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rep_method.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2001-2005
 *    Sleepycat Software.  All rights reserved.
 *
 * $Id: rep_method.c,v 12.18 2005/11/08 03:25:13 bostic Exp $
 */

#include "db_config.h"

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <stdlib.h>
#include <string.h>
#endif

#include "db_int.h"
#include "dbinc/db_page.h"
#include "dbinc/btree.h"
#include "dbinc/log.h"
#include "dbinc/txn.h"

static int  __rep_abort_prepared __P((DB_ENV *));
static int  __rep_bt_cmp __P((DB *, const DBT *, const DBT *));
static void __rep_config_map __P((DB_ENV *, u_int32_t *, u_int32_t *));
static int  __rep_restore_prepared __P((DB_ENV *));

/*
 * __rep_open --
 *    Replication-specific initialization of the DB_ENV structure.
 *
 * PUBLIC: int __rep_open __P((DB_ENV *));
 */
int
__rep_open(dbenv)
      DB_ENV *dbenv;
{
      DB_REP *db_rep;
      int ret;

      if ((ret = __os_calloc(dbenv, 1, sizeof(DB_REP), &db_rep)) != 0)
            return (ret);
      dbenv->rep_handle = db_rep;
      ret = __rep_region_init(dbenv);
      return (ret);
}

/*
 * __rep_get_config --
 *    Configure the replication subsystem.
 *
 * PUBLIC: int __rep_get_config __P((DB_ENV *, u_int32_t, int *));
 */
int
__rep_get_config(dbenv, which, onp)
      DB_ENV *dbenv;
      u_int32_t which;
      int *onp;
{
      DB_REP *db_rep;
      REP *rep;
      u_int32_t mapped;

#undef      OK_FLAGS
#define     OK_FLAGS                                        \
(DB_REP_CONF_BULK | DB_REP_CONF_DELAYCLIENT | DB_REP_CONF_NOAUTOINIT    \
    | DB_REP_CONF_NOWAIT)

      PANIC_CHECK(dbenv);
      ENV_REQUIRES_CONFIG(dbenv, dbenv->rep_handle,
          "rep_get_config", DB_INIT_REP);
      if (FLD_ISSET(which, ~OK_FLAGS))
            return (__db_ferr(dbenv, "DB_ENV->rep_get_config", 0));

      db_rep = dbenv->rep_handle;
      rep = db_rep->region;

      mapped = 0;
      __rep_config_map(dbenv, &which, &mapped);
      if (FLD_ISSET(rep->config, mapped))
            *onp = 1;
      else
            *onp = 0;
      return (0);
}

/*
 * __rep_set_config --
 *    Configure the replication subsystem.
 *
 * PUBLIC: int __rep_set_config __P((DB_ENV *, u_int32_t, int));
 */
int
__rep_set_config(dbenv, which, on)
      DB_ENV *dbenv;
      u_int32_t which;
      int on;
{
      DB_LOG *dblp;
      DB_REP *db_rep;
      LOG *lp;
      REP *rep;
      REP_BULK bulk;
      int ret;
      u_int32_t mapped, orig;

#undef      OK_FLAGS
#define     OK_FLAGS                                        \
(DB_REP_CONF_BULK | DB_REP_CONF_DELAYCLIENT | DB_REP_CONF_NOAUTOINIT    \
    | DB_REP_CONF_NOWAIT)

      PANIC_CHECK(dbenv);
      ENV_REQUIRES_CONFIG(dbenv, dbenv->rep_handle,
          "rep_config", DB_INIT_REP);
      if (FLD_ISSET(which, ~OK_FLAGS))
            return (__db_ferr(dbenv, "DB_ENV->rep_set_config", 0));

      dblp = dbenv->lg_handle;
      lp = dblp->reginfo.primary;
      db_rep = dbenv->rep_handle;
      rep = db_rep->region;

      mapped = ret = 0;
      __rep_config_map(dbenv, &which, &mapped);
      MUTEX_LOCK(dbenv, rep->mtx_clientdb);
      REP_SYSTEM_LOCK(dbenv);
      orig = rep->config;
      if (on)
            FLD_SET(rep->config, mapped);
      else
            FLD_CLR(rep->config, mapped);

      /*
       * Bulk transfer requires special processing if it is getting
       * toggled.
       */
      if (FLD_ISSET(rep->config, REP_C_BULK) &&
          !FLD_ISSET(orig, REP_C_BULK))
            db_rep->bulk = R_ADDR(&dblp->reginfo, lp->bulk_buf);
      REP_SYSTEM_UNLOCK(dbenv);
      /*
       * If turning bulk off and it was on, send out whatever is in the
       * buffer already.
       */
      if (FLD_ISSET(orig, REP_C_BULK) &&
          !FLD_ISSET(rep->config, REP_C_BULK) && lp->bulk_off != 0) {
            memset(&bulk, 0, sizeof(bulk));
            if (db_rep->bulk == NULL)
                  bulk.addr = R_ADDR(&dblp->reginfo, lp->bulk_buf);
            else
                  bulk.addr = db_rep->bulk;
            bulk.offp = &lp->bulk_off;
            bulk.len = lp->bulk_len;
            bulk.type = REP_BULK_LOG;
            bulk.eid = DB_EID_BROADCAST;
            bulk.flagsp = &lp->bulk_flags;
            ret = __rep_send_bulk(dbenv, &bulk, 0);
      }
      MUTEX_UNLOCK(dbenv, rep->mtx_clientdb);
      return (ret);
}

