fix(core.configuration): make snapshot storage more resilient [backport 5.6.0] (#5991)

* fix(core.configuration): make snapshot storage more resilient

This is a partial backport of the streaming optimization changes
introduced in #5734.

The changes improve memory efficiency during snapshot operations
by utilizing streaming APIs instead of storing multiple copies
of large snapshots in memory, making the snapshot storage process
more resilient to memory constraints.

Signed-off-by: MMaiero <[email protected]>

* Update kura/org.eclipse.kura.core.configuration/src/main/java/org/eclipse/kura/core/configuration/ConfigurationServiceImpl.java

Co-authored-by: Copilot <[email protected]>

* Partial implemented the changes suggested by copilot

Signed-off-by: MMaiero <[email protected]>

* Updated versions and cleanup

Signed-off-by: MMaiero <[email protected]>

* Aligned to develop on the file move

Signed-off-by: MMaiero <[email protected]>

---------

Signed-off-by: MMaiero <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: MMaiero

kura/distrib/config/kura.build.properties

@@ -13,7 +13,7 @@ org.eclipse.kura.core.keystore.version=1.6.0
 org.eclipse.kura.core.cloud.version=1.7.0
 org.eclipse.kura.core.cloud.factory.version=1.6.0
 org.eclipse.kura.core.comm.version=1.6.0
-org.eclipse.kura.core.configuration.version=2.6.0
+org.eclipse.kura.core.configuration.version=2.6.1-SNAPSHOT
 org.eclipse.kura.core.crypto.version=1.6.0
 org.eclipse.kura.deployment.agent.version=1.6.0
 org.eclipse.kura.core.deployment.version=1.7.0

kura/org.eclipse.kura.core.configuration/src/main/java/org/eclipse/kura/core/configuration/ConfigurationServiceImpl.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2011, 2022 Eurotech and/or its affiliates and others
+ * Copyright (c) 2011, 2025 Eurotech and/or its affiliates and others
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -21,9 +21,12 @@
 import java.io.FileReader;
 import java.io.IOException;
 import java.io.OutputStreamWriter;
-import java.io.UnsupportedEncodingException;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.nio.file.attribute.PosixFilePermission;
+import java.nio.file.attribute.PosixFilePermissions;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -45,6 +48,7 @@
 
 import org.eclipse.kura.KuraErrorCode;
 import org.eclipse.kura.KuraException;
+import org.eclipse.kura.KuraIOException;
 import org.eclipse.kura.KuraPartialSuccessException;
 import org.eclipse.kura.configuration.ComponentConfiguration;
 import org.eclipse.kura.configuration.ConfigurableComponent;
@@ -1174,40 +1178,69 @@ private void writeSnapshot(long sid, XmlComponentConfigurations conf) throws Kur
         // Encrypt the XML
         char[] encryptedXML = this.cryptoService.encryptAes(xmlResult.toCharArray());
 
+        File tempSnapshotFile = getTempSnapshotFile(fSnapshot);
+
         // Write the snapshot
-        FileOutputStream fos = null;
-        OutputStreamWriter osw = null;
         try {
+            try (FileOutputStream fos = new FileOutputStream(tempSnapshotFile);
+                OutputStreamWriter osw = new OutputStreamWriter(fos, StandardCharsets.UTF_8)) {
+                logger.debug("Writing temp snapshot - Saving {}...", tempSnapshotFile.getAbsolutePath());
+                osw.append(new String(encryptedXML));
+                osw.flush();
+                fos.flush();
+                fos.getFD().sync();
+                logger.debug("Writing temp snapshot - Saving {}... Done.", tempSnapshotFile.getAbsolutePath());
+            }
             logger.info("Writing snapshot - Saving {}...", fSnapshot.getAbsolutePath());
-            fos = new FileOutputStream(fSnapshot);
-            osw = new OutputStreamWriter(fos, "UTF-8");
-            osw.append(new String(encryptedXML));
-            osw.flush();
-            fos.flush();
-            fos.getFD().sync();
+            moveTempFile(fSnapshot, tempSnapshotFile);
             logger.info("Writing snapshot - Saving {}... Done.", fSnapshot.getAbsolutePath());
         } catch (FileNotFoundException e) {
             throw new KuraException(KuraErrorCode.INTERNAL_ERROR, e);
-        } catch (UnsupportedEncodingException e) {
-            throw new KuraException(KuraErrorCode.INTERNAL_ERROR, e);
         } catch (IOException e) {
-            throw new KuraException(KuraErrorCode.INTERNAL_ERROR, e);
+            throw new KuraIOException(e);
         } finally {
-            if (osw != null) {
+            if (tempSnapshotFile.exists()) {
                 try {
-                    osw.close();
+                    Files.delete(tempSnapshotFile.toPath());
                 } catch (IOException e) {
-
+                    // Ignore cleanup errors
                 }
             }
-            if (fos != null) {
-                try {
-                    fos.close();
-                } catch (IOException e) {
+        }
+    }
 
-                }
-            }
+    private void moveTempFile(File fSnapshot, File tempSnapshotFile) throws KuraIOException {
+        try {
+            setSnapshotFilePermissions(fSnapshot, tempSnapshotFile);
+            
+            // Consolidate snapshot writing
+            Files.move(tempSnapshotFile.toPath(), fSnapshot.toPath(), StandardCopyOption.REPLACE_EXISTING,
+                    StandardCopyOption.ATOMIC_MOVE);
+        } catch (IOException e) {
+            throw new KuraIOException(e);
+        }
+    }
+
+    private void setSnapshotFilePermissions(File fSnapshot, File tempSnapshotFile) throws IOException {
+        try {
+            Set<PosixFilePermission> perms = PosixFilePermissions.fromString("rw-------");
+            Files.setPosixFilePermissions(tempSnapshotFile.toPath(), perms);
+
+        } catch (UnsupportedOperationException e1) {
+            // POSIX permissions not supported on this file system, log and continue
+            logger.warn("Unable to set POSIX file permissions for snapshot file: {}", fSnapshot.getAbsolutePath(),
+                    e1);
+        }
+    }
+
+    private File getTempSnapshotFile(File fSnapshot) throws KuraIOException {
+        File tempSnapshotFile;
+        try {
+            tempSnapshotFile = File.createTempFile(fSnapshot.getName(), null, new File(fSnapshot.getParent()));
+        } catch (IOException ex) {
+            throw new KuraIOException(ex);
         }
+        return tempSnapshotFile;
     }
 
     private ComponentConfiguration getConfigurableComponentConfiguration(String pid) {