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rocksdb/file/writable_file_writer.cc

525 lines
16 KiB

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "file/writable_file_writer.h"
#include <algorithm>
#include <mutex>
#include "db/version_edit.h"
#include "monitoring/histogram.h"
#include "monitoring/iostats_context_imp.h"
#include "port/port.h"
#include "rocksdb/system_clock.h"
#include "test_util/sync_point.h"
#include "util/random.h"
#include "util/rate_limiter.h"
namespace ROCKSDB_NAMESPACE {
IOStatus WritableFileWriter::Append(const Slice& data) {
const char* src = data.data();
size_t left = data.size();
IOStatus s;
pending_sync_ = true;
TEST_KILL_RANDOM("WritableFileWriter::Append:0",
rocksdb_kill_odds * REDUCE_ODDS2);
// Calculate the checksum of appended data
UpdateFileChecksum(data);
{
IOSTATS_TIMER_GUARD(prepare_write_nanos);
TEST_SYNC_POINT("WritableFileWriter::Append:BeforePrepareWrite");
Introduce a new storage specific Env API (#5761) Summary: The current Env API encompasses both storage/file operations, as well as OS related operations. Most of the APIs return a Status, which does not have enough metadata about an error, such as whether its retry-able or not, scope (i.e fault domain) of the error etc., that may be required in order to properly handle a storage error. The file APIs also do not provide enough control over the IO SLA, such as timeout, prioritization, hinting about placement and redundancy etc. This PR separates out the file/storage APIs from Env into a new FileSystem class. The APIs are updated to return an IOStatus with metadata about the error, as well as to take an IOOptions structure as input in order to allow more control over the IO. The user can set both ```options.env``` and ```options.file_system``` to specify that RocksDB should use the former for OS related operations and the latter for storage operations. Internally, a ```CompositeEnvWrapper``` has been introduced that inherits from ```Env``` and redirects individual methods to either an ```Env``` implementation or the ```FileSystem``` as appropriate. When options are sanitized during ```DB::Open```, ```options.env``` is replaced with a newly allocated ```CompositeEnvWrapper``` instance if both env and file_system have been specified. This way, the rest of the RocksDB code can continue to function as before. This PR also ports PosixEnv to the new API by splitting it into two - PosixEnv and PosixFileSystem. PosixEnv is defined as a sub-class of CompositeEnvWrapper, and threading/time functions are overridden with Posix specific implementations in order to avoid an extra level of indirection. The ```CompositeEnvWrapper``` translates ```IOStatus``` return code to ```Status```, and sets the severity to ```kSoftError``` if the io_status is retryable. The error handling code in RocksDB can then recover the DB automatically. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5761 Differential Revision: D18868376 Pulled By: anand1976 fbshipit-source-id: 39efe18a162ea746fabac6360ff529baba48486f
5 years ago
writable_file_->PrepareWrite(static_cast<size_t>(GetFileSize()), left,
IOOptions(), nullptr);
}
// See whether we need to enlarge the buffer to avoid the flush
if (buf_.Capacity() - buf_.CurrentSize() < left) {
for (size_t cap = buf_.Capacity();
cap < max_buffer_size_; // There is still room to increase
cap *= 2) {
// See whether the next available size is large enough.
// Buffer will never be increased to more than max_buffer_size_.
size_t desired_capacity = std::min(cap * 2, max_buffer_size_);
if (desired_capacity - buf_.CurrentSize() >= left ||
(use_direct_io() && desired_capacity == max_buffer_size_)) {
buf_.AllocateNewBuffer(desired_capacity, true);
break;
}
}
}
// Flush only when buffered I/O
if (!use_direct_io() && (buf_.Capacity() - buf_.CurrentSize()) < left) {
if (buf_.CurrentSize() > 0) {
s = Flush();
if (!s.ok()) {
return s;
}
}
assert(buf_.CurrentSize() == 0);
}
// We never write directly to disk with direct I/O on.
