/usr/include/rocksdb/listener.h is in librocksdb-dev 5.8.8-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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// 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.
#pragma once
#include <memory>
#include <string>
#include <unordered_map>
#include <vector>
#include "rocksdb/compaction_job_stats.h"
#include "rocksdb/status.h"
#include "rocksdb/table_properties.h"
namespace rocksdb {
typedef std::unordered_map<std::string, std::shared_ptr<const TableProperties>>
TablePropertiesCollection;
class DB;
class ColumnFamilyHandle;
class Status;
struct CompactionJobStats;
enum CompressionType : unsigned char;
enum class TableFileCreationReason {
kFlush,
kCompaction,
kRecovery,
};
struct TableFileCreationBriefInfo {
// the name of the database where the file was created
std::string db_name;
// the name of the column family where the file was created.
std::string cf_name;
// the path to the created file.
std::string file_path;
// the id of the job (which could be flush or compaction) that
// created the file.
int job_id;
// reason of creating the table.
TableFileCreationReason reason;
};
struct TableFileCreationInfo : public TableFileCreationBriefInfo {
TableFileCreationInfo() = default;
explicit TableFileCreationInfo(TableProperties&& prop)
: table_properties(prop) {}
// the size of the file.
uint64_t file_size;
// Detailed properties of the created file.
TableProperties table_properties;
// The status indicating whether the creation was successful or not.
Status status;
};
enum class CompactionReason {
kUnknown,
// [Level] number of L0 files > level0_file_num_compaction_trigger
kLevelL0FilesNum,
// [Level] total size of level > MaxBytesForLevel()
kLevelMaxLevelSize,
// [Universal] Compacting for size amplification
kUniversalSizeAmplification,
// [Universal] Compacting for size ratio
kUniversalSizeRatio,
// [Universal] number of sorted runs > level0_file_num_compaction_trigger
kUniversalSortedRunNum,
// [FIFO] total size > max_table_files_size
kFIFOMaxSize,
// [FIFO] reduce number of files.
kFIFOReduceNumFiles,
// [FIFO] files with creation time < (current_time - interval)
kFIFOTtl,
// Manual compaction
kManualCompaction,
// DB::SuggestCompactRange() marked files for compaction
kFilesMarkedForCompaction,
};
enum class BackgroundErrorReason {
kFlush,
kCompaction,
kWriteCallback,
kMemTable,
};
#ifndef ROCKSDB_LITE
struct TableFileDeletionInfo {
// The name of the database where the file was deleted.
std::string db_name;
// The path to the deleted file.
std::string file_path;
// The id of the job which deleted the file.
int job_id;
// The status indicating whether the deletion was successful or not.
Status status;
};
struct FlushJobInfo {
// the name of the column family
std::string cf_name;
// the path to the newly created file
std::string file_path;
// the id of the thread that completed this flush job.
uint64_t thread_id;
// the job id, which is unique in the same thread.
int job_id;
// If true, then rocksdb is currently slowing-down all writes to prevent
// creating too many Level 0 files as compaction seems not able to
// catch up the write request speed. This indicates that there are
// too many files in Level 0.
bool triggered_writes_slowdown;
// If true, then rocksdb is currently blocking any writes to prevent
// creating more L0 files. This indicates that there are too many
// files in level 0. Compactions should try to compact L0 files down
// to lower levels as soon as possible.
bool triggered_writes_stop;
// The smallest sequence number in the newly created file
SequenceNumber smallest_seqno;
// The largest sequence number in the newly created file
SequenceNumber largest_seqno;
// Table properties of the table being flushed
TableProperties table_properties;
};
struct CompactionJobInfo {
CompactionJobInfo() = default;
explicit CompactionJobInfo(const CompactionJobStats& _stats) :
stats(_stats) {}
// the name of the column family where the compaction happened.
std::string cf_name;
// the status indicating whether the compaction was successful or not.
Status status;
// the id of the thread that completed this compaction job.
uint64_t thread_id;
// the job id, which is unique in the same thread.
int job_id;
// the smallest input level of the compaction.
int base_input_level;
// the output level of the compaction.
int output_level;
// the names of the compaction input files.
std::vector<std::string> input_files;
// the names of the compaction output files.
std::vector<std::string> output_files;
// Table properties for input and output tables.
