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 @@ private static ProtocolNegotiator createProtocolNegotiatorByType(
       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 @@ private static final class NettyTransportFactory implements ClientTransportFacto
       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 void createProtocolNegotiator_plaintextUpgrade() {
 
   @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 void createProtocolNegotiator_tlsWithClientContext() throws SSLException
   }
 
   @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;