Facilitate explicit channel shutdown.

src/main/java/com/google/cloud/genomics/utils/grpc/Example.java

@@ -1,7 +1,5 @@
 package com.google.cloud.genomics.utils.grpc;
 
-import io.grpc.Channel;
-
 import java.io.FileNotFoundException;
 import java.util.Iterator;
 
@@ -18,6 +16,7 @@
 import com.google.genomics.v1.StreamingVariantServiceGrpc.StreamingVariantServiceBlockingStub;
 
 public class Example {
+
   public static void main(String[] args) throws Exception {
     final String clientSecretsJson = "client_secrets.json";
     GenomicsFactory.OfflineAuth auth = null;
@@ -35,7 +34,7 @@ public static void main(String[] args) throws Exception {
       return;
     }
 
-    Channel channel = Channels.fromOfflineAuth(auth);
+    GenomicsChannel channel = GenomicsChannel.fromOfflineAuth(auth);
 
     // Regular RPC example: list all reference set assembly ids.
     ReferenceServiceV1BlockingStub refStub =
@@ -57,14 +56,17 @@ public static void main(String[] args) throws Exception {
         .setEnd(41277499)
         .build();
 
-    Iterator<StreamVariantsResponse> iter = varStub.streamVariants(varRequest);
-    while (iter.hasNext()) {
-      StreamVariantsResponse varResponse = iter.next();
-      System.out.println("Response:");
-      System.out.println(varResponse.toString());
-      System.out.println();
+    try {
+      Iterator<StreamVariantsResponse> iter = varStub.streamVariants(varRequest);
+      while (iter.hasNext()) {
+        StreamVariantsResponse varResponse = iter.next();
+        System.out.println("Response:");
+        System.out.println(varResponse.toString());
+        System.out.println();
+      }
+      System.out.println("Done");
+    } finally {
+      channel.shutdownNow();
     }
-    System.out.println("Done");
-    System.exit(0);
   }
 }

src/main/java/com/google/cloud/genomics/utils/grpc/Channels.java → src/main/java/com/google/cloud/genomics/utils/grpc/GenomicsChannel.java

@@ -3,9 +3,13 @@
 import com.google.auth.oauth2.GoogleCredentials;
 import com.google.cloud.genomics.utils.GenomicsFactory;
 
+import io.grpc.CallOptions;
 import io.grpc.Channel;
+import io.grpc.ChannelImpl;
+import io.grpc.ClientCall;
 import io.grpc.ClientInterceptors;
 import io.grpc.Metadata;
+import io.grpc.MethodDescriptor;
 import io.grpc.auth.ClientAuthInterceptor;
 import io.grpc.netty.GrpcSslContexts;
 import io.grpc.netty.NegotiationType;
@@ -18,47 +22,105 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 
 import javax.net.ssl.SSLException;
 
 /**
  * A convenience class for creating gRPC channels to the Google Genomics API.
  */
-public class Channels {
+public class GenomicsChannel extends Channel {
+  private static final String GENOMICS_ENDPOINT = "genomics.googleapis.com";
+  private static final String GENOMICS_SCOPE = "https://www.googleapis.com/auth/genomics";
   // TODO: This constant should come from grpc-java.
   private static final String API_KEY_HEADER = "X-Goog-Api-Key";
 
