netty: Eagerly create SslContext

Creating the SslContext can throw, generally due to broken ALPN. We want
that to propagate to the caller of build(), instead of within the
channel where it could easily cause hangs.

We still delay creation until actual build() time, since TLS is not
guaranteed to work and the application may be configuring plaintext or
similar later before calling build() where SslContext is unnecessary.

The only externally-visible change should be the exception handling.
I'd add a test, but the things throwing are static and trying to inject
them would be pretty messy.

Fixes #2599

netty/src/main/java/io/grpc/netty/NettyChannelBuilder.java

@@ -381,13 +381,6 @@ public final class NettyChannelBuilder
       case PLAINTEXT_UPGRADE:
         return ProtocolNegotiators.plaintextUpgrade();
       case TLS:
-        if (sslContext == null) {
-          try {
-            sslContext = GrpcSslContexts.forClient().build();
-          } catch (SSLException ex) {
-            throw new RuntimeException(ex);
-          }
-        }
         return ProtocolNegotiators.tls(sslContext, authority);
       default:
         throw new IllegalArgumentException("Unsupported negotiationType: " + negotiationType);
@@ -459,6 +452,13 @@ public final class NettyChannelBuilder
       this.channelType = channelType;
       this.negotiationType = negotiationType;
       this.channelOptions = new HashMap<ChannelOption<?>, Object>(channelOptions);
+      if (negotiationType == NegotiationType.TLS && sslContext == null) {
+        try {
+          sslContext = GrpcSslContexts.forClient().build();
+        } catch (SSLException ex) {
+          throw new RuntimeException(ex);
+        }
+      }
       this.sslContext = sslContext;
 
       if (transportCreationParamsFilterFactory == null) {

netty/src/test/java/io/grpc/netty/NettyChannelBuilderTest.java

@@ -143,16 +143,11 @@ public class NettyChannelBuilderTest {
 
   @Test
   public void createProtocolNegotiator_tlsWithNoContext() {
-    ProtocolNegotiator negotiator = NettyChannelBuilder.createProtocolNegotiator(
+    thrown.expect(NullPointerException.class);
+    NettyChannelBuilder.createProtocolNegotiator(
         "authority:1234",
         NegotiationType.TLS,
         noSslContext);
-
-    assertTrue(negotiator instanceof ProtocolNegotiators.TlsNegotiator);
-    ProtocolNegotiators.TlsNegotiator n = (TlsNegotiator) negotiator;
-
-    assertEquals("authority", n.getHost());
-    assertEquals(1234, n.getPort());
   }
 
   @Test
@@ -170,11 +165,11 @@ public class NettyChannelBuilderTest {
   }
 
   @Test
-  public void createProtocolNegotiator_tlsWithAuthorityFallback() {
+  public void createProtocolNegotiator_tlsWithAuthorityFallback() throws SSLException {
     ProtocolNegotiator negotiator = NettyChannelBuilder.createProtocolNegotiator(
         "bad_authority",
         NegotiationType.TLS,
-        noSslContext);
+        GrpcSslContexts.forClient().build());
 
     assertTrue(negotiator instanceof ProtocolNegotiators.TlsNegotiator);
     ProtocolNegotiators.TlsNegotiator n = (TlsNegotiator) negotiator;