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Posted to issues@flink.apache.org by zentol <gi...@git.apache.org> on 2017/01/26 15:01:35 UTC
[GitHub] flink pull request #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDire...
GitHub user zentol opened a pull request:
https://github.com/apache/flink/pull/3219
[FLINK-5659] Harden FileBaseUtils#deleteFileOrDirectory on WIndows
This PR hardens `FileBaseUtils#deleteFileOrDirectory` when the method is called concurrently on Windows.
`AccessDeniedException`s can be thrown when attempting to delete a file while a deletion is in progress. In order to delete a file it has to be opened, and as we all know you can't (easily) delete open files on Windows.
For this case we catch the exception, double-check whether the file is deleted by now, and throw the exception if it isn't, assuming a lack of permission prevented the deletion.
`DirectoryNotEmptyException`s can be thrown for directories for which a delete call for every file has succeeded, since the OS may be slow in updating the actual FileSystem.
For this case we wait for a bit (50 milliseconds, yeah it's that slow) and check whether the directory is empty by now. If it isn't we throw the exception assuming a concurrent creation of a new file in the given directory.
Note that neither changes are perfect; they are not guaranteed to prevent the issue. However, it no longer categorically fails for me \U0001f389, but only once every few hundred runs.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/zentol/flink 5659_fileutils_win
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/3219.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #3219
----
commit f372899c7cd8f5102421b986be1f1b87e32cf15f
Author: zentol <ch...@apache.org>
Date: 2017-01-26T14:47:11Z
[FLINK-5659] Harden FileBaseUtils#deleteFileOrDirectory on WIndows
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[GitHub] flink issue #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDirectory o...
Posted by StephanEwen <gi...@git.apache.org>.
Github user StephanEwen commented on the issue:
https://github.com/apache/flink/pull/3219
I think the semantics for Unix currently work well, I'd like to avoid the sleep there...
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[GitHub] flink pull request #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDire...
Posted by zentol <gi...@git.apache.org>.
Github user zentol commented on a diff in the pull request:
https://github.com/apache/flink/pull/3219#discussion_r98486443
--- Diff: flink-core/src/main/java/org/apache/flink/util/FileUtils.java ---
@@ -148,14 +158,49 @@ public static void deleteDirectory(File directory) throws IOException {
return;
}
- // delete the directory. this fails if the directory is not empty, meaning
- // if new files got concurrently created. we want to fail then.
- try {
- Files.delete(directory.toPath());
- }
- catch (NoSuchFileException ignored) {
- // if someone else deleted this concurrently, we don't mind
- // the result is the same for us, after all
+ java.nio.file.Path directoryPath = directory.toPath();
+ if (OperatingSystem.isWindows()) {
+ // delete the directory. this fails if the directory is not empty, meaning
+ // if new files got concurrently created. we want to fail then.
+ try {
+ Files.delete(directoryPath);
+ } catch (NoSuchFileException ignored) {
+ // if someone else deleted this concurrently, we don't mind
+ // the result is the same for us, after all
+ } catch (AccessDeniedException e) {
+ // This may occur on Windows if another process is currently
+ // deleting the file, since the file must be opened in order
+ // to delete it. We double check here to make sure the file
+ // was actually deleted by another process. Note that this
+ // isn't a perfect solution, but it's better than nothing.
+ if (Files.exists(directoryPath)) {
+ throw e;
+ }
+ } catch (DirectoryNotEmptyException e) {
+ // This may occur on Windows for some reason even for empty
+ // directories. Apparently there's a timing/visibility
+ // issue when concurrently deleting the contents of a directory
+ // and afterwards deleting the directory itself.
+ try {
+ Thread.sleep(50);
--- End diff --
It is intended that the thread hitting this exception never deletes the directory. The assumption is that another thread has a correct view over the directory and will actually delete it if possible.
We however must still check whether the directory is empty after *some* time so that we actually fail if a new file was created concurrently, to preserve existing behavior.
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[GitHub] flink pull request #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDire...
Posted by StephanEwen <gi...@git.apache.org>.
Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/3219#discussion_r98687559
--- Diff: flink-core/src/main/java/org/apache/flink/util/FileUtils.java ---
@@ -148,14 +158,49 @@ public static void deleteDirectory(File directory) throws IOException {
return;
}
- // delete the directory. this fails if the directory is not empty, meaning
- // if new files got concurrently created. we want to fail then.
