rbd: Use qemu-img to backup up a RBD snapshot to Secondary Storage

wido · wido · commit 8d2baf801720 · 2014-04-11T14:00:08.000+02:00
This reduces the amount of time and storage it takes dramatically. We no longer
do a full copy, but a sparse copy. The destination image is still in RAW
format, but we only copy over used blocks.

Qemu is also better in doing this then us doing it in Java code.
diff --git a/plugins/hypervisors/kvm/src/com/cloud/hypervisor/kvm/storage/KVMStorageProcessor.java b/plugins/hypervisors/kvm/src/com/cloud/hypervisor/kvm/storage/KVMStorageProcessor.java
@@ -21,7 +21,6 @@
 import static com.cloud.utils.S3Utils.mputFile;
 import static com.cloud.utils.S3Utils.putFile;
 
-import java.io.BufferedOutputStream;
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
@@ -49,9 +48,7 @@
 
 import com.ceph.rados.IoCTX;
 import com.ceph.rados.Rados;
-import com.ceph.rados.RadosException;
 import com.ceph.rbd.Rbd;
-import com.ceph.rbd.RbdException;
 import com.ceph.rbd.RbdImage;
 
 import org.apache.cloudstack.storage.command.AttachAnswer;
@@ -691,66 +688,48 @@ public Answer backupSnapshot(CopyCommand cmd) {
 
             long size = 0;
             /**
-             * RBD snapshots can't be copied using qemu-img, so we have to use
-             * the Java bindings for librbd here.
+             * Since Ceph version Dumpling (0.67.X) librbd / Qemu supports converting RBD
+             * snapshots to RAW/QCOW2 files directly.
              *
-             * These bindings will read the snapshot and write the contents to
-             * the secondary storage directly
-             *
-             * It will stop doing so if the amount of time spend is longer then
-             * cmds.timeout
+             * This reduces the amount of time and storage it takes to back up a snapshot dramatically
              */
             if (primaryPool.getType() == StoragePoolType.RBD) {
+                String rbdSnapshot = snapshotDisk.getPath() +  "@" + snapshotName;
+                String snapshotFile = snapshotDestPath + "/" + snapshotName;
                 try {
-                    Rados r = new Rados(primaryPool.getAuthUserName());
-                    r.confSet("mon_host", primaryPool.getSourceHost() + ":" + primaryPool.getSourcePort());
-                    r.confSet("key", primaryPool.getAuthSecret());
-                    r.confSet("client_mount_timeout", "30");
-                    r.connect();
-                    s_logger.debug("Succesfully connected to Ceph cluster at " + r.confGet("mon_host"));
-
-                    IoCTX io = r.ioCtxCreate(primaryPool.getSourceDir());
-                    Rbd rbd = new Rbd(io);
-                    RbdImage image = rbd.open(snapshotDisk.getName(), snapshotName);
+                    s_logger.debug("Attempting to backup RBD snapshot " + rbdSnapshot);
 
                     File snapDir = new File(snapshotDestPath);
-                    s_logger.debug("Attempting to create " + snapDir.getAbsolutePath() + " recursively");
+                    s_logger.debug("Attempting to create " + snapDir.getAbsolutePath() + " recursively for snapshot storage");
                     FileUtils.forceMkdir(snapDir);
 
-                    File snapFile = new File(snapshotDestPath + "/" + snapshotName);
-                    s_logger.debug("Backing up RBD snapshot to " + snapFile.getAbsolutePath());
-                    BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(snapFile));
-                    int chunkSize = 4194304;
-                    long offset = 0;
-                    while (true) {
-                        byte[] buf = new byte[chunkSize];
-
-                        int bytes = image.read(offset, buf, chunkSize);
-                        if (bytes <= 0) {
-                            break;
-                        }
-                        bos.write(buf, 0, bytes);
-                        offset += bytes;
-                    }
-                    s_logger.debug("Completed backing up RBD snapshot " + snapshotName + " to  " + snapFile.getAbsolutePath() + ". Bytes written: " + offset);
-                    size = offset;
-                    bos.close();
+                    QemuImgFile srcFile =
+                        new QemuImgFile(KVMPhysicalDisk.RBDStringBuilder(primaryPool.getSourceHost(), primaryPool.getSourcePort(), primaryPool.getAuthUserName(),
+                                                                         primaryPool.getAuthSecret(), rbdSnapshot));
+                    srcFile.setFormat(PhysicalDiskFormat.RAW);
 
-                    s_logger.debug("Attempting to remove snapshot RBD " + snapshotName + " from image " + snapshotDisk.getName());
-                    image.snapRemove(snapshotName);
+                    QemuImgFile destFile = new QemuImgFile(snapshotFile);
+                    destFile.setFormat(srcFile.getFormat());
 
-                    r.ioCtxDestroy(io);
-                } catch (RadosException e) {
-                    s_logger.error("A RADOS operation failed. The error was: " + e.getMessage());
-                    return new CopyCmdAnswer(e.toString());
-                } catch (RbdException e) {
-                    s_logger.error("A RBD operation on " + snapshotDisk.getName() + " failed. The error was: " + e.getMessage());
-                    return new CopyCmdAnswer(e.toString());
+                    s_logger.debug("Backing up RBD snapshot " + rbdSnapshot + " to " + snapshotFile);
+                    QemuImg q = new QemuImg(cmd.getWaitInMillSeconds());
+                    q.convert(srcFile, destFile);
+
+                    File snapFile = new File(snapshotFile);
+                    if(snapFile.exists()) {
+                        size = snapFile.length();
+                    }
+
+                    s_logger.debug("Finished backing up RBD snapshot " + rbdSnapshot + " to " + snapshotFile + " Snapshot size: " + size);
                 } catch (FileNotFoundException e) {
                     s_logger.error("Failed to open " + snapshotDestPath + ". The error was: " + e.getMessage());
                     return new CopyCmdAnswer(e.toString());
                 } catch (IOException e) {
-                    s_logger.debug("An I/O error occured during a snapshot operation on " + snapshotDestPath);
+                    s_logger.error("Failed to create " + snapshotDestPath + ". The error was: " + e.getMessage());
+                    return new CopyCmdAnswer(e.toString());
+                }  catch (QemuImgException e) {
+                    s_logger.error("Failed to backup the RBD snapshot from " + rbdSnapshot +
+                                   " to " + snapshotFile + " the error was: " + e.getMessage());
                     return new CopyCmdAnswer(e.toString());
                 }
             } else {
