diff --git a/core/CHANGES.md b/core/CHANGES.md
new file mode 100644
index 0000000000000000000000000000000000000000..26c675f9380a3ce5bf0f9f792b7eb8a9a7c906b6
--- /dev/null
+++ b/core/CHANGES.md
@@ -0,0 +1,60 @@
+When used as a latency under load benchmark YCSB in it's original form suffers from
+Coordinated Omission[1] and related measurement issue:
+
+* Load is controlled by response time
+* Measurement does not account for missing time
+* Measurement starts at beginning of request rather than at intended beginning
+* Measurement is limited in scope as the histogram does not provide data on overflow values
+
+To provide a minimal correction patch the following were implemented:
+
+1. Replace internal histogram implementation with HdrHistogram[2]:
+HdrHistogram offers a dynamic range of measurement at a given precision and will
+improve the fidelity of reporting. It allows capturing a much wider range of latencies.
+HdrHistogram also supports compressed loss-less serialization which enable capturing
+snapshot histograms from which lower resolution histograms can be constructed for plotting
+latency over time. Snapshot interval histograms are serialized on status reporting which
+must be enabled using the '-s' option.
+
+2. Track intended operation start and report latencies from that point in time:
+Assuming the benchmark sets a target schedule of execution in which every operation
+is supposed to happen at a given time the benchmark should measure the latency between
+intended start time and operation completion.
+This required the introduction of a new measurement point and inevitably
+includes measuring some of the internal preparation steps of the load generator.
+These overhead should be negligible in the context of a network hop, but could
+be corrected for by estimating the load-generator overheads (e.g. by measuring a
+no-op DB or by measuring the setup time for an operation and deducting that from total).
+This intended measurement point is only used when there is a target load (specified by
+the -target paramaeter)
+
+This branch supports the following new options:
+
+* -p measurementtype=[histogram|hdrhistogram|hdrhistogram+histogram|timeseries] (default=histogram)
+The new measurement types are hdrhistogram and hdrhistogram+histogram. Default is still
+histogram, which is the old histogram. Ultimately we would remove the old measurement types
+and use only HdrHistogram but the old measurement is left in there for comparison sake.
+
+* -p measurement.interval=[op|intended|both] (default=op)
+This new option deferentiates between measured intervals and adds the intended interval(as described)
+above, and the option to record both the op and intended for comparison.
+
+* -p hdrhistogram.fileoutput=[true|false] (default=false)
+This new option will enable periodical writes of the interval histogram into an output file. The path can be set using '-p hdrhistogram.output.path=<PATH>'.
+
+Example parameters:
+-target 1000 -s -p workload=com.yahoo.ycsb.workloads.CoreWorkload -p basicdb.verbose=false -p basicdb.simulatedelay=4 -p measurement.interval=both -p measurementtype=hdrhistogram -p hdrhistogram.fileoutput=true -p maxexecutiontime=60
+
+
+Further correction suggestions:
+
+1. Correction load control: currently after a pause the load generator will do
+operations back to back to catchup, this leads to a flat out throughput mode
+of testing as opposed to controlled load.
+
+2. Move to async model: Scenarios where Ops have no dependency could delegate the
+Op execution to a threadpool and thus separate the request rate control from the
+synchronous execution of Ops. Measurement would start on queuing for execution.
+
+1. https://groups.google.com/forum/#!msg/mechanical-sympathy/icNZJejUHfE/BfDekfBEs_sJ
+2. https://github.com/HdrHistogram/HdrHistogram
\ No newline at end of file
diff --git a/core/COORDINATED-OMISSION.md b/core/COORDINATED-OMISSION.md
deleted file mode 100644
index 0b3b663a66e7d25f8a3b081bdc92ca9ed475c67e..0000000000000000000000000000000000000000
--- a/core/COORDINATED-OMISSION.md
+++ /dev/null
@@ -1,27 +0,0 @@
-YCSB in it's original form suffers from Coordinated Omission[1]:
-* Load is controlled by response time
-* Measurement does not account for missing time
-* Measurement starts at beginning of request rather than at intended beginning
-To provide a minimal correction patch I propose:
-1. Replace internal histogram implementation with HdrHistogram:
-HdrHistogram offers a dynamic range of measurement at a given precision and will
-improve the fidelity of reporting. It allows capturing a much wider range of latencies.
