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rep_record.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2001-2005
 *    Sleepycat Software.  All rights reserved.
 *
 * $Id: rep_record.c,v 12.25 2005/10/20 18:57:13 bostic Exp $
 */

#include "db_config.h"

#ifndef NO_SYSTEM_INCLUDES
#if TIME_WITH_SYS_TIME
#include <sys/time.h>
#include <time.h>
#else
#if HAVE_SYS_TIME_H
#include <sys/time.h>
#else
#include <time.h>
#endif
#endif

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

#include "db_int.h"
#include "dbinc/db_page.h"
#include "dbinc/db_shash.h"
#include "dbinc/db_am.h"
#include "dbinc/lock.h"
#include "dbinc/log.h"
#include "dbinc/mp.h"
#include "dbinc/txn.h"

static int __rep_collect_txn __P((DB_ENV *, DB_LSN *, LSN_COLLECTION *));
static int __rep_do_ckp __P((DB_ENV *, DBT *, REP_CONTROL *));
static int __rep_getnext __P((DB_ENV *));
static int __rep_lsn_cmp __P((const void *, const void *));
static int __rep_newfile __P((DB_ENV *, REP_CONTROL *, DB_LSN *));
static int __rep_process_rec __P((DB_ENV *,
    REP_CONTROL *, DBT *, u_int32_t *, DB_LSN *));
static int __rep_remfirst __P((DB_ENV *, DBT *, DBT *));
static int __rep_resend_req __P((DB_ENV *, int));
static int __rep_skip_msg __P((DB_ENV *, REP *, int, u_int32_t));

/* Used to consistently designate which messages ought to be received where. */

#define     MASTER_ONLY(rep, rp) do {                             \
      if (!F_ISSET(rep, REP_F_MASTER)) {                    \
            RPRINT(dbenv, rep,                              \
            (dbenv, &mb, "Master record received on client"));    \
            REP_PRINT_MESSAGE(dbenv,                        \
                *eidp, rp, "rep_process_message");                \
            ret = EINVAL;                                   \
            goto errlock;                                   \
      }                                               \
} while (0)

#define     CLIENT_ONLY(rep, rp) do {                             \
      if (!F_ISSET(rep, REP_F_CLIENT)) {                    \
            RPRINT(dbenv, rep,                              \
                (dbenv, &mb, "Client record received on master"));      \
            REP_PRINT_MESSAGE(dbenv,                        \
                *eidp, rp, "rep_process_message");                \
            (void)__rep_send_message(dbenv,                       \
                DB_EID_BROADCAST, REP_DUPMASTER, NULL, NULL, 0, 0);     \
            ret = DB_REP_DUPMASTER;                         \
            goto errlock;                                   \
      }                                               \
} while (0)

/*
 * If a client is attempting to service a request it does not have,
 * call rep_skip_msg to skip this message and force a rerequest to the
 * sender.  We don't hold the mutex for the stats and may miscount.
 */
#define     CLIENT_REREQ do {                               \
      if (F_ISSET(rep, REP_F_CLIENT)) {                     \
            rep->stat.st_client_svc_req++;                        \
            if (ret == DB_NOTFOUND) {                       \
                  rep->stat.st_client_svc_miss++;                 \
                  ret = __rep_skip_msg(dbenv, rep, *eidp, rp->rectype);\
            }                                         \
      }                                               \
} while (0)

#define     MASTER_UPDATE(dbenv, renv) do {                             \
      REP_SYSTEM_LOCK(dbenv);                               \
      F_SET((renv), DB_REGENV_REPLOCKED);                   \
      (void)time(&(renv)->op_timestamp);                    \
      REP_SYSTEM_UNLOCK(dbenv);                             \
} while (0)

#define     RECOVERING_SKIP do {                                  \
      if (recovering) {                               \
            /* Not holding region mutex, may miscount */          \
            rep->stat.st_msgs_recover++;                    \
            ret = __rep_skip_msg(dbenv, rep, *eidp, rp->rectype); \
            goto errlock;                                   \
      }                                               \
} while (0)

/*
 * If we're recovering the log we only want log records that are in the
 * range we need to recover.  Otherwise we can end up storing a huge
 * number of "new" records, only to truncate the temp database later after
 * we run recovery.  If we are actively delaying a sync-up, we also skip
 * all incoming log records until the application requests sync-up.
 */
#define     RECOVERING_LOG_SKIP do {                              \
      if (F_ISSET(rep, REP_F_DELAY) ||                      \
          (recovering &&                                    \
          (!F_ISSET(rep, REP_F_RECOVER_LOG) ||              \
           log_compare(&rp->lsn, &rep->last_lsn) > 0))) {         \
            /* Not holding region mutex, may miscount */          \
            rep->stat.st_msgs_recover++;                    \
            ret = __rep_skip_msg(dbenv, rep, *eidp, rp->rectype); \
            goto errlock;                                   \
      }                                               \
} while (0)

#define     ANYSITE(rep)

/*
 * __rep_process_message --
 *
 * This routine takes an incoming message and processes it.
 *
 * control: contains the control fields from the record
 * rec: contains the actual record
 * eidp: contains the machine id of the sender of the message;
 *    in the case of a DB_NEWMASTER message, returns the eid
 *    of the new master.
 * ret_lsnp: On DB_REP_ISPERM and DB_REP_NOTPERM returns, contains the
 *    lsn of the maximum permanent or current not permanent log record
 *    (respectively).
 *
 * PUBLIC: int __rep_process_message __P((DB_ENV *, DBT *, DBT *, int *,
 * PUBLIC:     DB_LSN *));
 */
int
__rep_process_message(dbenv, control, rec, eidp, ret_lsnp)
      DB_ENV *dbenv;
      DBT *control, *rec;
      int *eidp;
      DB_LSN *ret_lsnp;
{
      DB_LOG *dblp;
      DB_LSN lsn;
      DB_REP *db_rep;
      DBT data_dbt;
      LOG *lp;
      REGENV *renv;
      REGINFO *infop;
      REP *rep;
      REP_CONTROL *rp;
      u_int32_t egen, gen;
      int cmp, recovering, ret;
      time_t savetime;
#ifdef DIAGNOSTIC
      DB_MSGBUF mb;
#endif

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

      /* Control argument must be non-Null. */
      if (control == NULL || control->size == 0) {
            __db_err(dbenv,
      "DB_ENV->rep_process_message: control argument must be specified");
            return (EINVAL);
      }

      if (!IS_REP_MASTER(dbenv) && !IS_REP_CLIENT(dbenv)) {
            __db_err(dbenv,
      "Environment not configured as replication master or client");
            return (EINVAL);
      }

      ret = 0;
      db_rep = dbenv->rep_handle;
      rep = db_rep->region;
      dblp = dbenv->lg_handle;
      lp = dblp->reginfo.primary;
      infop = dbenv->reginfo;
      renv = infop->primary;
      rp = (REP_CONTROL *)control->data;
      if (ret_lsnp != NULL)
            ZERO_LSN(*ret_lsnp);