// or we simply use it for its original purpose to accumulate many small
// chunks
if (use_direct_io() || (buf_.Capacity() >= left)) {
while (left > 0) {
size_t appended = buf_.Append(src, left);
left -= appended;
src += appended;
if (left > 0) {
s = Flush();
if (!s.ok()) {
break;
}
}
}
} else {
// Writing directly to file bypassing the buffer
assert(buf_.CurrentSize() == 0);
s = WriteBuffered(src, left);
}
TEST_KILL_RANDOM("WritableFileWriter::Append:1", rocksdb_kill_odds);
if (s.ok()) {
filesize_ += data.size();
}
return s;
}
IOStatus WritableFileWriter::Pad(const size_t pad_bytes) {
assert(pad_bytes < kDefaultPageSize);
size_t left = pad_bytes;
size_t cap = buf_.Capacity() - buf_.CurrentSize();
// Assume pad_bytes is small compared to buf_ capacity. So we always
// use buf_ rather than write directly to file in certain cases like
// Append() does.
while (left) {
size_t append_bytes = std::min(cap, left);
buf_.PadWith(append_bytes, 0);
left -= append_bytes;
if (left > 0) {
IOStatus s = Flush();
if (!s.ok()) {
return s;
}
}
cap = buf_.Capacity() - buf_.CurrentSize();
}
pending_sync_ = true;
filesize_ += pad_bytes;
return IOStatus::OK();
}
IOStatus WritableFileWriter::Close() {
// Do not quit immediately on failure the file MUST be closed
IOStatus s;
// Possible to close it twice now as we MUST close
// in __dtor, simply flushing is not enough
// Windows when pre-allocating does not fill with zeros
// also with unbuffered access we also set the end of data.
if (writable_file_.get() == nullptr) {
return s;
}
s = Flush(); // flush cache to OS
IOStatus interim;
// In direct I/O mode we write whole pages so
// we need to let the file know where data ends.
if (use_direct_io()) {
{
#ifndef ROCKSDB_LITE
FileOperationInfo::StartTimePoint start_ts;
if (ShouldNotifyListeners()) {
start_ts = FileOperationInfo::StartNow();
}
#endif
interim = writable_file_->Truncate(filesize_, IOOptions(), nullptr);
#ifndef ROCKSDB_LITE
if (ShouldNotifyListeners()) {
auto finish_ts = FileOperationInfo::FinishNow();
NotifyOnFileTruncateFinish(start_ts, finish_ts, s);
}
#endif
}
if (interim.ok()) {
{
#ifndef ROCKSDB_LITE
FileOperationInfo::StartTimePoint start_ts;
if (ShouldNotifyListeners()) {
start_ts = FileOperationInfo::StartNow();
}
#endif
interim = writable_file_->Fsync(IOOptions(), nullptr);
#ifndef ROCKSDB_LITE
if (ShouldNotifyListeners()) {
auto finish_ts = FileOperationInfo::FinishNow();
NotifyOnFileSyncFinish(start_ts, finish_ts, s,
FileOperationType::kFsync);
}
#endif
}
}
if (!interim.ok() && s.ok()) {
s = interim;
}
}
TEST_KILL_RANDOM("WritableFileWriter::Close:0", rocksdb_kill_odds);
{
#ifndef ROCKSDB_LITE
FileOperationInfo::StartTimePoint start_ts;
if (ShouldNotifyListeners()) {
start_ts = FileOperationInfo::StartNow();
}
#endif
interim = writable_file_->Close(IOOptions(), nullptr);
#ifndef ROCKSDB_LITE
if (ShouldNotifyListeners()) {
auto finish_ts = FileOperationInfo::FinishNow();
NotifyOnFileCloseFinish(start_ts, finish_ts, s);
}
#endif
}
if (!interim.ok() && s.ok()) {
s = interim;
}
writable_file_.reset();
TEST_KILL_RANDOM("WritableFileWriter::Close:1", rocksdb_kill_odds);
if (s.ok() && checksum_generator_ != nullptr && !checksum_finalized_) {
checksum_generator_->Finalize();
checksum_finalized_ = true;
}
return s;
}
// write out the cached data to the OS cache or storage if direct I/O
// enabled
IOStatus WritableFileWriter::Flush() {
IOStatus s;
TEST_KILL_RANDOM("WritableFileWriter::Flush:0",
rocksdb_kill_odds * REDUCE_ODDS2);
if (buf_.CurrentSize() > 0) {
if (use_direct_io()) {
#ifndef ROCKSDB_LITE
if (pending_sync_) {
s = WriteDirect();
}
#endif // !ROCKSDB_LITE
} else {
s = WriteBuffered(buf_.BufferStart(), buf_.CurrentSize());