static void
__rep_config_map(dbenv, inflagsp, outflagsp)
      DB_ENV *dbenv;
      u_int32_t *inflagsp, *outflagsp;
{
      COMPQUIET(dbenv, NULL);

      if (FLD_ISSET(*inflagsp, DB_REP_CONF_BULK)) {
            FLD_SET(*outflagsp, REP_C_BULK);
            FLD_CLR(*inflagsp, DB_REP_CONF_BULK);
      }
      if (FLD_ISSET(*inflagsp, DB_REP_CONF_DELAYCLIENT)) {
            FLD_SET(*outflagsp, REP_C_DELAYCLIENT);
            FLD_CLR(*inflagsp, DB_REP_CONF_DELAYCLIENT);
      }
      if (FLD_ISSET(*inflagsp, DB_REP_CONF_NOAUTOINIT)) {
            FLD_SET(*outflagsp, REP_C_NOAUTOINIT);
            FLD_CLR(*inflagsp, DB_REP_CONF_NOAUTOINIT);
      }
      if (FLD_ISSET(*inflagsp, DB_REP_CONF_NOWAIT)) {
            FLD_SET(*outflagsp, REP_C_NOWAIT);
            FLD_CLR(*inflagsp, DB_REP_CONF_NOWAIT);
      }
}

/*
 * __rep_start --
 *    Become a master or client, and start sending messages to participate
 * in the replication environment.  Must be called after the environment
 * is open.
 *
 * We must protect rep_start, which may change the world, with the rest
 * of the DB library.  Each API interface will count itself as it enters
 * the library.  Rep_start checks the following:
 *
 * rep->msg_th - this is the count of threads currently in rep_process_message
 * rep->start_th - this is set if a thread is in rep_start.
 * rep->handle_cnt - number of threads actively using a dbp in library.
 * rep->txn_cnt - number of active txns.
 * REP_F_READY - Replication flag that indicates that we wish to run
 * recovery, and want to prohibit new transactions from entering and cause
 * existing ones to return immediately (with a DB_LOCK_DEADLOCK error).
 *
 * There is also the renv->rep_timestamp which is updated whenever significant
 * events (i.e., new masters, log rollback, etc).  Upon creation, a handle
 * is associated with the current timestamp.  Each time a handle enters the
 * library it must check if the handle timestamp is the same as the one
 * stored in the replication region.  This prevents the use of handles on
 * clients that reference non-existent files whose creation was backed out
 * during a synchronizing recovery.
 *
 * PUBLIC: int __rep_start __P((DB_ENV *, DBT *, u_int32_t));
 */
int
__rep_start(dbenv, dbt, flags)
      DB_ENV *dbenv;
      DBT *dbt;
      u_int32_t flags;
{
      DB_LOG *dblp;
      DB_LSN lsn;
      DB_REP *db_rep;
      REP *rep;
      u_int32_t repflags;
      int announce, init_db, redo_prepared, ret, role_chg;
      int sleep_cnt, t_ret;
#ifdef DIAGNOSTIC
      DB_MSGBUF mb;
#endif

      PANIC_CHECK(dbenv);
      ENV_ILLEGAL_BEFORE_OPEN(dbenv, "DB_ENV->rep_start");
      ENV_REQUIRES_CONFIG(dbenv, dbenv->rep_handle, "rep_start", DB_INIT_REP);

      db_rep = dbenv->rep_handle;
      rep = db_rep->region;

      if ((ret = __db_fchk(dbenv, "DB_ENV->rep_start", flags,
          DB_REP_CLIENT | DB_REP_MASTER)) != 0)
            return (ret);

      /* Exactly one of CLIENT and MASTER must be specified. */
      if ((ret = __db_fcchk(dbenv,
          "DB_ENV->rep_start", flags, DB_REP_CLIENT, DB_REP_MASTER)) != 0)
            return (ret);
      if (!LF_ISSET(DB_REP_CLIENT | DB_REP_MASTER)) {
            __db_err(dbenv,
      "DB_ENV->rep_start: replication mode must be specified");
            return (EINVAL);
      }

      /* We need a transport function. */
      if (dbenv->rep_send == NULL) {
            __db_err(dbenv,
    "DB_ENV->set_rep_transport must be called before DB_ENV->rep_start");
            return (EINVAL);
      }

