Summary:
The old cleanup code had a race condition:
1. Test thread: DestroyDB() marked a file as trash
2. DeleteScheduler thread: Got the file's size and decided to delete it in chunks
3. Test thread: DestroyDir() deleted that trash file
4. DeleteScheduler thread: Began deleting in chunks starting by calling ReopenWritableFile(). Unfortunately this recreates the deleted trash file
5. Test thread: DestroyDir() fails to remove the parent directory because it contains the file created in 4.
6. Test thread: Checkpoint::Create() fails due to the directory already existing
It could be repro'd with the following patch/command.
Patch:
```
diff --git a/file/delete_scheduler.cc b/file/delete_scheduler.cc
index 8a2d1615d..337d24a60 100644
--- a/file/delete_scheduler.cc
+++ b/file/delete_scheduler.cc
@@ -317,6 +317,12 @@ Status DeleteScheduler::DeleteTrashFile(const std::string& path_in_trash,
&num_hard_links, nullptr);
if (my_status.ok()) {
if (num_hard_links == 1) {
+ // Give some time for DestroyDir() to delete file entries. Then, the
+ // below `ReopenWritableFile()` will recreate files, preventing the
+ // parent directory from being deleted.
+ if (rand() % 2 == 0) {
+ usleep(1000);
+ }
std::unique_ptr<FSWritableFile> wf;
my_status = fs_->ReopenWritableFile(path_in_trash, FileOptions(), &wf,
nullptr);
diff --git a/file/file_util.cc b/file/file_util.cc
index 43608fcdc..2cee1ad8e 100644
--- a/file/file_util.cc
+++ b/file/file_util.cc
@@ -263,6 +263,13 @@ Status DestroyDir(Env* env, const std::string& dir) {
}
}
+ // Give some time for the DeleteScheduler thread's ReopenWritableFile() to
+ // recreate deleted files
+ if (dir.find("checkpoint") != std::string::npos) {
+ fprintf(stderr, "waiting to destroy %s\n", dir.c_str());
+ usleep(10000);
+ }
+
if (s.ok()) {
s = env->DeleteDir(dir);
// DeleteDir might or might not report NotFound
```
Command:
```
TEST_TMPDIR=/dev/shm python3 tools/db_crashtest.py blackbox --simple --write_buffer_size=131072 --target_file_size_base=131072 --max_bytes_for_level_base=524288 --checkpoint_one_in=100 --clear_column_family_one_in=0 --max_key=1000 --value_size_mult=33 --sst_file_manager_bytes_per_truncate=4096 --sst_file_manager_bytes_per_sec=1048576 --interval=3 --compression_type=none --sync_fault_injection=1
```
Obviously we don't want to use scheduled deletion here as we need the checkpoint directory deleted immediately. I suspect the DestroyDir() was an attempt to fixup incomplete DestroyDB()s. Now that we expect DestroyDB() to be complete I removed that code.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/11389
Reviewed By: hx235
Differential Revision: D45137142
Pulled By: ajkr
fbshipit-source-id: 2af743d342c77cc414fd25fc4c9d7c9c6079ad24
Andrew Kryczka
6cac4c79d4