}
if (!s.ok()) {
return s;
}
}
{
#ifndef ROCKSDB_LITE
FileOperationInfo::StartTimePoint start_ts;
if (ShouldNotifyListeners()) {
start_ts = FileOperationInfo::StartNow();
}
#endif
s = writable_file_->Flush(IOOptions(), nullptr);
#ifndef ROCKSDB_LITE
if (ShouldNotifyListeners()) {
auto finish_ts = std::chrono::steady_clock::now();
NotifyOnFileFlushFinish(start_ts, finish_ts, s);
}
#endif
}
if (!s.ok()) {
return s;
}
// sync OS cache to disk for every bytes_per_sync_
// TODO: give log file and sst file different options (log
// files could be potentially cached in OS for their whole
// life time, thus we might not want to flush at all).
// We try to avoid sync to the last 1MB of data. For two reasons:
// (1) avoid rewrite the same page that is modified later.
// (2) for older version of OS, write can block while writing out
// the page.
// Xfs does neighbor page flushing outside of the specified ranges. We
// need to make sure sync range is far from the write offset.
if (!use_direct_io() && bytes_per_sync_) {
const uint64_t kBytesNotSyncRange =
1024 * 1024; // recent 1MB is not synced.
const uint64_t kBytesAlignWhenSync = 4 * 1024; // Align 4KB.
if (filesize_ > kBytesNotSyncRange) {
uint64_t offset_sync_to = filesize_ - kBytesNotSyncRange;
offset_sync_to -= offset_sync_to % kBytesAlignWhenSync;
assert(offset_sync_to >= last_sync_size_);
if (offset_sync_to > 0 &&
offset_sync_to - last_sync_size_ >= bytes_per_sync_) {
s = RangeSync(last_sync_size_, offset_sync_to - last_sync_size_);
last_sync_size_ = offset_sync_to;
}
}
}
return s;
}
std::string WritableFileWriter::GetFileChecksum() {
if (checksum_generator_ != nullptr) {
assert(checksum_finalized_);
return checksum_generator_->GetChecksum();
} else {
return kUnknownFileChecksum;
}
}
const char* WritableFileWriter::GetFileChecksumFuncName() const {
if (checksum_generator_ != nullptr) {
return checksum_generator_->Name();
} else {
return kUnknownFileChecksumFuncName;
}
}
IOStatus WritableFileWriter::Sync(bool use_fsync) {
IOStatus s = Flush();
if (!s.ok()) {
return s;
}
TEST_KILL_RANDOM("WritableFileWriter::Sync:0", rocksdb_kill_odds);
if (!use_direct_io() && pending_sync_) {
s = SyncInternal(use_fsync);
if (!s.ok()) {
return s;
}
}
TEST_KILL_RANDOM("WritableFileWriter::Sync:1", rocksdb_kill_odds);
pending_sync_ = false;
return IOStatus::OK();
}
IOStatus WritableFileWriter::SyncWithoutFlush(bool use_fsync) {
if (!writable_file_->IsSyncThreadSafe()) {
return IOStatus::NotSupported(
"Can't WritableFileWriter::SyncWithoutFlush() because "
"WritableFile::IsSyncThreadSafe() is false");
}
TEST_SYNC_POINT("WritableFileWriter::SyncWithoutFlush:1");
IOStatus s = SyncInternal(use_fsync);
TEST_SYNC_POINT("WritableFileWriter::SyncWithoutFlush:2");
return s;
}
IOStatus WritableFileWriter::SyncInternal(bool use_fsync) {
IOStatus s;
IOSTATS_TIMER_GUARD(fsync_nanos);
TEST_SYNC_POINT("WritableFileWriter::SyncInternal:0");
auto prev_perf_level = GetPerfLevel();
IOSTATS_CPU_TIMER_GUARD(cpu_write_nanos, clock_);
#ifndef ROCKSDB_LITE
FileOperationInfo::StartTimePoint start_ts;
if (ShouldNotifyListeners()) {
start_ts = FileOperationInfo::StartNow();
}
#endif
if (use_fsync) {