-We could add controls for corrected/uncorrected measurement. This is appropriate for a
-uniform load test, but not for other loads. The mixing of different Ops also makes
-this correction unreliable. This could work for a global histogram.
-2. Track intended operation start and report latencies from that point in time:
-This will require the introduction of a new measurement point and will inevitably
-include measuring some of the internal preparation steps of the load generator.
-These overhead should be negligible in the context of a network hop, but could
-be corrected for by estimating the load-generator overheads (e.g. by measuring a
-no-op DB).
-
-Further correction suggestions:
-1. Correction load control: currently after a pause the load generator will do
-operations back to back to catchup, this leads to a flat out throughput mode
-of testing as opposed to controlled load.
-2. Move to async model: Scenarios where Ops have no dependency could delegate the
-Op execution to a threadpool and thus separate the request rate control from the
-synchronous execution of Ops. Measurement would start on queuing for execution.
-
-1. https://groups.google.com/forum/#!msg/mechanical-sympathy/icNZJejUHfE/BfDekfBEs_sJ
\ No newline at end of file
diff --git a/core/src/main/java/com/yahoo/ycsb/Client.java b/core/src/main/java/com/yahoo/ycsb/Client.java
index f68352f4cc67f365e98a105221ef2694bd89be17..cd3cc805faf0b5773fd6cbab1dfc3c7ff77e80ad 100644
--- a/core/src/main/java/com/yahoo/ycsb/Client.java
+++ b/core/src/main/java/com/yahoo/ycsb/Client.java
@@ -154,8 +154,6 @@ class ClientThread extends Thread
Properties _props;
long _targetOpsTickNs;
final Measurements _measurements;
- final boolean _measureFromIntendedDeadline;
-
/**
* Constructor.
@@ -169,7 +167,7 @@ class ClientThread extends Thread
* @param opcount the number of operations (transactions or inserts) to do
* @param targetperthreadperms target number of operations per thread per ms
*/
- public ClientThread(DB db, boolean dotransactions, Workload workload, int threadid, int threadcount, Properties props, int opcount, double targetperthreadperms, boolean measureFromIntendedDeadline)
+ public ClientThread(DB db, boolean dotransactions, Workload workload, int threadid, int threadcount, Properties props, int opcount, double targetperthreadperms)
{
//TODO: consider removing threadcount and threadid
_db=db;
@@ -185,8 +183,6 @@ class ClientThread extends Thread
_threadcount=threadcount;
_props=props;
_measurements = Measurements.getMeasurements();
- //System.out.println("Interval = "+interval);
- _measureFromIntendedDeadline = false;
}
public int getOpsDone()
@@ -299,8 +295,7 @@ class ClientThread extends Thread
// delay until next tick
long deadline = startTimeNanos + _opsdone*_targetOpsTickNs;
sleepUntil(deadline);
- if(_measureFromIntendedDeadline)
- _measurements.setIntendedStartTimeNs(deadline);
+ _measurements.setIntendedStartTimeNs(deadline);
}
}
@@ -368,9 +363,6 @@ public class Client
*/
public static final String MAX_EXECUTION_TIME = "maxexecutiontime";
- private static final String CO_CORRECT_PROPERTY = "co.correct";
-
- private static final String DEFAULT_CO_CORRECT = "true";
public static void usageMessage()
{
@@ -735,7 +727,6 @@ public class Client
opcount=Integer.parseInt(props.getProperty(RECORD_COUNT_PROPERTY, DEFAULT_RECORD_COUNT));
}
}
- boolean measureFromIntendedDeadline = Boolean.parseBoolean(props.getProperty(CO_CORRECT_PROPERTY, DEFAULT_CO_CORRECT));
Vector<Thread> threads=new Vector<Thread>();
for (int threadid=0; threadid<threadcount; threadid++)
@@ -752,7 +743,7 @@ public class Client
}
- Thread t=new ClientThread(db,dotransactions,workload,threadid,threadcount,props,opcount/threadcount,targetperthreadperms, measureFromIntendedDeadline);
+ Thread t=new ClientThread(db,dotransactions,workload,threadid,threadcount,props,opcount/threadcount, targetperthreadperms);
