diff --git a/google-cloud-core/pom.xml b/google-cloud-core/pom.xml
index 190cbe8ec854..d395b23313f9 100644
--- a/google-cloud-core/pom.xml
+++ b/google-cloud-core/pom.xml
@@ -111,7 +111,7 @@
     <dependency>
       <groupId>com.google.api</groupId>
       <artifactId>gax</artifactId>
-      <version>0.0.27-SNAPSHOT</version>
+      <version>0.0.27</version>
       <exclusions>
         <exclusion>
           <groupId>io.grpc</groupId>
diff --git a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/MessagesProcessor.java b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/MessagesProcessor.java
index 855f2d3b5545..32e00bbb7322 100644
--- a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/MessagesProcessor.java
+++ b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/MessagesProcessor.java
@@ -17,19 +17,16 @@
 package com.google.cloud.pubsub;
 
 import com.google.api.gax.bundling.FlowController;
-import com.google.auth.Credentials;
 import com.google.cloud.Clock;
 import com.google.cloud.pubsub.Subscriber.MessageReceiver;
 import com.google.cloud.pubsub.Subscriber.MessageReceiver.AckReply;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.Lists;
 import com.google.common.primitives.Ints;
-import com.google.common.util.concurrent.AbstractService;
 import com.google.common.util.concurrent.FutureCallback;
 import com.google.common.util.concurrent.Futures;
 import com.google.pubsub.v1.PubsubMessage;
 import com.google.pubsub.v1.ReceivedMessage;
-import io.grpc.Status;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
diff --git a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/PollingSubscriberConnection.java b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/PollingSubscriberConnection.java
index ec292451029e..e5328cce07ae 100644
--- a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/PollingSubscriberConnection.java
+++ b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/PollingSubscriberConnection.java
@@ -40,7 +40,6 @@
 import io.grpc.Channel;
 import io.grpc.StatusRuntimeException;
 import io.grpc.auth.MoreCallCredentials;
-import java.util.Iterator;
 import java.util.List;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
diff --git a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/PubSub.java b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/PubSub.java
index ee1d6cfe0f56..9439e4665baf 100644
--- a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/PubSub.java
+++ b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/PubSub.java
@@ -16,14 +16,11 @@
 
 package com.google.cloud.pubsub;
 
-import com.google.auto.value.AutoValue;
 import com.google.cloud.AsyncPage;
 import com.google.cloud.GrpcServiceOptions.ExecutorFactory;
 import com.google.cloud.Page;
 import com.google.cloud.Policy;
 import com.google.cloud.Service;
-import com.google.common.base.Optional;
-import com.google.common.base.Preconditions;
 import java.io.IOException;
 import java.util.List;
 import java.util.Map;
diff --git a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/Publisher.java b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/Publisher.java
index 8428cce91e90..9013b94bef43 100644
--- a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/Publisher.java
+++ b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/Publisher.java
@@ -143,8 +143,9 @@ public interface Publisher {
    * #getMaxOutstandingRequestBytes()} & {@link #getMaxOutstandingElementCount()}).
    *
    * <p>If set to false, a publish call will fail with either {@link
-   * RequestByteMaxOutstandingReachedException} or {@link ElementCountMaxOutstandingReachedException}, as
-   * appropriate, when flow control limits are reached.
+   * RequestByteMaxOutstandingReachedException} or {@link
+   * ElementCountMaxOutstandingReachedException}, as appropriate, when flow control limits are
+   * reached.
    */
   boolean failOnFlowControlLimits();
 
@@ -250,8 +251,8 @@ public Builder setFlowControlSettings(FlowController.Settings flowControlSetting
 
