JAVA-2389: Make minimum value for max staleness either 90 seconds or …

…the heartbeat frequency plus the idle write period, whichever is greatest

driver-core/src/main/com/mongodb/ConnectionString.java

@@ -158,7 +158,9 @@
  * <li>{@code maxStalenessSeconds=seconds}. The maximum staleness in seconds. For use with any non-primary read preference, the driver
  * estimates the staleness of each secondary, based on lastWriteDate values provided in server isMaster responses, and selects only those
  * secondaries whose staleness is less than or equal to maxStalenessSeconds.  Not providing the parameter or explicitly setting it to -1
- * indicates that there should be no max staleness check.
+ * indicates that there should be no max staleness check. The maximum staleness feature is designed to prevent badly-lagging servers from
+ * being selected. The staleness estimate is imprecise and shouldn't be used to try to select "up-to-date" secondaries.  The minimum value
+ * is either 90 seconds, or the heartbeat frequency plus 10 seconds, whichever is greatest.
  * </li>
  * </ul>
  * <p>Authentication configuration:</p>
@@ -448,7 +450,7 @@ private WriteConcern createWriteConcern(final Map<String, List<String>> optionsM
     private ReadPreference createReadPreference(final Map<String, List<String>> optionsMap) {
         String readPreferenceType = null;
         List<TagSet> tagSetList = new ArrayList<TagSet>();
-        double maxStalenessSeconds = -1;
+        long maxStalenessSeconds = -1;
 
         for (final String key : READ_PREFERENCE_KEYS) {
             String value = getLastValue(optionsMap, key);
@@ -459,7 +461,7 @@ private ReadPreference createReadPreference(final Map<String, List<String>> opti
             if (key.equals("readpreference")) {
                 readPreferenceType = value;
             } else if (key.equals("maxstalenessseconds")) {
-                 maxStalenessSeconds = Double.parseDouble(value);
+                 maxStalenessSeconds = parseInteger(value, "maxstalenessseconds");
             } else if (key.equals("readpreferencetags")) {
                 for (final String cur : optionsMap.get(key)) {
                     TagSet tagSet = getTags(cur.trim());
@@ -601,15 +603,14 @@ private Map<String, List<String>> parseOptions(final String optionsPart) {
     }
 
     private ReadPreference buildReadPreference(final String readPreferenceType,
-                                               final List<TagSet> tagSetList, final double maxStalenessSeconds) {
+                                               final List<TagSet> tagSetList, final long maxStalenessSeconds) {
         if (readPreferenceType != null) {
             if (tagSetList.isEmpty() && maxStalenessSeconds == -1) {
                 return ReadPreference.valueOf(readPreferenceType);
             } else if (maxStalenessSeconds == -1) {
                return ReadPreference.valueOf(readPreferenceType, tagSetList);
             } else {
-                return ReadPreference.valueOf(readPreferenceType, tagSetList,
-                        Math.round(maxStalenessSeconds * 1000), TimeUnit.MILLISECONDS);
+                return ReadPreference.valueOf(readPreferenceType, tagSetList, maxStalenessSeconds, TimeUnit.SECONDS);
             }
         } else if (!(tagSetList.isEmpty() && maxStalenessSeconds == -1)) {
             throw new IllegalArgumentException("Read preference mode must be specified if "