Introduce a new storage specific Env API (#5761) Summary: The current Env API encompasses both storage/file operations, as well as OS related operations. Most of the APIs return a Status, which does not have enough metadata about an error, such as whether its retry-able or not, scope (i.e fault domain) of the error etc., that may be required in order to properly handle a storage error. The file APIs also do not provide enough control over the IO SLA, such as timeout, prioritization, hinting about placement and redundancy etc. This PR separates out the file/storage APIs from Env into a new FileSystem class. The APIs are updated to return an IOStatus with metadata about the error, as well as to take an IOOptions structure as input in order to allow more control over the IO. The user can set both ```options.env``` and ```options.file_system``` to specify that RocksDB should use the former for OS related operations and the latter for storage operations. Internally, a ```CompositeEnvWrapper``` has been introduced that inherits from ```Env``` and redirects individual methods to either an ```Env``` implementation or the ```FileSystem``` as appropriate. When options are sanitized during ```DB::Open```, ```options.env``` is replaced with a newly allocated ```CompositeEnvWrapper``` instance if both env and file_system have been specified. This way, the rest of the RocksDB code can continue to function as before. This PR also ports PosixEnv to the new API by splitting it into two - PosixEnv and PosixFileSystem. PosixEnv is defined as a sub-class of CompositeEnvWrapper, and threading/time functions are overridden with Posix specific implementations in order to avoid an extra level of indirection. The ```CompositeEnvWrapper``` translates ```IOStatus``` return code to ```Status```, and sets the severity to ```kSoftError``` if the io_status is retryable. The error handling code in RocksDB can then recover the DB automatically. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5761 Differential Revision: D18868376 Pulled By: anand1976 fbshipit-source-id: 39efe18a162ea746fabac6360ff529baba48486f
5 years ago
s = writable_file_->Fsync(IOOptions(), nullptr);
} else {
Introduce a new storage specific Env API (#5761) Summary: The current Env API encompasses both storage/file operations, as well as OS related operations. Most of the APIs return a Status, which does not have enough metadata about an error, such as whether its retry-able or not, scope (i.e fault domain) of the error etc., that may be required in order to properly handle a storage error. The file APIs also do not provide enough control over the IO SLA, such as timeout, prioritization, hinting about placement and redundancy etc. This PR separates out the file/storage APIs from Env into a new FileSystem class. The APIs are updated to return an IOStatus with metadata about the error, as well as to take an IOOptions structure as input in order to allow more control over the IO. The user can set both ```options.env``` and ```options.file_system``` to specify that RocksDB should use the former for OS related operations and the latter for storage operations. Internally, a ```CompositeEnvWrapper``` has been introduced that inherits from ```Env``` and redirects individual methods to either an ```Env``` implementation or the ```FileSystem``` as appropriate. When options are sanitized during ```DB::Open```, ```options.env``` is replaced with a newly allocated ```CompositeEnvWrapper``` instance if both env and file_system have been specified. This way, the rest of the RocksDB code can continue to function as before. This PR also ports PosixEnv to the new API by splitting it into two - PosixEnv and PosixFileSystem. PosixEnv is defined as a sub-class of CompositeEnvWrapper, and threading/time functions are overridden with Posix specific implementations in order to avoid an extra level of indirection. The ```CompositeEnvWrapper``` translates ```IOStatus``` return code to ```Status```, and sets the severity to ```kSoftError``` if the io_status is retryable. The error handling code in RocksDB can then recover the DB automatically. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5761 Differential Revision: D18868376 Pulled By: anand1976 fbshipit-source-id: 39efe18a162ea746fabac6360ff529baba48486f
