From 791437a905bf5cb6ce61aecdc222dd4baaf78939 Mon Sep 17 00:00:00 2001
From: Rene Pfeuffer <rene.pfeuffer@cloudogu.com>
Date: Thu, 5 Dec 2019 07:57:47 +0100
Subject: [PATCH] Use copy on write in repository db

---
 .../scm/repository/xml/MetadataStore.java     |  6 +++-
 .../scm/repository/xml/PathDatabase.java      | 36 +++++++++++--------
 2 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/scm-dao-xml/src/main/java/sonia/scm/repository/xml/MetadataStore.java b/scm-dao-xml/src/main/java/sonia/scm/repository/xml/MetadataStore.java
index f22180ff9a..3a81f54fb2 100644
--- a/scm-dao-xml/src/main/java/sonia/scm/repository/xml/MetadataStore.java
+++ b/scm-dao-xml/src/main/java/sonia/scm/repository/xml/MetadataStore.java
@@ -5,6 +5,7 @@ import org.slf4j.LoggerFactory;
 import sonia.scm.ContextEntry;
 import sonia.scm.repository.InternalRepositoryException;
 import sonia.scm.repository.Repository;
+import sonia.scm.store.CopyOnWrite;
 import sonia.scm.store.StoreConstants;
 import sonia.scm.update.UpdateStepRepositoryMetadataAccess;
 
@@ -43,7 +44,10 @@ public class MetadataStore implements UpdateStepRepositoryMetadataAccess<Path> {
     try {
       Marshaller marshaller = jaxbContext.createMarshaller();
       marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
-      marshaller.marshal(repository, resolveDataPath(path).toFile());
+      CopyOnWrite.withTemporaryFile(
+        temp -> marshaller.marshal(repository, temp.toFile()),
+        resolveDataPath(path)
+      );
     } catch (JAXBException ex) {
       throw new InternalRepositoryException(repository, "failed write repository metadata", ex);
     }
diff --git a/scm-dao-xml/src/main/java/sonia/scm/repository/xml/PathDatabase.java b/scm-dao-xml/src/main/java/sonia/scm/repository/xml/PathDatabase.java
index 70698aed59..c895b69840 100644
--- a/scm-dao-xml/src/main/java/sonia/scm/repository/xml/PathDatabase.java
+++ b/scm-dao-xml/src/main/java/sonia/scm/repository/xml/PathDatabase.java
@@ -4,6 +4,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import sonia.scm.ContextEntry;
 import sonia.scm.repository.InternalRepositoryException;
+import sonia.scm.store.CopyOnWrite;
 import sonia.scm.xml.IndentXMLStreamWriter;
 import sonia.scm.xml.XmlStreams;
 
@@ -40,23 +41,28 @@ class PathDatabase {
     ensureParentDirectoryExists();
     LOG.trace("write repository path database to {}", storePath);
 
-    try (IndentXMLStreamWriter writer = XmlStreams.createWriter(storePath)) {
-      writer.writeStartDocument(ENCODING, VERSION);
+    CopyOnWrite.withTemporaryFile(
+      temp -> {
+        try (IndentXMLStreamWriter writer = XmlStreams.createWriter(temp)) {
+          writer.writeStartDocument(ENCODING, VERSION);
 
-      writeRepositoriesStart(writer, creationTime, lastModified);
-      for (Map.Entry<String, Path> e : pathDatabase.entrySet()) {
-        writeRepository(writer, e.getKey(), e.getValue());
-      }
-      writer.writeEndElement();
+          writeRepositoriesStart(writer, creationTime, lastModified);
+          for (Map.Entry<String, Path> e : pathDatabase.entrySet()) {
+            writeRepository(writer, e.getKey(), e.getValue());
+          }
+          writer.writeEndElement();
 
-      writer.writeEndDocument();
-    } catch (XMLStreamException | IOException ex) {
-      throw new InternalRepositoryException(
-        ContextEntry.ContextBuilder.entity(Path.class, storePath.toString()).build(),
-        "failed to write repository path database",
-        ex
-      );
-    }
+          writer.writeEndDocument();
+        } catch (XMLStreamException | IOException ex) {
+          throw new InternalRepositoryException(
+            ContextEntry.ContextBuilder.entity(Path.class, storePath.toString()).build(),
+            "failed to write repository path database",
+            ex
+          );
+        }
+      },
+      storePath
+    );
   }
 
   private void ensureParentDirectoryExists() {