      /*
       * Acquire the replication lock.
       */
      REP_SYSTEM_LOCK(dbenv);
      if (rep->start_th != 0) {
            /*
             * If we're racing with a thread in rep_start, then
             * just ignore the message and return.
             */
            RPRINT(dbenv, rep, (dbenv, &mb,
                "Racing rep_start, ignore message."));
            if (F_ISSET(rp, DB_LOG_PERM))
                  ret = DB_REP_IGNORE;
            REP_SYSTEM_UNLOCK(dbenv);
            goto out;
      }
      rep->msg_th++;
      gen = rep->gen;
      recovering = rep->in_recovery || F_ISSET(rep, REP_F_RECOVER_MASK);
      savetime = renv->rep_timestamp;

      rep->stat.st_msgs_processed++;
      REP_SYSTEM_UNLOCK(dbenv);

      REP_PRINT_MESSAGE(dbenv, *eidp, rp, "rep_process_message");

      /* Complain if we see an improper version number. */
      if (rp->rep_version != DB_REPVERSION) {
            __db_err(dbenv,
                "unexpected replication message version %lu, expected %d",
                (u_long)rp->rep_version, DB_REPVERSION);
            ret = EINVAL;
            goto errlock;
      }
      if (rp->log_version != DB_LOGVERSION) {
            __db_err(dbenv,
                "unexpected log record version %lu, expected %d",
                (u_long)rp->log_version, DB_LOGVERSION);
            ret = EINVAL;
            goto errlock;
      }

      /*
       * Check for generation number matching.  Ignore any old messages
       * except requests that are indicative of a new client that needs
       * to get in sync.
       */
      if (rp->gen < gen && rp->rectype != REP_ALIVE_REQ &&
          rp->rectype != REP_NEWCLIENT && rp->rectype != REP_MASTER_REQ &&
          rp->rectype != REP_DUPMASTER) {
            /*
             * We don't hold the rep mutex, and could miscount if we race.
             */
            rep->stat.st_msgs_badgen++;
            if (F_ISSET(rp, DB_LOG_PERM))
                  ret = DB_REP_IGNORE;
            goto errlock;
      }

      if (rp->gen > gen) {
            /*
             * If I am a master and am out of date with a lower generation
             * number, I am in bad shape and should downgrade.
             */
            if (F_ISSET(rep, REP_F_MASTER)) {
                  rep->stat.st_dupmasters++;
                  ret = DB_REP_DUPMASTER;
                  if (rp->rectype != REP_DUPMASTER)
                        (void)__rep_send_message(dbenv,
                            DB_EID_BROADCAST, REP_DUPMASTER,
                            NULL, NULL, 0, 0);
                  goto errlock;
            }

            /*
             * I am a client and am out of date.  If this is an election,
             * or a response from the first site I contacted, then I can
             * accept the generation number and participate in future
             * elections and communication. Otherwise, I need to hear about
             * a new master and sync up.
             */
            if (rp->rectype == REP_ALIVE ||
                rp->rectype == REP_VOTE1 || rp->rectype == REP_VOTE2) {
                  REP_SYSTEM_LOCK(dbenv);
                  RPRINT(dbenv, rep, (dbenv, &mb,
                      "Updating gen from %lu to %lu",
                      (u_long)gen, (u_long)rp->gen));
                  rep->master_id = DB_EID_INVALID;
                  gen = rep->gen = rp->gen;
                  /*
                   * Updating of egen will happen when we process the
                   * message below for each message type.
                   */
                  REP_SYSTEM_UNLOCK(dbenv);
                  if (rp->rectype == REP_ALIVE)
                        (void)__rep_send_message(dbenv,
                            DB_EID_BROADCAST, REP_MASTER_REQ, NULL,
                            NULL, 0, 0);
            } else if (rp->rectype != REP_NEWMASTER) {
                  /*
                   * Ignore this message, retransmit if needed.
                   */
                  if (__rep_check_doreq(dbenv, rep))
                        (void)__rep_send_message(dbenv,
                            DB_EID_BROADCAST, REP_MASTER_REQ,
                            NULL, NULL, 0, 0);
                  goto errlock;
            }
            /*
             * If you get here, then you're a client and either you're
             * in an election or you have a NEWMASTER or an ALIVE message
             * whose processing will do the right thing below.
             */
      }

      /*
       * We need to check if we're in recovery and if we are
       * then we need to ignore any messages except VERIFY*, VOTE*,
       * NEW* and ALIVE_REQ, or backup related messages: UPDATE*,
       * PAGE* and FILE*.  We need to also accept LOG messages
       * if we're copying the log for recovery/backup.
       */
      switch (rp->rectype) {
      case REP_ALIVE:
            /*
             * Handle even if we're recovering.
             */
            ANYSITE(rep);
            egen = *(u_int32_t *)rec->data;
            REP_SYSTEM_LOCK(dbenv);
            RPRINT(dbenv, rep, (dbenv, &mb,
                "Received ALIVE egen of %lu, mine %lu",
                (u_long)egen, (u_long)rep->egen));
            if (egen > rep->egen) {
                  /*
                   * We're changing egen, need to clear out any old
                   * election information.
                   */
                  __rep_elect_done(dbenv, rep);
                  rep->egen = egen;
            }
            REP_SYSTEM_UNLOCK(dbenv);
            break;
      case REP_ALIVE_REQ:
            /*
             * Handle even if we're recovering.
             */
            ANYSITE(rep);
            dblp = dbenv->lg_handle;
            LOG_SYSTEM_LOCK(dbenv);
            lsn = ((LOG *)dblp->reginfo.primary)->lsn;
            LOG_SYSTEM_UNLOCK(dbenv);
            REP_SYSTEM_LOCK(dbenv);
            egen = rep->egen;
            REP_SYSTEM_UNLOCK(dbenv);
            data_dbt.data = &egen;
            data_dbt.size = sizeof(egen);
            (void)__rep_send_message(dbenv,
                *eidp, REP_ALIVE, &lsn, &data_dbt, 0, 0);
            break;
      case REP_ALL_REQ:
            RECOVERING_SKIP;
            ret = __rep_allreq(dbenv, rp, *eidp);
            CLIENT_REREQ;
            break;
      case REP_BULK_LOG:
            RECOVERING_LOG_SKIP;
            CLIENT_ONLY(rep, rp);
            ret = __rep_bulk_log(dbenv, rp, rec, savetime, ret_lsnp);
            break;
      case REP_BULK_PAGE:
            /*
             * Handle even if we're recovering.
             */
            CLIENT_ONLY(rep, rp);
            ret = __rep_bulk_page(dbenv, *eidp, rp, rec);
            break;
      case REP_DUPMASTER:
            /*
             * Handle even if we're recovering.
             */
            if (F_ISSET(rep, REP_F_MASTER))
                  ret = DB_REP_DUPMASTER;
            break;
#ifdef NOTYET
      case REP_FILE: /* TODO */
            CLIENT_ONLY(rep, rp);
            break;
      case REP_FILE_REQ:
            ret = __rep_send_file(dbenv, rec, *eidp);
            break;
#endif
      case REP_FILE_FAIL:
            /*
             * Handle even if we're recovering.
             */
            CLIENT_ONLY(rep, rp);
            /*
             * XXX
             */
            break;
      case REP_LOG:
      case REP_LOG_MORE:
            RECOVERING_LOG_SKIP;
            CLIENT_ONLY(rep, rp);
            ret = __rep_log(dbenv, rp, rec, savetime, ret_lsnp);
            break;
      case REP_LOG_REQ:
            RECOVERING_SKIP;
            ret = __rep_logreq(dbenv, rp, rec, *eidp);
            CLIENT_REREQ;
            break;
      case REP_NEWSITE:
            /*
             * Handle even if we're recovering.
             */
            /* We don't hold the rep mutex, and may miscount. */
            rep->stat.st_newsites++;

