JAVA-1151: Fail fast if HdrHistogram is not in the classpath.

olim7t · olim7t · commit 63e44b3765ca · 2016-04-19T11:50:29.000+02:00
diff --git a/changelog/README.md b/changelog/README.md
@@ -4,6 +4,7 @@
 
 - [bug] JAVA-1132: Executing bound statement with no variables results in exception with protocol v1.
 - [improvement] JAVA-1040: SimpleStatement parameters support in QueryLogger.
+- [improvement] JAVA-1151: Fail fast if HdrHistogram is not in the classpath.
 
 Merged from 2.1 branch:
 
diff --git a/driver-core/src/main/java/com/datastax/driver/core/PerHostPercentileTracker.java b/driver-core/src/main/java/com/datastax/driver/core/PerHostPercentileTracker.java
@@ -76,6 +76,12 @@ private PerHostPercentileTracker(long highestTrackableLatencyMillis, int numberO
                                      int numberOfHosts,
                                      int minRecordedValues,
                                      long intervalMs) {
+        try {
+            Histogram.class.getName();
+        } catch (NoClassDefFoundError e) {
+            throw new IllegalStateException("HdrHistogram seems to be missing from the classpath. " +
+                    "Make sure you depend on it explicitly (the driver declares it as optional).", e);
+        }
         this.highestTrackableLatencyMillis = highestTrackableLatencyMillis;
         this.numberOfSignificantValueDigits = numberOfSignificantValueDigits;
         this.minRecordedValues = minRecordedValues;