5 years ago
s = writable_file_->Sync(IOOptions(), nullptr);
}
#ifndef ROCKSDB_LITE
if (ShouldNotifyListeners()) {
auto finish_ts = std::chrono::steady_clock::now();
NotifyOnFileSyncFinish(
start_ts, finish_ts, s,
use_fsync ? FileOperationType::kFsync : FileOperationType::kSync);
}
#endif
SetPerfLevel(prev_perf_level);
return s;
}
IOStatus WritableFileWriter::RangeSync(uint64_t offset, uint64_t nbytes) {
IOSTATS_TIMER_GUARD(range_sync_nanos);
TEST_SYNC_POINT("WritableFileWriter::RangeSync:0");
#ifndef ROCKSDB_LITE
FileOperationInfo::StartTimePoint start_ts;
if (ShouldNotifyListeners()) {
start_ts = FileOperationInfo::StartNow();
}
#endif
IOStatus s = writable_file_->RangeSync(offset, nbytes, IOOptions(), nullptr);
#ifndef ROCKSDB_LITE
if (ShouldNotifyListeners()) {
auto finish_ts = std::chrono::steady_clock::now();
NotifyOnFileRangeSyncFinish(offset, nbytes, start_ts, finish_ts, s);
}
#endif
return s;
}
// This method writes to disk the specified data and makes use of the rate
// limiter if available
IOStatus WritableFileWriter::WriteBuffered(const char* data, size_t size) {
IOStatus s;
assert(!use_direct_io());
const char* src = data;
size_t left = size;
while (left > 0) {
size_t allowed;
if (rate_limiter_ != nullptr) {
allowed = rate_limiter_->RequestToken(
left, 0 /* alignment */, writable_file_->GetIOPriority(), stats_,
RateLimiter::OpType::kWrite);
} else {
allowed = left;
}
{
IOSTATS_TIMER_GUARD(write_nanos);
TEST_SYNC_POINT("WritableFileWriter::Flush:BeforeAppend");
#ifndef ROCKSDB_LITE
FileOperationInfo::StartTimePoint start_ts;
Introduce a new storage specific Env API (#5761) Summary: The current Env API encompasses both storage/file operations, as well as OS related operations. Most of the APIs return a Status, which does not have enough metadata about an error, such as whether its retry-able or not, scope (i.e fault domain) of the error etc., that may be required in order to properly handle a storage error. The file APIs also do not provide enough control over the IO SLA, such as timeout, prioritization, hinting about placement and redundancy etc. This PR separates out the file/storage APIs from Env into a new FileSystem class. The APIs are updated to return an IOStatus with metadata about the error, as well as to take an IOOptions structure as input in order to allow more control over the IO. The user can set both ```options.env``` and ```options.file_system``` to specify that RocksDB should use the former for OS related operations and the latter for storage operations. Internally, a ```CompositeEnvWrapper``` has been introduced that inherits from ```Env``` and redirects individual methods to either an ```Env``` implementation or the ```FileSystem``` as appropriate. When options are sanitized during ```DB::Open```, ```options.env``` is replaced with a newly allocated ```CompositeEnvWrapper``` instance if both env and file_system have been specified. This way, the rest of the RocksDB code can continue to function as before. This PR also ports PosixEnv to the new API by splitting it into two - PosixEnv and PosixFileSystem. PosixEnv is defined as a sub-class of CompositeEnvWrapper, and threading/time functions are overridden with Posix specific implementations in order to avoid an extra level of indirection. The ```CompositeEnvWrapper``` translates ```IOStatus``` return code to ```Status```, and sets the severity to ```kSoftError``` if the io_status is retryable. The error handling code in RocksDB can then recover the DB automatically. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5761 Differential Revision: D18868376 Pulled By: anand1976 fbshipit-source-id: 39efe18a162ea746fabac6360ff529baba48486f