            /* This is a rebroadcast; simply tell the application. */
            if (F_ISSET(rep, REP_F_MASTER)) {
                  dblp = dbenv->lg_handle;
                  lp = dblp->reginfo.primary;
                  LOG_SYSTEM_LOCK(dbenv);
                  lsn = lp->lsn;
                  LOG_SYSTEM_UNLOCK(dbenv);
                  (void)__rep_send_message(dbenv,
                      *eidp, REP_NEWMASTER, &lsn, NULL, 0, 0);
            }
            ret = DB_REP_NEWSITE;
            break;
      case REP_NEWCLIENT:
            /*
             * Handle even if we're recovering.
             */
            /*
             * This message was received and should have resulted in the
             * application entering the machine ID in its machine table.
             * We respond to this with an ALIVE to send relevant information
             * to the new client (if we are a master, we'll send a
             * NEWMASTER, so we only need to send the ALIVE if we're a
             * client).  But first, broadcast the new client's record to
             * all the clients.
             */
            (void)__rep_send_message(dbenv,
                DB_EID_BROADCAST, REP_NEWSITE, &rp->lsn, rec, 0, 0);

            ret = DB_REP_NEWSITE;

            if (F_ISSET(rep, REP_F_CLIENT)) {
                  REP_SYSTEM_LOCK(dbenv);
                  egen = rep->egen;
                  if (*eidp == rep->master_id)
                        rep->master_id = DB_EID_INVALID;
                  REP_SYSTEM_UNLOCK(dbenv);
                  data_dbt.data = &egen;
                  data_dbt.size = sizeof(egen);
                  (void)__rep_send_message(dbenv, DB_EID_BROADCAST,
                      REP_ALIVE, &rp->lsn, &data_dbt, 0, 0);
                  break;
            }
            /* FALLTHROUGH */
      case REP_MASTER_REQ:
            RECOVERING_SKIP;
            if (F_ISSET(rep, REP_F_MASTER)) {
                  LOG_SYSTEM_LOCK(dbenv);
                  lsn = lp->lsn;
                  LOG_SYSTEM_UNLOCK(dbenv);
                  (void)__rep_send_message(dbenv,
                      DB_EID_BROADCAST, REP_NEWMASTER, &lsn, NULL, 0, 0);
            }
            /*
             * If there is no master, then we could get into a state
             * where an old client lost the initial ALIVE message and
             * is calling an election under an old gen and can
             * never get to the current gen.
             */
            if (F_ISSET(rep, REP_F_CLIENT) && rp->gen < gen) {
                  REP_SYSTEM_LOCK(dbenv);
                  egen = rep->egen;
                  if (*eidp == rep->master_id)
                        rep->master_id = DB_EID_INVALID;
                  REP_SYSTEM_UNLOCK(dbenv);
                  data_dbt.data = &egen;
                  data_dbt.size = sizeof(egen);
                  (void)__rep_send_message(dbenv, *eidp,
                      REP_ALIVE, &rp->lsn, &data_dbt, 0, 0);
            }
            break;
      case REP_NEWFILE:
            RECOVERING_LOG_SKIP;
            CLIENT_ONLY(rep, rp);
            ret = __rep_apply(dbenv, rp, rec, ret_lsnp, NULL);
            break;
      case REP_NEWMASTER:
            /*
             * Handle even if we're recovering.
             */
            ANYSITE(rep);
            if (F_ISSET(rep, REP_F_MASTER) &&
                *eidp != dbenv->rep_eid) {
                  /* We don't hold the rep mutex, and may miscount. */
                  rep->stat.st_dupmasters++;
                  ret = DB_REP_DUPMASTER;
                  (void)__rep_send_message(dbenv,
                      DB_EID_BROADCAST, REP_DUPMASTER, NULL, NULL, 0, 0);
                  break;
            }
            ret = __rep_new_master(dbenv, rp, *eidp);
            break;
      case REP_PAGE:
      case REP_PAGE_MORE:
            /*
             * Handle even if we're recovering.
             */
            CLIENT_ONLY(rep, rp);
            ret = __rep_page(dbenv, *eidp, rp, rec);
            break;
      case REP_PAGE_FAIL:
            /*
             * Handle even if we're recovering.
             */
            CLIENT_ONLY(rep, rp);
            ret = __rep_page_fail(dbenv, *eidp, rec);
            break;
      case REP_PAGE_REQ:
            /*
             * Handle even if we're recovering.
             */
            MASTER_UPDATE(dbenv, renv);
            ret = __rep_page_req(dbenv, *eidp, rec);
            CLIENT_REREQ;
            break;
      case REP_REREQUEST:
            /*
             * Handle even if we're recovering.  Don't do a master
             * check.
             */
            CLIENT_ONLY(rep, rp);
            /*
             * Don't hold any mutex, may miscount.
             */
            rep->stat.st_client_rerequests++;
            ret = __rep_resend_req(dbenv, 1);
            break;
      case REP_UPDATE:
            /*
             * Handle even if we're recovering.
             */
            CLIENT_ONLY(rep, rp);
            ret = __rep_update_setup(dbenv, *eidp, rp, rec);
            break;
      case REP_UPDATE_REQ:
            /*
             * Handle even if we're recovering.
             */
            MASTER_ONLY(rep, rp);
            infop = dbenv->reginfo;
            renv = infop->primary;
            MASTER_UPDATE(dbenv, renv);
            ret = __rep_update_req(dbenv, *eidp);
            break;
      case REP_VERIFY:
            if (recovering) {
                  MUTEX_LOCK(dbenv, rep->mtx_clientdb);
                  cmp = log_compare(&lp->verify_lsn, &rp->lsn);
                  MUTEX_UNLOCK(dbenv, rep->mtx_clientdb);
                  /*
                   * If this is not the verify record I want, skip it.
                   */
                  if (cmp != 0) {
                        ret = __rep_skip_msg(
                            dbenv, rep, *eidp, rp->rectype);
                        break;
                  }
            }
            CLIENT_ONLY(rep, rp);
            ret = __rep_verify(dbenv, rp, rec, *eidp, savetime);
            break;
      case REP_VERIFY_FAIL:
            /*
             * Handle even if we're recovering.
             */
            CLIENT_ONLY(rep, rp);
            ret = __rep_verify_fail(dbenv, rp, *eidp);
            break;
      case REP_VERIFY_REQ:
            RECOVERING_SKIP;
            ret = __rep_verify_req(dbenv, rp, *eidp);
            CLIENT_REREQ;
            break;
      case REP_VOTE1:
            /*
             * Handle even if we're recovering.
             */
            ret = __rep_vote1(dbenv, rp, rec, *eidp);
            break;
      case REP_VOTE2:
            /*
             * Handle even if we're recovering.
             */
            ret = __rep_vote2(dbenv, rec, eidp);
            break;
      default:
            __db_err(dbenv,
      "DB_ENV->rep_process_message: unknown replication message: type %lu",
               (u_long)rp->rectype);
            ret = EINVAL;
            break;
      }