      /*
       * If we are about to become (or stay) a master.  Let's flush the log
       * to close any potential holes that might happen when upgrading from
       * client to master status.
       */
      if (LF_ISSET(DB_REP_MASTER) && (ret = __log_flush(dbenv, NULL)) != 0)
            return (ret);

      REP_SYSTEM_LOCK(dbenv);
      /*
       * We only need one thread to start-up replication, so if
       * there is another thread in rep_start, we'll let it finish
       * its work and have this thread simply return.
       */
      if (rep->start_th != 0) {
            /*
             * There is already someone in rep_start.  Return.
             */
            RPRINT(dbenv, rep, (dbenv, &mb, "Thread already in rep_start"));
            goto err;
      } else
            rep->start_th = 1;

      role_chg = (!F_ISSET(rep, REP_F_MASTER) && LF_ISSET(DB_REP_MASTER)) ||
          (!F_ISSET(rep, REP_F_CLIENT) && LF_ISSET(DB_REP_CLIENT));

      /*
       * Wait for any active txns or mpool ops to complete, and
       * prevent any new ones from occurring, only if we're
       * changing roles.  If we are not changing roles, then we
       * only need to coordinate with msg_th.
       */
      if (role_chg) {
            if ((ret = __rep_lockout(dbenv, rep, 0)) != 0)
                  goto errunlock;
      } else {
            for (sleep_cnt = 0; rep->msg_th != 0;) {
                  if (++sleep_cnt % 60 == 0)
                        __db_err(dbenv,
      "DB_ENV->rep_start waiting %d minutes for replication message thread",
                            sleep_cnt / 60);
                  REP_SYSTEM_UNLOCK(dbenv);
                  __os_sleep(dbenv, 1, 0);
                  REP_SYSTEM_LOCK(dbenv);
            }
      }

      if (rep->eid == DB_EID_INVALID)
            rep->eid = dbenv->rep_eid;

      if (LF_ISSET(DB_REP_MASTER)) {
            if (role_chg) {
                  /*
                   * If we're upgrading from having been a client,
                   * preclose, so that we close our temporary database
                   * and any files we opened while doing a rep_apply.
                   * If we don't we can infinitely leak file ids if
                   * the master crashed with files open (the likely
                   * case).  If we don't close them we can run into
                   * problems if we try to remove that file or long
                   * running applications end up with an unbounded
                   * number of used fileids, each getting written
                   * on checkpoint.  Just close them.
                   */
                  if ((ret = __rep_preclose(dbenv)) != 0)
                        goto errunlock;
            }

            redo_prepared = 0;
            if (!F_ISSET(rep, REP_F_MASTER)) {
                  /* Master is not yet set. */
                  if (role_chg) {
                        if (rep->w_gen > rep->recover_gen)
                              rep->gen = ++rep->w_gen;
                        else if (rep->gen > rep->recover_gen)
                              rep->gen++;
                        else
                              rep->gen = rep->recover_gen + 1;
                        /*
                         * There could have been any number of failed
                         * elections, so jump the gen if we need to now.
                         */
                        if (rep->egen > rep->gen)
                              rep->gen = rep->egen;
                        redo_prepared = 1;
                  } else if (rep->gen == 0)
                        rep->gen = rep->recover_gen + 1;
                  if (F_ISSET(rep, REP_F_MASTERELECT)) {
                        __rep_elect_done(dbenv, rep);
                        F_CLR(rep, REP_F_MASTERELECT);
                  }
                  if (rep->egen <= rep->gen)
                        rep->egen = rep->gen + 1;
                  RPRINT(dbenv, rep, (dbenv, &mb,
                      "New master gen %lu, egen %lu",
                      (u_long)rep->gen, (u_long)rep->egen));
            }
            rep->master_id = rep->eid;
            /*
             * Note, setting flags below implicitly clears out
             * REP_F_NOARCHIVE, REP_F_INIT and REP_F_READY.
             */
            rep->flags = REP_F_MASTER;
            rep->start_th = 0;
            REP_SYSTEM_UNLOCK(dbenv);
            dblp = (DB_LOG *)dbenv->lg_handle;
            LOG_SYSTEM_LOCK(dbenv);
            lsn = ((LOG *)dblp->reginfo.primary)->lsn;
            LOG_SYSTEM_UNLOCK(dbenv);

            /*
             * Send the NEWMASTER message first so that clients know
             * subsequent messages are coming from the right master.
             * We need to perform all actions below no master what
             * regarding errors.
             */
            (void)__rep_send_message(dbenv,
                DB_EID_BROADCAST, REP_NEWMASTER, &lsn, NULL, 0, 0);
            ret = 0;
            if (role_chg) {
                  ret = __txn_reset(dbenv);
                  REP_SYSTEM_LOCK(dbenv);
                  F_CLR(rep, REP_F_READY);
                  rep->in_recovery = 0;
                  REP_SYSTEM_UNLOCK(dbenv);
            }
            /*
             * Take a transaction checkpoint so that our new generation
             * number get written to the log.
             */
            if ((t_ret = __txn_checkpoint(dbenv, 0, 0, DB_FORCE)) != 0 &&
                ret == 0)
                  ret = t_ret;
            if (redo_prepared &&
                (t_ret = __rep_restore_prepared(dbenv)) != 0 && ret == 0)
                  ret = t_ret;
      } else {
            init_db = 0;
            announce = role_chg || rep->master_id == DB_EID_INVALID;

