Log Manager, which writes out transactional logs. More...

Detailed Description

Log Manager, which writes out transactional logs.

This package contains classes that control transactional logging.

Decentralized Logging: Unlike traditional log manager in DBMS, this log manager is decentralized, meaning each log writer writes to its own file concurrently. This eliminates the bottleneck in log manager when there are a large number of cores. The basic idea to guarantee serializability is the epoch-based commit protocol, which does the check on all loggers before returning the results to client in a way similar to group-commit.

Thread-private log buffer: Each ThreadLoadBugger instance maintains a thread-local log buffer that is filled by the thread without any synchronization or blocking. The logger collects them and writes them out to log files. A single log writer handles one or more transactional threads (cores), and a single NUMA node hosts one or more log writers.

Log Writer: Each Logger instance writes out files suffixed with ordinal (eg ".0", ".1"...). The older logs files are deactivated and deleted after log gleaner consumes them.

Global Durable Epoch: An important job of Log Manager is to maintain the global durable epoch. Log manager is the module to determine when it's safe to advance the global durable epoch. It makes sure all loggers flushed their logs up to the epoch, invoked required fsync(), and also takes a savepoint before it announces the new global durable epoch.

Collaboration diagram for Log Manager:

Modules
	Log Types
	Defines the content and apply logic of transactional operatrions.

Files
file	common_log_types.hpp
	Declares common log types used in all packages.

file	fwd.hpp
	Forward declarations of classes in log manager package.

file	log_id.hpp
	Typedefs of ID types used in log package.

Classes
struct	foedus::log::FillerLogType
	A dummy log type to fill up a sector in log files. More...

struct	foedus::log::EpochMarkerLogType
	A log type to declare a switch of epoch in a logger or the engine. More...

struct	foedus::log::EpochHistory
	Represents an event where a logger switched its epoch. More...

struct	foedus::log::LogRange
	a contiguous range of log entries that might span multiple files. More...

class	foedus::log::LogManager
	Log Manager class that provides API to write/read transaction logs. More...

class	foedus::log::LogManagerPimpl
	Pimpl object of LogManager. More...

struct	foedus::log::LogOptions
	Set of options for log manager. More...

class	foedus::log::Logger
	A log writer that writes out buffered logs to stable storages. More...

class	foedus::log::LoggerRef
	A view of Logger object for other SOCs and master engine. More...

class	foedus::log::MetaLogBuffer
	A single log buffer for metadata (eg create/drop storage). More...

class	foedus::log::MetaLogger
	A log writer for metadata operation. More...

struct	foedus::log::ThreadEpockMark
	A thread-buffer's epoch marker, which indicates where a thread switched an epoch. More...

struct	foedus::log::ThreadLogBufferMeta
	Metadata part of ThreadLogBuffer, without the actual buffer which is way way larger. More...

struct	foedus::log::ThreadLogBuffer::OffsetRange

class	foedus::log::ThreadLogBuffer
	A thread-local log buffer. More...

Typedefs
typedef uint16_t	foedus::log::LoggerId
	Typedef for an ID of Logger. More...

typedef uint32_t	foedus::log::LogFileOrdinal
	Ordinal of log files (eg "log.0", "log.1"). More...

Typedef Documentation

Ordinal of log files (eg "log.0", "log.1").

Each logger outputs log files whose filename is suffixed with an ordinal. Each log file

Definition at line 46 of file log_id.hpp.

Typedef for an ID of Logger.

ID of Logger is merely an ordinal without holes. In other words, "(loggers_per_node * NUMA_node_id) + ordinal_in_node".

Definition at line 36 of file log_id.hpp.