- try {
- Files.delete(directory.toPath());
- }
- catch (NoSuchFileException ignored) {
- // if someone else deleted this concurrently, we don't mind
- // the result is the same for us, after all
+ java.nio.file.Path directoryPath = directory.toPath();
+ if (OperatingSystem.isWindows()) {
+ // delete the directory. this fails if the directory is not empty, meaning
+ // if new files got concurrently created. we want to fail then.
+ try {
+ Files.delete(directoryPath);
+ } catch (NoSuchFileException ignored) {
+ // if someone else deleted this concurrently, we don't mind
+ // the result is the same for us, after all
+ } catch (AccessDeniedException e) {
+ // This may occur on Windows if another process is currently
+ // deleting the file, since the file must be opened in order
+ // to delete it. We double check here to make sure the file
+ // was actually deleted by another process. Note that this
+ // isn't a perfect solution, but it's better than nothing.
+ if (Files.exists(directoryPath)) {
+ throw e;
+ }
+ } catch (DirectoryNotEmptyException e) {
+ // This may occur on Windows for some reason even for empty
+ // directories. Apparently there's a timing/visibility
+ // issue when concurrently deleting the contents of a directory
+ // and afterwards deleting the directory itself.
+ try {
+ Thread.sleep(50);
--- End diff --
Then I do not understand the comment above. It reads like that can happen even if there is no other thread attempting to delete the directory?
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[GitHub] flink pull request #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDire...
Posted by zentol <gi...@git.apache.org>.
Github user zentol commented on a diff in the pull request:
https://github.com/apache/flink/pull/3219#discussion_r99568502
--- Diff: flink-core/src/main/java/org/apache/flink/util/FileUtils.java ---
@@ -116,6 +118,14 @@ else if (file.exists()) {
}
catch (NoSuchFileException e) {
// if the file is already gone (concurrently), we don't mind
+ } catch (AccessDeniedException e) {
--- End diff --
Is it ok to special case this inside the catch block? (I.e for windows check again, otherwise rethrow?
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[GitHub] flink pull request #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDire...
Posted by StephanEwen <gi...@git.apache.org>.
Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/3219#discussion_r98482840
--- Diff: flink-core/src/main/java/org/apache/flink/util/FileUtils.java ---
@@ -148,14 +158,49 @@ public static void deleteDirectory(File directory) throws IOException {
return;
}
- // delete the directory. this fails if the directory is not empty, meaning
- // if new files got concurrently created. we want to fail then.
- try {
- Files.delete(directory.toPath());
- }
- catch (NoSuchFileException ignored) {
- // if someone else deleted this concurrently, we don't mind
- // the result is the same for us, after all
+ java.nio.file.Path directoryPath = directory.toPath();
+ if (OperatingSystem.isWindows()) {
+ // delete the directory. this fails if the directory is not empty, meaning
+ // if new files got concurrently created. we want to fail then.
+ try {
+ Files.delete(directoryPath);
+ } catch (NoSuchFileException ignored) {
+ // if someone else deleted this concurrently, we don't mind
+ // the result is the same for us, after all
+ } catch (AccessDeniedException e) {
+ // This may occur on Windows if another process is currently
+ // deleting the file, since the file must be opened in order
+ // to delete it. We double check here to make sure the file
+ // was actually deleted by another process. Note that this
+ // isn't a perfect solution, but it's better than nothing.
+ if (Files.exists(directoryPath)) {
+ throw e;
+ }
+ } catch (DirectoryNotEmptyException e) {
+ // This may occur on Windows for some reason even for empty
+ // directories. Apparently there's a timing/visibility
+ // issue when concurrently deleting the contents of a directory
+ // and afterwards deleting the directory itself.
+ try {
+ Thread.sleep(50);
--- End diff --
I am wondering if it makes sense to have a something like 10-20 retries here, with 5ms delay.
The current implementation also does not remove the directory when initially seeing the `DirectoryNotEmptyException`, it simply suppresses the exception when the directory ends up empty 50ms later, but leaves the directory itself there.
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[GitHub] flink issue #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDirectory o...
Posted by StephanEwen <gi...@git.apache.org>.
Github user StephanEwen commented on the issue:
https://github.com/apache/flink/pull/3219
I added a few more thoughts on how we could improve the behavior of the function.
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[GitHub] flink issue #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDirectory o...
Posted by zentol <gi...@git.apache.org>.
Github user zentol commented on the issue:
https://github.com/apache/flink/pull/3219
That could work. Are you worried about the added sleep in case of an `DirectoryNotEmptyException`?
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[GitHub] flink issue #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDirectory o...
