rocksdb/db/error_handler.cc
Yanqin Jin e66199d848 First step towards handling MANIFEST write error (#6949)
Summary:
This PR provides preliminary support for handling IO error during MANIFEST write.
File write/sync is not guaranteed to be atomic. If we encounter an IOError while writing/syncing to the MANIFEST file, we cannot be sure about the state of the MANIFEST file. The version edits may or may not have reached the file. During cleanup, if we delete the newly-generated SST files referenced by the pending version edit(s), but the version edit(s) actually are persistent in the MANIFEST, then next recovery attempt will process the version edits(s) and then fail since the SST files have already been deleted.
One approach is to truncate the MANIFEST after write/sync error, so that it is safe to delete the SST files. However, file truncation may not be supported on certain file systems. Therefore, we take the following approach.
If an IOError is detected during MANIFEST write/sync, we disable file deletions for the faulty database. Depending on whether the IOError is retryable (set by underlying file system), either RocksDB or application can call `DB::Resume()`, or simply shutdown and restart. During `Resume()`, RocksDB will try to switch to a new MANIFEST and write all existing in-memory version storage in the new file. If this succeeds, then RocksDB may proceed. If all recovery is completed, then file deletions will be re-enabled.
Note that multiple threads can call `LogAndApply()` at the same time, though only one of them will be going through the process MANIFEST write, possibly batching the version edits of other threads. When the leading MANIFEST writer finishes, all of the MANIFEST writing threads in this batch will have the same IOError. They will all call `ErrorHandler::SetBGError()` in which file deletion will be disabled.

Possible future directions:
- Add an `ErrorContext` structure so that it is easier to pass more info to `ErrorHandler`. Currently, as in this example, a new `BackgroundErrorReason` has to be added.

Test plan (dev server):
make check
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6949

Reviewed By: anand1976

Differential Revision: D22026020

Pulled By: riversand963

fbshipit-source-id: f3c68a2ef45d9b505d0d625c7c5e0c88495b91c8
2020-06-24 19:07:08 -07:00