errlock:
      REP_SYSTEM_LOCK(dbenv);
      rep->msg_th--;
      REP_SYSTEM_UNLOCK(dbenv);
out:
      if (ret == 0 && F_ISSET(rp, DB_LOG_PERM)) {
            if (ret_lsnp != NULL)
                  *ret_lsnp = rp->lsn;
            ret = DB_REP_NOTPERM;
      }
      return (ret);
}

/*
 * __rep_apply --
 *
 * Handle incoming log records on a client, applying when possible and
 * entering into the bookkeeping table otherwise.  This routine manages
 * the state of the incoming message stream -- processing records, via
 * __rep_process_rec, when possible and enqueuing in the __db.rep.db
 * when necessary.  As gaps in the stream are filled in, this is where
 * we try to process as much as possible from __db.rep.db to catch up.
 *
 * PUBLIC: int __rep_apply __P((DB_ENV *, REP_CONTROL *,
 * PUBLIC:     DBT *, DB_LSN *, int *));
 */
int
__rep_apply(dbenv, rp, rec, ret_lsnp, is_dupp)
      DB_ENV *dbenv;
      REP_CONTROL *rp;
      DBT *rec;
      DB_LSN *ret_lsnp;
      int *is_dupp;
{
      DB_REP *db_rep;
      DBT control_dbt, key_dbt;
      DBT rec_dbt;
      DB *dbp;
      DB_LOG *dblp;
      DB_LSN max_lsn;
      LOG *lp;
      REP *rep;
      u_int32_t rectype;
      int cmp, ret;
#ifdef DIAGNOSTIC
      DB_MSGBUF mb;
#endif

      db_rep = dbenv->rep_handle;
      rep = db_rep->region;
      dbp = db_rep->rep_db;
      rectype = 0;
      ret = 0;
      memset(&control_dbt, 0, sizeof(control_dbt));
      memset(&rec_dbt, 0, sizeof(rec_dbt));
      ZERO_LSN(max_lsn);

      dblp = dbenv->lg_handle;
      MUTEX_LOCK(dbenv, rep->mtx_clientdb);
      lp = dblp->reginfo.primary;
      REP_SYSTEM_LOCK(dbenv);
      if (F_ISSET(rep, REP_F_RECOVER_LOG) &&
          log_compare(&lp->ready_lsn, &rep->first_lsn) < 0)
            lp->ready_lsn = rep->first_lsn;
      REP_SYSTEM_UNLOCK(dbenv);
      cmp = log_compare(&rp->lsn, &lp->ready_lsn);

      if (cmp == 0) {
            if ((ret =
                __rep_process_rec(dbenv, rp, rec, &rectype, &max_lsn)) != 0)
                  goto err;
            /*
             * If we get the record we are expecting, reset
             * the count of records we've received and are applying
             * towards the request interval.
             */
            lp->rcvd_recs = 0;
            ZERO_LSN(lp->max_wait_lsn);

            while (ret == 0 &&
                log_compare(&lp->ready_lsn, &lp->waiting_lsn) == 0) {
                  /*
                   * We just filled in a gap in the log record stream.
                   * Write subsequent records to the log.
                   */
gap_check:
                  if ((ret =
                      __rep_remfirst(dbenv, &control_dbt, &rec_dbt)) != 0)
                        goto err;

                  rp = (REP_CONTROL *)control_dbt.data;
                  rec = &rec_dbt;
                  if ((ret = __rep_process_rec(dbenv,
                      rp, rec, &rectype, &max_lsn)) != 0)
                        goto err;

                  /*
                   * We may miscount, as we don't hold the rep mutex.
                   */
                  --rep->stat.st_log_queued;

                  /*
                   * Since we just filled a gap in the log stream, and
                   * we're writing subsequent records to the log, we want
                   * to use rcvd_recs and wait_recs so that we will
                   * request the next gap if we end up with a gap and
                   * a lot of records still in the temp db, but not
                   * request if it is near the end of the temp db and
                   * likely to arrive on its own shortly.  We want to
                   * avoid requesting the record in that case.  Also
                   * reset max_wait_lsn because the next gap is a
                   * fresh gap.
                   */
                  lp->rcvd_recs = rep->stat.st_log_queued;
                  lp->wait_recs = rep->request_gap;

                  if ((ret = __rep_getnext(dbenv)) == DB_NOTFOUND) {
                        lp->rcvd_recs = 0;
                        ret = 0;
                        break;
                  } else if (ret != 0)
                        goto err;
            }