threads.add(t);
//t.start();
diff --git a/core/src/main/java/com/yahoo/ycsb/DBWrapper.java b/core/src/main/java/com/yahoo/ycsb/DBWrapper.java
index 9882f38183e03ebad654f870de77496594c09f01..50b314bb75196708eca4b030e9d66d78e9954ddc 100644
--- a/core/src/main/java/com/yahoo/ycsb/DBWrapper.java
+++ b/core/src/main/java/com/yahoo/ycsb/DBWrapper.java
@@ -69,11 +69,11 @@ public class DBWrapper extends DB
*/
public void cleanup() throws DBException
{
- long ist=_measurements.getIntendedtartTimeNs();
- long st = System.nanoTime();
+ long ist=_measurements.getIntendedtartTimeNs();
+ long st = System.nanoTime();
_db.cleanup();
- long en=System.nanoTime();
- measure(ist, st, en);
+ long en=System.nanoTime();
+ measure("CLEANUP",ist, st, en);
}
/**
@@ -91,7 +91,7 @@ public class DBWrapper extends DB
long st = System.nanoTime();
int res=_db.read(table,key,fields,result);
long en=System.nanoTime();
- measure(ist, st, en);
+ measure("READ",ist, st, en);
_measurements.reportReturnCode("READ",res);
return res;
}
@@ -112,14 +112,14 @@ public class DBWrapper extends DB
long st = System.nanoTime();
int res=_db.scan(table,startkey,recordcount,fields,result);
long en=System.nanoTime();
- measure(ist, st, en);
+ measure("SCAN",ist, st, en);
_measurements.reportReturnCode("SCAN",res);
return res;
}
- private void measure(long intendedStartTimeNanos, long startTimeNanos, long endTimeNanos) {
- _measurements.measure("CLEANUP", (int)((endTimeNanos-startTimeNanos)/1000));
- _measurements.measureIntended("CLEANUP", (int)((endTimeNanos-intendedStartTimeNanos)/1000));
+ private void measure(String op, long intendedStartTimeNanos, long startTimeNanos, long endTimeNanos) {
+ _measurements.measure(op, (int)((endTimeNanos-startTimeNanos)/1000));
+ _measurements.measureIntended(op, (int)((endTimeNanos-intendedStartTimeNanos)/1000));
}
/**
@@ -137,7 +137,7 @@ public class DBWrapper extends DB
long st = System.nanoTime();
int res=_db.update(table,key,values);
long en=System.nanoTime();
- measure(ist, st, en);
+ measure("UPDATE",ist, st, en);
_measurements.reportReturnCode("UPDATE",res);
return res;
}
@@ -157,7 +157,7 @@ public class DBWrapper extends DB
long st = System.nanoTime();
int res=_db.insert(table,key,values);
long en=System.nanoTime();
- measure(ist, st, en);
+ measure("INSERT",ist, st, en);
_measurements.reportReturnCode("INSERT",res);
return res;
}
@@ -175,7 +175,7 @@ public class DBWrapper extends DB
long st = System.nanoTime();
int res=_db.delete(table,key);
long en=System.nanoTime();
- measure(ist, st, en);
+ measure("DELETE",ist, st, en);
_measurements.reportReturnCode("DELETE",res);
return res;
}
diff --git a/core/src/main/java/com/yahoo/ycsb/measurements/Measurements.java b/core/src/main/java/com/yahoo/ycsb/measurements/Measurements.java
index dc2e5f3e65c26678ddcb240c3d4e08f343a699a1..0a85888fbdc962a121da671163fd4ad4fa7a43f8 100644
--- a/core/src/main/java/com/yahoo/ycsb/measurements/Measurements.java
+++ b/core/src/main/java/com/yahoo/ycsb/measurements/Measurements.java
@@ -34,6 +34,8 @@ public class Measurements
public static final String MEASUREMENT_TYPE_PROPERTY = "measurementtype";
private static final String MEASUREMENT_TYPE_PROPERTY_DEFAULT = "histogram";
+ private static final String MEASUREMENT_INTERVAL = "measurement.interval";
+ private static final String MEASUREMENT_INTERVAL_DEFAULT = "op";
static Measurements singleton=null;
@@ -56,10 +58,10 @@ public class Measurements
return singleton;
}
- final ConcurrentHashMap<String,OneMeasurement> opToMesurementMap;
- final ConcurrentHashMap<String,OneMeasurement> opToIntendedMesurementMap;
- final int measurementType;
-
+ final ConcurrentHashMap<String,OneMeasurement> _opToMesurementMap;
+ final ConcurrentHashMap<String,OneMeasurement> _opToIntendedMesurementMap;
+ final int _measurementType;
+ final int _measurementInterval;
private Properties _props;
/**
