Reads a MetaLog. More...

#include <MetaLogReader.h>

Collaboration diagram for Hypertable::MetaLog::Reader:

Public Types
enum	Flags { LOAD_ALL_ENTITIES =1 }

Public Member Functions
	Reader (FilesystemPtr &fs, DefinitionPtr &definition, int flags=0)
	Constructor. More...

	Reader (FilesystemPtr &fs, DefinitionPtr &definition, const std::string &path, int flags=0)
	Constructor. More...

void	get_entities (std::vector< EntityPtr > &entities)
	Returns latest version of all entities. More...

void	get_all_entities (std::vector< EntityPtr > &entities)
	Returns all versions of all entities. More...

void	reload ()
	Loads MetaLog. More...

int32_t	next_file_number ()
	Returns next unused numeric file name. More...

void	load_file (const std::string &fname)
	Loads MetaLog file. More...

uint16_t	version ()
	Returns MetaLog Definition version read from log file header. More...

Private Member Functions
void	verify_backup (int32_t file_num)
	Sanity check local backup file. More...

void	read_header (int fd, int64_t *offsetp)
	Reads the log file header. More...

Private Attributes
FilesystemPtr	m_fs
	Smart pointer to Filesystem object. More...

MetaLog::DefinitionPtr	m_definition
	Smart pointer to MetaLog Definition. More...

std::string	m_path
	Path name of MetaLog directory. More...

int	m_flags
	Flags that control read behavior. More...

std::deque< int32_t >	m_file_nums
	Vector of numeric file names found in log directory. More...

std::map< EntityHeader, EntityPtr >	m_entity_map
	Map containing latest version of each Entity read from MetaLog. More...

std::vector< EntityPtr >	m_entities
	Vector containing all versions of each Entity read from MetaLog. More...

std::string	m_backup_path
	Local backup path initialized in primary_metalog_reader_constructor. More...

uint16_t	m_version
	MetaLog Definition version read from log file header. More...

Detailed Description

Reads a MetaLog.

This class is part of a group of generic meta log manipulation classes. A meta log is a server state log and is currently used by both the RangeServer and the Master servers. The set of valid MetaLog::Entity classes are defined by a MetaLog::Definition class that is defined for each server. This class reads a meta log and provides access to the latest versions of live MetaLog entities that have been persisted in the log.

Definition at line 56 of file MetaLogReader.h.

Constructor & Destructor Documentation

Reader::Reader	(	FilesystemPtr &	fs,
		DefinitionPtr &	definition,
		int	flags = `0`
	)

Constructor.

Constructs and empty object. This constructor is used when opening a specific MetaLog fragment file and is typically followed by a call to load_file().

Parameters

fs	Smart pointer to Filesystem object
definition	Smart pointer to Definition object
flags	Flags that control reading behavior

Definition at line 52 of file MetaLogReader.cc.

Reader::Reader	(	FilesystemPtr &	fs,
		DefinitionPtr &	definition,
		const std::string &	path,
		int	flags = `0`
	)

Constructor.

This constructor initializes the Reader and loads the MetaLog specified by path. It initializes m_backup_path as follows:

$data_dir     = Config::properties->get_str("Hypertable.DataDirectory");
$name         = m_definition->name();
$backup_label = m_definition->backup_label()
m_backup_path = $data_dir/run/log_backup/$name/$backup_label

It then calls reload() to load the MetaLog.

Parameters

fs	Smart pointer to Filesystem object
definition	Smart pointer to Definition object
path	Path to MetaLog directory
flags	Flags that control reading behavior

Definition at line 57 of file MetaLogReader.cc.

Member Function Documentation

void Reader::get_all_entities ( std::vector< EntityPtr > & entities )

Returns all versions of all entities.

Parameters

entities Reference to vector to hold returned entities

Definition at line 79 of file MetaLogReader.cc.

void Reader::get_entities ( std::vector< EntityPtr > & entities )

Returns latest version of all entities.

Parameters

entities Reference to vector to hold returned entities

Definition at line 73 of file MetaLogReader.cc.

void Reader::load_file ( const std::string & fname )

Loads MetaLog file.

This method opens fname and reads the header with a call to read_header(). It then reads each Entity from the file by first reading and decoding the EntityHeader. If the flags field of the header has the EntityHeader::FLAG_REMOVE bit set, it is purged from m_entity_map and skipped. Otherwise, the entity is constructed with a call to the Definition::create() of m_definition, afterwhich the entity's state is decoded with a call to the entity's Entity::decode() method and it is inserted into both m_entity_map and m_entities. If a read comes up short, this method will throw an Exception with error code Error::METALOG_ENTRY_TRUNCATED. If there is a checksum mis-match, it will throw an Exception with error code Error::METALOG_CHECKSUM_MISMATCH. If after the complete file is read, if an EntityRecover was not encountered, an Exception is thrown with error code Error::METALOG_MISSING_RECOVER_ENTITY.