            /*
             * If we're changing roles from master to client or if
             * we never were any role at all, we need to init the db.
             */
            if (role_chg || !F_ISSET(rep, REP_F_CLIENT)) {
                  rep->master_id = DB_EID_INVALID;
                  init_db = 1;
            }
            /* Zero out everything except recovery and tally flags. */
            repflags = F_ISSET(rep, REP_F_NOARCHIVE |
                REP_F_RECOVER_MASK | REP_F_TALLY);
            FLD_SET(repflags, REP_F_CLIENT);

            rep->flags = repflags;
            REP_SYSTEM_UNLOCK(dbenv);

            /*
             * Abort any prepared transactions that were restored
             * by recovery.  We won't be able to create any txns of
             * our own until they're resolved, but we can't resolve
             * them ourselves;  the master has to.  If any get
             * resolved as commits, we'll redo them when commit
             * records come in.  Aborts will simply be ignored.
             */
            if ((ret = __rep_abort_prepared(dbenv)) != 0)
                  goto errlock;

            MUTEX_LOCK(dbenv, rep->mtx_clientdb);
            ret = __rep_client_dbinit(dbenv, init_db, REP_DB);
            MUTEX_UNLOCK(dbenv, rep->mtx_clientdb);
            if (ret != 0)
                  goto errlock;
            REP_SYSTEM_LOCK(dbenv);
            rep->start_th = 0;
            if (role_chg) {
                  F_CLR(rep, REP_F_READY);
                  rep->in_recovery = 0;
            }
            REP_SYSTEM_UNLOCK(dbenv);

            /*
             * If this client created a newly replicated environment,
             * then announce the existence of this client.  The master
             * should respond with a message that will tell this client
             * the current generation number and the current LSN.  This
             * will allow the client to either perform recovery or
             * simply join in.
             */
            if (announce)
                  (void)__rep_send_message(dbenv,
                      DB_EID_BROADCAST, REP_NEWCLIENT, NULL, dbt, 0, 0);
            else
                  (void)__rep_send_message(dbenv,
                      DB_EID_BROADCAST, REP_ALIVE_REQ, NULL, NULL, 0, 0);
      }

      if (0) {
            /*
             * We have separate labels for errors.  If we're returning an
             * error before we've set start_th, we use 'err'.  If
             * we are erroring while holding the region mutex, then we use
             * 'errunlock' label.  If we're erroring without holding the rep
             * mutex we must use 'errlock'.
             */
errlock:    REP_SYSTEM_LOCK(dbenv);
errunlock:  rep->start_th = 0;
            if (role_chg) {
                  F_CLR(rep, REP_F_READY);
                  rep->in_recovery = 0;
            }
err:        REP_SYSTEM_UNLOCK(dbenv);
      }
      return (ret);
}

/*
 * __rep_client_dbinit --
 *
 * Initialize the LSN database on the client side.  This is called from the
 * client initialization code.  The startup flag value indicates if
 * this is the first thread/process starting up and therefore should create
 * the LSN database.  This routine must be called once by each process acting
 * as a client.
 *
 * Assumes caller holds appropriate mutex.
 *
 * PUBLIC: int __rep_client_dbinit __P((DB_ENV *, int, repdb_t));
 */
int
__rep_client_dbinit(dbenv, startup, which)
      DB_ENV *dbenv;
      int startup;
      repdb_t which;
{
      DB_REP *db_rep;
      DB *dbp, **rdbpp;
      REP *rep;
      int ret, t_ret;
      u_int32_t flags;
      const char *name;

      PANIC_CHECK(dbenv);
      db_rep = dbenv->rep_handle;
      rep = db_rep->region;
      dbp = NULL;

#define     REPDBNAME   "__db.rep.db"
#define     REPPAGENAME     "__db.reppg.db"

      if (which == REP_DB) {
            name = REPDBNAME;
            rdbpp = &db_rep->rep_db;
      } else {
            name = REPPAGENAME;
            rdbpp = &rep->file_dbp;
      }
      /* Check if this has already been called on this environment. */
      if (*rdbpp != NULL)
            return (0);

      if (startup) {
            if ((ret = db_create(&dbp, dbenv, 0)) != 0)
                  goto err;
            /*
             * Ignore errors, because if the file doesn't exist, this
             * is perfectly OK.
             */
            (void)__db_remove(dbp, NULL, name, NULL, DB_FORCE);
      }

      if ((ret = db_create(&dbp, dbenv, 0)) != 0)
            goto err;
      if (which == REP_DB &&
          (ret = __bam_set_bt_compare(dbp, __rep_bt_cmp)) != 0)
            goto err;

