
-source = "git+https://github.com/bluejekyll/trust-dns?rev=5c966b86e7d847ad14344e494237e162dc635de0#5c966b86e7d847ad14344e494237e162dc635de0"
+source = "git+https://github.com/bluejekyll/trust-dns#660ca00c9b9ff0cbd675d3ff594bf072d87eb223"
 dependencies = [
  "byteorder 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "failure 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1230,7 +1255,7 @@ dependencies = [
  "idna 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "socket2 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-executor 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1245,7 +1270,7 @@ dependencies = [
 [[package]]
 name = "trust-dns-resolver"
 version = "0.9.0"
-source = "git+https://github.com/bluejekyll/trust-dns?rev=5c966b86e7d847ad14344e494237e162dc635de0#5c966b86e7d847ad14344e494237e162dc635de0"
+source = "git+https://github.com/bluejekyll/trust-dns#660ca00c9b9ff0cbd675d3ff594bf072d87eb223"
 dependencies = [
  "cfg-if 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "failure 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1257,7 +1282,7 @@ dependencies = [
  "resolv-conf 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "trust-dns-proto 0.4.0 (git+https://github.com/bluejekyll/trust-dns?rev=5c966b86e7d847ad14344e494237e162dc635de0)",
+ "trust-dns-proto 0.4.0 (git+https://github.com/bluejekyll/trust-dns)",
 ]
 
 [[package]]
@@ -1432,6 +1457,7 @@ dependencies = [
 "checksum cc 1.0.15 (registry+https://github.com/rust-lang/crates.io-index)" = "0ebb87d1116151416c0cf66a0e3fb6430cccd120fd6300794b4dfaa050ac40ba"
 "checksum cfg-if 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "d4c819a1287eb618df47cc647173c5c4c66ba19d888a6e50d605672aed3140de"
 "checksum chrono 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7c20ebe0b2b08b0aeddba49c609fe7957ba2e33449882cb186a180bc60682fa9"
+"checksum cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "ddfc5b9aa5d4507acaf872de71051dfd0e309860e88966e1051e462a077aac4f"
 "checksum codegen 0.1.0 (git+https://github.com/carllerche/codegen)" = "<none>"
 "checksum crc 1.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "bd5d02c0aac6bd68393ed69e00bbc2457f3e89075c6349db7189618dc4ddc1d7"
 "checksum crossbeam-deque 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "fe8153ef04a7594ded05b427ffad46ddeaf22e63fd48d42b3e1e3bb4db07cae7"
@@ -1500,6 +1526,8 @@ dependencies = [
 "checksum quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6e920b65c65f10b2ae65c831a81a073a89edd28c7cce89475bff467ab4167a"
 "checksum quote 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "1eca14c727ad12702eb4b6bfb5a232287dcf8385cb8ca83a3eeaf6519c44c408"
 "checksum rand 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "eba5f8cb59cc50ed56be8880a5c7b496bfd9bd26394e176bc67884094145c2c5"
+"checksum rand 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7a89abf8d34faf9783692392dca7bcdc6e82fa84eca86ccb6301ec87f3497185"
+"checksum rand_core 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1b7a5f27547c49e5ccf8a586db3f3782fd93cf849780b21853b9d981db203302"
 "checksum redox_syscall 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)" = "0d92eecebad22b767915e4d529f89f28ee96dbbf5a4810d2b844373f136417fd"
 "checksum redox_termios 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7e891cfe48e9100a70a3b6eb652fef28920c117d366339687bd5576160db0f76"
 "checksum regex 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "75ecf88252dce580404a22444fc7d626c01815debba56a7f4f536772a5ff19d3"
@@ -1547,8 +1575,8 @@ dependencies = [
 "checksum tower-reconnect 0.1.0 (git+https://github.com/tower-rs/tower)" = "<none>"
 "checksum tower-service 0.1.0 (git+https://github.com/tower-rs/tower)" = "<none>"
 "checksum tower-util 0.1.0 (git+https://github.com/tower-rs/tower)" = "<none>"
-"checksum trust-dns-proto 0.4.0 (git+https://github.com/bluejekyll/trust-dns?rev=5c966b86e7d847ad14344e494237e162dc635de0)" = "<none>"
+"checksum trust-dns-proto 0.4.0 (git+https://github.com/bluejekyll/trust-dns)" = "<none>"
-"checksum trust-dns-resolver 0.9.0 (git+https://github.com/bluejekyll/trust-dns?rev=5c966b86e7d847ad14344e494237e162dc635de0)" = "<none>"
+"checksum trust-dns-resolver 0.9.0 (git+https://github.com/bluejekyll/trust-dns)" = "<none>"
 "checksum try-lock 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ee2aa4715743892880f70885373966c83d73ef1b0838a664ef0c76fffd35e7c2"
 "checksum ucd-util 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "fd2be2d6639d0f8fe6cdda291ad456e23629558d466e2789d2c3e9892bda285d"
 "checksum unicode-bidi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "49f2bd0c6468a8230e1db229cff8029217cf623c767ea5d60bfbd42729ea54d5"

proxy/Cargo.toml

@@ -37,7 +37,7 @@ tokio-signal = "0.2"
 prost = "0.3.0"
 prost-types = "0.3.0"
 