Parameters

fname Full pathname of MetaLog file to load

Exceptions

%Exception with code Error::METALOG_ENTRY_TRUNCATED, or Error::METALOG_CHECKSUM_MISMATCH, or Error::METALOG_MISSING_RECOVER_ENTITY, or one of the exceptions returned by Client::open_buffered(), or Client::read().

Definition at line 133 of file MetaLogReader.cc.

int32_t Hypertable::MetaLog::Reader::next_file_number ( )

inline

Returns next unused numeric file name.

This method returns #m_next_filenum which is set during the log directory scan by taking the largest numerically named file and adding one.

Returns: Next unused numeric file name.

Definition at line 120 of file MetaLogReader.h.

void Reader::read_header	(	int	fd,
		int64_t *	offsetp
	)

private

Reads the log file header.

Reads and decodes the log file header (MetaLog::Header). If the read comes up short or the name in the header does not match what is returned by the Definition::name() method of m_definition, an Exception is thrown with error code Error::METALOG_BAD_HEADER. If the version read from the header is greater than what is returned by Definition::version() method of m_definition, an exception is thrown with error code Error::METALOG_VERSION_MISMATCH. Otherwise, m_version is set to the version read from the header, and *offsetp is incremented by the length of the header.

Parameters

fd	Open file descriptor for MetaLog file
offsetp	Pointer to current offset within the file

Exceptions

Exception with code Error::METALOG_BAD_HEADER or Error::METALOG_VERSION_MISMATCH, or one of the exceptions thrown by Client::read()

Definition at line 223 of file MetaLogReader.cc.

void Reader::reload ( )

Loads MetaLog.

This method scans the MetaLog directory with a call to scan_log_directory() and then loads the largest numerically named file in the directory with a call to load_file(). The m_file_nums vector is populated with the numeric file names found in log directory. This method propagates all exceptions of type Error::METALOG_ERROR and converts all other exceptions to Error::METALOG_READ_ERROR and rethrows.

Exceptions

Exception with one of the Error::METALOG_ERROR codes.

Definition at line 84 of file MetaLogReader.cc.

void Reader::verify_backup ( int32_t file_num )

private

Sanity check local backup file.

This method throws an Exception with error code Error::METALOG_BACKUP_FILE_MISMATCH if the backup file with numeric name file_num exists and has size less than the corresponding file in the FS. Otherwise it returns successfuly.

Parameters

file_num Numeric file name of file for which to verify backup

Definition at line 114 of file MetaLogReader.cc.

uint16_t Hypertable::MetaLog::Reader::version ( )

inline

Returns MetaLog Definition version read from log file header.

Returns: MetaLog Definition version read from log file header.

Definition at line 151 of file MetaLogReader.h.

Member Data Documentation

std::string Hypertable::MetaLog::Reader::m_backup_path

private

Local backup path initialized in primary_metalog_reader_constructor.

Definition at line 206 of file MetaLogReader.h.

MetaLog::DefinitionPtr Hypertable::MetaLog::Reader::m_definition

private

Smart pointer to MetaLog Definition.

Definition at line 188 of file MetaLogReader.h.

std::vector<EntityPtr> Hypertable::MetaLog::Reader::m_entities

private

Vector containing all versions of each Entity read from MetaLog.

Definition at line 203 of file MetaLogReader.h.

std::map<EntityHeader, EntityPtr> Hypertable::MetaLog::Reader::m_entity_map

private

Map containing latest version of each Entity read from MetaLog.

Definition at line 200 of file MetaLogReader.h.

std::deque<int32_t> Hypertable::MetaLog::Reader::m_file_nums

private

Vector of numeric file names found in log directory.

Definition at line 197 of file MetaLogReader.h.

int Hypertable::MetaLog::Reader::m_flags

private

Flags that control read behavior.

Definition at line 194 of file MetaLogReader.h.

FilesystemPtr Hypertable::MetaLog::Reader::m_fs

private

Smart pointer to Filesystem object.

Definition at line 185 of file MetaLogReader.h.

std::string Hypertable::MetaLog::Reader::m_path

private

Path name of MetaLog directory.

Definition at line 191 of file MetaLogReader.h.

uint16_t Hypertable::MetaLog::Reader::m_version

private

MetaLog Definition version read from log file header.

Definition at line 209 of file MetaLogReader.h.

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

/home/doug/src/hypertable/src/cc/Hypertable/Lib/MetaLogReader.h
/home/doug/src/hypertable/src/cc/Hypertable/Lib/MetaLogReader.cc

Public Types

Public Member Functions

Private Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation