Add sequence distribution type to cassandra stress: fix problem with setSeed()

Patch by Ben Slater; reviewed by Stefania Alborghetti for CASSANDRA-12490

tools/cqlstress-counter-example.yaml

@@ -48,11 +48,10 @@ table_definition: |
 #      GAUSSIAN(min..max,mean,stdev)        A gaussian/normal distribution, with explicitly defined mean and stdev
 #      UNIFORM(min..max)                    A uniform distribution over the range [min, max]
 #      FIXED(val)                           A fixed distribution, always returning the same value
-#      SEQ(min..max)                        A fixed sequence, returning values from min to max sequentially, wrapping if necessary.
+#      SEQ(min..max)                        A fixed sequence, returning values in the range min to max sequentially (starting based on seed), wrapping if necessary.
 #      Aliases: extr, gauss, normal, norm, weibull
 #
 #      If preceded by ~, the distribution is inverted
-#
 # Defaults for all columns are size: uniform(4..8), population: uniform(1..100B), cluster: fixed(1)
 #
 

tools/cqlstress-example.yaml

@@ -59,7 +59,7 @@ table_definition: |
 #      GAUSSIAN(min..max,mean,stdev)        A gaussian/normal distribution, with explicitly defined mean and stdev
 #      UNIFORM(min..max)                    A uniform distribution over the range [min, max]
 #      FIXED(val)                           A fixed distribution, always returning the same value
-#      SEQ(min..max)                        A fixed sequence, returning values from min to max sequentially, wrapping if necessary.
+#      SEQ(min..max)                        A fixed sequence, returning values in the range min to max sequentially (starting based on seed), wrapping if necessary.
 #      Aliases: extr, gauss, normal, norm, weibull
 #
 #      If preceded by ~, the distribution is inverted

tools/cqlstress-insanity-example.yaml

@@ -58,7 +58,7 @@ table_definition: |
 #      GAUSSIAN(min..max,mean,stdev)        A gaussian/normal distribution, with explicitly defined mean and stdev
 #      UNIFORM(min..max)                    A uniform distribution over the range [min, max]
 #      FIXED(val)                           A fixed distribution, always returning the same value
-#      SEQ(min..max)                        A fixed sequence, returning values from min to max sequentially, wrapping if necessary.
+#      SEQ(min..max)                        A fixed sequence, returning values in the range min to max sequentially (starting based on seed), wrapping if necessary.
 #      Aliases: extr, gauss, normal, norm, weibull
 #
 #      If preceded by ~, the distribution is inverted

tools/stress/src/org/apache/cassandra/stress/generate/DistributionSequence.java

@@ -63,7 +63,10 @@ public class DistributionSequence extends Distribution
     }
 
     @Override
-    public void setSeed(long seed){}
+    public void setSeed(long seed)
+    {
+        next.set(seed);
+    }
 
 }
 

tools/stress/src/org/apache/cassandra/stress/settings/OptionDistribution.java

@@ -124,7 +124,7 @@ public class OptionDistribution extends Option
                 GroupedOptions.formatMultiLine("GAUSSIAN(min..max,mean,stdev)", "A gaussian/normal distribution, with explicitly defined mean and stdev"),
                 GroupedOptions.formatMultiLine("UNIFORM(min..max)", "A uniform distribution over the range [min, max]"),
                 GroupedOptions.formatMultiLine("FIXED(val)", "A fixed distribution, always returning the same value"),
-                GroupedOptions.formatMultiLine("SEQ(min..max)", "A fixed sequence, returning values from min to max sequentially, wrapping if necessary."),
+                GroupedOptions.formatMultiLine("SEQ(min..max)", "A fixed sequence, returning values in the range min to max sequentially (starting based on seed), wrapping if necessary."),
                 "Preceding the name with ~ will invert the distribution, e.g. ~exp(1..10) will yield 10 most, instead of least, often",
                 "Aliases: extr, qextr, gauss, normal, norm, weibull"
         );

tools/stress/test/unit/org/apache/cassandra/stress/generate/DistributionSequenceTest.java

@@ -96,4 +96,35 @@ public class DistributionSequenceTest
         assertEquals(Long.MAX_VALUE, dist.inverseCumProb(1d));
 
     }
+
+    @Test
+    public void setSeed() throws Exception
+    {
+        Distribution dist = OptionDistribution.get("seq(1..10)").get();
+        assertTrue(dist instanceof DistributionSequence);
+
+        for (int seed=1; seed<500; seed+=seed)
+        {
+            dist.setSeed(seed);
+            assertEquals(1, dist.minValue());
+            assertEquals(10, dist.maxValue());
+            assertEquals(5, dist.average());
+
+            assertEquals(1, dist.inverseCumProb(0d));
+            assertEquals(10, dist.inverseCumProb(1d));
+
+            long last = dist.next();
+            for (int i = 0; i < 9; i++)
+            {
+                long next = dist.next();
+                if (next>1)
+                {
+                    assertEquals(next, last + 1); //increase by one each step
+                }else{
+                    assertEquals(last, 10); //wrap after the end
+                }
+                last = next;
+            }
+        }
+    }
 }