Summary:
Remove double buffering on RandomRead on Windows.
With more logic appear in file reader/write Read no longer
obeys forwarding calls to Windows implementation.
Previously direct_io (unbuffered) was only available on Windows
but now is supported as generic.
We remove intermediate buffering on Windows.
Remove random_access_max_buffer_size option which was windows specific.
Non-zero values for that opton introduced unnecessary lock contention.
Remove Env::EnableReadAhead(), Env::ShouldForwardRawRequest() that are
no longer necessary.
Add aligned buffer reads for cases when requested reads exceed read ahead size.
Closes https://github.com/facebook/rocksdb/pull/2105
Differential Revision: D4847770
Pulled By: siying
fbshipit-source-id: 8ab48f8e854ab498a4fd398a6934859792a2788f
Summary:
also change variable name `direct_io_` to `use_direct_io_` in WritableFile to make it consistent with read path.
Closes https://github.com/facebook/rocksdb/pull/1770
Differential Revision: D4416435
Pulled By: lightmark
fbshipit-source-id: 4143c53
EnvLibrados is a customized RocksDB Env to use RADOS as the backend file system of RocksDB. It overrides all file system related API of default Env. The easiest way to use it is just like following:
std::string db_name = "test_db";
std::string config_path = "path/to/ceph/config";
DB* db;
Options options;
options.env = EnvLibrados(db_name, config_path);
Status s = DB::Open(options, kDBPath, &db);
Then EnvLibrados will forward all file read/write operation to the RADOS cluster assigned by config_path. Default pool is db_name+"_pool".
There are some options that users could set for EnvLibrados.
- write_buffer_size. This variable is the max buffer size for WritableFile. After reaching the buffer_max_size, EnvLibrados will sync buffer content to RADOS, then clear buffer.
- db_pool. Rather than using default pool, users could set their own db pool name
- wal_dir. The dir for WAL files. Because RocksDB only has 2-level structure (dir_name/file_name), the format of wal_dir is "/dir_name"(CAN'T be "/dir1/dir2"). Default wal_dir is "/wal".
- wal_pool. Corresponding pool name for WAL files. Default value is db_name+"_wal_pool"
The example of setting options looks like following:
db_name = "test_db";
db_pool = db_name+"_pool";
wal_dir = "/wal";
wal_pool = db_name+"_wal_pool";
write_buffer_size = 1 << 20;
env_ = new EnvLibrados(db_name, config, db_pool, wal_dir, wal_pool, write_buffer_size);
DB* db;
Options options;
options.env = env_;
// The last level dir name should match the dir name in prefix_pool_map
options.wal_dir = "/tmp/wal";
// open DB
Status s = DB::Open(options, kDBPath, &db);
Librados is required to compile EnvLibrados. Then use "$make LIBRADOS=1" to compile RocksDB. If you want to only compile EnvLibrados test, just run "$ make env_librados_test LIBRADOS=1". To run env_librados_test, you need to have a running RADOS cluster with the configure file located in "../ceph/src/ceph.conf" related to "rocksdb/".
