stasis-aries-wal/stasis/logger/logger2.h

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/**
 * @file
 *
 * Interface to Stasis' log file.
 *
 * @ingroup LOGGING_DISCIPLINE
 *
 * $Id$
 *
 */


#ifndef __LOGGER2_H__
#define __LOGGER2_H__

#include <stasis/common.h>

/**
   Contains the state needed by the logging layer to perform
   operations on a transaction.
 */
typedef struct TransactionLog {
  int xid;
  lsn_t prevLSN;
  lsn_t recLSN;
  pthread_mutex_t mut;
} TransactionLog;

typedef struct stasis_log_t stasis_log_t;

#include <stasis/operations.h>

/**
   A callback function that allows logHandle's iterator to stop
   returning log entries depending on the context in which it was
   called.
*/
typedef int (guard_fcn_t)(const LogEntry *, void *);


typedef enum {
  LOG_FORCE_COMMIT, LOG_FORCE_WAL
} stasis_log_force_mode_t;

/**
   XXX TransactionTable should be private to transactional2.c!
*/
extern TransactionLog stasis_transaction_table[MAX_TRANSACTIONS];



struct stasis_log_t {
  /**
     Needed by sizeofLogEntry
  */
  lsn_t (*sizeof_internal_entry)(struct stasis_log_t* log, const LogEntry * e);

  /**
     Append a log entry to the end of the log.

     @param e This call sets e->LSN to entry's offset.
     @return 0 on success
  */
  int (*write_entry)(struct stasis_log_t* log, LogEntry * e);

  /**
     Read a log entry, given its LSN.
     @param lsn  The lsn of the log entry to be read.
  */
  const LogEntry* (*read_entry)(struct stasis_log_t* log, lsn_t lsn);

  /**
     Given a log entry, return the LSN of the next entry.
  */
  lsn_t (*next_entry)(struct stasis_log_t* log, const LogEntry * e);

  /**
     This function returns the LSN of the most recent
     log entry that has not been flushed to disk.  If the entire log
     is flushed, this function returns the LSN of the entry that will
     be allocated the next time the log is appended to.

     @param log The log file, which may or may not support durability.
     @param mode The mode in which the log entries must have been forced.
  */
  lsn_t (*first_unstable_lsn)(struct stasis_log_t* log,
                              stasis_log_force_mode_t mode);
  /**
     This function returns the LSN of the next log entry passed to
     write_entry.  This shouldn't be used to determine which entry a
     particular call will assign; rather it is used to provide a lower
     bound on the LSN of newly-loaded LSN-free pages.
  */
  lsn_t (*next_available_lsn)(struct stasis_log_t* log);
  /**
     Force any enqueued, unwritten entries to disk
  */
  void (*force_tail)(struct stasis_log_t* log, stasis_log_force_mode_t mode);

  /**
      @param lsn The first lsn that will be available after truncation.
      @return 0 on success
  */
  int (*truncate)(struct stasis_log_t* log, lsn_t lsn);

  /**
     Returns the LSN of the first entry of the log.  If the log is
     empty, return the LSN that will be assigned to the next log
     entry that is appended to the log.
  */
  lsn_t (*truncation_point)(struct stasis_log_t* log);
  /**
     @return 0 on success
  */
  int (*close)(struct stasis_log_t* log);

  int (*is_durable)(struct stasis_log_t* log);

  void* impl;
};

/**
   @todo get rid of this!
 */
extern stasis_log_t* stasis_log_file;

/**
   Synchronously make a prefix of the log durable.

   This method uses group commit to reduce the number of calls to
   force_tail().

   Durability is guaranteed in an implementation-specific way.

   @param log A log that already contains the entries to be forced to disk.
   @param lsn Log entries up to and including the one that overlaps lsn will
              be durable after this call returns.
   @param mode The durability mode associated with this call.

   @see stasis_log_force_mode_t
   @see logger2.h for information about force_tail().
 */
void LogForce(stasis_log_t* log, lsn_t lsn, stasis_log_force_mode_t mode);

/**
   Inform the logging layer that a new transaction has begun, and
   obtain a handle.
*/
void LogTransBegin(stasis_log_t* log, int xid, TransactionLog* l);

/**
   Write a transaction PREPARE to the log tail.  Blocks until the
   prepare record is stable.

   @return the lsn of the prepare log entry
*/
lsn_t LogTransPrepare(stasis_log_t* log, TransactionLog * l);
/**
   Write a transaction COMMIT to the log tail.  Blocks until the commit
   record is stable.

   @return the lsn of the commit log entry.
*/
lsn_t LogTransCommit(stasis_log_t* log, TransactionLog * l);

/**
   Write a transaction ABORT to the log tail.  Does not force the log.

   @return the lsn of the abort log entry.
*/
lsn_t LogTransAbort(stasis_log_t* log, TransactionLog * l);

/**
   Write a end transaction record.  This entry tells recovery's undo
   phase that it may safely ignore the transaction.
*/
lsn_t LogTransEnd (stasis_log_t* log, TransactionLog * l);

/**
   LogUpdate writes an UPDATELOG log record to the log tail.  It
   also interprets its operation argument to the extent necessary for
   allocating and laying out the log entry.  Finally, it updates the
   state of the parameter l.
*/
LogEntry * LogUpdate(stasis_log_t* log,
                     TransactionLog * l, Page * p, unsigned int operation,
                     const byte * arg, size_t arg_size);

/**
   Write a compensation log record.  These records are used to allow
   for efficient recovery, and possibly for log truncation.  They
   record the completion of undo operations, amongst other things.

   @return the lsn of the CLR entry that was written to the log.
   (Needed so that the lsn slot of the page in question can be
   updated.)
*/
lsn_t LogCLR(stasis_log_t* log, const LogEntry * e);

lsn_t LogDummyCLR(stasis_log_t* log, int xid,
                  lsn_t prev_lsn, lsn_t compensated_lsn);



#endif