driver-core/src/main/com/mongodb/ReadPreference.java

@@ -138,10 +138,12 @@ public static ReadPreference nearest() {
     /**
      * Gets a read preference that forces reads to the primary if available, otherwise to a secondary.
      *
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return ReadPreference which reads primary if available.
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static ReadPreference primaryPreferred(final long maxStaleness, final TimeUnit timeUnit) {
         return new PrimaryPreferredReadPreference(Collections.<TagSet>emptyList(), maxStaleness, timeUnit);
@@ -155,10 +157,12 @@ public static ReadPreference primaryPreferred(final long maxStaleness, final Tim
      * and selects only those secondaries whose staleness is less than or equal to maxStaleness.
      * </p>
      *
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return ReadPreference which reads secondary.
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static ReadPreference secondary(final long maxStaleness, final TimeUnit timeUnit) {
         return new SecondaryReadPreference(Collections.<TagSet>emptyList(), maxStaleness, timeUnit);
@@ -172,10 +176,12 @@ public static ReadPreference secondary(final long maxStaleness, final TimeUnit t
      * The driver estimates the staleness of each secondary, based on lastWriteDate values provided in server isMaster responses,
      * and selects only those secondaries whose staleness is less than or equal to maxStaleness.
      * </p>     *
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return ReadPreference which reads secondary if available, otherwise from primary.
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static ReadPreference secondaryPreferred(final long maxStaleness, final TimeUnit timeUnit) {
         return new SecondaryPreferredReadPreference(Collections.<TagSet>emptyList(), maxStaleness, timeUnit);
@@ -189,10 +195,12 @@ public static ReadPreference secondaryPreferred(final long maxStaleness, final T
      * and selects only those secondaries whose staleness is less than or equal to maxStaleness.
      * </p>
      *
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return ReadPreference which reads nearest
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static ReadPreference nearest(final long maxStaleness, final TimeUnit timeUnit) {
         return new NearestReadPreference(Collections.<TagSet>emptyList(), maxStaleness, timeUnit);
@@ -252,10 +260,12 @@ public static TaggableReadPreference nearest(final TagSet tagSet) {
      * </p>
      *
      * @param tagSet the set of tags to limit the list of secondaries to.
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return ReadPreference which reads primary if available, otherwise a secondary respective of tags.\
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static TaggableReadPreference primaryPreferred(final TagSet tagSet,
                                                           final long maxStaleness, final TimeUnit timeUnit) {
@@ -271,10 +281,12 @@ public static TaggableReadPreference primaryPreferred(final TagSet tagSet,
      * </p>
      *
      * @param tagSet the set of tags to limit the list of secondaries to
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return ReadPreference which reads secondary respective of tags.
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static TaggableReadPreference secondary(final TagSet tagSet,
                                                    final long maxStaleness, final TimeUnit timeUnit) {
@@ -290,10 +302,12 @@ public static TaggableReadPreference secondary(final TagSet tagSet,
      * and selects only those secondaries whose staleness is less than or equal to maxStaleness.
      * </p>     *
      * @param tagSet the set of tags to limit the list of secondaries to
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return ReadPreference which reads secondary if available respective of tags, otherwise from primary irrespective of tags.
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static TaggableReadPreference secondaryPreferred(final TagSet tagSet,
                                                             final long maxStaleness, final TimeUnit timeUnit) {
@@ -310,10 +324,12 @@ public static TaggableReadPreference secondaryPreferred(final TagSet tagSet,
      * </p>
      *
      * @param tagSet the set of tags to limit the list of secondaries to
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return ReadPreference which reads nearest node respective of tags.
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static TaggableReadPreference nearest(final TagSet tagSet,
                                                  final long maxStaleness, final TimeUnit timeUnit) {
@@ -388,10 +404,12 @@ public static TaggableReadPreference nearest(final List<TagSet> tagSetList) {
      * </p>
      *
      * @param tagSetList the list of tag sets to limit the list of secondaries to
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return ReadPreference which reads primary if available, otherwise a secondary respective of tags.
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static TaggableReadPreference primaryPreferred(final List<TagSet> tagSetList,
                                                           final long maxStaleness, final TimeUnit timeUnit) {
@@ -413,10 +431,12 @@ public static TaggableReadPreference primaryPreferred(final List<TagSet> tagSetL
      * </p>
      *
      * @param tagSetList the list of tag sets to limit the list of secondaries to
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return ReadPreference which reads secondary respective of tags.
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static TaggableReadPreference secondary(final List<TagSet> tagSetList,
                                                    final long maxStaleness, final TimeUnit timeUnit) {
@@ -438,10 +458,12 @@ public static TaggableReadPreference secondary(final List<TagSet> tagSetList,
      * </p>
      *
      * @param tagSetList the list of tag sets to limit the list of secondaries to
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return ReadPreference which reads secondary if available respective of tags, otherwise from primary irrespective of tags.
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static TaggableReadPreference secondaryPreferred(final List<TagSet> tagSetList,
                                                             final long maxStaleness, final TimeUnit timeUnit) {
@@ -463,10 +485,12 @@ public static TaggableReadPreference secondaryPreferred(final List<TagSet> tagSe
      * </p>
      *
      * @param tagSetList the list of tag sets to limit the list of secondaries to
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return ReadPreference which reads nearest node respective of tags.
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static TaggableReadPreference nearest(final List<TagSet> tagSetList,
                                                  final long maxStaleness, final TimeUnit timeUnit) {
@@ -527,10 +551,12 @@ public static TaggableReadPreference valueOf(final String name, final List<TagSe
      *
      * @param name the name of the read preference
      * @param tagSetList the list of tag sets
-     * @param maxStaleness the max allowable staleness of secondaries.
+     * @param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
+     *                     plus 10 seconds, whichever is greatest.
      * @param timeUnit the time unit of maxStaleness
      * @return the taggable read preference
      * @since 3.4
+     * @see TaggableReadPreference#getMaxStaleness(TimeUnit)
      */
     public static TaggableReadPreference valueOf(final String name, final List<TagSet> tagSetList, final long maxStaleness,
                                                  final TimeUnit timeUnit) {

driver-core/src/main/com/mongodb/TaggableReadPreference.java

@@ -23,7 +23,7 @@
 import com.mongodb.connection.ServerType;
 import org.bson.BsonArray;
 import org.bson.BsonDocument;
-import org.bson.BsonDouble;
+import org.bson.BsonInt64;
 import org.bson.BsonString;
 
 import java.util.ArrayList;
@@ -36,12 +36,16 @@
 import static java.lang.String.format;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.concurrent.TimeUnit.NANOSECONDS;
+import static java.util.concurrent.TimeUnit.SECONDS;
 
 /**
  * Abstract class for all preference which can be combined with tags
  */
 @Immutable
 public abstract class TaggableReadPreference extends ReadPreference {
+    private static final int SMALLEST_MAX_STALENESS_MS = 90000;
+    private static final int IDLE_WRITE_PERIOD_MS = 10000;
+
     private final List<TagSet> tagSetList = new ArrayList<TagSet>();
     private final Long maxStalenessMS;
 
@@ -73,7 +77,7 @@ public BsonDocument toDocument() {
         }
 
         if (maxStalenessMS != null) {
-            readPrefObject.put("maxStalenessSeconds", new BsonDouble(maxStalenessMS / 1000.0));
+            readPrefObject.put("maxStalenessSeconds", new BsonInt64(MILLISECONDS.toSeconds(maxStalenessMS)));
         }
         return readPrefObject;
     }
@@ -90,12 +94,18 @@ public List<TagSet> getTagSetList() {
 
     /**
      * Gets the maximum acceptable staleness of a secondary in order to be considered for read operations.
-     *
+     * <p>
+     * The maximum staleness feature is designed to prevent badly-lagging servers from being selected. The staleness estimate is imprecise
+     * and shouldn't be used to try to select "up-to-date" secondaries.
+     * </p>
+     * <p>
+     * The driver estimates the staleness of each secondary, based on lastWriteDate values provided in server isMaster responses,
+     * and selects only those secondaries whose staleness is less than or equal to maxStaleness.
+     * </p>
      * @param timeUnit the time unit in which to return the value
      * @return the maximum acceptable staleness in the given time unit, or null if the value is not set
-     *
-     * @since 3.4
      * @mongodb.server.release 3.4
+     * @since 3.4
      */
     public Long getMaxStaleness(final TimeUnit timeUnit) {
         notNull("timeUnit", timeUnit);
@@ -176,16 +186,22 @@ protected List<ServerDescription> selectFreshServers(final ClusterDescription cl
             return servers;
         }
 
+        if (servers.isEmpty()) {
+            return servers;
+        }
+
         long heartbeatFrequencyMS = clusterDescription.getServerSettings().getHeartbeatFrequency(MILLISECONDS);
 
-        ServerDescription mostUpToDateServerDescription = getMostUpToDateServerDescription(clusterDescription);
-        if (mostUpToDateServerDescription != null
-                    && getMaxStaleness(MILLISECONDS) < heartbeatFrequencyMS + mostUpToDateServerDescription.getIdleWritePeriodMillis()) {
-            throw new MongoConfigurationException(format("Max staleness (%d ms) must be at least the heartbeat period (%d ms) "
-                                                                 + "plus the idle write period (%d ms)",
-                    getMaxStaleness(MILLISECONDS), heartbeatFrequencyMS, mostUpToDateServerDescription.getIdleWritePeriodMillis()));
+        if (getMaxStaleness(MILLISECONDS) < Math.max(SMALLEST_MAX_STALENESS_MS, heartbeatFrequencyMS + IDLE_WRITE_PERIOD_MS)) {
+            if (SMALLEST_MAX_STALENESS_MS > heartbeatFrequencyMS + IDLE_WRITE_PERIOD_MS){
+                throw new MongoConfigurationException(format("Max staleness (%d sec) must be at least 90 seconds",
+                        getMaxStaleness(SECONDS)));
+            } else {
+                throw new MongoConfigurationException(format("Max staleness (%d ms) must be at least the heartbeat period (%d ms) "
+                                                                     + "plus the idle write period (%d ms)",
+                        getMaxStaleness(MILLISECONDS), heartbeatFrequencyMS, IDLE_WRITE_PERIOD_MS));
+            }
         }
-
         List<ServerDescription> freshServers = new ArrayList<ServerDescription>(servers.size());
 
         ServerDescription primary = findPrimary(clusterDescription);
@@ -200,7 +216,7 @@ && getMaxStaleness(MILLISECONDS) < heartbeatFrequencyMS + mostUpToDateServerDesc
                     }
                 }
             }
-        } else   {
+        } else {
             ServerDescription mostUpdateToDateSecondary = findMostUpToDateSecondary(clusterDescription);
             for (ServerDescription cur : servers) {
                 if (mostUpdateToDateSecondary.getLastWriteDate().getTime() - cur.getLastWriteDate().getTime() + heartbeatFrequencyMS
@@ -363,7 +379,7 @@ public List<ServerDescription> chooseForReplicaSet(final ClusterDescription clus
                 }
             }
             return selectedServers;
-       }
+        }
     }
 
     /**