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new 368f2f6 HDFS-15590. namenode fails to start when ordered snapshot
deletion feature is disabled (#2326)
368f2f6 is described below
commit 368f2f637e8dfeecdda8db2dbb1445beac053ac2
Author: bshashikant <[email protected]>
AuthorDate: Thu Sep 24 14:00:41 2020 +0530
HDFS-15590. namenode fails to start when ordered snapshot deletion feature
is disabled (#2326)
---
.../snapshot/DirectorySnapshottableFeature.java | 18 ++++++++++++++++++
.../server/namenode/snapshot/SnapshotManager.java | 9 ++++++---
.../org/apache/hadoop/hdfs/TestSnapshotCommands.java | 4 ++--
.../snapshot/TestOrderedSnapshotDeletion.java | 20 ++++++++++++++++++++
4 files changed, 46 insertions(+), 5 deletions(-)
diff --git
a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/DirectorySnapshottableFeature.java
b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/DirectorySnapshottableFeature.java
index 7a47ab4..8a215b5 100644
---
a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/DirectorySnapshottableFeature.java
+++
b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/DirectorySnapshottableFeature.java
@@ -241,6 +241,24 @@ public class DirectorySnapshottableFeature extends
DirectoryWithSnapshotFeature
throws SnapshotException {
final int i = searchSnapshot(DFSUtil.string2Bytes(snapshotName));
if (i < 0) {
+ // considering a sequence like this with snapshots S1 and s2
+ // 1. Ordered snapshot deletion feature is turned on
+ // 2. Delete S2 creating edit log entry for S2 deletion
+ // 3. Delete S1
+ // 4. S2 gets deleted by snapshot gc thread creating edit log record for
+ // S2 deletion again
+ // 5. Disable Ordered snapshot deletion feature
+ // 6. Restarting Namenode
+ // In this case, when edit log replay happens actual deletion of S2
+ // will happen when first edit log for S2 deletion gets replayed and
+ // the second edit log record replay for S2 deletion will fail as
snapshot
+ // won't exist thereby failing the Namenode start
+ // The idea here is to check during edit log replay, if a certain
snapshot
+ // is not found and the ordered snapshot deletion is off, ignore the
error
+ if (!snapshotManager.isSnapshotDeletionOrdered() &&
+ !snapshotManager.isImageLoaded()) {
+ return null;
+ }
throw new SnapshotException("Cannot delete snapshot " + snapshotName
+ " from path " + snapshotRoot.getFullPathName()
+ ": the snapshot does not exist.");
diff --git
a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/SnapshotManager.java
b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/SnapshotManager.java
index 04d6b71..2c183f7 100644
---
a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/SnapshotManager.java
+++
b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/SnapshotManager.java
@@ -479,10 +479,10 @@ public class SnapshotManager implements
SnapshotStatsMXBean {
void checkSnapshotLimit(int limit, int snapshotCount, String type)
throws SnapshotException {
if (snapshotCount >= limit) {
- String msg = "there are already " + (snapshotCount + 1)
+ String msg = "there are already " + snapshotCount
+ " snapshot(s) and the " + type + " snapshot limit is "
+ limit;
- if (fsdir.isImageLoaded()) {
+ if (isImageLoaded()) {
// We have reached the maximum snapshot limit
throw new SnapshotException(
"Failed to create snapshot: " + msg);
@@ -492,7 +492,10 @@ public class SnapshotManager implements
SnapshotStatsMXBean {
}
}
}
-
+
+ boolean isImageLoaded() {
+ return fsdir.isImageLoaded();
+ }
/**
* Delete a snapshot for a snapshottable directory
* @param snapshotName Name of the snapshot to be deleted
diff --git
a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestSnapshotCommands.java
b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestSnapshotCommands.java
index 2b5a69d..32ac298 100644
---
a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestSnapshotCommands.java
+++
b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestSnapshotCommands.java
@@ -128,8 +128,8 @@ public class TestSnapshotCommands {
DFSTestUtil.FsShellRun("-createSnapshot /sub3 sn2", 0,
"Created snapshot /sub3/.snapshot/sn2", conf);
DFSTestUtil.FsShellRun("-createSnapshot /sub3 sn3", 1,
- "Failed to add snapshot: there are already 3 snapshot(s) and "
- + "the max snapshot limit is 3", conf);
+ "Failed to create snapshot: there are already 3 snapshot(s) and "
+ + "the per directory snapshot limit is 3", conf);
}
@Test
diff --git
a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestOrderedSnapshotDeletion.java
b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestOrderedSnapshotDeletion.java
index efb72d1..60e8601 100644
---
a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestOrderedSnapshotDeletion.java
+++
b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestOrderedSnapshotDeletion.java
@@ -195,6 +195,26 @@ public class TestOrderedSnapshotDeletion {
assertXAttrSet("s1", hdfs, null);
}
+ @Test(timeout = 6000000)
+ public void testOrderedDeletionWithRestart() throws Exception {
+ DistributedFileSystem hdfs = cluster.getFileSystem();
+ hdfs.mkdirs(snapshottableDir);
+ hdfs.allowSnapshot(snapshottableDir);
+
+ final Path sub0 = new Path(snapshottableDir, "sub0");
+ hdfs.mkdirs(sub0);
+ hdfs.createSnapshot(snapshottableDir, "s0");
+
+ final Path sub1 = new Path(snapshottableDir, "sub1");
+ hdfs.mkdirs(sub1);
+ hdfs.createSnapshot(snapshottableDir, "s1");
+ assertXAttrSet("s1", hdfs, null);
+ assertXAttrSet("s1", hdfs, null);
+ cluster.getNameNode().getConf().
+ setBoolean(DFS_NAMENODE_SNAPSHOT_DELETION_ORDERED, false);
+ cluster.restartNameNodes();
+ }
+
@Test(timeout = 60000)
public void testSnapshotXattrWithDisablingXattr() throws Exception {
DistributedFileSystem hdfs = cluster.getFileSystem();
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