@@ -67,33 +69,54 @@ public class Measurements
*/
public Measurements(Properties props)
{
- opToMesurementMap=new ConcurrentHashMap<String,OneMeasurement>();
- opToIntendedMesurementMap=new ConcurrentHashMap<String,OneMeasurement>();
+ _opToMesurementMap=new ConcurrentHashMap<String,OneMeasurement>();
+ _opToIntendedMesurementMap=new ConcurrentHashMap<String,OneMeasurement>();
_props=props;
String mTypeString = _props.getProperty(MEASUREMENT_TYPE_PROPERTY, MEASUREMENT_TYPE_PROPERTY_DEFAULT);
if (mTypeString.equals("histogram"))
{
- measurementType=0;
+ _measurementType = 0;
}
else if (mTypeString.equals("hdrhistogram"))
{
- measurementType=1;
+ _measurementType = 1;
}
- else if (mTypeString.equals("hdrhistogram+buckethistogram"))
+ else if (mTypeString.equals("hdrhistogram+histogram"))
{
- measurementType=2;
+ _measurementType = 2;
}
- else
+ else if (mTypeString.equals("timeseries"))
{
- measurementType=3;
+ _measurementType = 3;
+ }
+ else {
+ throw new IllegalArgumentException("unknown "+MEASUREMENT_TYPE_PROPERTY+"="+mTypeString);
}
+
+ String mIntervalString = _props.getProperty(MEASUREMENT_INTERVAL, MEASUREMENT_INTERVAL_DEFAULT);
+ if (mIntervalString.equals("op"))
+ {
+ _measurementInterval = 0;
+ }
+ else if (mIntervalString.equals("intended"))
+ {
+ _measurementInterval = 1;
+ }
+ else if (mIntervalString.equals("both"))
+ {
+ _measurementInterval = 2;
+ }
+ else {
+ throw new IllegalArgumentException("unknown "+MEASUREMENT_INTERVAL+"="+mIntervalString);
+ }
+
}
OneMeasurement constructOneMeasurement(String name)
{
- switch (measurementType)
+ switch (_measurementType)
{
case 0:
return new OneMeasurementHistogram(name, _props);
@@ -119,17 +142,21 @@ public class Measurements
}
}
}
- ThreadLocal<StartTimeHolder> tls = new ThreadLocal<Measurements.StartTimeHolder>(){
+ ThreadLocal<StartTimeHolder> tlIntendedStartTime = new ThreadLocal<Measurements.StartTimeHolder>(){
protected StartTimeHolder initialValue() {
return new StartTimeHolder();
- };
+ };
};
public void setIntendedStartTimeNs(long time){
- tls.get().time=time;
+ if(_measurementInterval==0)
+ return;
+ tlIntendedStartTime.get().time=time;
}
public long getIntendedtartTimeNs(){
- return tls.get().startTime();
+ if(_measurementInterval==0)
+ return 0L;
+ return tlIntendedStartTime.get().startTime();
}
/**
@@ -138,6 +165,8 @@ public class Measurements
*/
public void measure(String operation, int latency)
{
+ if(_measurementInterval==1)
+ return;
try
{
OneMeasurement m = getOpMeasurement(operation);
@@ -157,6 +186,8 @@ public class Measurements
*/
public void measureIntended(String operation, int latency)
{
+ if(_measurementInterval==0)
+ return;
try
{
OneMeasurement m = getOpIntendedMeasurement(operation);
@@ -172,11 +203,11 @@ public class Measurements
}
private OneMeasurement getOpMeasurement(String operation) {
- OneMeasurement m = opToMesurementMap.get(operation);
+ OneMeasurement m = _opToMesurementMap.get(operation);
if(m == null)
{
m = constructOneMeasurement(operation);
- OneMeasurement oldM = opToMesurementMap.putIfAbsent(operation, m);
+ OneMeasurement oldM = _opToMesurementMap.putIfAbsent(operation, m);
if(oldM != null)
{
m = oldM;
@@ -185,11 +216,12 @@ public class Measurements
return m;
}
private OneMeasurement getOpIntendedMeasurement(String operation) {
- OneMeasurement m = opToIntendedMesurementMap.get(operation);
+ OneMeasurement m = _opToIntendedMesurementMap.get(operation);
if(m == null)
{
- m = constructOneMeasurement("Intended-"+operation);
- OneMeasurement oldM = opToIntendedMesurementMap.putIfAbsent(operation, m);
+ final String name = _measurementInterval==1 ? operation : "Intended-" + operation;
+ m = constructOneMeasurement(name);
+ OneMeasurement oldM = _opToIntendedMesurementMap.putIfAbsent(operation, m);
if(oldM != null)
{
m = oldM;
@@ -198,11 +230,13 @@ public class Measurements
return m;
}
/**
- * Report a return code for a single DB operaiton.
