fix: check Compute Engine environment for DirectPath (#1250)

gax-grpc/src/main/java/com/google/api/gax/grpc/InstantiatingGrpcChannelProvider.java

@@ -44,10 +44,12 @@
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
+import com.google.common.io.CharStreams;
 import io.grpc.ManagedChannel;
 import io.grpc.ManagedChannelBuilder;
 import io.grpc.alts.ComputeEngineChannelBuilder;
 import java.io.IOException;
+import java.io.InputStreamReader;
 import java.util.Map;
 import java.util.concurrent.Executor;
 import java.util.concurrent.ScheduledExecutorService;
@@ -74,6 +76,8 @@ public final class InstantiatingGrpcChannelProvider implements TransportChannelP
   static final long DIRECT_PATH_KEEP_ALIVE_TIMEOUT_SECONDS = 20;
   // reduce the thundering herd problem of too many channels trying to (re)connect at the same time
   static final int MAX_POOL_SIZE = 1000;
+  static final String GCE_PRODUCTION_NAME_PRIOR_2016 = "Google";
+  static final String GCE_PRODUCTION_NAME_AFTER_2016 = "Google Compute Engine";
 
   private final int processorCount;
   private final Executor executor;
@@ -234,6 +238,26 @@ private boolean isDirectPathEnabled(String serviceAddress) {
     return false;
   }
 
+  // DirectPath should only be used on Compute Engine.
+  // Notice Windows is supported for now.
+  static boolean isOnComputeEngine() {
+    String osName = System.getProperty("os.name");
+    if ("Linux".equals(osName)) {
+      String cmd = "cat /sys/class/dmi/id/product_name";
+      try {
+        Process process = Runtime.getRuntime().exec(new String[] {"/bin/sh", "-c", cmd});
+        process.waitFor();
+        String result =
+            CharStreams.toString(new InputStreamReader(process.getInputStream(), "UTF-8"));
+        return result.contains(GCE_PRODUCTION_NAME_PRIOR_2016)
+            || result.contains(GCE_PRODUCTION_NAME_AFTER_2016);
+      } catch (IOException | InterruptedException e) {
+        return false;
+      }
+    }
+    return false;
+  }
+
   private ManagedChannel createSingleChannel() throws IOException {
     GrpcHeaderInterceptor headerInterceptor =
         new GrpcHeaderInterceptor(headerProvider.getHeaders());
@@ -250,7 +274,9 @@ private ManagedChannel createSingleChannel() throws IOException {
     ManagedChannelBuilder builder;
 
     // TODO(weiranf): Add API in ComputeEngineCredentials to check default service account.
-    if (isDirectPathEnabled(serviceAddress) && credentials instanceof ComputeEngineCredentials) {
+    if (isDirectPathEnabled(serviceAddress)
+        && credentials instanceof ComputeEngineCredentials
+        && isOnComputeEngine()) {
       builder = ComputeEngineChannelBuilder.forAddress(serviceAddress, port);
       // Set default keepAliveTime and keepAliveTimeout when directpath environment is enabled.
       // Will be overridden by user defined values if any.

gax-grpc/src/test/java/com/google/api/gax/grpc/InstantiatingGrpcChannelProviderTest.java

@@ -219,7 +219,11 @@ public void testWithGCECredentials() throws IOException {
     ApiFunction<ManagedChannelBuilder, ManagedChannelBuilder> channelConfigurator =
         new ApiFunction<ManagedChannelBuilder, ManagedChannelBuilder>() {
           public ManagedChannelBuilder apply(ManagedChannelBuilder channelBuilder) {
-            assertThat(channelBuilder instanceof ComputeEngineChannelBuilder).isTrue();
+            if (InstantiatingGrpcChannelProvider.isOnComputeEngine()) {
+              assertThat(channelBuilder instanceof ComputeEngineChannelBuilder).isTrue();
+            } else {
+              assertThat(channelBuilder instanceof ComputeEngineChannelBuilder).isFalse();
+            }
             return channelBuilder;
           }
         };
@@ -234,7 +238,11 @@ public ManagedChannelBuilder apply(ManagedChannelBuilder channelBuilder) {
             .withEndpoint("localhost:8080");
 
     assertThat(provider.needsCredentials()).isTrue();
-    provider = provider.withCredentials(ComputeEngineCredentials.create());
+    if (InstantiatingGrpcChannelProvider.isOnComputeEngine()) {
+      provider = provider.withCredentials(ComputeEngineCredentials.create());
+    } else {
+      provider = provider.withCredentials(CloudShellCredentials.create(3000));
+    }
     assertThat(provider.needsCredentials()).isFalse();
 
     provider.getTransportChannel().shutdownNow();