     /**
      * Whether to fail publish when reaching any of the flow control limits, with either a {@link
-     * RequestByteMaxOutstandingReachedException} or {@link ElementCountMaxOutstandingReachedException} as
-     * appropriate.
+     * RequestByteMaxOutstandingReachedException} or {@link
+     * ElementCountMaxOutstandingReachedException} as appropriate.
      *
      * <p>If set to false, then publish operations will block the current thread until the
      * outstanding requests go under the limits.
diff --git a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/Subscriber.java b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/Subscriber.java
index a193510f398a..ba5931b09248 100644
--- a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/Subscriber.java
+++ b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/Subscriber.java
@@ -37,9 +37,9 @@
  *
  * <p>A {@link Subscriber} allows you to provide an implementation of a {@link MessageReceiver
  * receiver} to which messages are going to be delivered as soon as they are received by the
- * subscriber. The delivered messages then can be {@link AckReply#ACK acked} or {@link
- * AckReply#NACK nacked} at will as they get processed by the receiver. Nacking a
- * messages implies a later redelivery of such message.
+ * subscriber. The delivered messages then can be {@link AckReply#ACK acked} or {@link AckReply#NACK
+ * nacked} at will as they get processed by the receiver. Nacking a messages implies a later
+ * redelivery of such message.
  *
  * <p>The subscriber handles the ack management, by automatically extending the ack deadline while
  * the message is being processed, to then issue the ack or nack of such message when the processing
@@ -54,38 +54,38 @@
  *       in memory before the receiver either ack or nack them.
  * </ul>
  *
- * <p>If no credentials are provided, the {@link Publisher} will use application default
- * credentials through {@link GoogleCredentials#getApplicationDefault}.
+ * <p>If no credentials are provided, the {@link Publisher} will use application default credentials
+ * through {@link GoogleCredentials#getApplicationDefault}.
  *
  * <p>For example, a {@link Subscriber} can be constructed and used to receive messages as follows:
  *
- * <pre>
- *  MessageReceiver receiver =
- *      message -> {
- *        // ... process message ...
- *        return Futures.immediateFuture(AckReply.ACK);
- *      });
+ * <pre>{@code
+ * MessageReceiver receiver = new MessageReceiver() {
+ *   @Override
+ *   public ListenableFuture<AckReply> receiveMessage(PubsubMessage message) {
+ *     // ... process message ...
+ *     return Futures.immediateFuture(AckReply.ACK);
+ *   }
+ * }
  *
- *  Subscriber subscriber =
- *      Subscriber.Builder.newBuilder(MY_SUBSCRIPTION, receiver)
- *          .setMaxBundleAcks(100)
- *          .build();
+ * Subscriber subscriber =
+ *     Subscriber.Builder.newBuilder(MY_SUBSCRIPTION, receiver)
+ *         .setMaxBundleAcks(100)
+ *         .build();
  *
- *  subscriber.startAsync();
+ * subscriber.startAsync();
  *
- *  ... recommended, listen for fatal errors that break the subscriber streaming ...
- *  subscriber.addListener(
-        new Listener() {
-          @Override
-          public void failed(State from, Throwable failure) {
-            System.out.println("Subscriber faile with error: " + failure);
-          }
-        },
-        Executors.newSingleThreadExecutor());
+ * // ... recommended, listen for fatal errors that break the subscriber streaming ...
+ * subscriber.addListener(new Listener() {
+ *   @Override
+ *   public void failed(State from, Throwable failure) {
+ *     System.out.println("Subscriber faile with error: " + failure);
+ *   }
+ * }, Executors.newSingleThreadExecutor());
  *
- *  ... and when done with the subscriber ...
- *  subscriber.stopAsync();
- * </pre>
+ * // ... and when done with the subscriber ...
+ * subscriber.stopAsync();
+ * }</pre>
  */
 public interface Subscriber extends Service {
   String PUBSUB_API_ADDRESS = "pubsub.googleapis.com";
@@ -129,13 +129,11 @@ public static enum AckReply {
    *
    * <p><b>When limits are enforced, no more messages will be dispatched to the {@link
    * MessageReceiver} but due to the gRPC and HTTP/2 buffering and congestion control window
-   * management, still some extra bytes could be kept at lower layers.
+   * management, still some extra bytes could be kept at lower layers.</b>
    */
   Optional<Integer> getMaxOutstandingElementCount();
 
-  /**
-   * Maximum number of outstanding (i.e. pending to process) bytes before limits are enforced.
-   */
+  /** Maximum number of outstanding (i.e. pending to process) bytes before limits are enforced. */
   Optional<Integer> getMaxOutstandingRequestBytes();
 
