LogCabin::Storage::Log Class Reference

This interface is used by RaftConsensus to store log entries and metadata. More...

#include <Log.h>

Inheritance diagram for LogCabin::Storage::Log:

List of all members.

Classes
class	Sync
	An interface for flushing newly appended log entries to stable storage. More...
Public Types
typedef Protocol::Raft::Entry	Entry
	The type of a log entry (the same format that's used in AppendEntries).
Public Member Functions
	Log ()
virtual	~Log ()
virtual std::pair< uint64_t, uint64_t >	append (const std::vector< const Entry * > &entries)=0
	Start to append new entries to the log.
virtual const Entry &	getEntry (uint64_t index) const =0
	Look up an entry by its log index.
virtual uint64_t	getLogStartIndex () const =0
	Get the index of the first entry in the log (whether or not this entry exists).
virtual uint64_t	getLastLogIndex () const =0
	Get the index of the most recent entry in the log.
virtual std::string	getName () const =0
	Return the name of the log implementation as it would be specified in the config file.
virtual uint64_t	getSizeBytes () const =0
	Get the size of the entire log in bytes.
void	syncComplete (std::unique_ptr< Sync > sync)
	Release resources attached to the Sync object.
virtual std::unique_ptr< Sync >	takeSync ()=0
	Get and remove the Log's Sync object in order to wait on it.
virtual void	truncatePrefix (uint64_t firstIndex)=0
	Delete the log entries before the given index.
virtual void	truncateSuffix (uint64_t lastIndex)=0
	Delete the log entries past the given index.
virtual void	updateMetadata ()=0
	Call this after changing metadata.
virtual void	updateServerStats (Protocol::ServerStats &serverStats) const
	Add information about the log's state to the given structure.
Public Attributes
Protocol::RaftLogMetadata::Metadata	metadata
	Opaque metadata that the log keeps track of.
Protected Member Functions
virtual void	syncCompleteVirtual (std::unique_ptr< Sync > sync)
	See syncComplete().
	Log (const Log &)
Log &	operator= (const Log &)
Friends
std::ostream &	operator<< (std::ostream &os, const Log &log)
	Print out a Log for debugging purposes.

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Detailed Description

This interface is used by RaftConsensus to store log entries and metadata.

Typically, implementations will persist the log entries and metadata to stable storage (but MemoryLog keeps it all in volatile memory).

Definition at line 40 of file Log.h.

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Member Typedef Documentation

typedef Protocol::Raft::Entry LogCabin::Storage::Log::Entry

The type of a log entry (the same format that's used in AppendEntries).

Reimplemented in LogCabin::Storage::SimpleFileLog.

Definition at line 77 of file Log.h.

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Constructor & Destructor Documentation

LogCabin::Storage::Log::Log

(

)

Definition at line 45 of file Log.cc.

LogCabin::Storage::Log::~Log

(

)

[virtual]

Definition at line 50 of file Log.cc.

LogCabin::Storage::Log::Log

(

const Log &

)

[protected]

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Member Function Documentation

virtual std::pair<uint64_t, uint64_t> LogCabin::Storage::Log::append

(

const std::vector< const Entry * > &

entries

)

[pure virtual]

Start to append new entries to the log.

The entries may not be on disk yet when this returns; see Sync.

Parameters:

entries

Entries to place at the end of the log.

Returns:

Range of indexes of the new entries in the log, inclusive.

Implemented in LogCabin::Storage::SegmentedLog, LogCabin::Storage::SimpleFileLog, and LogCabin::Storage::MemoryLog.

virtual const Entry& LogCabin::Storage::Log::getEntry

(

uint64_t

index

)

const [pure virtual]

Look up an entry by its log index.

Parameters:

index

Must be in the range [getLogStartIndex(), getLastLogIndex()]. Otherwise, this will crash the server.

Returns:

The entry corresponding to that index. This reference is only guaranteed to be valid until the next time the log is modified.

Implemented in LogCabin::Storage::SegmentedLog, LogCabin::Storage::SimpleFileLog, and LogCabin::Storage::MemoryLog.

virtual uint64_t LogCabin::Storage::Log::getLogStartIndex

(

)

const [pure virtual]

Get the index of the first entry in the log (whether or not this entry exists).

Returns:

1 for logs that have never had truncatePrefix called, otherwise the largest index passed to truncatePrefix.

Implemented in LogCabin::Storage::SegmentedLog, LogCabin::Storage::SimpleFileLog, and LogCabin::Storage::MemoryLog.

virtual uint64_t LogCabin::Storage::Log::getLastLogIndex

(

)

const [pure virtual]

Get the index of the most recent entry in the log.