+  // NOTE: Unfortunately we need to keep a handle to both of these since Channel does not expose
+  // the shutdown method and the ClientInterceptors do not return the ChannelImpl instance.
+  private final ChannelImpl channelImpl;
+  private final Channel delegate;
+
+  private ChannelImpl getGenomicsChannelImpl() throws SSLException {
+    // Java 8's implementation of GCM ciphers is extremely slow. Therefore we disable
+    // them here.
+    List<String> defaultCiphers =
+        GrpcSslContexts.forClient().ciphers(null).build().cipherSuites();
+    List<String> performantCiphers = new ArrayList<>();
+    for (String cipher : defaultCiphers) {
+      if (!cipher.contains("GCM")) {
+        performantCiphers.add(cipher);
+      }
+    }
+
+    return NettyChannelBuilder.forAddress(GENOMICS_ENDPOINT, 443)
+        .negotiationType(NegotiationType.TLS)
+        .sslContext(GrpcSslContexts.forClient().ciphers(performantCiphers).build())
+        .build();
+  }
+
+  private GenomicsChannel(String apiKey) throws SSLException {
+    channelImpl = getGenomicsChannelImpl();
+    Metadata.Headers headers = new Metadata.Headers();
+    Metadata.Key<String> apiKeyHeaderKey =
+        Metadata.Key.of(API_KEY_HEADER, Metadata.ASCII_STRING_MARSHALLER);
+    headers.put(apiKeyHeaderKey, apiKey);
+    delegate = ClientInterceptors.intercept(channelImpl,
+        MetadataUtils.newAttachHeadersInterceptor(headers)); 
+  }
+
+  private GenomicsChannel(GoogleCredentials creds) throws SSLException {
+    channelImpl = getGenomicsChannelImpl();
+    creds = creds.createScoped(
+        Arrays.asList(GENOMICS_SCOPE));
+    ClientAuthInterceptor interceptor = new ClientAuthInterceptor(creds,
+        Executors.newSingleThreadExecutor());
+    delegate = ClientInterceptors.intercept(channelImpl, interceptor);
+  }
+
+  @Override
+  public <RequestT, ResponseT> ClientCall<RequestT, ResponseT> newCall(
+      MethodDescriptor<RequestT, ResponseT> arg0, CallOptions arg1) {
+    return delegate.newCall(arg0, arg1);
+  }
+
+  /**
+   * @see io.grpc.ChannelImpl#shutdownNow()
+   */
+  public void shutdownNow() {
+    channelImpl.shutdownNow();
+  }
+
+  /**
+   * @throws InterruptedException 
+   * @see io.grpc.ChannelImpl#shutdown()
+   * @see io.grpc.ChannelImpl#awaitTermination(long, TimeUnit)
+   */
+  public void shutdown(long timeout, TimeUnit unit) throws InterruptedException {
+    channelImpl.shutdown().awaitTermination(timeout, unit);
+  }
+
   /**
    * Creates a new gRPC channel to the Google Genomics API, using the application
    * default credentials for auth.
    */
-  public static Channel fromDefaultCreds() throws IOException {
+  public static GenomicsChannel fromDefaultCreds() throws IOException {
     return fromCreds(GoogleCredentials.getApplicationDefault());
   }
 
   /**
    * Creates a new gRPC channel to the Google Genomics API, using the provided
    * api key for auth.
    */
-  public static Channel fromApiKey(String apiKey) throws SSLException {
-    Metadata.Headers headers = new Metadata.Headers();
-    Metadata.Key<String> apiKeyHeaderKey =
-        Metadata.Key.of(API_KEY_HEADER, Metadata.ASCII_STRING_MARSHALLER);
-    headers.put(apiKeyHeaderKey, apiKey);
-    return ClientInterceptors.intercept(getGenomicsChannel(),
-        MetadataUtils.newAttachHeadersInterceptor(headers));
+  public static GenomicsChannel fromApiKey(String apiKey) throws SSLException {
+    return new GenomicsChannel(apiKey);
   }
 
   /**
    * Creates a new gRPC channel to the Google Genomics API, using the provided
    * credentials for auth.
    */
-  public static Channel fromCreds(GoogleCredentials creds) throws IOException {
-    creds = creds.createScoped(
-        Arrays.asList("https://www.googleapis.com/auth/genomics"));
-    ClientAuthInterceptor interceptor = new ClientAuthInterceptor(creds,
-        Executors.newSingleThreadExecutor());
-    return ClientInterceptors.intercept(getGenomicsChannel(), interceptor);     
+  public static GenomicsChannel fromCreds(GoogleCredentials creds) throws IOException {
+    return new GenomicsChannel(creds);
   }
 
   /**
@@ -73,34 +135,15 @@ public static Channel fromCreds(GoogleCredentials creds) throws IOException {
    * @throws IOException
    * @throws GeneralSecurityException
    */
-  public static Channel fromOfflineAuth(GenomicsFactory.OfflineAuth auth) throws IOException, GeneralSecurityException {
+  public static GenomicsChannel fromOfflineAuth(GenomicsFactory.OfflineAuth auth) throws IOException, GeneralSecurityException {
     if(auth.hasUserCredentials()) {
       return fromCreds(auth.getUserCredentials());
 // TODO: https://github.com/googlegenomics/utils-java/issues/51      
 //    } else if(auth.hasApiKey()) {
-//      return fromApiKey(auth.apiKey);
+//      return new Channels(auth.apiKey);
     }
     // Fall back to Default Credentials if the user did not specify user credentials or an api key.
     return fromDefaultCreds();
   }
-
-  private static Channel getGenomicsChannel() throws SSLException {
-    // Java 8's implementation of GCM ciphers is extremely slow. Therefore we disable
-    // them here.
-    List<String> defaultCiphers =
-        GrpcSslContexts.forClient().ciphers(null).build().cipherSuites();
-    List<String> performantCiphers = new ArrayList<>();
-    for (String cipher : defaultCiphers) {
-      if (!cipher.contains("GCM")) {
-        performantCiphers.add(cipher);
-      }
-    }
-
-    Channel channel = NettyChannelBuilder.forAddress("genomics.googleapis.com", 443)
-        .negotiationType(NegotiationType.TLS)
-        .sslContext(GrpcSslContexts.forClient().ciphers(performantCiphers).build())
-        .build();
-    return channel;
-  }
 }
 

