[MDEV-13852] MyRocks/Windows: SyncWAL() is not supported for this implementation of WAL file Created: 2017-09-20  Updated: 2018-05-11  Resolved: 2018-05-11

Status: Closed
Project: MariaDB Server
Component/s: Storage Engine - RocksDB
Fix Version/s: 10.2.15

Type: Task Priority: Major
Reporter: Sergei Petrunia Assignee: Sergei Petrunia
Resolution: Fixed Votes: 0
Labels: None

Issue Links:
Relates
relates to MDEV-12427 rocksdb.write_sync fails with "SyncWA... Closed
relates to MDEV-15144 January 2018: Merge MyRocks from upst... Closed

 Description   

After the merge of recent changes from the upstream, the following error appeared on Windows:

http://buildbot.askmonty.org/buildbot/builders/winx64-packages/builds/4936/steps/test/logs/stdio

2017-09-19 20:35:52 3272 [ERROR] RocksDB: Failed to write to WAL (dictionary), Status Code: 3, Status: Not implemented: SyncWAL() is not supported for this implementation of WAL file

This didn't happen before. Need to investigate.

  • main 10.2 branch has MyRocks without this error
  • bb-10.2-mariarocks-merge branch has newer MyRocks where the error occurs.

 Comments   
Comment by Sergei Petrunia [ 2017-09-20 ]

varun, can you investigate please? Elena and Wlad know how to get to Windows boxes.

Comment by Sergei Petrunia [ 2017-09-20 ]

See also MDEV-12427 . Does current MariaDB-10.2 ever call SyncWAL ? (I think yes). What happens when it is called on Windows?

It looks rather unlikely that write_sync.test was the only test that would suffer from an absent SyncWAL implementation although I would not rule this out. Please check.

Comment by Sergei Petrunia [ 2017-10-10 ]

The error comes from here

>	ha_rocksdb.dll!rocksdb::DBImpl::SyncWAL() Line 661	C++	Symbols loaded.
 
 	ha_rocksdb.dll!rocksdb::DBImpl::FlushWAL(bool sync) Line 638	C++	Symbols loaded.
 
 	ha_rocksdb.dll!rocksdb::DBImpl::WriteImpl(const rocksdb::WriteOptions & write_options, rocksdb::WriteBatch * my_batch, rocksdb::WriteCallback * callback, unsigned __int64 * log_used, unsigned __int64 log_ref, bool disable_memtable, unsigned __int64 * seq_used) Line 304	C++	Symbols loaded.
 
 	ha_rocksdb.dll!rocksdb::DBImpl::Write(const rocksdb::WriteOptions & write_options, rocksdb::WriteBatch * my_batch) Line 49	C++	Symbols loaded.
 
 	ha_rocksdb.dll!myrocks::Rdb_dict_manager::commit(rocksdb::WriteBatch * const batch, const bool & sync) Line 4511	C++	Symbols loaded.
 
 	ha_rocksdb.dll!myrocks::Rdb_dict_manager::rollback_ongoing_index_creation() Line 4966	C++	Symbols loaded.
 
 	ha_rocksdb.dll!myrocks::Rdb_dict_manager::init(rocksdb::DB * const rdb_dict, myrocks::Rdb_cf_manager * const cf_manager) Line 4465	C++	Symbols loaded.
 
 	ha_rocksdb.dll!myrocks::rocksdb_init_func(void * const p) Line 4123	C++	Symbols loaded.
 
 	mysqld.exe!ha_initialize_handlerton(st_plugin_int * plugin) Line 520	C++	Symbols loaded.
 
 	mysqld.exe!plugin_initialize(st_mem_root * tmp_root, st_plugin_int * plugin, int * argc, char * * argv, bool options_only) Line 1413	C++	Symbols loaded.
 
 	mysqld.exe!plugin_init(int * argc, char * * argv, int flags) Line 1694	C++	Symbols loaded.

Comment by Sergei Petrunia [ 2017-10-10 ]

The new code sets DBOptions::concurrent_prepare to TRUE (see e.g. rdb_init_rocksdb_db_options).

Changing it to FALSE removes the assert there, but then I get the same "SyncWAL() is not supported for this implementation of WAL file" error here:

>	ha_rocksdb.dll!rocksdb::DBImpl::SyncWAL() Line 662	C++	Symbols loaded.
 
 	ha_rocksdb.dll!rocksdb::DBImpl::FlushWAL(bool sync) Line 638	C++	Symbols loaded.
 
 	ha_rocksdb.dll!rocksdb::StackableDB::FlushWAL(bool sync) Line 273	C++	Symbols loaded.
 
 	ha_rocksdb.dll!myrocks::Rdb_background_thread::run() Line 11730	C++	Symbols loaded.
 
 	ha_rocksdb.dll!myrocks::Rdb_thread::thread_func(void * const thread_ptr) Line 35	C++	Symbols loaded.

Comment by Sergei Petrunia [ 2017-10-10 ]

It doesn't seem to be possible to run on Windows currently.

void Rdb_background_thread::run() at some point calls

      const rocksdb::Status s = rdb->FlushWAL(true);

which calls DBImpl::FlushWAL(sync=true)
which calls DBImpl::SyncWAL()

where it makes this check

  !it->writer->file()->writable_file()->IsSyncThreadSafe()

On Linux, PosixWritableFile::IsSyncThreadSafe() returns true.

For Windows, I was not able to find any implementation in port/win that would have IsSyncThreadSafe() return true.

Comment by Vladislav Vaintroub [ 2017-11-17 ]

psergey, are you going to file this bug in rocksdb bug tracker? If not , I can do that.

I implemented a hackish workaround for now, by using patched header file for win_io.h where IsSyncThreadSafe returns true, in https://github.com/mariadb/server/commit/689168be1240cf61d0ea17529e79660e98d15b46

Comment by Sergei Petrunia [ 2018-04-16 ]

Should be fixed in the recent merge

Comment by Sergei Petrunia [ 2018-05-11 ]

Closing as upstream has fixed this and we merged the fix. (i've also removed our workaround)

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