            /*
             * Check if we're at a gap in the table and if so, whether we
             * need to ask for any records.
             */
            if (!IS_ZERO_LSN(lp->waiting_lsn) &&
                log_compare(&lp->ready_lsn, &lp->waiting_lsn) != 0) {
                  /*
                   * We got a record and processed it, but we may
                   * still be waiting for more records.  If we
                   * filled a gap we keep a count of how many other
                   * records are in the temp database and if we should
                   * request the next gap at this time.
                   */
                  if (__rep_check_doreq(dbenv, rep) && (ret =
                      __rep_loggap_req(dbenv, rep, &rp->lsn, 0)) != 0)
                        goto err;
            } else {
                  lp->wait_recs = 0;
                  ZERO_LSN(lp->max_wait_lsn);
            }

      } else if (cmp > 0) {
            /*
             * The LSN is higher than the one we were waiting for.
             * This record isn't in sequence; add it to the temporary
             * database, update waiting_lsn if necessary, and perform
             * calculations to determine if we should issue requests
             * for new records.
             */
            memset(&key_dbt, 0, sizeof(key_dbt));
            key_dbt.data = rp;
            key_dbt.size = sizeof(*rp);
            if (lp->wait_recs == 0) {
                  /*
                   * This is a new gap. Initialize the number of
                   * records that we should wait before requesting
                   * that it be resent.  We grab the limits out of
                   * the rep without the mutex.
                   */
                  lp->wait_recs = rep->request_gap;
                  lp->rcvd_recs = 0;
                  ZERO_LSN(lp->max_wait_lsn);
            }
            if (__rep_check_doreq(dbenv, rep) &&
                (ret = __rep_loggap_req(dbenv, rep, &rp->lsn, 0) != 0))
                  goto err;

            ret = __db_put(dbp, NULL, &key_dbt, rec, DB_NOOVERWRITE);
            rep->stat.st_log_queued++;
            rep->stat.st_log_queued_total++;
            if (rep->stat.st_log_queued_max < rep->stat.st_log_queued)
                  rep->stat.st_log_queued_max = rep->stat.st_log_queued;

            if (ret == DB_KEYEXIST)
                  ret = 0;
            if (ret != 0)
                  goto done;

            if (IS_ZERO_LSN(lp->waiting_lsn) ||
                log_compare(&rp->lsn, &lp->waiting_lsn) < 0)
                  lp->waiting_lsn = rp->lsn;

            /*
             * If this is permanent; let the caller know that we have
             * not yet written it to disk, but we've accepted it.
             */
            if (ret == 0 && F_ISSET(rp, DB_LOG_PERM)) {
                  max_lsn = rp->lsn;
                  ret = DB_REP_NOTPERM;
            }
            goto done;
      } else {
            /*
             * We may miscount if we race, since we
             * don't currently hold the rep mutex.
             */
            rep->stat.st_log_duplicated++;
            if (is_dupp != NULL)
                  *is_dupp = 1;
            if (F_ISSET(rp, DB_LOG_PERM))
                  max_lsn = lp->max_perm_lsn;
            goto done;
      }

      /* Check if we need to go back into the table. */
      if (ret == 0 && log_compare(&lp->ready_lsn, &lp->waiting_lsn) == 0)
            goto gap_check;

done:
err:  /* Check if we need to go back into the table. */
      REP_SYSTEM_LOCK(dbenv);
      if (ret == 0 &&
          F_ISSET(rep, REP_F_RECOVER_LOG) &&
          log_compare(&lp->ready_lsn, &rep->last_lsn) >= 0) {
            rep->last_lsn = max_lsn;
            ZERO_LSN(max_lsn);
            ret = DB_REP_LOGREADY;
      }
      REP_SYSTEM_UNLOCK(dbenv);

      if (ret == 0 && !F_ISSET(rep, REP_F_RECOVER_LOG) &&
          !IS_ZERO_LSN(max_lsn)) {
            if (ret_lsnp != NULL)
                  *ret_lsnp = max_lsn;
            ret = DB_REP_ISPERM;
            DB_ASSERT(log_compare(&max_lsn, &lp->max_perm_lsn) >= 0);
            lp->max_perm_lsn = max_lsn;
      }
      MUTEX_UNLOCK(dbenv, rep->mtx_clientdb);

      /*
       * Startup is complete when we process our first live record.  However,
       * we want to return DB_REP_STARTUPDONE on the first record we can --
       * but other return values trump this one.  We know we've processed at
       * least one record when rectype is non-zero.
       */
      if (ret == 0 && !F_ISSET(rp, DB_LOG_RESEND) &&
          rectype != 0 && rep->stat.st_startup_complete == 0) {
            rep->stat.st_startup_complete = 1;
            ret = DB_REP_STARTUPDONE;
      }
      if (ret == 0 && rp->rectype == REP_NEWFILE && lp->db_log_autoremove)
            __log_autoremove(dbenv);
      if (control_dbt.data != NULL)
            __os_ufree(dbenv, control_dbt.data);
      if (rec_dbt.data != NULL)
            __os_ufree(dbenv, rec_dbt.data);

      if (ret == DB_REP_NOTPERM && !F_ISSET(rep, REP_F_RECOVER_LOG) &&
          !IS_ZERO_LSN(max_lsn) && ret_lsnp != NULL)
            *ret_lsnp = max_lsn;

#ifdef DIAGNOSTIC
      if (ret == DB_REP_ISPERM)
            RPRINT(dbenv, rep, (dbenv, &mb, "Returning ISPERM [%lu][%lu]",
                (u_long)max_lsn.file, (u_long)max_lsn.offset));
      else if (ret == DB_REP_LOGREADY)
            RPRINT(dbenv, rep, (dbenv, &mb,
                "Returning LOGREADY up to [%lu][%lu]",
                (u_long)rep->last_lsn.file,
                (u_long)rep->last_lsn.offset));
      else if (ret == DB_REP_NOTPERM)
            RPRINT(dbenv, rep, (dbenv, &mb, "Returning NOTPERM [%lu][%lu]",
                (u_long)max_lsn.file, (u_long)max_lsn.offset));
      else if (ret == DB_REP_STARTUPDONE)
            RPRINT(dbenv, rep, (dbenv, &mb,
                "Returning STARTUPDONE [%lu][%lu]",
                (u_long)rp->lsn.file, (u_long)rp->lsn.offset));
      else if (ret != 0)
            RPRINT(dbenv, rep, (dbenv, &mb, "Returning %d [%lu][%lu]", ret,
                (u_long)max_lsn.file, (u_long)max_lsn.offset));
#endif
      return (ret);
}