Posted by StephanEwen <gi...@git.apache.org>.
Github user StephanEwen commented on the issue:
https://github.com/apache/flink/pull/3219
Uff, okay, I see the problem. Windows FileSystem semantics are not as easy to handle as Unix.
How about we special case the method for Windows? Use `OperatingSystem.isWindows()` and in that case, do it different (like you suggested), but keep the Unix code path as it is?
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[GitHub] flink pull request #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDire...
Posted by StephanEwen <gi...@git.apache.org>.
Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/3219#discussion_r98477980
--- Diff: flink-core/src/main/java/org/apache/flink/util/FileUtils.java ---
@@ -116,6 +118,14 @@ else if (file.exists()) {
}
catch (NoSuchFileException e) {
// if the file is already gone (concurrently), we don't mind
+ } catch (AccessDeniedException e) {
--- End diff --
Can we special case this also for Windows? Should never occur on Unix (and should throw an exception if it happens)...
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[GitHub] flink pull request #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDire...
Posted by zentol <gi...@git.apache.org>.
Github user zentol commented on a diff in the pull request:
https://github.com/apache/flink/pull/3219#discussion_r99576850
--- Diff: flink-core/src/main/java/org/apache/flink/util/FileUtils.java ---
@@ -148,14 +158,49 @@ public static void deleteDirectory(File directory) throws IOException {
return;
}
- // delete the directory. this fails if the directory is not empty, meaning
- // if new files got concurrently created. we want to fail then.
- try {
- Files.delete(directory.toPath());
- }
- catch (NoSuchFileException ignored) {
- // if someone else deleted this concurrently, we don't mind
- // the result is the same for us, after all
+ java.nio.file.Path directoryPath = directory.toPath();
+ if (OperatingSystem.isWindows()) {
+ // delete the directory. this fails if the directory is not empty, meaning
+ // if new files got concurrently created. we want to fail then.
+ try {
+ Files.delete(directoryPath);
+ } catch (NoSuchFileException ignored) {
+ // if someone else deleted this concurrently, we don't mind
+ // the result is the same for us, after all
+ } catch (AccessDeniedException e) {
+ // This may occur on Windows if another process is currently
+ // deleting the file, since the file must be opened in order
+ // to delete it. We double check here to make sure the file
+ // was actually deleted by another process. Note that this
+ // isn't a perfect solution, but it's better than nothing.
+ if (Files.exists(directoryPath)) {
+ throw e;
+ }
+ } catch (DirectoryNotEmptyException e) {
+ // This may occur on Windows for some reason even for empty
+ // directories. Apparently there's a timing/visibility
+ // issue when concurrently deleting the contents of a directory
+ // and afterwards deleting the directory itself.
+ try {
+ Thread.sleep(50);
--- End diff --
It only happens when multiple threads are involved; running the test with 1 thread works like charm.
This whole thing is just strange. I've made some debugging and what happened is that multiple threads delete the same file, and verify the deletion using `Files.exists(filename)`. All of them pass. A few seconds later we hit the `DirectoryNotEmptyException`, check the contents again and what do you know, the file *which we just verified to be deleted* still exists.
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[GitHub] flink pull request #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDire...
Posted by zentol <gi...@git.apache.org>.
Github user zentol closed the pull request at:
https://github.com/apache/flink/pull/3219
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[GitHub] flink issue #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDirectory o...
Posted by zentol <gi...@git.apache.org>.
Github user zentol commented on the issue:
https://github.com/apache/flink/pull/3219
@StephanEwen I've update the PR. The `deleteDirectory()` method now has separate paths for windows and unix.
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[GitHub] flink pull request #3219: [FLINK-5659] Harden FileBaseUtils#deleteFileOrDire...
Posted by StephanEwen <gi...@git.apache.org>.
Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/3219#discussion_r98478136
--- Diff: flink-core/src/main/java/org/apache/flink/util/FileUtils.java ---
@@ -148,14 +158,49 @@ public static void deleteDirectory(File directory) throws IOException {
return;
}
- // delete the directory. this fails if the directory is not empty, meaning
- // if new files got concurrently created. we want to fail then.
- try {
- Files.delete(directory.toPath());
- }
- catch (NoSuchFileException ignored) {
- // if someone else deleted this concurrently, we don't mind
- // the result is the same for us, after all
+ java.nio.file.Path directoryPath = directory.toPath();
+ if (OperatingSystem.isWindows()) {
+ // delete the directory. this fails if the directory is not empty, meaning
--- End diff --
How about moving this to a separate method for readability?
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