405 lines
15 KiB
C++

// Copyright (c) 2018-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).
//
#include "db/error_handler.h"
#include "db/db_impl/db_impl.h"
#include "db/event_helpers.h"
#include "file/sst_file_manager_impl.h"
namespace ROCKSDB_NAMESPACE {
// Maps to help decide the severity of an error based on the
// BackgroundErrorReason, Code, SubCode and whether db_options.paranoid_checks
// is set or not. There are 3 maps, going from most specific to least specific
// (i.e from all 4 fields in a tuple to only the BackgroundErrorReason and
// paranoid_checks). The less specific map serves as a catch all in case we miss
// a specific error code or subcode.
std::map<std::tuple<BackgroundErrorReason, Status::Code, Status::SubCode, bool>,
Status::Severity>
ErrorSeverityMap = {
// Errors during BG compaction
{std::make_tuple(BackgroundErrorReason::kCompaction,
Status::Code::kIOError, Status::SubCode::kNoSpace,
true),
Status::Severity::kSoftError},
{std::make_tuple(BackgroundErrorReason::kCompaction,
Status::Code::kIOError, Status::SubCode::kNoSpace,
false),
Status::Severity::kNoError},
{std::make_tuple(BackgroundErrorReason::kCompaction,
Status::Code::kIOError, Status::SubCode::kSpaceLimit,
true),
Status::Severity::kHardError},
// Errors during BG flush
{std::make_tuple(BackgroundErrorReason::kFlush, Status::Code::kIOError,
Status::SubCode::kNoSpace, true),
Status::Severity::kHardError},
{std::make_tuple(BackgroundErrorReason::kFlush, Status::Code::kIOError,
Status::SubCode::kNoSpace, false),
Status::Severity::kNoError},
{std::make_tuple(BackgroundErrorReason::kFlush, Status::Code::kIOError,
Status::SubCode::kSpaceLimit, true),
Status::Severity::kHardError},
// Errors during Write
{std::make_tuple(BackgroundErrorReason::kWriteCallback,
Status::Code::kIOError, Status::SubCode::kNoSpace,
true),
Status::Severity::kHardError},
{std::make_tuple(BackgroundErrorReason::kWriteCallback,
Status::Code::kIOError, Status::SubCode::kNoSpace,
false),
Status::Severity::kHardError},
// Errors during MANIFEST write
{std::make_tuple(BackgroundErrorReason::kManifestWrite,
Status::Code::kIOError, Status::SubCode::kNoSpace,
true),
Status::Severity::kHardError},
{std::make_tuple(BackgroundErrorReason::kManifestWrite,
Status::Code::kIOError, Status::SubCode::kNoSpace,
false),
Status::Severity::kHardError},
};
std::map<std::tuple<BackgroundErrorReason, Status::Code, bool>,
Status::Severity>
DefaultErrorSeverityMap = {
// Errors during BG compaction
{std::make_tuple(BackgroundErrorReason::kCompaction,
Status::Code::kCorruption, true),
Status::Severity::kUnrecoverableError},
{std::make_tuple(BackgroundErrorReason::kCompaction,
Status::Code::kCorruption, false),
Status::Severity::kNoError},
{std::make_tuple(BackgroundErrorReason::kCompaction,
Status::Code::kIOError, true),
Status::Severity::kFatalError},
{std::make_tuple(BackgroundErrorReason::kCompaction,
Status::Code::kIOError, false),
Status::Severity::kNoError},
// Errors during BG flush
{std::make_tuple(BackgroundErrorReason::kFlush,
Status::Code::kCorruption, true),
Status::Severity::kUnrecoverableError},
{std::make_tuple(BackgroundErrorReason::kFlush,
Status::Code::kCorruption, false),
Status::Severity::kNoError},
{std::make_tuple(BackgroundErrorReason::kFlush, Status::Code::kIOError,
true),
Status::Severity::kFatalError},
{std::make_tuple(BackgroundErrorReason::kFlush, Status::Code::kIOError,
false),
Status::Severity::kNoError},
// Errors during Write
{std::make_tuple(BackgroundErrorReason::kWriteCallback,
Status::Code::kCorruption, true),
Status::Severity::kUnrecoverableError},
{std::make_tuple(BackgroundErrorReason::kWriteCallback,
Status::Code::kCorruption, false),
Status::Severity::kNoError},
{std::make_tuple(BackgroundErrorReason::kWriteCallback,
Status::Code::kIOError, true),
Status::Severity::kFatalError},
{std::make_tuple(BackgroundErrorReason::kWriteCallback,
Status::Code::kIOError, false),
Status::Severity::kNoError},
{std::make_tuple(BackgroundErrorReason::kManifestWrite,
Status::Code::kIOError, true),
Status::Severity::kFatalError},
{std::make_tuple(BackgroundErrorReason::kManifestWrite,
Status::Code::kIOError, false),
Status::Severity::kFatalError},
};
std::map<std::tuple<BackgroundErrorReason, bool>, Status::Severity>
DefaultReasonMap = {