/*
 * __rep_process_txn --
 *
 * This is the routine that actually gets a transaction ready for
 * processing.
 *
 * PUBLIC: int __rep_process_txn __P((DB_ENV *, DBT *));
 */
int
__rep_process_txn(dbenv, rec)
      DB_ENV *dbenv;
      DBT *rec;
{
      DBT data_dbt, *lock_dbt;
      DB_LOCKREQ req, *lvp;
      DB_LOGC *logc;
      DB_LSN prev_lsn, *lsnp;
      DB_REP *db_rep;
      DB_TXNHEAD *txninfo;
      LSN_COLLECTION lc;
      REP *rep;
      __txn_regop_args *txn_args;
      __txn_xa_regop_args *prep_args;
      u_int32_t lockid, rectype;
      u_int i;
      int ret, t_ret;

      db_rep = dbenv->rep_handle;
      rep = db_rep->region;
      logc = NULL;
      txn_args = NULL;
      prep_args = NULL;
      txninfo = NULL;

      memset(&data_dbt, 0, sizeof(data_dbt));
      if (F_ISSET(dbenv, DB_ENV_THREAD))
            F_SET(&data_dbt, DB_DBT_REALLOC);

      /*
       * There are two phases:  First, we have to traverse backwards through
       * the log records gathering the list of all LSNs in the transaction.
       * Once we have this information, we can loop through and then apply it.
       *
       * We may be passed a prepare (if we're restoring a prepare on upgrade)
       * instead of a commit (the common case).  Check which it is and behave
       * appropriately.
       */
      memcpy(&rectype, rec->data, sizeof(rectype));
      memset(&lc, 0, sizeof(lc));
      if (rectype == DB___txn_regop) {
            /*
             * We're the end of a transaction.  Make sure this is
             * really a commit and not an abort!
             */
            if ((ret = __txn_regop_read(dbenv, rec->data, &txn_args)) != 0)
                  return (ret);
            if (txn_args->opcode != TXN_COMMIT) {
                  __os_free(dbenv, txn_args);
                  return (0);
            }
            prev_lsn = txn_args->prev_lsn;
            lock_dbt = &txn_args->locks;
      } else {
            /* We're a prepare. */
            DB_ASSERT(rectype == DB___txn_xa_regop);

            if ((ret =
                __txn_xa_regop_read(dbenv, rec->data, &prep_args)) != 0)
                  return (ret);
            prev_lsn = prep_args->prev_lsn;
            lock_dbt = &prep_args->locks;
      }

      /* Get locks. */
      if ((ret = __lock_id(dbenv, &lockid, NULL)) != 0)
            goto err1;

      if ((ret =
            __lock_get_list(dbenv, lockid, 0, DB_LOCK_WRITE, lock_dbt)) != 0)
            goto err;

      /* Phase 1.  Get a list of the LSNs in this transaction, and sort it. */
      if ((ret = __rep_collect_txn(dbenv, &prev_lsn, &lc)) != 0)
            goto err;
      qsort(lc.array, lc.nlsns, sizeof(DB_LSN), __rep_lsn_cmp);

      /*
       * The set of records for a transaction may include dbreg_register
       * records.  Create a txnlist so that they can keep track of file
       * state between records.
       */
      if ((ret = __db_txnlist_init(dbenv, 0, 0, NULL, &txninfo)) != 0)
            goto err;

      /* Phase 2: Apply updates. */
      if ((ret = __log_cursor(dbenv, &logc)) != 0)
            goto err;
      for (lsnp = &lc.array[0], i = 0; i < lc.nlsns; i++, lsnp++) {
            if ((ret = __log_c_get(logc, lsnp, &data_dbt, DB_SET)) != 0) {
                  __db_err(dbenv, "failed to read the log at [%lu][%lu]",
                      (u_long)lsnp->file, (u_long)lsnp->offset);
                  goto err;
            }
            if ((ret = __db_dispatch(dbenv, dbenv->recover_dtab,
                dbenv->recover_dtab_size, &data_dbt, lsnp,
                DB_TXN_APPLY, txninfo)) != 0) {
                  __db_err(dbenv, "transaction failed at [%lu][%lu]",
                      (u_long)lsnp->file, (u_long)lsnp->offset);
                  goto err;
            }
      }

err:  memset(&req, 0, sizeof(req));
      req.op = DB_LOCK_PUT_ALL;
      if ((t_ret =
           __lock_vec(dbenv, lockid, 0, &req, 1, &lvp)) != 0 && ret == 0)
            ret = t_ret;

      if ((t_ret = __lock_id_free(dbenv, lockid)) != 0 && ret == 0)
            ret = t_ret;

err1: if (txn_args != NULL)
            __os_free(dbenv, txn_args);
      if (prep_args != NULL)
            __os_free(dbenv, prep_args);
      if (lc.array != NULL)
            __os_free(dbenv, lc.array);

      if (logc != NULL && (t_ret = __log_c_close(logc)) != 0 && ret == 0)
            ret = t_ret;

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

      if (F_ISSET(&data_dbt, DB_DBT_REALLOC) && data_dbt.data != NULL)
            __os_ufree(dbenv, data_dbt.data);

      if (ret == 0)
            /*
             * We don't hold the rep mutex, and could miscount if we race.
             */
            rep->stat.st_txns_applied++;

      return (ret);
}

/*
 * __rep_collect_txn
 *    Recursive function that will let us visit every entry in a transaction
 *    chain including all child transactions so that we can then apply
 *    the entire transaction family at once.
 */
static int
__rep_collect_txn(dbenv, lsnp, lc)
      DB_ENV *dbenv;
      DB_LSN *lsnp;
      LSN_COLLECTION *lc;
{
      __txn_child_args *argp;
      DB_LOGC *logc;
      DB_LSN c_lsn;
      DBT data;
      u_int32_t rectype;
      u_int nalloc;
      int ret, t_ret;

      memset(&data, 0, sizeof(data));
      F_SET(&data, DB_DBT_REALLOC);

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

      while (!IS_ZERO_LSN(*lsnp) &&
          (ret = __log_c_get(logc, lsnp, &data, DB_SET)) == 0) {
            memcpy(&rectype, data.data, sizeof(rectype));
            if (rectype == DB___txn_child) {
                  if ((ret = __txn_child_read(dbenv,
                      data.data, &argp)) != 0)
                        goto err;
                  c_lsn = argp->c_lsn;
                  *lsnp = argp->prev_lsn;
                  __os_free(dbenv, argp);
                  ret = __rep_collect_txn(dbenv, &c_lsn, lc);
            } else {
                  if (lc->nalloc < lc->nlsns + 1) {
                        nalloc = lc->nalloc == 0 ? 20 : lc->nalloc * 2;
                        if ((ret = __os_realloc(dbenv,
                            nalloc * sizeof(DB_LSN), &lc->array)) != 0)
                              goto err;
                        lc->nalloc = nalloc;
                  }
                  lc->array[lc->nlsns++] = *lsnp;