// The map is keyed by values from input_files and output_files.
TablePropertiesCollection table_properties;
// Reason to run the compaction
CompactionReason compaction_reason;
// Compression algorithm used for output files
CompressionType compression;
// If non-null, this variable stores detailed information
// about this compaction.
CompactionJobStats stats;
};
struct MemTableInfo {
// the name of the column family to which memtable belongs
std::string cf_name;
// Sequence number of the first element that was inserted
// into the memtable.
SequenceNumber first_seqno;
// Sequence number that is guaranteed to be smaller than or equal
// to the sequence number of any key that could be inserted into this
// memtable. It can then be assumed that any write with a larger(or equal)
// sequence number will be present in this memtable or a later memtable.
SequenceNumber earliest_seqno;
// Total number of entries in memtable
uint64_t num_entries;
// Total number of deletes in memtable
uint64_t num_deletes;
};
struct ExternalFileIngestionInfo {
// the name of the column family
std::string cf_name;
// Path of the file outside the DB
std::string external_file_path;
// Path of the file inside the DB
std::string internal_file_path;
// The global sequence number assigned to keys in this file
SequenceNumber global_seqno;
// Table properties of the table being flushed
TableProperties table_properties;
};
// A call-back function to RocksDB which will be called when the compaction
// iterator is compacting values. It is mean to be returned from
// EventListner::GetCompactionEventListner() at the beginning of compaction
// job.
class CompactionEventListener {
public:
enum CompactionListenerValueType {
kValue,
kMergeOperand,
kDelete,
kSingleDelete,
kRangeDelete,
kBlobIndex,
kInvalid,
};
virtual void OnCompaction(int level, const Slice& key,
CompactionListenerValueType value_type,
const Slice& existing_value,
const SequenceNumber& sn, bool is_new) = 0;
virtual ~CompactionEventListener() = default;
};
// EventListener class contains a set of call-back functions that will
// be called when specific RocksDB event happens such as flush. It can
// be used as a building block for developing custom features such as
// stats-collector or external compaction algorithm.
//
// Note that call-back functions should not run for an extended period of
// time before the function returns, otherwise RocksDB may be blocked.
// For example, it is not suggested to do DB::CompactFiles() (as it may
// run for a long while) or issue many of DB::Put() (as Put may be blocked
// in certain cases) in the same thread in the EventListener callback.
// However, doing DB::CompactFiles() and DB::Put() in another thread is
// considered safe.
//
// [Threading] All EventListener callback will be called using the
// actual thread that involves in that specific event. For example, it
// is the RocksDB background flush thread that does the actual flush to
// call EventListener::OnFlushCompleted().
//
// [Locking] All EventListener callbacks are designed to be called without
// the current thread holding any DB mutex. This is to prevent potential
// deadlock and performance issue when using EventListener callback
// in a complex way. However, all EventListener call-back functions
// should not run for an extended period of time before the function
// returns, otherwise RocksDB may be blocked. For example, it is not
// suggested to do DB::CompactFiles() (as it may run for a long while)
// or issue many of DB::Put() (as Put may be blocked in certain cases)
// in the same thread in the EventListener callback. However, doing
// DB::CompactFiles() and DB::Put() in a thread other than the
// EventListener callback thread is considered safe.
class EventListener {
public:
// A call-back function to RocksDB which will be called whenever a
// registered RocksDB flushes a file. The default implementation is
// no-op.
//
// Note that the this function must be implemented in a way such that
// it should not run for an extended period of time before the function
// returns. Otherwise, RocksDB may be blocked.
virtual void OnFlushCompleted(DB* /*db*/,
const FlushJobInfo& /*flush_job_info*/) {}
// A call-back function to RocksDB which will be called before a
// RocksDB starts to flush memtables. The default implementation is
// no-op.
//
// Note that the this function must be implemented in a way such that
// it should not run for an extended period of time before the function
// returns. Otherwise, RocksDB may be blocked.
virtual void OnFlushBegin(DB* /*db*/,
const FlushJobInfo& /*flush_job_info*/) {}
// A call-back function for RocksDB which will be called whenever
// a SST file is deleted. Different from OnCompactionCompleted and
// OnFlushCompleted, this call-back is designed for external logging
// service and thus only provide string parameters instead
// of a pointer to DB. Applications that build logic basic based
// on file creations and deletions is suggested to implement
// OnFlushCompleted and OnCompactionCompleted.
