- Tighten the thread-safety protection on the "BulkImportReport.getJsonReport()" method.

- Update dependencies.
- Code polishing.

build.gradle

@@ -49,7 +49,7 @@ dependencies {
     implementation group: 'org.apache.commons', name: 'commons-lang3', version: '3.14.0'
 
     // https://mvnrepository.com/artifact/org.apache.commons/commons-compress
-    implementation("org.apache.commons:commons-compress:1.26.1") {
+    implementation("org.apache.commons:commons-compress:1.26.2") {
         exclude group: 'com.github.luben', module: 'zstd-jni'
     }
     implementation 'com.github.luben:zstd-jni:1.5.6-3'  // Even though this is part of the above dependency, the Apache commons rarely updates it, while the zstd team makes improvements very often.
@@ -116,7 +116,7 @@ dependencies {
     implementation 'org.json:json:20240303' // This is used only in "ParquetFileUtils.createRemoteParquetDirectories()". TODO - Replace it with "gson".
 
     // https://mvnrepository.com/artifact/com.google.code.gson/gson
-    implementation 'com.google.code.gson:gson:2.10.1'
+    implementation 'com.google.code.gson:gson:2.11.0'
 
     // https://mvnrepository.com/artifact/io.micrometer/micrometer-registry-prometheus
     runtimeOnly 'io.micrometer:micrometer-registry-prometheus:1.13.0'

src/main/java/eu/openaire/urls_controller/models/BulkImportReport.java

@@ -9,7 +9,10 @@ import com.google.gson.Gson;
 import eu.openaire.urls_controller.util.GenericUtils;
 
 import java.util.Collection;
+import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 
 
 @JsonInclude(JsonInclude.Include.NON_NULL)
@@ -34,6 +37,8 @@ public class BulkImportReport {
     @JsonProperty
     private Map<String, Collection<String>> eventsMap;
 
+    transient private final Lock reportLock = new ReentrantLock(true);
+
 
     public BulkImportReport(String provenance, String reportLocation, String reportID) {
         this.provenance = provenance;
@@ -47,13 +52,16 @@ public class BulkImportReport {
     }
 
     /**
-     * Synchronize it to avoid concurrency issues when concurrent calls are made to the same bulkImport-Report object.
+     * Synchronize it with a lock, to avoid concurrency issues when concurrent calls are made to the same bulkImport-Report object.
      * */
-    public synchronized String getJsonReport()
+    public String getJsonReport()
     {
+        reportLock.lock();
         //Convert the LinkedHashMultiMap<String, String> to Map<String, Collection<String>>, since Gson cannot serialize Multimaps.
-        eventsMap = eventsMultimap.asMap();
-        return gson.toJson(this, BulkImportReport.class);
+        eventsMap = new HashMap<>(eventsMultimap.asMap());  // Make sure we use a clone of the original data, in order to avoid any exception in the "gson.toJson()" method, when at the same time another thread modifies the "eventsMultimap".
+        String reportToReturn = gson.toJson(this, BulkImportReport.class);
+        reportLock.unlock();
+        return reportToReturn;
     }
 
     public String getProvenance() {

src/main/java/eu/openaire/urls_controller/services/UrlsServiceImpl.java

@@ -564,7 +564,7 @@ public class UrlsServiceImpl implements UrlsService {
             Throwable cause = e.getCause();
             String exMsg;
             if ( (cause != null) && ((exMsg = cause.getMessage()) != null) && exMsg.contains("Connection refused") ) {
-                logger.error(errorMsg + " | The worker has probably crashed, since we received a \"Connection refused\"!");
+                logger.error(errorMsg + " | The worker has probably crashed, since we received a \"Connection refused\" message!");
                 workerInfo.setHasShutdown(true);    // Avoid sending possible shutdown-Requests later on. Also show a specific message if this Worker requests new assignments in the future.
             } else
                 logger.error(errorMsg, e);

src/main/java/eu/openaire/urls_controller/util/FileUtils.java

@@ -462,7 +462,7 @@ public class FileUtils {
         if ( shouldLockThreads )    // In case multiple threads write to the same file. for ex. during the bulk-import procedure.
             fileAccessLock.lock();
 
-        // TODO - Make this method to be synchronized be specific file, not in general.
+        // TODO - Make this method to be synchronized for the specific file, not in general.
         // TODO - NOW: Multiple bulkImport procedures (with diff DIRs), are blocked while writing to DIFFERENT files..
 
         try ( BufferedWriter bufferedWriter = new BufferedWriter(Files.newBufferedWriter(Paths.get(fileFullPath)), halfMb) )