[server] Handle deletion/undeletion flags

1 files changed, 73 insertions, 0 deletions

diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/StorageUseCheck.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/StorageUseCheck.java
new file mode 100644
index 00000000..a91e6535
--- /dev/null
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/StorageUseCheck.java
@@ -0,0 +1,73 @@
+package org.openslx.bwlp.sat;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.UUID;
+
+import org.apache.commons.io.FileUtils;
+import org.apache.log4j.Logger;
+import org.openslx.bwlp.sat.util.Configuration;
+import org.openslx.bwlp.sat.util.FileSystem;
+import org.openslx.util.QuickTimer.Task;
+
+/**
+ * As it might have catastrophic results if two instances of this server operate
+ * on the same file storage, we write a randomly generated id to a file on the
+ * storage, and check it periodically. If it changed, we bail out in complete
+ * panic.
+ */
+public class StorageUseCheck extends Task {
+
+	private static final Logger LOGGER = Logger.getLogger(StorageUseCheck.class);
+
+	private final String uuid = UUID.randomUUID().toString();
+
+	private final File canary = new File(Configuration.getVmStoreProdPath(), "dozmod.lock");
+
+	private boolean created = false;
+
+	public StorageUseCheck() {
+		if (FileSystem.waitForStorage()) {
+			createCanary();
+		}
+	}
+
+	private void createCanary() {
+		if (!FileSystem.isStorageMounted()) {
+			LOGGER.warn("Cannot check storage lock, storage not mounted");
+			return;
+		}
+		if (!created || !canary.exists()) {
+			try {
+				FileUtils.write(canary, uuid);
+			} catch (IOException e) {
+				LOGGER.fatal("Cannot write lock file to VMStore", e);
+				System.exit(1);
+			}
+			created = true;
+		} else {
+			String canaryContents;
+			try {
+				canaryContents = FileUtils.readFileToString(canary);
+			} catch (IOException e) {
+				LOGGER.warn("Lock file cannot be accessed. Cannot ensure exclusive use of VMStore", e);
+				return;
+			}
+			if (!canaryContents.equals(uuid)) {
+				LOGGER.fatal("Lock file content changed. Another server instance is using the VMStore."
+						+ " Will exit immediately to prevent any damages.");
+				try {
+					FileUtils.write(canary, uuid);
+				} catch (IOException e) {
+				}
+				System.exit(1);
+			}
+		}
+	}
+
+	@Override
+	public void fire() {
+		createCanary();
+	}
+
+}