      /* Allow writes to this database on a client. */
      F_SET(dbp, DB_AM_CL_WRITER);

      flags = DB_NO_AUTO_COMMIT |
          (startup ? DB_CREATE : 0) |
          (F_ISSET(dbenv, DB_ENV_THREAD) ? DB_THREAD : 0);

      if ((ret = __db_open(dbp, NULL, name, NULL,
          (which == REP_DB ? DB_BTREE : DB_RECNO),
          flags, 0, PGNO_BASE_MD)) != 0)
            goto err;

      *rdbpp= dbp;

      if (0) {
err:        if (dbp != NULL &&
                (t_ret = __db_close(dbp, NULL, DB_NOSYNC)) != 0 && ret == 0)
                  ret = t_ret;
            *rdbpp = NULL;
      }

      return (ret);
}

/*
 * __rep_bt_cmp --
 *
 * Comparison function for the LSN table.  We use the entire control
 * structure as a key (for simplicity, so we don't have to merge the
 * other fields in the control with the data field), but really only
 * care about the LSNs.
 */
static int
__rep_bt_cmp(dbp, dbt1, dbt2)
      DB *dbp;
      const DBT *dbt1, *dbt2;
{
      DB_LSN lsn1, lsn2;
      REP_CONTROL *rp1, *rp2;

      COMPQUIET(dbp, NULL);

      rp1 = dbt1->data;
      rp2 = dbt2->data;

      (void)__ua_memcpy(&lsn1, &rp1->lsn, sizeof(DB_LSN));
      (void)__ua_memcpy(&lsn2, &rp2->lsn, sizeof(DB_LSN));

      if (lsn1.file > lsn2.file)
            return (1);

      if (lsn1.file < lsn2.file)
            return (-1);

      if (lsn1.offset > lsn2.offset)
            return (1);

      if (lsn1.offset < lsn2.offset)
            return (-1);

      return (0);
}

/*
 * __rep_abort_prepared --
 *    Abort any prepared transactions that recovery restored.
 *
 *    This is used by clients that have just run recovery, since
 * they cannot/should not call txn_recover and handle prepared transactions
 * themselves.
 */
static int
__rep_abort_prepared(dbenv)
      DB_ENV *dbenv;
{
#define     PREPLISTSIZE      50
      DB_PREPLIST prep[PREPLISTSIZE], *p;
      DB_TXNMGR *mgr;
      DB_TXNREGION *region;
      int do_aborts, ret;
      long count, i;
      u_int32_t op;

      mgr = dbenv->tx_handle;
      region = mgr->reginfo.primary;

      do_aborts = 0;
      TXN_SYSTEM_LOCK(dbenv);
      if (region->stat.st_nrestores != 0)
            do_aborts = 1;
      TXN_SYSTEM_UNLOCK(dbenv);

      if (do_aborts) {
            op = DB_FIRST;
            do {
                  if ((ret = __txn_recover(dbenv,
                      prep, PREPLISTSIZE, &count, op)) != 0)
                        return (ret);
                  for (i = 0; i < count; i++) {
                        p = &prep[i];
                        if ((ret = __txn_abort(p->txn)) != 0)
                              return (ret);
                  }
                  op = DB_NEXT;
            } while (count == PREPLISTSIZE);
      }

      return (0);
}

/*
 * __rep_restore_prepared --
 *    Restore to a prepared state any prepared but not yet committed
 * transactions.
 *
 *    This performs, in effect, a "mini-recovery";  it is called from
 * __rep_start by newly upgraded masters.  There may be transactions that an
 * old master prepared but did not resolve, which we need to restore to an
 * active state.
 */
static int
__rep_restore_prepared(dbenv)
      DB_ENV *dbenv;
{
      DB_LOGC *logc;
      DB_LSN ckp_lsn, lsn;
      DB_TXNHEAD *txninfo;
      DBT rec;
      __txn_ckp_args *ckp_args;
      __txn_regop_args *regop_args;
      __txn_xa_regop_args *prep_args;
      int ret, t_ret;
      u_int32_t hi_txn, low_txn, rectype, status;

      txninfo = NULL;
      ckp_args = NULL;
      prep_args = NULL;
      regop_args = NULL;
      ZERO_LSN(ckp_lsn);
      ZERO_LSN(lsn);

      if ((ret = __log_cursor(dbenv, &logc)) != 0)
            return (ret);

