Add default retry params that align with SLA (#860)

* Add default retry params that align with SLA

* modify default retry params to conform with datastore, storage, and bigquery sla

* Javadoc adjustments

Author: ajkannan

gcloud-java-core/src/main/java/com/google/gcloud/RetryParams.java

@@ -48,12 +48,16 @@ public final class RetryParams implements Serializable {
 
   private static final long serialVersionUID = -8492751576749007700L;
 
+  /**
+   * Note that App Engine Standard Environment front-end modules have a 60 second deadline for HTTP
+   * requests. For that reason, we set the default total retry period to less than 60 seconds.
+   */
+  public static final long DEFAULT_TOTAL_RETRY_PERIOD_MILLIS = 50_000L;
   public static final int DEFAULT_RETRY_MIN_ATTEMPTS = 3;
   public static final int DEFAULT_RETRY_MAX_ATTEMPTS = 6;
-  public static final long DEFAULT_INITIAL_RETRY_DELAY_MILLIS = 250L;
-  public static final long DEFAULT_MAX_RETRY_DELAY_MILLIS = 10_000L;
+  public static final long DEFAULT_INITIAL_RETRY_DELAY_MILLIS = 1000L;
+  public static final long DEFAULT_MAX_RETRY_DELAY_MILLIS = 32_000L;
   public static final double DEFAULT_RETRY_DELAY_BACKOFF_FACTOR = 2.0;
-  public static final long DEFAULT_TOTAL_RETRY_PERIOD_MILLIS = 50_000L;
 
   private final int retryMinAttempts;
   private final int retryMaxAttempts;
@@ -62,6 +66,9 @@ public final class RetryParams implements Serializable {
   private final double retryDelayBackoffFactor;
   private final long totalRetryPeriodMillis;
 
+  // Some services may have different backoff requirements listed in their SLAs. Be sure to override
+  // ServiceOptions.defaultRetryParams() in options subclasses when the service's backoff
+  // requirement differs from the default parameters used here.
   private static final RetryParams DEFAULT_INSTANCE = new RetryParams(new Builder());
   private static final RetryParams NO_RETRIES =
       builder().retryMaxAttempts(1).retryMinAttempts(1).build();
@@ -156,7 +163,9 @@ public Builder retryDelayBackoffFactor(double retryDelayBackoffFactor) {
     }
 
     /**
-     * Sets totalRetryPeriodMillis.
+     * Sets totalRetryPeriodMillis. Note that App Engine Standard Environment front-end modules have
+     * a 60 second deadline for HTTP requests. For that reason, you should set the total retry
+     * period to under 60 seconds if you are using it on an App Engine front-end module.
      *
      * @param totalRetryPeriodMillis the totalRetryPeriodMillis to set
      * @return the Builder for chaining
@@ -295,4 +304,8 @@ public String toString() {
   public static Builder builder() {
     return new Builder();
   }
+
+  public Builder toBuilder() {
+    return new Builder(this);
+  }
 }

gcloud-java-core/src/main/java/com/google/gcloud/ServiceOptions.java

@@ -333,7 +333,7 @@ protected ServiceOptions(Class<? extends ServiceFactory<ServiceT, OptionsT>> ser
     authCredentials =
         builder.authCredentials != null ? builder.authCredentials : defaultAuthCredentials();
     authCredentialsState = authCredentials != null ? authCredentials.capture() : null;
-    retryParams = firstNonNull(builder.retryParams, RetryParams.defaultInstance());
+    retryParams = firstNonNull(builder.retryParams, defaultRetryParams());
     serviceFactory = firstNonNull(builder.serviceFactory,
         getFromServiceLoader(serviceFactoryClass, defaultServiceFactory()));
     serviceFactoryClassName = serviceFactory.getClass().getName();
@@ -654,6 +654,15 @@ private static <T> T newInstance(String className) throws IOException, ClassNotF
 
   public abstract <B extends Builder<ServiceT, ServiceRpcT, OptionsT, B>> B toBuilder();
 
+  /**
+   * Some services may have different backoff requirements listed in their SLAs. Be sure to override
+   * this method in options subclasses when the service's backoff requirement differs from the
+   * default parameters listed in {@link RetryParams}.
+   */
+  protected RetryParams defaultRetryParams() {
+    return RetryParams.defaultInstance();
+  }
+
   private static <T> T getFromServiceLoader(Class<? extends T> clazz, T defaultInstance) {
     return Iterables.getFirst(ServiceLoader.load(clazz), defaultInstance);
   }