//
// Note that if applications would like to use the passed reference
// outside this function call, they should make copies from the
// returned value.
virtual void OnTableFileDeleted(const TableFileDeletionInfo& /*info*/) {}
// A call-back function for RocksDB which will be called whenever
// a registered RocksDB compacts a file. The default implementation
// is a no-op.
//
// Note that this function must be implemented in a way such that
// it should not run for an extended period of time before the function
// returns. Otherwise, RocksDB may be blocked.
//
// @param db a pointer to the rocksdb instance which just compacted
// a file.
// @param ci a reference to a CompactionJobInfo struct. 'ci' is released
// after this function is returned, and must be copied if it is needed
// outside of this function.
virtual void OnCompactionCompleted(DB* /*db*/,
const CompactionJobInfo& /*ci*/) {}
// A call-back function for RocksDB which will be called whenever
// a SST file is created. Different from OnCompactionCompleted and
// OnFlushCompleted, this call-back is designed for external logging
// service and thus only provide string parameters instead
// of a pointer to DB. Applications that build logic basic based
// on file creations and deletions is suggested to implement
// OnFlushCompleted and OnCompactionCompleted.
//
// Historically it will only be called if the file is successfully created.
// Now it will also be called on failure case. User can check info.status
// to see if it succeeded or not.
//
// Note that if applications would like to use the passed reference
// outside this function call, they should make copies from these
// returned value.
virtual void OnTableFileCreated(const TableFileCreationInfo& /*info*/) {}
// A call-back function for RocksDB which will be called before
// a SST file is being created. It will follow by OnTableFileCreated after
// the creation finishes.
//
// Note that if applications would like to use the passed reference
// outside this function call, they should make copies from these
// returned value.
virtual void OnTableFileCreationStarted(
const TableFileCreationBriefInfo& /*info*/) {}
// A call-back function for RocksDB which will be called before
// a memtable is made immutable.
//
// Note that the this function must be implemented in a way such that
// it should not run for an extended period of time before the function
// returns. Otherwise, RocksDB may be blocked.
//
// Note that if applications would like to use the passed reference
// outside this function call, they should make copies from these
// returned value.
virtual void OnMemTableSealed(
const MemTableInfo& /*info*/) {}
// A call-back function for RocksDB which will be called before
// a column family handle is deleted.
//
// Note that the this function must be implemented in a way such that
// it should not run for an extended period of time before the function
// returns. Otherwise, RocksDB may be blocked.
// @param handle is a pointer to the column family handle to be deleted
// which will become a dangling pointer after the deletion.
virtual void OnColumnFamilyHandleDeletionStarted(ColumnFamilyHandle* handle) {
}
// A call-back function for RocksDB which will be called after an external
// file is ingested using IngestExternalFile.
//
// Note that the this function will run on the same thread as
// IngestExternalFile(), if this function is blocked, IngestExternalFile()
// will be blocked from finishing.
virtual void OnExternalFileIngested(
DB* /*db*/, const ExternalFileIngestionInfo& /*info*/) {}
// A call-back function for RocksDB which will be called before setting the
// background error status to a non-OK value. The new background error status
// is provided in `bg_error` and can be modified by the callback. E.g., a
// callback can suppress errors by resetting it to Status::OK(), thus
// preventing the database from entering read-only mode. We do not provide any
// guarantee when failed flushes/compactions will be rescheduled if the user
// suppresses an error.
//
// Note that this function can run on the same threads as flush, compaction,
// and user writes. So, it is extremely important not to perform heavy
// computations or blocking calls in this function.
virtual void OnBackgroundError(BackgroundErrorReason /* reason */,
Status* /* bg_error */) {}
// Factory method to return CompactionEventListener. If multiple listeners
// provides CompactionEventListner, only the first one will be used.
virtual CompactionEventListener* GetCompactionEventListener() {
return nullptr;
}
virtual ~EventListener() {}
};
#else
class EventListener {
};
#endif // ROCKSDB_LITE
} // namespace rocksdb
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