Fix parallel controller iteration count synchronization (#96)

- Add ParentIterationVariables wrapper to delegate iteration count to parent thread
- Inject custom variables into parallel threads to maintain iteration consistency
- Add Maven Shade plugin to bundle dependencies and resolve GUI loading issues

Author: diego-ferrand

parallel/pom.xml

@@ -39,6 +39,37 @@
 
     <build>
         <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-shade-plugin</artifactId>
+                <version>3.2.4</version>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>shade</goal>
+                        </goals>
+                        <configuration>
+                            <createDependencyReducedPom>false</createDependencyReducedPom>
+                            <filters>
+                                <filter>
+                                    <artifact>*:*</artifact>
+                                    <excludes>
+                                        <exclude>META-INF/*.SF</exclude>
+                                        <exclude>META-INF/*.DSA</exclude>
+                                        <exclude>META-INF/*.RSA</exclude>
+                                    </excludes>
+                                </filter>
+                            </filters>
+                            <transformers>
+                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+                                    <mainClass>com.blazemeter.jmeter.controller.ParallelSampler</mainClass>
+                                </transformer>
+                            </transformers>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
             <plugin>
                 <groupId>org.sonatype.plugins</groupId>
                 <artifactId>nexus-staging-maven-plugin</artifactId>

parallel/src/main/java/com/blazemeter/jmeter/controller/ParallelSampler.java

@@ -247,13 +247,43 @@ private void injectVariables(JMeterThread jmThread, JMeterContext threadContext)
                 Class<JMeterThread> cls = JMeterThread.class;
                 Field vars = cls.getDeclaredField("threadVars");
                 vars.setAccessible(true);
-                vars.set(jmThread, threadContext.getVariables());
+                
+                JMeterVariables parentVars = threadContext.getVariables();
+                JMeterVariables customVars = new ParentIterationVariables(parentVars, threadContext.getThread());
+                vars.set(jmThread, customVars);
             } catch (Throwable ex) {
                 log.warn("Cannot inject variables into parallel thread ", ex);
             }
         }
     }
 
+    /**
+     * Custom JMeterVariables implementation that delegates to parent thread's variables
+     * but returns the parent thread's iteration count instead of this thread's iteration count.
+     */
+    private static class ParentIterationVariables extends JMeterVariables {
+        private final JMeterVariables parentVars;
+
+        public ParentIterationVariables(JMeterVariables parentVars, JMeterThread parentThread) {
+            this.parentVars = parentVars;
+        }
+
+        @Override
+        public int getIteration() {
+            return parentVars.getIteration();
+        }
+
+        @Override
+        public String get(String key) {
+            return parentVars.get(key);
+        }
+
+        @Override
+        public void put(String key, String value) {
+            parentVars.put(key, value);
+        }
+    }
+
     private void changeVariablesMap() {
         try {
             JMeterContext context = this.getThreadContext();