// Errors during BG compaction
{std::make_tuple(BackgroundErrorReason::kCompaction, true),
Status::Severity::kFatalError},
{std::make_tuple(BackgroundErrorReason::kCompaction, false),
Status::Severity::kNoError},
// Errors during BG flush
{std::make_tuple(BackgroundErrorReason::kFlush, true),
Status::Severity::kFatalError},
{std::make_tuple(BackgroundErrorReason::kFlush, false),
Status::Severity::kNoError},
// Errors during Write
{std::make_tuple(BackgroundErrorReason::kWriteCallback, true),
Status::Severity::kFatalError},
{std::make_tuple(BackgroundErrorReason::kWriteCallback, false),
Status::Severity::kFatalError},
// Errors during Memtable update
{std::make_tuple(BackgroundErrorReason::kMemTable, true),
Status::Severity::kFatalError},
{std::make_tuple(BackgroundErrorReason::kMemTable, false),
Status::Severity::kFatalError},
};
void ErrorHandler::CancelErrorRecovery() {
#ifndef ROCKSDB_LITE
db_mutex_->AssertHeld();
// We'll release the lock before calling sfm, so make sure no new
// recovery gets scheduled at that point
auto_recovery_ = false;
SstFileManagerImpl* sfm = reinterpret_cast<SstFileManagerImpl*>(
db_options_.sst_file_manager.get());
if (sfm) {
// This may or may not cancel a pending recovery
db_mutex_->Unlock();
bool cancelled = sfm->CancelErrorRecovery(this);
db_mutex_->Lock();
if (cancelled) {
recovery_in_prog_ = false;
}
}
#endif
}
// This is the main function for looking at an error during a background
// operation and deciding the severity, and error recovery strategy. The high
// level algorithm is as follows -
// 1. Classify the severity of the error based on the ErrorSeverityMap,
// DefaultErrorSeverityMap and DefaultReasonMap defined earlier
// 2. Call a Status code specific override function to adjust the severity
// if needed. The reason for this is our ability to recover may depend on
// the exact options enabled in DBOptions
// 3. Determine if auto recovery is possible. A listener notification callback
// is called, which can disable the auto recovery even if we decide its
// feasible
// 4. For Status::NoSpace() errors, rely on SstFileManagerImpl to control
// the actual recovery. If no sst file manager is specified in DBOptions,
// a default one is allocated during DB::Open(), so there will always be
// one.
// This can also get called as part of a recovery operation. In that case, we
// also track the error separately in recovery_error_ so we can tell in the
// end whether recovery succeeded or not
Status ErrorHandler::SetBGError(const Status& bg_err, BackgroundErrorReason reason) {
db_mutex_->AssertHeld();
if (bg_err.ok()) {
return Status::OK();
}
bool paranoid = db_options_.paranoid_checks;
Status::Severity sev = Status::Severity::kFatalError;
Status new_bg_err;
bool found = false;
{
auto entry = ErrorSeverityMap.find(std::make_tuple(reason, bg_err.code(),
bg_err.subcode(), paranoid));
if (entry != ErrorSeverityMap.end()) {
sev = entry->second;
found = true;
}
}
if (!found) {
auto entry = DefaultErrorSeverityMap.find(std::make_tuple(reason,
bg_err.code(), paranoid));
if (entry != DefaultErrorSeverityMap.end()) {
sev = entry->second;
found = true;
}
}
if (!found) {
auto entry = DefaultReasonMap.find(std::make_tuple(reason, paranoid));
if (entry != DefaultReasonMap.end()) {
sev = entry->second;
}
}
new_bg_err = Status(bg_err, sev);
// Check if recovery is currently in progress. If it is, we will save this
// error so we can check it at the end to see if recovery succeeded or not
if (recovery_in_prog_ && recovery_error_.ok()) {
recovery_error_ = new_bg_err;
}
bool auto_recovery = auto_recovery_;
if (new_bg_err.severity() >= Status::Severity::kFatalError && auto_recovery) {
auto_recovery = false;
}
// Allow some error specific overrides
if (new_bg_err == Status::NoSpace()) {
new_bg_err = OverrideNoSpaceError(new_bg_err, &auto_recovery);
}
if (!new_bg_err.ok()) {
Status s = new_bg_err;
EventHelpers::NotifyOnBackgroundError(db_options_.listeners, reason, &s,
db_mutex_, &auto_recovery);
if (!s.ok() && (s.severity() > bg_error_.severity())) {
bg_error_ = s;
} else {
// This error is less severe than previously encountered error. Don't
// take any further action
return bg_error_;
}
}
if (auto_recovery) {
recovery_in_prog_ = true;
// Kick-off error specific recovery
if (bg_error_ == Status::NoSpace()) {