+ * Report a return code for a single DB operation.
*/
public void reportReturnCode(String operation, int code)
{
- OneMeasurement m = getOpMeasurement(operation);
+ OneMeasurement m = _measurementInterval==1 ?
+ getOpIntendedMeasurement(operation) :
+ getOpMeasurement(operation);
m.reportReturnCode(code);
}
@@ -214,11 +248,11 @@ public class Measurements
*/
public void exportMeasurements(MeasurementsExporter exporter) throws IOException
{
- for (OneMeasurement measurement : opToMesurementMap.values())
+ for (OneMeasurement measurement : _opToMesurementMap.values())
{
measurement.exportMeasurements(exporter);
}
- for (OneMeasurement measurement : opToIntendedMesurementMap.values())
+ for (OneMeasurement measurement : _opToIntendedMesurementMap.values())
{
measurement.exportMeasurements(exporter);
}
@@ -230,11 +264,11 @@ public class Measurements
public synchronized String getSummary()
{
String ret="";
- for (OneMeasurement m : opToMesurementMap.values())
+ for (OneMeasurement m : _opToMesurementMap.values())
{
ret+=m.getSummary()+" ";
}
- for (OneMeasurement m : opToIntendedMesurementMap.values())
+ for (OneMeasurement m : _opToIntendedMesurementMap.values())
{
ret+=m.getSummary()+" ";
}
diff --git a/core/src/main/java/com/yahoo/ycsb/measurements/OneMeasurementHdrHistogram.java b/core/src/main/java/com/yahoo/ycsb/measurements/OneMeasurementHdrHistogram.java
index 1ed37733d5dd63573087197e38538df78acebab0..fa0735f854f758b59d07c6c15de07b89ccef8cb4 100644
--- a/core/src/main/java/com/yahoo/ycsb/measurements/OneMeasurementHdrHistogram.java
+++ b/core/src/main/java/com/yahoo/ycsb/measurements/OneMeasurementHdrHistogram.java
@@ -17,7 +17,11 @@
package com.yahoo.ycsb.measurements;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
import java.io.IOException;
+import java.io.PrintStream;
import java.text.DecimalFormat;
import java.util.Map;
import java.util.Properties;
@@ -25,6 +29,7 @@ import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
import org.HdrHistogram.Histogram;
+import org.HdrHistogram.HistogramLogWriter;
import org.HdrHistogram.Recorder;
import com.yahoo.ycsb.measurements.exporter.MeasurementsExporter;
@@ -36,9 +41,11 @@ import com.yahoo.ycsb.measurements.exporter.MeasurementsExporter;
*
*/
public class OneMeasurementHdrHistogram extends OneMeasurement {
-
- Recorder histogram = new Recorder(3);
+ // we need one log per measurement histogram
+ final PrintStream log;
+ final HistogramLogWriter histogramLogWriter;
+ final Recorder histogram = new Recorder(3);
final ConcurrentHashMap<Integer, AtomicInteger> returncodes;
Histogram totalHistogram;
@@ -46,6 +53,23 @@ public class OneMeasurementHdrHistogram extends OneMeasurement {
public OneMeasurementHdrHistogram(String name, Properties props) {
super(name);
returncodes = new ConcurrentHashMap<Integer, AtomicInteger>();
+ boolean shouldLog = Boolean.parseBoolean(props.getProperty("hdrhistogram.fileoutput", "false"));
+ if (!shouldLog) {
+ log = null;
+ histogramLogWriter = null;
+ return;
+ }
+ try {
+ final String hdrOutputFilename = props.getProperty("hdrhistogram.output.path", "") +name+".hdr";
