Update StatisticFactory.java (#91)

Do not preload `TPStatistic` since it lacks a default constructor; but do preload specified TPStatistics.

Author: vjkoskela

src/main/java/com/arpnetworking/tsdcore/statistics/StatisticFactory.java

@@ -15,11 +15,12 @@
  */
 package com.arpnetworking.tsdcore.statistics;
 
+import com.arpnetworking.steno.Logger;
+import com.arpnetworking.steno.LoggerFactory;
 import com.arpnetworking.utility.InterfaceDatabase;
 import com.arpnetworking.utility.ReflectionsDatabase;
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Maps;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 import java.lang.reflect.Constructor;
 import java.lang.reflect.InvocationTargetException;
@@ -62,25 +63,33 @@ public Optional<Statistic> tryGetStatistic(final String name) {
         final Optional<Statistic> registeredStatistic =
                 Optional.ofNullable(STATISTICS_BY_NAME_AND_ALIAS.get(name));
         if (!registeredStatistic.isPresent()) {
-            final Matcher matcher = PERCENTILE_STATISTIC_PATTERN.matcher(name);
-            if (matcher.matches()) {
-                try {
-                    final String percentileString = matcher.group("percentile").replace('p', '.');
-                    final double percentile = Double.parseDouble(percentileString);
-                    final Statistic statistic = new TPStatistic(percentile);
-                    checkedPut(STATISTICS_BY_NAME_AND_ALIAS, statistic);
-                    return Optional.of(statistic);
-                } catch (final NumberFormatException e) {
-                    LOGGER.error(String.format(
-                            "Invalid percentile statistic; name=%s",
-                            name));
-                    return registeredStatistic;
-                }
+            final Optional<Statistic> statistic = getPercentileStatistic(name);
+            if (statistic.isPresent()) {
+                checkedPut(STATISTICS_BY_NAME_AND_ALIAS, statistic.get());
+                return statistic;
             }
         }
         return registeredStatistic;
     }
 
+    private static Optional<Statistic> getPercentileStatistic(final String name) {
+        final Matcher matcher = PERCENTILE_STATISTIC_PATTERN.matcher(name);
+        if (matcher.matches()) {
+            try {
+                final String percentileString = matcher.group("percentile").replace('p', '.');
+                final double percentile = Double.parseDouble(percentileString);
+                final Statistic statistic = new TPStatistic(percentile);
+                return Optional.of(statistic);
+            } catch (final NumberFormatException e) {
+                LOGGER.error()
+                        .setMessage("Invalid percentile statistic")
+                        .addData("name", name)
+                        .log();
+            }
+        }
+        return Optional.empty();
+    }
+    
     private static void checkedPut(final ConcurrentMap<String, Statistic> map, final Statistic statistic) {
         checkedPut(map, statistic, statistic.getName());
         for (final String alias : statistic.getAliases()) {
@@ -106,14 +115,16 @@ private static void checkedPut(final ConcurrentMap<String, Statistic> map, final
     private static final Pattern PERCENTILE_STATISTIC_PATTERN = Pattern.compile("^[t]?p(?<percentile>[0-9]+(?:(\\.|p)[0-9]+)?)$");
     private static final ConcurrentMap<String, Statistic> STATISTICS_BY_NAME_AND_ALIAS;
     private static final InterfaceDatabase INTERFACE_DATABASE = ReflectionsDatabase.newInstance();
+    private static final ImmutableList<String> PERCENTILE_STATISTICS_TO_PRELOAD = ImmutableList.of("p75", "p90", "p95", "p99", "p99.9");
     private static final Logger LOGGER = LoggerFactory.getLogger(StatisticFactory.class);
 
     static {
         // NOTE: Do not put log messages in static blocks since they can lock the logger thread!
         final ConcurrentMap<String, Statistic> statisticByNameAndAlias = Maps.newConcurrentMap();
         final Set<Class<? extends Statistic>> statisticClasses = INTERFACE_DATABASE.findClassesWithInterface(Statistic.class);
         for (final Class<? extends Statistic> statisticClass : statisticClasses) {
-            if (!statisticClass.isInterface() && !Modifier.isAbstract(statisticClass.getModifiers())) {
+            if (!statisticClass.isInterface() && !Modifier.isAbstract(statisticClass.getModifiers()) 
+                    && !TPStatistic.class.equals(statisticClass)) {
                 try {
                     final Constructor<? extends Statistic> constructor = statisticClass.getDeclaredConstructor();
                     if (!constructor.isAccessible()) {
@@ -126,6 +137,17 @@ private static void checkedPut(final ConcurrentMap<String, Statistic> map, final
                 }
             }
         }
+        for (final String percentileStatisticName : PERCENTILE_STATISTICS_TO_PRELOAD) {
+            final Optional<Statistic> statistic = getPercentileStatistic(percentileStatisticName);
+            if (statistic.isPresent()) {
+                checkedPut(statisticByNameAndAlias, statistic.get());
+            } else {
+                LOGGER.warn()
+                        .setMessage("Unable to load statistic")
+                        .addData("name", percentileStatisticName)
+                        .log();
+            }
+        }
         STATISTICS_BY_NAME_AND_ALIAS = statisticByNameAndAlias;
     }
 }