RecoverFromNoSpace();
}
}
return bg_error_;
}
Status ErrorHandler::SetBGError(const IOStatus& bg_io_err,
BackgroundErrorReason reason) {
db_mutex_->AssertHeld();
if (bg_io_err.ok()) {
return Status::OK();
}
if (recovery_in_prog_ && recovery_error_.ok()) {
recovery_error_ = bg_io_err;
}
if (BackgroundErrorReason::kManifestWrite == reason) {
// Always returns ok
db_->DisableFileDeletionsWithLock();
}
Status new_bg_io_err = bg_io_err;
Status s;
if (bg_io_err.GetDataLoss()) {
// FIrst, data loss is treated as unrecoverable error. So it can directly
// overwrite any existing bg_error_.
bool auto_recovery = false;
Status bg_err(new_bg_io_err, Status::Severity::kUnrecoverableError);
bg_error_ = bg_err;
EventHelpers::NotifyOnBackgroundError(db_options_.listeners, reason, &s,
db_mutex_, &auto_recovery);
return bg_error_;
} else if (bg_io_err.GetRetryable()) {
// Second, check if the error is a retryable IO error or not. if it is
// retryable error and its severity is higher than bg_error_, overwrite
// the bg_error_ with new error.
// In current stage, treat retryable error as HardError. No automatic
// recovery.
bool auto_recovery = false;
Status bg_err(new_bg_io_err, Status::Severity::kHardError);
EventHelpers::NotifyOnBackgroundError(db_options_.listeners, reason, &s,
db_mutex_, &auto_recovery);
if (bg_err.severity() > bg_error_.severity()) {
bg_error_ = bg_err;
}
return bg_error_;
} else {
s = SetBGError(new_bg_io_err, reason);
}
return s;
}
Status ErrorHandler::OverrideNoSpaceError(Status bg_error,
bool* auto_recovery) {
#ifndef ROCKSDB_LITE
if (bg_error.severity() >= Status::Severity::kFatalError) {
return bg_error;
}
if (db_options_.sst_file_manager.get() == nullptr) {
// We rely on SFM to poll for enough disk space and recover
*auto_recovery = false;
return bg_error;
}
if (db_options_.allow_2pc &&
(bg_error.severity() <= Status::Severity::kSoftError)) {
// Don't know how to recover, as the contents of the current WAL file may
// be inconsistent, and it may be needed for 2PC. If 2PC is not enabled,
// we can just flush the memtable and discard the log
*auto_recovery = false;
return Status(bg_error, Status::Severity::kFatalError);
}
{
uint64_t free_space;
if (db_options_.env->GetFreeSpace(db_options_.db_paths[0].path,
&free_space) == Status::NotSupported()) {
*auto_recovery = false;
}
}
return bg_error;
#else
(void)auto_recovery;
return Status(bg_error, Status::Severity::kFatalError);
#endif
}
void ErrorHandler::RecoverFromNoSpace() {
#ifndef ROCKSDB_LITE
SstFileManagerImpl* sfm =
reinterpret_cast<SstFileManagerImpl*>(db_options_.sst_file_manager.get());
// Inform SFM of the error, so it can kick-off the recovery
if (sfm) {
sfm->StartErrorRecovery(this, bg_error_);
}
#endif
}
Status ErrorHandler::ClearBGError() {
#ifndef ROCKSDB_LITE
db_mutex_->AssertHeld();
// Signal that recovery succeeded
if (recovery_error_.ok()) {
Status old_bg_error = bg_error_;
bg_error_ = Status::OK();
recovery_in_prog_ = false;
EventHelpers::NotifyOnErrorRecoveryCompleted(db_options_.listeners,
old_bg_error, db_mutex_);
}
return recovery_error_;
#else
return bg_error_;
#endif
}
Status ErrorHandler::RecoverFromBGError(bool is_manual) {
#ifndef ROCKSDB_LITE
InstrumentedMutexLock l(db_mutex_);
if (is_manual) {
// If its a manual recovery and there's a background recovery in progress
// return busy status
if (recovery_in_prog_) {
return Status::Busy();
}
recovery_in_prog_ = true;
}
if (bg_error_.severity() == Status::Severity::kSoftError) {
// Simply clear the background error and return
recovery_error_ = Status::OK();
return ClearBGError();
}
// Reset recovery_error_. We will use this to record any errors that happen
// during the recovery process. While recovering, the only operations that
// can generate background errors should be the flush operations
recovery_error_ = Status::OK();
Status s = db_->ResumeImpl();
// For manual recover, shutdown, and fatal error cases, set
// recovery_in_prog_ to false. For automatic background recovery, leave it
// as is regardless of success or failure as it will be retried
if (is_manual || s.IsShutdownInProgress() ||
bg_error_.severity() >= Status::Severity::kFatalError) {
recovery_in_prog_ = false;
}
return s;
#else
(void)is_manual;
return bg_error_;
#endif
}
} // namespace ROCKSDB_NAMESPACE