feat(bigtable): populate alts field in channel entry (#2702)

* feat(bigtable): populate alts field in channel entry

* WIP

Author: sushanb

google-cloud-bigtable/pom.xml

@@ -204,6 +204,10 @@
       <groupId>io.grpc</groupId>
       <artifactId>grpc-netty-shaded</artifactId>
     </dependency>
+    <dependency>
+      <groupId>io.grpc</groupId>
+      <artifactId>grpc-alts</artifactId>
+    </dependency>
     <dependency>
       <groupId>io.grpc</groupId>
       <artifactId>grpc-protobuf</artifactId>

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/gaxx/grpc/BigtableChannelPool.java

@@ -30,6 +30,7 @@
 import io.grpc.Metadata;
 import io.grpc.MethodDescriptor;
 import io.grpc.Status;
+import io.grpc.alts.AltsContextUtil;
 import java.io.IOException;
 import java.time.Clock;
 import java.util.ArrayList;
@@ -565,9 +566,8 @@ static class Entry implements BigtableChannelObserver {
     }
 
     void checkAndSetIsAlts(ClientCall<?, ?> call) {
-      // TODO(populate ALTS holder)
-      boolean result = false;
-      isAltsHolder.compareAndSet(null, result);
+      boolean currentIsAlts = AltsContextUtil.check(call);
+      isAltsHolder.set(currentIsAlts);
     }
 
     ManagedChannel getManagedChannel() {

google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/gaxx/grpc/BigtableChannelPoolTest.java

@@ -21,6 +21,7 @@
 
 import com.google.api.gax.grpc.ChannelFactory;
 import com.google.common.collect.Iterables;
+import io.grpc.Attributes;
 import io.grpc.CallOptions;
 import io.grpc.ClientCall;
 import io.grpc.ManagedChannel;
@@ -112,6 +113,8 @@ public void setUp() throws IOException {
     // Capture the listener when start is called
     // Configure mockClientCall.start to capture the listener
     doNothing().when(mockClientCall).start(listenerCaptor.capture(), any(Metadata.class));
+    // Default to no ALTS context
+    when(mockClientCall.getAttributes()).thenReturn(Attributes.EMPTY);
   }
 
   private BigtableChannelPool.Entry getSingleEntry() {
@@ -233,4 +236,16 @@ public void testMixedRpcs() {
     assertThat(entry.getAndResetErrorCount()).isEqualTo(1); // The last failure
     assertThat(entry.totalOutstandingRpcs()).isEqualTo(0);
   }
+
+  @Test
+  public void testNonAltsChannelReturnsFalse() {
+    // empty attributes
+    // cannot test true value as logic is complicated.
+    // alts check looks at  attributes.get(AltsProtocolNegotiator.AUTH_CONTEXT_KEY);
+    when(mockClientCall.getAttributes()).thenReturn(Attributes.EMPTY);
+    BigtableChannelPool.Entry entry = getSingleEntry();
+    assertThat(entry.isAltsHolder.get()).isNull();
+    startCall(unaryMethodDescriptor);
+    assertThat(entry.isAltsChannel()).isFalse();
+  }
 }