5 years ago
uint64_t old_size = writable_file_->GetFileSize(IOOptions(), nullptr);
if (ShouldNotifyListeners()) {
start_ts = FileOperationInfo::StartNow();
old_size = next_write_offset_;
}
#endif
{
auto prev_perf_level = GetPerfLevel();
IOSTATS_CPU_TIMER_GUARD(cpu_write_nanos, clock_);
Introduce a new storage specific Env API (#5761) Summary: The current Env API encompasses both storage/file operations, as well as OS related operations. Most of the APIs return a Status, which does not have enough metadata about an error, such as whether its retry-able or not, scope (i.e fault domain) of the error etc., that may be required in order to properly handle a storage error. The file APIs also do not provide enough control over the IO SLA, such as timeout, prioritization, hinting about placement and redundancy etc. This PR separates out the file/storage APIs from Env into a new FileSystem class. The APIs are updated to return an IOStatus with metadata about the error, as well as to take an IOOptions structure as input in order to allow more control over the IO. The user can set both ```options.env``` and ```options.file_system``` to specify that RocksDB should use the former for OS related operations and the latter for storage operations. Internally, a ```CompositeEnvWrapper``` has been introduced that inherits from ```Env``` and redirects individual methods to either an ```Env``` implementation or the ```FileSystem``` as appropriate. When options are sanitized during ```DB::Open```, ```options.env``` is replaced with a newly allocated ```CompositeEnvWrapper``` instance if both env and file_system have been specified. This way, the rest of the RocksDB code can continue to function as before. This PR also ports PosixEnv to the new API by splitting it into two - PosixEnv and PosixFileSystem. PosixEnv is defined as a sub-class of CompositeEnvWrapper, and threading/time functions are overridden with Posix specific implementations in order to avoid an extra level of indirection. The ```CompositeEnvWrapper``` translates ```IOStatus``` return code to ```Status```, and sets the severity to ```kSoftError``` if the io_status is retryable. The error handling code in RocksDB can then recover the DB automatically. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5761 Differential Revision: D18868376 Pulled By: anand1976 fbshipit-source-id: 39efe18a162ea746fabac6360ff529baba48486f
5 years ago
s = writable_file_->Append(Slice(src, allowed), IOOptions(), nullptr);
SetPerfLevel(prev_perf_level);
}
#ifndef ROCKSDB_LITE
if (ShouldNotifyListeners()) {
auto finish_ts = std::chrono::steady_clock::now();
NotifyOnFileWriteFinish(old_size, allowed, start_ts, finish_ts, s);
}
#endif
if (!s.ok()) {
return s;
}
}
IOSTATS_ADD(bytes_written, allowed);
TEST_KILL_RANDOM("WritableFileWriter::WriteBuffered:0", rocksdb_kill_odds);
left -= allowed;
src += allowed;
}
buf_.Size(0);
return s;
}
void WritableFileWriter::UpdateFileChecksum(const Slice& data) {
if (checksum_generator_ != nullptr) {
checksum_generator_->Update(data.data(), data.size());
}
}
// This flushes the accumulated data in the buffer. We pad data with zeros if
// necessary to the whole page.
// However, during automatic flushes padding would not be necessary.
// We always use RateLimiter if available. We move (Refit) any buffer bytes
// that are left over the
// whole number of pages to be written again on the next flush because we can
// only write on aligned
// offsets.