      /*
       * We need to consider the set of records between the most recent
       * checkpoint LSN and the end of the log;  any txn in that
       * range, and only txns in that range, could still have been
       * active, and thus prepared but not yet committed (PBNYC),
       * when the old master died.
       *
       * Find the most recent checkpoint LSN, and get the record there.
       * If there is no checkpoint in the log, start off by getting
       * the very first record in the log instead.
       */
      memset(&rec, 0, sizeof(DBT));
      if ((ret = __txn_getckp(dbenv, &lsn)) == 0) {
            if ((ret = __log_c_get(logc, &lsn, &rec, DB_SET)) != 0)  {
                  __db_err(dbenv,
                      "Checkpoint record at LSN [%lu][%lu] not found",
                      (u_long)lsn.file, (u_long)lsn.offset);
                  goto err;
            }

            if ((ret = __txn_ckp_read(dbenv, rec.data, &ckp_args)) != 0) {
                  __db_err(dbenv,
                      "Invalid checkpoint record at [%lu][%lu]",
                      (u_long)lsn.file, (u_long)lsn.offset);
                  goto err;
            }

            ckp_lsn = ckp_args->ckp_lsn;
            __os_free(dbenv, ckp_args);

            if ((ret = __log_c_get(logc, &ckp_lsn, &rec, DB_SET)) != 0) {
                  __db_err(dbenv,
                      "Checkpoint LSN record [%lu][%lu] not found",
                      (u_long)ckp_lsn.file, (u_long)ckp_lsn.offset);
                  goto err;
            }
      } else if ((ret = __log_c_get(logc, &lsn, &rec, DB_FIRST)) != 0) {
            if (ret == DB_NOTFOUND) {
                  /* An empty log means no PBNYC txns. */
                  ret = 0;
                  goto done;
            }
            __db_err(dbenv, "Attempt to get first log record failed");
            goto err;
      }

      /*
       * We use the same txnlist infrastructure that recovery does;
       * it demands an estimate of the high and low txnids for
       * initialization.
       *
       * First, the low txnid.
       */
      do {
            /* txnid is after rectype, which is a u_int32. */
            memcpy(&low_txn,
                (u_int8_t *)rec.data + sizeof(u_int32_t), sizeof(low_txn));
            if (low_txn != 0)
                  break;
      } while ((ret = __log_c_get(logc, &lsn, &rec, DB_NEXT)) == 0);

      /* If there are no txns, there are no PBNYC txns. */
      if (ret == DB_NOTFOUND) {
            ret = 0;
            goto done;
      } else if (ret != 0)
            goto err;

      /* Now, the high txnid. */
      if ((ret = __log_c_get(logc, &lsn, &rec, DB_LAST)) != 0) {
            /*
             * Note that DB_NOTFOUND is unacceptable here because we
             * had to have looked at some log record to get this far.
             */
            __db_err(dbenv, "Final log record not found");
            goto err;
      }
      do {
            /* txnid is after rectype, which is a u_int32. */
            memcpy(&hi_txn,
                (u_int8_t *)rec.data + sizeof(u_int32_t), sizeof(hi_txn));
            if (hi_txn != 0)
                  break;
      } while ((ret = __log_c_get(logc, &lsn, &rec, DB_PREV)) == 0);
      if (ret == DB_NOTFOUND) {
            ret = 0;
            goto done;
      } else if (ret != 0)
            goto err;

      /* We have a high and low txnid.  Initialise the txn list. */
      if ((ret =
          __db_txnlist_init(dbenv, low_txn, hi_txn, NULL, &txninfo)) != 0)
            goto err;

      /*
       * Now, walk backward from the end of the log to ckp_lsn.  Any
       * prepares that we hit without first hitting a commit or
       * abort belong to PBNYC txns, and we need to apply them and
       * restore them to a prepared state.
       *
       * Note that we wind up applying transactions out of order.
       * Since all PBNYC txns still held locks on the old master and
       * were isolated, this should be safe.
       */
      for (ret = __log_c_get(logc, &lsn, &rec, DB_LAST);
          ret == 0 && log_compare(&lsn, &ckp_lsn) > 0;
          ret = __log_c_get(logc, &lsn, &rec, DB_PREV)) {
            memcpy(&rectype, rec.data, sizeof(rectype));
            switch (rectype) {
            case DB___txn_regop:
                  /*
                   * It's a commit or abort--but we don't care
                   * which!  Just add it to the list of txns
                   * that are resolved.
                   */
                  if ((ret = __txn_regop_read(dbenv, rec.data,
                      &regop_args)) != 0)
                        goto err;

                  ret = __db_txnlist_find(dbenv,
                      txninfo, regop_args->txnid->txnid, &status);
                  if (ret == DB_NOTFOUND)
                        ret = __db_txnlist_add(dbenv, txninfo,
                            regop_args->txnid->txnid,
                            regop_args->opcode, &lsn);
                  else if (ret != 0)
                        goto err;
                  __os_free(dbenv, regop_args);
                  break;
            case DB___txn_xa_regop:
                  /*
                   * It's a prepare.  If its not aborted and
                   * we haven't put the txn on our list yet, it
                   * hasn't been resolved, so apply and restore it.
                   */
                  if ((ret = __txn_xa_regop_read(dbenv, rec.data,
                      &prep_args)) != 0)
                        goto err;
                  ret = __db_txnlist_find(dbenv, txninfo,
                      prep_args->txnid->txnid, &status);
                  if (ret == DB_NOTFOUND) {
                        if (prep_args->opcode == TXN_ABORT)
                              ret = __db_txnlist_add(dbenv, txninfo,
                                  prep_args->txnid->txnid,
                                  prep_args->opcode, &lsn);
                        else if ((ret =
                            __rep_process_txn(dbenv, &rec)) == 0)
                              ret = __txn_restore_txn(dbenv,
                                  &lsn, prep_args);
                  } else if (ret != 0)
                        goto err;
                  __os_free(dbenv, prep_args);
                  break;
            default:
                  continue;
            }
      }