Returns:

The index of the most recent entry in the log, or getLogStartIndex() - 1 if the log is empty.

Implemented in LogCabin::Storage::SegmentedLog, LogCabin::Storage::SimpleFileLog, and LogCabin::Storage::MemoryLog.

virtual std::string LogCabin::Storage::Log::getName

(

)

const [pure virtual]

Return the name of the log implementation as it would be specified in the config file.

Implemented in LogCabin::Storage::SegmentedLog, LogCabin::Storage::SimpleFileLog, and LogCabin::Storage::MemoryLog.

virtual uint64_t LogCabin::Storage::Log::getSizeBytes

(

)

const [pure virtual]

Get the size of the entire log in bytes.

Implemented in LogCabin::Storage::SegmentedLog, LogCabin::Storage::SimpleFileLog, and LogCabin::Storage::MemoryLog.

void LogCabin::Storage::Log::syncComplete

(

std::unique_ptr< Sync >

sync

)

[inline]

Release resources attached to the Sync object.

Call this after waiting on the Sync object.

Definition at line 136 of file Log.h.

virtual void LogCabin::Storage::Log::syncCompleteVirtual

(

std::unique_ptr< Sync >

sync

)

[inline, protected, virtual]

See syncComplete().

Intended for subclasses to override.

Definition at line 144 of file Log.h.

virtual std::unique_ptr<Sync> LogCabin::Storage::Log::takeSync

(

)

[pure virtual]

Get and remove the Log's Sync object in order to wait on it.

This Sync object must later be returned to the Log with syncComplete().

While takeSync() and syncComplete() may not be done concurrently with other Log operations, Sync::wait() may be done concurrently with all operations except truncateSuffix().

Implemented in LogCabin::Storage::SegmentedLog, LogCabin::Storage::SimpleFileLog, and LogCabin::Storage::MemoryLog.

virtual void LogCabin::Storage::Log::truncatePrefix

(

uint64_t

firstIndex

)

[pure virtual]

Delete the log entries before the given index.

Once you truncate a prefix from the log, there's no way to undo this. The entries may still be on disk when this returns and file descriptors and other resources may remain open; see Sync.

Parameters:

firstIndex

After this call, the log will contain no entries indexed less than firstIndex. This can be any log index, including 0 and those past the end of the log.

Implemented in LogCabin::Storage::SegmentedLog, LogCabin::Storage::SimpleFileLog, and LogCabin::Storage::MemoryLog.

virtual void LogCabin::Storage::Log::truncateSuffix

(

uint64_t

lastIndex

)

[pure virtual]

Delete the log entries past the given index.

This will not affect the log start index.

Parameters:

lastIndex

After this call, the log will contain no entries indexed greater than lastIndex. This can be any log index, including 0 and those past the end of the log.

Warning:

Callers should wait() on all Sync object prior to calling truncateSuffix(). This never happens on leaders, so it's not a real limitation, but things may go wonky otherwise.

Implemented in LogCabin::Storage::SegmentedLog, LogCabin::Storage::SimpleFileLog, and LogCabin::Storage::MemoryLog.

virtual void LogCabin::Storage::Log::updateMetadata

(

)

[pure virtual]

Call this after changing metadata.

Implemented in LogCabin::Storage::SegmentedLog, LogCabin::Storage::SimpleFileLog, and LogCabin::Storage::MemoryLog.

virtual void LogCabin::Storage::Log::updateServerStats

(

Protocol::ServerStats &

serverStats

)

const [inline, virtual]

Add information about the log's state to the given structure.

Used for diagnostics.

Reimplemented in LogCabin::Storage::SegmentedLog.

Definition at line 192 of file Log.h.

Log& LogCabin::Storage::Log::operator=

(

const Log &

)

[protected]

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Friends And Related Function Documentation

std::ostream& operator<<	(	std::ostream &	os,
		const Log &	log
	)		[friend]

Print out a Log for debugging purposes.

Definition at line 55 of file Log.cc.

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Member Data Documentation

Protocol::RaftLogMetadata::Metadata LogCabin::Storage::Log::metadata

Opaque metadata that the log keeps track of.

Reimplemented in LogCabin::Storage::SegmentedLog, and LogCabin::Storage::SimpleFileLog.

Definition at line 197 of file Log.h.

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The documentation for this class was generated from the following files:

• Storage/Log.h
• Storage/Log.cc