                  /*
                   * Explicitly copy the previous lsn.  The record
                   * starts with a u_int32_t record type, a u_int32_t
                   * txn id, and then the DB_LSN (prev_lsn) that we
                   * want.  We copy explicitly because we have no idea
                   * what kind of record this is.
                   */
                  memcpy(lsnp, (u_int8_t *)data.data +
                      sizeof(u_int32_t) + sizeof(u_int32_t),
                      sizeof(DB_LSN));
            }

            if (ret != 0)
                  goto err;
      }
      if (ret != 0)
            __db_err(dbenv, "collect failed at: [%lu][%lu]",
                (u_long)lsnp->file, (u_long)lsnp->offset);

err:  if ((t_ret = __log_c_close(logc)) != 0 && ret == 0)
            ret = t_ret;
      if (data.data != NULL)
            __os_ufree(dbenv, data.data);
      return (ret);
}

/*
 * __rep_lsn_cmp --
 *    qsort-type-compatible wrapper for log_compare.
 */
static int
__rep_lsn_cmp(lsn1, lsn2)
      const void *lsn1, *lsn2;
{

      return (log_compare((DB_LSN *)lsn1, (DB_LSN *)lsn2));
}

/*
 * __rep_newfile --
 *    NEWFILE messages have the LSN of the last record in the previous
 * log file.  When applying a NEWFILE message, make sure we haven't already
 * swapped files.
 */
static int
__rep_newfile(dbenv, rc, lsnp)
      DB_ENV *dbenv;
      REP_CONTROL *rc;
      DB_LSN *lsnp;
{
      DB_LOG *dblp;
      LOG *lp;

      dblp = dbenv->lg_handle;
      lp = dblp->reginfo.primary;

      if (rc->lsn.file + 1 > lp->lsn.file)
            return (__log_newfile(dblp, lsnp, 0));
      else {
            /* We've already applied this NEWFILE.  Just ignore it. */
            *lsnp = lp->lsn;
            return (0);
      }
}

/*
 * __rep_do_ckp --
 * Perform the memp_sync necessary for this checkpoint without holding the
 * REP->mtx_clientdb.  Callers of this function must hold REP->mtx_clientdb
 * and must not be holding the region mutex.
 */
static int
__rep_do_ckp(dbenv, rec, rp)
      DB_ENV *dbenv;
      DBT *rec;
      REP_CONTROL *rp;
{
      DB_LSN ckp_lsn;
      DB_REP *db_rep;
      int ret;

      db_rep = dbenv->rep_handle;

      MUTEX_UNLOCK(dbenv, db_rep->region->mtx_clientdb);

      DB_TEST_WAIT(dbenv, dbenv->test_check);

      /* Sync the memory pool. */
      memcpy(&ckp_lsn, (u_int8_t *)rec->data +
          SSZ(__txn_ckp_args, ckp_lsn), sizeof(DB_LSN));
      ret = __memp_sync(dbenv, &ckp_lsn);

      /* Update the last_ckp in the txn region. */
      if (ret == 0)
            ret = __txn_updateckp(dbenv, &rp->lsn);
      else {
            __db_err(dbenv, "Error syncing ckp [%lu][%lu]",
                (u_long)ckp_lsn.file, (u_long)ckp_lsn.offset);
            ret = __db_panic(dbenv, ret);
      }
      MUTEX_LOCK(dbenv, db_rep->region->mtx_clientdb);

      return (ret);
}

/*
 * __rep_remfirst --
 * Remove the first entry from the __db.rep.db
 */
static int
__rep_remfirst(dbenv, cntrl, rec)
      DB_ENV *dbenv;
      DBT *cntrl;
      DBT *rec;
{
      DB *dbp;
      DBC *dbc;
      DB_REP *db_rep;
      int ret, t_ret;

      db_rep = dbenv->rep_handle;
      dbp = db_rep->rep_db;

      if ((ret = __db_cursor(dbp, NULL, &dbc, 0)) != 0)
            return (ret);

      /* The DBTs need to persist through another call. */
      F_SET(cntrl, DB_DBT_REALLOC);
      F_SET(rec, DB_DBT_REALLOC);
      if ((ret = __db_c_get(dbc, cntrl, rec, DB_RMW | DB_FIRST)) == 0)
            ret = __db_c_del(dbc, 0);
      if ((t_ret = __db_c_close(dbc)) != 0 && ret == 0)
            ret = t_ret;

      return (ret);
}

/*
 * __rep_getnext --
 * Get the next record out of the __db.rep.db table.
 */
static int
__rep_getnext(dbenv)
      DB_ENV *dbenv;
{
      DB *dbp;
      DB_REP *db_rep;
      DB_LOG *dblp;
      DBC *dbc;
      DBT lsn_dbt, nextrec_dbt;
      LOG *lp;
      REP_CONTROL *rp;
      int ret, t_ret;

      dblp = dbenv->lg_handle;
      lp = dblp->reginfo.primary;

      db_rep = dbenv->rep_handle;
      dbp = db_rep->rep_db;

      if ((ret = __db_cursor(dbp, NULL, &dbc, 0)) != 0)
            return (ret);

      /*
       * Update waiting_lsn.  We need to move it
       * forward to the LSN of the next record
       * in the queue.
       *
       * If the next item in the database is a log
       * record--the common case--we're not
       * interested in its contents, just in its LSN.
       * Optimize by doing a partial get of the data item.
       */
      memset(&nextrec_dbt, 0, sizeof(nextrec_dbt));
      F_SET(&nextrec_dbt, DB_DBT_PARTIAL);
      nextrec_dbt.ulen = nextrec_dbt.dlen = 0;

      memset(&lsn_dbt, 0, sizeof(lsn_dbt));
      ret = __db_c_get(dbc, &lsn_dbt, &nextrec_dbt, DB_FIRST);
      if (ret != DB_NOTFOUND && ret != 0)
            goto err;

      if (ret == DB_NOTFOUND) {
            ZERO_LSN(lp->waiting_lsn);
            /*
             * Whether or not the current record is
             * simple, there's no next one, and
             * therefore we haven't got anything
             * else to do right now.  Break out.
             */
            goto err;
      }
      rp = (REP_CONTROL *)lsn_dbt.data;
      lp->waiting_lsn = rp->lsn;

err:  if ((t_ret = __db_c_close(dbc)) != 0 && ret == 0)
            ret = t_ret;
      return (ret);
}