      /* It's not an error to have hit the beginning of the log. */
      if (ret == DB_NOTFOUND)
            ret = 0;

done:
err:  t_ret = __log_c_close(logc);

      if (txninfo != NULL)
            __db_txnlist_end(dbenv, txninfo);

      return (ret == 0 ? t_ret : ret);
}

/*
 * PUBLIC: int __rep_get_limit __P((DB_ENV *, u_int32_t *, u_int32_t *));
 */
int
__rep_get_limit(dbenv, gbytesp, bytesp)
      DB_ENV *dbenv;
      u_int32_t *gbytesp, *bytesp;
{
      DB_REP *db_rep;
      REP *rep;

      PANIC_CHECK(dbenv);
      ENV_REQUIRES_CONFIG(dbenv, dbenv->rep_handle, "rep_get_limit",
          DB_INIT_REP);

      if (!REP_ON(dbenv)) {
            __db_err(dbenv,
    "DB_ENV->get_rep_limit: database environment not properly initialized");
            return (__db_panic(dbenv, EINVAL));
      }
      db_rep = dbenv->rep_handle;
      rep = db_rep->region;

      if (gbytesp != NULL)
            *gbytesp = rep->gbytes;
      if (bytesp != NULL)
            *bytesp = rep->bytes;

      return (0);
}

/*
 * __rep_set_limit --
 *    Set a limit on the amount of data that will be sent during a single
 * invocation of __rep_process_message.
 *
 * PUBLIC: int __rep_set_limit __P((DB_ENV *, u_int32_t, u_int32_t));
 */
int
__rep_set_limit(dbenv, gbytes, bytes)
      DB_ENV *dbenv;
      u_int32_t gbytes, bytes;
{
      DB_REP *db_rep;
      REP *rep;

      PANIC_CHECK(dbenv);
      ENV_ILLEGAL_BEFORE_OPEN(dbenv, "DB_ENV->rep_set_limit");
      ENV_REQUIRES_CONFIG(dbenv, dbenv->rep_handle, "rep_set_limit",
          DB_INIT_REP);

      if (!REP_ON(dbenv)) {
            __db_err(dbenv,
    "DB_ENV->set_rep_limit: database environment not properly initialized");
            return (__db_panic(dbenv, EINVAL));
      }
      db_rep = dbenv->rep_handle;
      rep = db_rep->region;
      REP_SYSTEM_LOCK(dbenv);
      if (bytes > GIGABYTE) {
            gbytes += bytes / GIGABYTE;
            bytes = bytes % GIGABYTE;
      }
      rep->gbytes = gbytes;
      rep->bytes = bytes;
      REP_SYSTEM_UNLOCK(dbenv);

      return (0);
}

/*
 * __rep_set_request --
 *    Set the minimum and maximum number of log records that we wait
 *    before retransmitting.
 *
 * !!!
 * UNDOCUMENTED.
 *
 * PUBLIC: int __rep_set_request __P((DB_ENV *, u_int32_t, u_int32_t));
 */
int
__rep_set_request(dbenv, min, max)
      DB_ENV *dbenv;
      u_int32_t min, max;
{
      LOG *lp;
      DB_LOG *dblp;
      DB_REP *db_rep;
      REP *rep;

      PANIC_CHECK(dbenv);
      ENV_ILLEGAL_BEFORE_OPEN(dbenv, "DB_ENV->rep_set_request");
      ENV_REQUIRES_CONFIG(dbenv, dbenv->rep_handle, "rep_set_request",
          DB_INIT_REP);

      if (!REP_ON(dbenv)) {
            __db_err(dbenv,
    "DB_ENV->set_rep_request: database environment not properly initialized");
            return (__db_panic(dbenv, EINVAL));
      }
      db_rep = dbenv->rep_handle;
      rep = db_rep->region;

      /*
       * We acquire the mtx_region or mtx_clientdb mutexes as needed.
       */
      REP_SYSTEM_LOCK(dbenv);
      rep->request_gap = min;
      rep->max_gap = max;
      REP_SYSTEM_UNLOCK(dbenv);

