feat: add property to disable FunctionProperty caching

Author: vlsi

bin/jmeter.properties

@@ -1055,6 +1055,12 @@ csvdataset.file.encoding_list=UTF-8|UTF-16|ISO-8859-15|US-ASCII
 # ORO PatternCacheLRU size
 #oro.patterncache.size=1000
 
+# Cache function execution during test execution
+# By default, JMeter caches function properties, however, it might cause unexpected results
+# when the component is shared across threads and the expression depends on the thread variables.
+# The caching behaviour would likely change in the upcoming versions
+#function.cache.per.iteration=true
+
 #TestBeanGui
 #
 #propertyEditorSearchPath=null

src/core/src/main/java/org/apache/jmeter/testelement/property/FunctionProperty.java

@@ -21,17 +21,24 @@
 import org.apache.jmeter.testelement.TestElement;
 import org.apache.jmeter.threads.JMeterContext;
 import org.apache.jmeter.threads.JMeterContextService;
+import org.apache.jmeter.util.JMeterUtils;
 
 /**
  * Class that implements the Function property
  */
 public class FunctionProperty extends AbstractProperty {
     private static final long serialVersionUID = 233L;
+    private static final boolean FUNCTION_CACHE_PER_ITERATION =
+            JMeterUtils.getPropDefault("function.cache.per.iteration", true);
 
     private transient CompoundVariable function;
 
     private int testIteration = -1;
 
+    /**
+     * The cache will be removed in the subsequent releases.
+     * For now, it is kept for backward compatibility.
+     */
     private String cacheValue;
 
     public FunctionProperty(String name, CompoundVariable func) {
@@ -47,7 +54,7 @@ public FunctionProperty() {
     public void setObjectValue(Object v) {
         if (v instanceof CompoundVariable && !isRunningVersion()) {
             function = (CompoundVariable) v;
-        } else {
+        } else if (FUNCTION_CACHE_PER_ITERATION) {
             cacheValue = v.toString();
         }
     }
@@ -87,7 +94,7 @@ public String getStringValue() {
             log.debug("Not running version, return raw function string");
             return function.getRawParameters();
         }
-        if(!ctx.isSamplingStarted()) {
+        if (!FUNCTION_CACHE_PER_ITERATION || !ctx.isSamplingStarted()) {
             return function.execute();
         }
         log.debug("Running version, executing function");

xdocs/changes.xml

@@ -97,6 +97,7 @@ Summary
 
 <h3>General</h3>
 <ul>
+<li>Added property <code>function.cache.per.iteration</code> to disable function property caching</li>
 </ul>
 
 <ch_section>Non-functional changes</ch_section>

xdocs/usermanual/properties_reference.xml

@@ -1339,6 +1339,14 @@ JMETER-SERVER</source>
     ORO PatternCacheLRU size.<br/>
     Defaults to: <code>1000</code>
 </property>
+<property name="function.cache.per.iteration">
+    <p>Cache function execution during test execution.</p>
+    <p>By default, JMeter caches function properties during a test iteration, however,
+    it might cause unexpected results when a component is shared across threads and the expression depends on
+    the thread variables.</p>
+    <note>The caching behaviour would likely be disabled in the upcoming versions</note>
+    Defaults to: <code>true</code>
+</property>
 <property name="propertyEditorSearchPath">
     TestBeanGui<br/>
     Defaults to: <code>null</code>