src/main/java/com/google/cloud/genomics/utils/grpc/ReadStreamIterator.java

@@ -36,7 +36,8 @@
  */
 public class ReadStreamIterator extends ForwardingIterator<StreamReadsResponse> {
   protected final Predicate<Read> shardPredicate;
-  private Iterator<StreamReadsResponse> delegate;
+  protected final Iterator<StreamReadsResponse> delegate;
+  protected final GenomicsChannel genomicsChannel;
 
   /**
    * Create a stream iterator that can enforce shard boundary semantics.
@@ -56,8 +57,9 @@ public ReadStreamIterator(StreamReadsRequest request, GenomicsFactory.OfflineAut
         ShardBoundary.getStrictReadPredicate(request.getStart()) :
           null;
 
+    genomicsChannel = GenomicsChannel.fromOfflineAuth(auth);
     StreamingReadServiceGrpc.StreamingReadServiceBlockingStub readStub =
-        StreamingReadServiceGrpc.newBlockingStub(Channels.fromOfflineAuth(auth));
+        StreamingReadServiceGrpc.newBlockingStub(genomicsChannel);
 
     delegate = readStub.streamReads(request);
   }
@@ -67,11 +69,30 @@ protected Iterator<StreamReadsResponse> delegate() {
     return delegate;
   }
 
+  /**
+   * @see java.util.Iterator#hasNext()
+   */
+  public boolean hasNext() {
+    try {
+      return delegate.hasNext();
+    } catch (RuntimeException e) {
+      genomicsChannel.shutdownNow();
+      throw e;
+    }
+  }
+
   /**
    * @see java.util.Iterator#next()
    */
   public StreamReadsResponse next() {
-    StreamReadsResponse response = delegate.next();
+    StreamReadsResponse response = null;
+    try {
+      response = delegate.next();
+    } catch (RuntimeException e) {
+      genomicsChannel.shutdownNow();
+      throw e;
+    }
+
     if(null == shardPredicate) {
       return response;
     }

src/main/java/com/google/cloud/genomics/utils/grpc/VariantStreamIterator.java

@@ -36,7 +36,8 @@
  */
 public class VariantStreamIterator extends ForwardingIterator<StreamVariantsResponse> {
   protected final Predicate<Variant> shardPredicate;
-  protected Iterator<StreamVariantsResponse> delegate;
+  protected final Iterator<StreamVariantsResponse> delegate;
+  protected final GenomicsChannel genomicsChannel;
 
   /**
    * Create a stream iterator that can enforce shard boundary semantics.
@@ -56,8 +57,9 @@ public VariantStreamIterator(StreamVariantsRequest request, GenomicsFactory.Offl
         ShardBoundary.getStrictVariantPredicate(request.getStart()) :
           null;
 
+    genomicsChannel = GenomicsChannel.fromOfflineAuth(auth);
     StreamingVariantServiceGrpc.StreamingVariantServiceBlockingStub variantStub =
-        StreamingVariantServiceGrpc.newBlockingStub(Channels.fromOfflineAuth(auth));
+        StreamingVariantServiceGrpc.newBlockingStub(genomicsChannel);
 
 
     delegate = variantStub.streamVariants(request);
@@ -68,11 +70,30 @@ protected Iterator<StreamVariantsResponse> delegate() {
     return delegate;
   }
 
+  /**
+   * @see java.util.Iterator#hasNext()
+   */
+  public boolean hasNext() {
+    try {
+      return delegate.hasNext();
+    } catch (RuntimeException e) {
+      genomicsChannel.shutdownNow();
+      throw e;
+    }
+  }
+
   /**
    * @see java.util.Iterator#next()
    */
   public StreamVariantsResponse next() {
-    StreamVariantsResponse response = delegate.next();
+    StreamVariantsResponse response = null;
+    try {
+      response = delegate.next();
+    } catch (RuntimeException e) {
+      genomicsChannel.shutdownNow();
+      throw e;
+    }
+
     if(null == shardPredicate) {
       return response;
     }