#ifndef ROCKSDB_LITE
IOStatus WritableFileWriter::WriteDirect() {
assert(use_direct_io());
IOStatus s;
const size_t alignment = buf_.Alignment();
assert((next_write_offset_ % alignment) == 0);
// Calculate whole page final file advance if all writes succeed
size_t file_advance = TruncateToPageBoundary(alignment, buf_.CurrentSize());
// Calculate the leftover tail, we write it here padded with zeros BUT we
// will write
// it again in the future either on Close() OR when the current whole page
// fills out
size_t leftover_tail = buf_.CurrentSize() - file_advance;
// Round up and pad
buf_.PadToAlignmentWith(0);
const char* src = buf_.BufferStart();
uint64_t write_offset = next_write_offset_;
size_t left = buf_.CurrentSize();
while (left > 0) {
// Check how much is allowed
size_t size;
if (rate_limiter_ != nullptr) {
size = rate_limiter_->RequestToken(left, buf_.Alignment(),
writable_file_->GetIOPriority(),
stats_, RateLimiter::OpType::kWrite);
} else {
size = left;
}
{
IOSTATS_TIMER_GUARD(write_nanos);
TEST_SYNC_POINT("WritableFileWriter::Flush:BeforeAppend");
FileOperationInfo::StartTimePoint start_ts;
if (ShouldNotifyListeners()) {
start_ts = FileOperationInfo::StartNow();
}
// direct writes must be positional
Introduce a new storage specific Env API (#5761) Summary: The current Env API encompasses both storage/file operations, as well as OS related operations. Most of the APIs return a Status, which does not have enough metadata about an error, such as whether its retry-able or not, scope (i.e fault domain) of the error etc., that may be required in order to properly handle a storage error. The file APIs also do not provide enough control over the IO SLA, such as timeout, prioritization, hinting about placement and redundancy etc. This PR separates out the file/storage APIs from Env into a new FileSystem class. The APIs are updated to return an IOStatus with metadata about the error, as well as to take an IOOptions structure as input in order to allow more control over the IO. The user can set both ```options.env``` and ```options.file_system``` to specify that RocksDB should use the former for OS related operations and the latter for storage operations. Internally, a ```CompositeEnvWrapper``` has been introduced that inherits from ```Env``` and redirects individual methods to either an ```Env``` implementation or the ```FileSystem``` as appropriate. When options are sanitized during ```DB::Open```, ```options.env``` is replaced with a newly allocated ```CompositeEnvWrapper``` instance if both env and file_system have been specified. This way, the rest of the RocksDB code can continue to function as before. This PR also ports PosixEnv to the new API by splitting it into two - PosixEnv and PosixFileSystem. PosixEnv is defined as a sub-class of CompositeEnvWrapper, and threading/time functions are overridden with Posix specific implementations in order to avoid an extra level of indirection. The ```CompositeEnvWrapper``` translates ```IOStatus``` return code to ```Status```, and sets the severity to ```kSoftError``` if the io_status is retryable. The error handling code in RocksDB can then recover the DB automatically. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5761 Differential Revision: D18868376 Pulled By: anand1976 fbshipit-source-id: 39efe18a162ea746fabac6360ff529baba48486f
5 years ago
s = writable_file_->PositionedAppend(Slice(src, size), write_offset,
IOOptions(), nullptr);
if (ShouldNotifyListeners()) {
auto finish_ts = std::chrono::steady_clock::now();
NotifyOnFileWriteFinish(write_offset, size, start_ts, finish_ts, s);
}
if (!s.ok()) {
buf_.Size(file_advance + leftover_tail);
return s;
}
}
IOSTATS_ADD(bytes_written, size);
left -= size;
src += size;
write_offset += size;
assert((next_write_offset_ % alignment) == 0);
}
if (s.ok()) {
// Move the tail to the beginning of the buffer
// This never happens during normal Append but rather during
// explicit call to Flush()/Sync() or Close()
buf_.RefitTail(file_advance, leftover_tail);
// This is where we start writing next time which may or not be
// the actual file size on disk. They match if the buffer size
// is a multiple of whole pages otherwise filesize_ is leftover_tail
// behind
next_write_offset_ += file_advance;
}
return s;
}
#endif // !ROCKSDB_LITE
} // namespace ROCKSDB_NAMESPACE