DnsNameResolver for case grpc#1 and grpc#2

Author: zpencer

core/src/main/java/io/grpc/internal/DnsNameResolver.java

@@ -44,6 +44,7 @@
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.URI;
+import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -165,36 +166,32 @@ public void run() {
         }
         try {
           InetSocketAddress destination = InetSocketAddress.createUnresolved(host, port);
-          ProxyParameters maybeNullParams = proxyDetector.proxyFor(destination);
+          ProxyParameters proxyParams = proxyDetector.proxyFor(destination);
           Attributes attrs = Attributes.newBuilder()
-                .set(ProxyDetector.ATTR_KEY_PROXY_PARAMS, maybeNullParams)
+                .set(ProxyDetector.ATTR_KEY_PROXY_PARAMS, proxyParams)
                 .build();
 
-          ResolutionResults resolvedInetAddrs;
+          ResolutionResults resolvedInetAddrs = null;
           try {
             resolvedInetAddrs = delegateResolver.resolve(host);
-          } catch (Exception e) {
-            synchronized (DnsNameResolver.this) {
-              if (shutdown) {
-                return;
-              }
-              // Because timerService is the single-threaded GrpcUtil.TIMER_SERVICE in production,
-              // we need to delegate the blocking work to the executor
-              resolutionTask =
-                  timerService.schedule(new LogExceptionRunnable(resolutionRunnableOnExecutor),
-                      1, TimeUnit.MINUTES);
+          } catch (UnknownHostException e) {
+            // It is OK for a host to be unresolvable, assuming the proxy can resolve it
+            if (proxyParams == null) {
+              handleError(savedListener, e);
+              return;
             }
-            savedListener.onError(Status.UNAVAILABLE.withCause(e));
+          } catch (Exception e) {
+            handleError(savedListener, e);
             return;
           }
           ArrayList<EquivalentAddressGroup> servers = new ArrayList<EquivalentAddressGroup>();
-          if (resolvedInetAddrs.addresses.isEmpty()) {
-            servers.add(new EquivalentAddressGroup(destination));
-          } else {
+          if (resolvedInetAddrs != null) {
             // Each address forms an EAG
             for (InetAddress inetAddr : resolvedInetAddrs.addresses) {
               servers.add(new EquivalentAddressGroup(new InetSocketAddress(inetAddr, port), attrs));
             }
+          } else {
+            servers.add(new EquivalentAddressGroup(destination, attrs));
           }
           savedListener.onAddresses(servers, Attributes.EMPTY);
         } finally {
@@ -205,6 +202,20 @@ public void run() {
       }
     };
 
+  private void handleError(Listener listener, Exception e) {
+    synchronized (DnsNameResolver.this) {
+      if (shutdown) {
+        return;
+      }
+      // Because timerService is the single-threaded GrpcUtil.TIMER_SERVICE in production,
+      // we need to delegate the blocking work to the executor
+      resolutionTask =
+          timerService.schedule(new LogExceptionRunnable(resolutionRunnableOnExecutor),
+              1, TimeUnit.MINUTES);
+    }
+    listener.onError(Status.UNAVAILABLE.withCause(e));
+  }
+
   private final Runnable resolutionRunnableOnExecutor = new Runnable() {
       @Override
       public void run() {