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https://issues.apache.org/jira/browse/HDFS-10263?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jing Zhao updated HDFS-10263:
-----------------------------
Component/s: snapshots
namenode
> Provide symmetric entries in reversed snapshot diff report
> ----------------------------------------------------------
>
> Key: HDFS-10263
> URL: https://issues.apache.org/jira/browse/HDFS-10263
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode, snapshots
> Reporter: Yongjun Zhang
> Assignee: Jing Zhao
>
> Steps to reproduce:
> 1. Take a snapshot s1 at:
> {code}
> drwxr-xr-x - yzhang supergroup 0 2016-04-05 14:48 /target/bar
> -rw-r--r-- 1 yzhang supergroup 1024 2016-04-05 14:48 /target/bar/f1
> drwxr-xr-x - yzhang supergroup 0 2016-04-05 14:48 /target/foo
> -rw-r--r-- 1 yzhang supergroup 1024 2016-04-05 14:48 /target/foo/f1
> {code}
> 2. Make the following change:
> {code}
> private int changeData7(Path dir) throws Exception {
> final Path foo = new Path(dir, "foo");
> final Path foo2 = new Path(dir, "foo2");
> final Path foo_f1 = new Path(foo, "f1");
> final Path foo2_f2 = new Path(foo2, "f2");
> final Path foo2_f1 = new Path(foo2, "f1");
> final Path foo_d1 = new Path(foo, "d1");
> final Path foo_d1_f3 = new Path(foo_d1, "f3");
> int numDeletedAndModified = 0;
> dfs.rename(foo, foo2);
> dfs.delete(foo2_f1, true);
>
> DFSTestUtil.createFile(dfs, foo_f1, BLOCK_SIZE, DATA_NUM, 0L);
> DFSTestUtil.appendFile(dfs, foo_f1, (int) BLOCK_SIZE);
> dfs.rename(foo_f1, foo2_f2);
> numDeletedAndModified += 1; // "M ./foo"
> DFSTestUtil.createFile(dfs, foo_d1_f3, BLOCK_SIZE, DATA_NUM, 0L);
> return numDeletedAndModified;
> }
> {code}
> that results in
> {code}
> drwxr-xr-x - yzhang supergroup 0 2016-04-05 14:48 /target/bar
> -rw-r--r-- 1 yzhang supergroup 1024 2016-04-05 14:48 /target/bar/f1
> drwxr-xr-x - yzhang supergroup 0 2016-04-05 14:48 /target/foo
> drwxr-xr-x - yzhang supergroup 0 2016-04-05 14:48 /target/foo/d1
> -rw-r--r-- 1 yzhang supergroup 1024 2016-04-05 14:48 /target/foo/d1/f3
> drwxr-xr-x - yzhang supergroup 0 2016-04-05 14:48 /target/foo2
> -rw-r--r-- 1 yzhang supergroup 2048 2016-04-05 14:48 /target/foo2/f2
> {code}
> 3. take snapshot s2 here
> 4. Do the following to revert the change done in step 2
> {code}
> private int revertChangeData7(Path dir) throws Exception {
> final Path foo = new Path(dir, "foo");
> final Path foo2 = new Path(dir, "foo2");
> final Path foo_f1 = new Path(foo, "f1");
> final Path foo2_f2 = new Path(foo2, "f2");
> final Path foo2_f1 = new Path(foo2, "f1");
> final Path foo_d1 = new Path(foo, "d1");
> final Path foo_d1_f3 = new Path(foo_d1, "f3");
> int numDeletedAndModified = 0;
>
> dfs.delete(foo_d1, true);
> dfs.rename(foo2_f2, foo_f1);
>
> dfs.delete(foo, true);
>
> DFSTestUtil.createFile(dfs, foo2_f1, BLOCK_SIZE, DATA_NUM, 0L);
> DFSTestUtil.appendFile(dfs, foo2_f1, (int) BLOCK_SIZE);
> dfs.rename(foo2, foo);
>
> return numDeletedAndModified;
> }
> {code}
> that get the following results:
> {code}
> drwxr-xr-x - yzhang supergroup 0 2016-04-05 14:48 /target/bar
> -rw-r--r-- 1 yzhang supergroup 1024 2016-04-05 14:48 /target/bar/f1
> drwxr-xr-x - yzhang supergroup 0 2016-04-05 14:48 /target/foo
> -rw-r--r-- 1 yzhang supergroup 2048 2016-04-05 14:48 /target/foo/f1
> {code}
> 4. Take snapshot s3 here.
> Below is the different snapshots
> {code}
> s1-s2: Difference between snapshot s1 and snapshot s2 under directory /target:
> M .
> + ./foo
> R ./foo -> ./foo2
> M ./foo
> + ./foo/f2
> - ./foo/f1
> s2-s1: Difference between snapshot s2 and snapshot s1 under directory /target:
> M .
> - ./foo
> R ./foo2 -> ./foo
> M ./foo
> - ./foo/f2
> + ./foo/f1
> s2-s3: Difference between snapshot s2 and snapshot s3 under directory /target:
> M .
> - ./foo
> R ./foo2 -> ./foo
> M ./foo2
> + ./foo2/f1
> - ./foo2/f2
> s3-s2: Difference between snapshot s3 and snapshot s2 under directory /target:
> M .
> + ./foo
> R ./foo -> ./foo2
> M ./foo2
> - ./foo2/f1
> + ./foo2/f2
> {code}
> The s2-s1 snapshot is supposed to be the same as s2-s3, because the change
> from s2 to s3 is an exact reversion of the change from s1 to s2. We can see
> that s1 and s3 have same file structures.
> However, the resulted shown above is not. I expect the following part
> {code}
> M ./foo
> - ./foo/f2
> + ./foo/f1
> {code}
> in s2-s1 diff should be
> {code}
> M ./foo2
> + ./foo2/f1
> - ./foo2/f2
> {code}
> (same as in s2-s3)
> instead.
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