   /** Builder of {@link Subscriber Subscribers}. */
diff --git a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/Subscription.java b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/Subscription.java
index f0f589410300..6f07c120c66c 100644
--- a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/Subscription.java
+++ b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/Subscription.java
@@ -18,14 +18,10 @@
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
-import com.google.cloud.GrpcServiceOptions;
 import com.google.cloud.Policy;
-import com.google.cloud.pubsub.PubSub.PullOption;
 import com.google.common.base.Function;
-
 import java.io.IOException;
 import java.io.ObjectInputStream;
-import java.util.Iterator;
 import java.util.List;
 import java.util.Objects;
 import java.util.concurrent.Future;
@@ -41,18 +37,12 @@
  * processed and the Pub/Sub system can delete it from the subscription; a non-success response
  * indicates that the Pub/Sub server should resend it (implicit "nack").
  *
- * <p>In a pull subscription, the subscribing application must explicitly pull messages using one of
- * {@link PubSub#pull(String, int)}, {@link PubSub#pullAsync(String, int)} or
- * {@link PubSub#pullAsync(String, PubSub.MessageProcessor callback, PubSub.PullOption...)}.
- * When messages are pulled with {@link PubSub#pull(String, int)} or
- * {@link PubSub#pullAsync(String, int)} the subscribing application must also explicitly
- * acknowledge them using one of {@link PubSub#ack(String, Iterable)},
- * {@link PubSub#ack(String, String, String...)}, {@link PubSub#ackAsync(String, Iterable)} or
- * {@link PubSub#ackAsync(String, String, String...)}.
+ * <p>In a pull subscription, the subscribing application must pull messages using {@link
+ * PubSub#getSubscriber(SubscriptionInfo, Subscriber.MessageReceiver)}.
  *
- * <p>{@code Subscription} adds a layer of service-related functionality over
- * {@link SubscriptionInfo}. Objects of this class are immutable. To get a {@code Subscription}
- * object with the most recent information use {@link #reload} or {@link #reloadAsync}.
+ * <p>{@code Subscription} adds a layer of service-related functionality over {@link
+ * SubscriptionInfo}. Objects of this class are immutable. To get a {@code Subscription} object with
+ * the most recent information use {@link #reload} or {@link #reloadAsync}.
  *
  * @see <a href="https://cloud.google.com/pubsub/overview#data_model">Pub/Sub Data Model</a>
  * @see <a href="https://cloud.google.com/pubsub/subscriber">Subscriber Guide</a>
diff --git a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/SubscriptionInfo.java b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/SubscriptionInfo.java
index 5bbc4cd161bc..b7ddc5bea16f 100644
--- a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/SubscriptionInfo.java
+++ b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/SubscriptionInfo.java
@@ -20,10 +20,8 @@
 
 import com.google.cloud.pubsub.spi.v1.SubscriberClient;
 import com.google.common.base.MoreObjects;
-
 import java.io.Serializable;
 import java.util.Objects;
-import java.util.concurrent.TimeUnit;
 
 /**
  * A Google Cloud Pub/Sub subscription. A subscription represents the stream of messages from a
@@ -36,14 +34,8 @@
  * processed and the Pub/Sub system can delete it from the subscription; a non-success response
  * indicates that the Pub/Sub server should resend it (implicit "nack").
  *
- * <p>In a pull subscription, the subscribing application must explicitly pull messages using one of
- * {@link PubSub#pull(String, int)}, {@link PubSub#pullAsync(String, int)} or
- * {@link PubSub#pullAsync(String, PubSub.MessageProcessor callback, PubSub.PullOption...)}.
- * When messages are pulled with {@link PubSub#pull(String, int)} or
- * {@link PubSub#pullAsync(String, int)} the subscribing application must also explicitly
- * acknowledge them using one of {@link PubSub#ack(String, Iterable)},
- * {@link PubSub#ack(String, String, String...)}, {@link PubSub#ackAsync(String, Iterable)} or
- * {@link PubSub#ackAsync(String, String, String...)}.
+ * <p>In a pull subscription, the subscribing application must pull messages using {@link
+ * PubSub#getSubscriber(SubscriptionInfo, Subscriber.MessageReceiver)}.
  *
  * @see <a href="https://cloud.google.com/pubsub/overview#data_model">Pub/Sub Data Model</a>
  * @see <a href="https://cloud.google.com/pubsub/subscriber">Subscriber Guide</a>
@@ -140,10 +132,10 @@ public abstract static class Builder {
      * acknowledge the message. After message delivery but before the ack deadline expires and
      * before the message is acknowledged, it is an outstanding message and will not be delivered
      * again during that time (on a best-effort basis). For pull subscriptions, this value is used
-     * as the initial value for the ack deadline. To override the ack deadline value for a given
-     * message, use {@link PubSub#modifyAckDeadline(String, int, TimeUnit, Iterable)}. For push
-     * delivery, this value is used to set the request timeout for the call to the push endpoint.
-     * This value must be between 10 and 600 seconds, if not specified, 10 seconds is used.
+     * as the initial value for the ack deadline, and {@link Subscriber} automatically renews
+     * unprocessed messages. For push delivery, this value is used to set the request timeout for
+     * the call to the push endpoint. This value must be between 10 and 600 seconds, if not
+     * specified, 10 seconds is used.
      */
     @Deprecated
     public abstract Builder ackDeadLineSeconds(int ackDeadLineSeconds);
@@ -153,10 +145,10 @@ public abstract static class Builder {
      * acknowledge the message. After message delivery but before the ack deadline expires and
      * before the message is acknowledged, it is an outstanding message and will not be delivered
      * again during that time (on a best-effort basis). For pull subscriptions, this value is used
-     * as the initial value for the ack deadline. To override the ack deadline value for a given
-     * message, use {@link PubSub#modifyAckDeadline(String, int, TimeUnit, Iterable)}. For push
-     * delivery, this value is used to set the request timeout for the call to the push endpoint.
-     * This value must be between 10 and 600 seconds, if not specified, 10 seconds is used.
+     * as the initial value for the ack deadline. , and {@link Subscriber} automatically renews
+     * unprocessed messages. For push delivery, this value is used to set the request timeout for
+     * the call to the push endpoint. This value must be between 10 and 600 seconds, if not
+     * specified, 10 seconds is used.
      */
     public abstract Builder setAckDeadLineSeconds(int ackDeadLineSeconds);
 