-trust-dns-resolver = { default-features = false, git = "https://github.com/bluejekyll/trust-dns", rev = "5c966b86e7d847ad14344e494237e162dc635de0" }
+trust-dns-resolver = { default-features = false, git = "https://github.com/bluejekyll/trust-dns" }
 
 tokio-connect         = { git = "https://github.com/carllerche/tokio-connect" }
 tower-service         = { git = "https://github.com/tower-rs/tower" }

proxy/src/dns.rs

@@ -4,18 +4,19 @@ use std::net::IpAddr;
 use std::time::Instant;
 use tokio::timer::Delay;
 use transport;
-use trust_dns_resolver;
+use trust_dns_resolver::{
-use trust_dns_resolver::config::{ResolverConfig, ResolverOpts};
+    self,
-use trust_dns_resolver::error::{ResolveError, ResolveErrorKind};
+    config::{ResolverConfig, ResolverOpts},
-use trust_dns_resolver::ResolverFuture;
+    error::{ResolveError, ResolveErrorKind},
-use trust_dns_resolver::lookup_ip::LookupIp;
+    lookup_ip::LookupIp,
+    AsyncResolver,
+};
 
 use config::Config;
 
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 pub struct Resolver {
-    config: ResolverConfig,
+    resolver: AsyncResolver,
-    opts: ResolverOpts,
 }
 
 pub enum IpAddrFuture {
@@ -60,23 +61,42 @@ impl AsRef<str> for Name {
     }
 }
 
+
 impl Resolver {
 
     /// Construct a new `Resolver` from the system configuration and Conduit's
     /// environment variables.
     ///
+    /// # Returns
+    ///
+    /// Either a tuple containing a new `Resolver` and the background task to
+    /// drive that resolver's futures, or an error if the system configuration
+    /// could not be parsed.
+    ///
     /// TODO: Make this infallible, like it is in the `domain` crate.
-    pub fn new(env_config: &Config) -> Result<Self, ResolveError> {
+    pub fn from_system_config_and_env(env_config: &Config)
+        -> Result<(Self, impl Future<Item = (), Error = ()> + Send), ResolveError> {
         let (config, opts) = trust_dns_resolver::system_conf::read_system_conf()?;
-        let mut opts = env_config.configure_resolver_opts(opts);
+        let opts = env_config.configure_resolver_opts(opts);
-        // Disable Trust-DNS's caching.
-        opts.cache_size = 0;
         trace!("DNS config: {:?}", &config);
         trace!("DNS opts: {:?}", &opts);
-        Ok(Resolver {
+        Ok(Self::new(config, opts))
-            config,
+    }
-            opts,
+
-        })
+
+    /// NOTE: It would be nice to be able to return a named type rather than
+    ///       `impl Future` for the background future; it would be called
+    ///       `Background` or `ResolverBackground` if that were possible.
+    pub fn new(config: ResolverConfig,  mut opts: ResolverOpts)
+        -> (Self, impl Future<Item = (), Error = ()> + Send)
+    {
+        // Disable Trust-DNS's caching.
+        opts.cache_size = 0;
+        let (resolver, background) = AsyncResolver::new(config, opts);
+        let resolver = Resolver {
+            resolver,
+        };
+        (resolver, background)
     }
 
     pub fn resolve_one_ip(&self, host: &transport::Host) -> IpAddrFuture {
@@ -120,12 +140,17 @@ impl Resolver {
     fn lookup_ip(self, &Name(ref name): &Name)
         -> impl Future<Item = LookupIp, Error = ResolveError>
     {
-        let name = name.clone(); // TODO: ref-count names.
+        self.resolver.lookup_ip(name.as_str())
-        let resolver = ResolverFuture::new(
+    }
-            self.config,
+}
-            self.opts
+
-        );
+/// Note: `AsyncResolver` does not implement `Debug`, so we must manually
-        resolver.and_then(move |r| r.lookup_ip(name.as_str()))
+///       implement this.
+impl fmt::Debug for Resolver {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("Resolver")
+            .field("resolver", &"...")
+            .finish()
     }
 }
 

proxy/src/lib.rs

@@ -213,7 +213,7 @@ where
             &taps,
         );
 
-        let dns_resolver = dns::Resolver::new(&config)
+        let (dns_resolver, dns_bg) = dns::Resolver::from_system_config_and_env(&config)
             .unwrap_or_else(|e| {
                 // TODO: Make DNS configuration infallible.
                 panic!("invalid DNS configuration: {:?}", e);
@@ -313,10 +313,11 @@ where
                     let metrics_server = telemetry.serve_metrics(metrics_listener);
 
                     let fut = ::logging::admin().bg("resolver").future(resolver_bg)
-                        .join4(
+                        .join5(
                             ::logging::admin().bg("telemetry").future(telemetry),
                             tap.map_err(|_| {}),
                             metrics_server.map_err(|_| {}),
+                            ::logging::admin().bg("dns-resolver").future(dns_bg),
                         ).map(|_| {});
 
                     rt.spawn(Box::new(fut));