      MUTEX_LOCK(dbenv, rep->mtx_clientdb);
      dblp = dbenv->lg_handle;
      if (dblp != NULL && (lp = dblp->reginfo.primary) != NULL) {
            lp->wait_recs = 0;
            lp->rcvd_recs = 0;
      }
      MUTEX_UNLOCK(dbenv, rep->mtx_clientdb);

      return (0);
}

/*
 * __rep_set_transport --
 *    Set the transport function for replication.
 *
 * PUBLIC: int __rep_set_rep_transport __P((DB_ENV *, int,
 * PUBLIC:     int (*)(DB_ENV *, const DBT *, const DBT *, const DB_LSN *,
 * PUBLIC:     int, u_int32_t)));
 */
int
__rep_set_rep_transport(dbenv, eid, f_send)
      DB_ENV *dbenv;
      int eid;
      int (*f_send) __P((DB_ENV *, const DBT *, const DBT *, const DB_LSN *,
          int, u_int32_t));
{
      PANIC_CHECK(dbenv);

      if (f_send == NULL) {
            __db_err(dbenv,
      "DB_ENV->set_rep_transport: no send function specified");
            return (EINVAL);
      }
      if (eid < 0) {
            __db_err(dbenv,
      "DB_ENV->set_rep_transport: eid must be greater than or equal to 0");
            return (EINVAL);
      }
      dbenv->rep_send = f_send;
      dbenv->rep_eid = eid;
      return (0);
}

/*
 * __rep_flush --
 *    Re-push the last log record to all clients, in case they've lost
 *    messages and don't know it.
 *
 * PUBLIC: int __rep_flush __P((DB_ENV *));
 */
int
__rep_flush(dbenv)
      DB_ENV *dbenv;
{
      DBT rec;
      DB_LOGC *logc;
      DB_LSN lsn;
      int ret, t_ret;

      PANIC_CHECK(dbenv);
      ENV_REQUIRES_CONFIG(dbenv, dbenv->rep_handle, "rep_flush", DB_INIT_REP);

      if ((ret = __log_cursor(dbenv, &logc)) != 0)
            return (ret);

      memset(&rec, 0, sizeof(rec));
      memset(&lsn, 0, sizeof(lsn));

      if ((ret = __log_c_get(logc, &lsn, &rec, DB_LAST)) != 0)
            goto err;

      (void)__rep_send_message(dbenv,
          DB_EID_BROADCAST, REP_LOG, &lsn, &rec, 0, 0);

err:  if ((t_ret = __log_c_close(logc)) != 0 && ret == 0)
            ret = t_ret;
      return (ret);
}

/*
 * __rep_sync --
 *    Force a synchronization to occur between this client and the master.
 *    This is the other half of configuring DELAYCLIENT.
 *
 * PUBLIC: int __rep_sync __P((DB_ENV *, u_int32_t));
 */
int
__rep_sync(dbenv, flags)
      DB_ENV *dbenv;
      u_int32_t flags;
{
      DB_LOG *dblp;
      DB_LSN lsn;
      DB_REP *db_rep;
      LOG *lp;
      REP *rep;
      int master;
      u_int32_t type;

      COMPQUIET(flags, 0);
      PANIC_CHECK(dbenv);
      ENV_REQUIRES_CONFIG(dbenv, dbenv->rep_handle,
          "rep_sync", DB_INIT_REP);

      dblp = dbenv->lg_handle;
      lp = dblp->reginfo.primary;
      db_rep = dbenv->rep_handle;
      rep = db_rep->region;

      /*
       * Simple cases.  If we're not in the DELAY state we have nothing
       * to do.  If we don't know who the master is, send a MASTER_REQ.
       */
      MUTEX_LOCK(dbenv, rep->mtx_clientdb);
      lsn = lp->verify_lsn;
      MUTEX_UNLOCK(dbenv, rep->mtx_clientdb);
      REP_SYSTEM_LOCK(dbenv);
      master = rep->master_id;
      if (master == DB_EID_INVALID) {
            REP_SYSTEM_UNLOCK(dbenv);
            (void)__rep_send_message(dbenv, DB_EID_BROADCAST,
                REP_MASTER_REQ, NULL, NULL, 0, 0);
            return (0);
      }
      /*
       * We want to hold the rep mutex to test and then clear the
       * DELAY flag.  Racing threads in here could otherwise result
       * in dual data streams.
       */
      if (!F_ISSET(rep, REP_F_DELAY)) {
            REP_SYSTEM_UNLOCK(dbenv);
            return (0);
      }

      /*
       * If we get here, we clear the delay flag and kick off a
       * synchronization.  From this point forward, we will
       * synchronize until the next time the master changes.
       */
      F_CLR(rep, REP_F_DELAY);
      REP_SYSTEM_UNLOCK(dbenv);
      /*
       * When we set REP_F_DELAY, we set verify_lsn to the real verify
       * lsn if we need to verify, or we zeroed it out if this is a client
       * that needs to sync up from the beginning.  So, send the type
       * of message now that __rep_new_master delayed sending.
       */
      if (IS_ZERO_LSN(lsn))
            type = REP_ALL_REQ;
      else
            type = REP_VERIFY_REQ;
      (void)__rep_send_message(dbenv, master, type, &lsn, NULL, 0,
          DB_REP_ANYWHERE);
      return (0);
}

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