+ log = new PrintStream(new FileOutputStream(hdrOutputFilename), false);
+ } catch (FileNotFoundException e) {
+ throw new RuntimeException("Failed to open hdr histogram output file",e);
+ }
+ histogramLogWriter = new HistogramLogWriter(log);
+ histogramLogWriter.outputComment("[Logging for: " + name + "]");
+ histogramLogWriter.outputLogFormatVersion();
+ histogramLogWriter.outputStartTime(System.currentTimeMillis());
+ histogramLogWriter.outputLegend();
}
/**
@@ -84,7 +108,12 @@ public class OneMeasurementHdrHistogram extends OneMeasurement {
@Override
public void exportMeasurements(MeasurementsExporter exporter) throws IOException {
// accumulate the last interval which was not caught by status thread
- getIntervalHistogramAndAccumulate();
+ Histogram intervalHistogram = getIntervalHistogramAndAccumulate();
+ if(histogramLogWriter != null) {
+ histogramLogWriter.outputIntervalHistogram(intervalHistogram);
+ // we can close now
+ log.close();
+ }
exporter.write(getName(), "Operations", totalHistogram.getTotalCount());
exporter.write(getName(), "AverageLatency(us)", totalHistogram.getMean());
exporter.write(getName(), "MinLatency(us)", totalHistogram.getMinValue());
@@ -95,7 +124,6 @@ public class OneMeasurementHdrHistogram extends OneMeasurement {
for (Map.Entry<Integer, AtomicInteger> entry : returncodes.entrySet()) {
exporter.write(getName(), "Return=" + entry.getKey(), entry.getValue().get());
}
-
}
/**
@@ -106,6 +134,11 @@ public class OneMeasurementHdrHistogram extends OneMeasurement {
@Override
public String getSummary() {
Histogram intervalHistogram = getIntervalHistogramAndAccumulate();
+ // we use the summary interval as the histogram file interval.
+ if(histogramLogWriter != null) {
+ histogramLogWriter.outputIntervalHistogram(intervalHistogram);
+ }
+
DecimalFormat d = new DecimalFormat("#.##");
return "[" + getName() +
": Count=" + intervalHistogram.getTotalCount() +
diff --git a/core/src/main/java/com/yahoo/ycsb/workloads/CoreWorkload.java b/core/src/main/java/com/yahoo/ycsb/workloads/CoreWorkload.java
index 5e65c18c0c5f9aa571b77c8f97210673febb58a7..b4a477b40e8371eca90a8da07b2a4b7aaae9ac59 100644
--- a/core/src/main/java/com/yahoo/ycsb/workloads/CoreWorkload.java
+++ b/core/src/main/java/com/yahoo/ycsb/workloads/CoreWorkload.java
@@ -353,6 +353,8 @@ public class CoreWorkload extends Workload
double scanproportion=Double.parseDouble(p.getProperty(SCAN_PROPORTION_PROPERTY,SCAN_PROPORTION_PROPERTY_DEFAULT));
double readmodifywriteproportion=Double.parseDouble(p.getProperty(READMODIFYWRITE_PROPORTION_PROPERTY,READMODIFYWRITE_PROPORTION_PROPERTY_DEFAULT));
recordcount=Integer.parseInt(p.getProperty(Client.RECORD_COUNT_PROPERTY, Client.DEFAULT_RECORD_COUNT));
+ if(recordcount == 0)
+ recordcount = Integer.MAX_VALUE;
String requestdistrib=p.getProperty(REQUEST_DISTRIBUTION_PROPERTY,REQUEST_DISTRIBUTION_PROPERTY_DEFAULT);
int maxscanlength=Integer.parseInt(p.getProperty(MAX_SCAN_LENGTH_PROPERTY,MAX_SCAN_LENGTH_PROPERTY_DEFAULT));
String scanlengthdistrib=p.getProperty(SCAN_LENGTH_DISTRIBUTION_PROPERTY,SCAN_LENGTH_DISTRIBUTION_PROPERTY_DEFAULT);