@@ -333,13 +325,13 @@ public PushConfig getPushConfig() {
 
   /**
    * Returns the maximum time after a subscriber receives a message before the subscriber should
-   * acknowledge the message. After message delivery but before the ack deadline expires and
-   * before the message is acknowledged, it is an outstanding message and will not be delivered
-   * again during that time (on a best-effort basis). For pull subscriptions, this value is used
-   * as the initial value for the ack deadline. To override the ack deadline value for a given
-   * message, use {@link PubSub#modifyAckDeadline(String, int, TimeUnit, Iterable)}. For push
-   * delivery, this value is used to set the request timeout for the call to the push endpoint. This
-   * value must be between 10 and 600 seconds, if not specified, 10 seconds is used.
+   * acknowledge the message. After message delivery but before the ack deadline expires and before
+   * the message is acknowledged, it is an outstanding message and will not be delivered again
+   * during that time (on a best-effort basis). For pull subscriptions, this value is used as the
+   * initial value for the ack deadline, and {@link Subscriber} automatically renews unprocessed
+   * messages. For push delivery, this value is used to set the request timeout for the call to the
+   * push endpoint. This value must be between 10 and 600 seconds, if not specified, 10 seconds is
+   * used.
    */
   @Deprecated
   public long ackDeadlineSeconds() {
@@ -348,13 +340,13 @@ public long ackDeadlineSeconds() {
 
   /**
    * Returns the maximum time after a subscriber receives a message before the subscriber should
-   * acknowledge the message. After message delivery but before the ack deadline expires and
-   * before the message is acknowledged, it is an outstanding message and will not be delivered
-   * again during that time (on a best-effort basis). For pull subscriptions, this value is used
-   * as the initial value for the ack deadline. To override the ack deadline value for a given
-   * message, use {@link PubSub#modifyAckDeadline(String, int, TimeUnit, Iterable)}. For push
-   * delivery, this value is used to set the request timeout for the call to the push endpoint. This
-   * value must be between 10 and 600 seconds, if not specified, 10 seconds is used.
+   * acknowledge the message. After message delivery but before the ack deadline expires and before
+   * the message is acknowledged, it is an outstanding message and will not be delivered again
+   * during that time (on a best-effort basis). For pull subscriptions, this value is used as the
+   * initial value for the ack deadline, and {@link Subscriber} automatically renews unprocessed
+   * messages. For push delivery, this value is used to set the request timeout for the call to the
+   * push endpoint. This value must be between 10 and 600 seconds, if not specified, 10 seconds is
+   * used.
    */
   public long getAckDeadlineSeconds() {
     return ackDeadlineSeconds;
diff --git a/google-cloud-pubsub/src/test/java/com/google/cloud/pubsub/PublisherImplTest.java b/google-cloud-pubsub/src/test/java/com/google/cloud/pubsub/PublisherImplTest.java
index 74bf9e28f53b..bd906b33ca74 100644
--- a/google-cloud-pubsub/src/test/java/com/google/cloud/pubsub/PublisherImplTest.java
+++ b/google-cloud-pubsub/src/test/java/com/google/cloud/pubsub/PublisherImplTest.java
@@ -410,7 +410,10 @@ public void testBuilderInvalidArguments() {
     }
     try {
       builder.setBundlingSettings(
-          Publisher.DEFAULT_BUNDLING_SETTINGS.toBuilder().setRequestByteThreshold((Long)null).build());
+          Publisher.DEFAULT_BUNDLING_SETTINGS
+              .toBuilder()
+              .setRequestByteThreshold((Long) null)
+              .build());
       fail("Should have thrown an NullPointerException");
     } catch (NullPointerException expected) {
       // Expected
@@ -454,7 +457,10 @@ public void testBuilderInvalidArguments() {
         Publisher.DEFAULT_BUNDLING_SETTINGS.toBuilder().setElementCountThreshold(1).build());
     try {
       builder.setBundlingSettings(
-          Publisher.DEFAULT_BUNDLING_SETTINGS.toBuilder().setElementCountThreshold((Long)null).build());
+          Publisher.DEFAULT_BUNDLING_SETTINGS
+              .toBuilder()
+              .setElementCountThreshold((Long) null)
+              .build());
       fail("Should have thrown an NullPointerException");
     } catch (NullPointerException expected) {
       // Expected