/*
 * __rep_process_rec --
 *
 * Given a record in 'rp', process it.  In the case of a NEWFILE, that means
 * potentially switching files.  In the case of a checkpoint, it means doing
 * the checkpoint, and in other cases, it means simply writing the record into
 * the log.
 */
static int
__rep_process_rec(dbenv, rp, rec, typep, ret_lsnp)
      DB_ENV *dbenv;
      REP_CONTROL *rp;
      DBT *rec;
      u_int32_t *typep;
      DB_LSN *ret_lsnp;
{
      DB *dbp;
      DB_LOG *dblp;
      DB_REP *db_rep;
      DBT control_dbt, key_dbt, rec_dbt;
      LOG *lp;
      REP *rep;
      u_int32_t txnid;
      int ret, t_ret;

      db_rep = dbenv->rep_handle;
      rep = db_rep->region;
      dbp = db_rep->rep_db;
      dblp = dbenv->lg_handle;
      lp = dblp->reginfo.primary;
      ret = 0;

      if (rp->rectype == REP_NEWFILE) {
            ret = __rep_newfile(dbenv, rp, &lp->ready_lsn);

            /* Make this evaluate to a simple rectype. */
            *typep = 0;
            return (0);
      }

      memcpy(typep, rec->data, sizeof(*typep));
      memset(&control_dbt, 0, sizeof(control_dbt));
      memset(&rec_dbt, 0, sizeof(rec_dbt));

      /*
       * We write all records except for checkpoint records here.
       * All non-checkpoint records need to appear in the log before
       * we take action upon them (i.e., we enforce write-ahead logging).
       * However, we can't write the checkpoint record here until the
       * data buffers are actually written to disk, else we are creating
       * an invalid log -- one that says all data before a certain point
       * has been written to disk.
       *
       * If two threads are both processing the same checkpoint record
       * (because, for example, it was resent and the original finally
       * arrived), we handle that below by checking for the existence of
       * the log record when we add it to the replication database.
       *
       * Any log records that arrive while we are processing the checkpoint
       * are added to the bookkeeping database because ready_lsn is not yet
       * updated to point after the checkpoint record.
       */
      if (*typep != DB___txn_ckp || F_ISSET(rep, REP_F_RECOVER_LOG)) {
            if ((ret = __log_rep_put(dbenv, &rp->lsn, rec)) != 0)
                  return (ret);
            rep->stat.st_log_records++;
            if (F_ISSET(rep, REP_F_RECOVER_LOG)) {
                  *ret_lsnp = rp->lsn;
                  goto out;
            }
      }

      switch (*typep) {
      case DB___dbreg_register:
            /*
             * DB opens occur in the context of a transaction, so we can
             * simply handle them when we process the transaction.  Closes,
             * however, are not transaction-protected, so we have to
             * handle them here.
             *
             * Note that it should be unsafe for the master to do a close
             * of a file that was opened in an active transaction, so we
             * should be guaranteed to get the ordering right.
             */
            memcpy(&txnid, (u_int8_t *)rec->data +
                SSZ(__dbreg_register_args, txnid), sizeof(u_int32_t));
            if (txnid == TXN_INVALID)
                  ret = __db_dispatch(dbenv, dbenv->recover_dtab,
                      dbenv->recover_dtab_size, rec, &rp->lsn,
                      DB_TXN_APPLY, NULL);
            break;
      case DB___txn_regop:
            /*
             * If an application is doing app-specific recovery
             * and acquires locks while applying a transaction,
             * it can deadlock.  Any other locks held by this
             * thread should have been discarded in the
             * __rep_process_txn error path, so if we simply
             * retry, we should eventually succeed.
             */
            do {
                  ret = 0;
                  if (!F_ISSET(db_rep, DBREP_OPENFILES)) {
                        ret = __txn_openfiles(dbenv, NULL, 1);
                        F_SET(db_rep, DBREP_OPENFILES);
                  }
                  if (ret == 0)
                        ret = __rep_process_txn(dbenv, rec);
            } while (ret == DB_LOCK_DEADLOCK);

            /* Now flush the log unless we're running TXN_NOSYNC. */
            if (ret == 0 && !F_ISSET(dbenv, DB_ENV_TXN_NOSYNC))
                  ret = __log_flush(dbenv, NULL);
            if (ret != 0) {
                  __db_err(dbenv, "Error processing txn [%lu][%lu]",
                      (u_long)rp->lsn.file, (u_long)rp->lsn.offset);
                  ret = __db_panic(dbenv, ret);
            }
            break;
      case DB___txn_xa_regop:
            ret = __log_flush(dbenv, NULL);
            break;
      case DB___txn_ckp:
            /*
             * We do not want to hold the REP->mtx_clientdb mutex while
             * syncing the mpool, so if we get a checkpoint record we are
             * supposed to process, add it to the __db.rep.db, do the
             * memp_sync and then go back and process it later, when the
             * sync has finished.  If this record is already in the table,
             * then some other thread will process it, so simply return
             * REP_NOTPERM.
             */
            memset(&key_dbt, 0, sizeof(key_dbt));
            key_dbt.data = rp;
            key_dbt.size = sizeof(*rp);

            /*
             * We want to put this record into the tmp DB only if
             * it doesn't exist, so use DB_NOOVERWRITE.
             */
            ret = __db_put(dbp, NULL, &key_dbt, rec, DB_NOOVERWRITE);
            if (ret == DB_KEYEXIST) {
                  if (ret_lsnp != NULL)
                        *ret_lsnp = rp->lsn;
                  ret = DB_REP_NOTPERM;
            }
            if (ret != 0)
                  break;

            /*
             * Now, do the checkpoint.  Regardless of
             * whether the checkpoint succeeds or not,
             * we need to remove the record we just put
             * in the temporary database.  If the
             * checkpoint failed, return an error.  We
             * will act like we never received the
             * checkpoint.
             */
            if ((ret = __rep_do_ckp(dbenv, rec, rp)) == 0)
                  ret = __log_rep_put(dbenv, &rp->lsn, rec);
            if ((t_ret = __rep_remfirst(dbenv,
                &control_dbt, &rec_dbt)) != 0 && ret == 0)
                  ret = t_ret;
            break;
      default:
            break;
      }

out:
      if (ret == 0 && F_ISSET(rp, DB_LOG_PERM))
            *ret_lsnp = rp->lsn;
      if (control_dbt.data != NULL)
            __os_ufree(dbenv, control_dbt.data);
      if (rec_dbt.data != NULL)
            __os_ufree(dbenv, rec_dbt.data);

      return (ret);
}

/*
 * __rep_resend_req --
 *    We might have dropped a message, we need to resend our request.
 *    The request we send is dependent on what recovery state we're in.
 *    The caller holds no locks.
 */
static int
__rep_resend_req(dbenv, rereq)
      DB_ENV *dbenv;
      int rereq;
{

      DB_LOG *dblp;
      DB_LSN lsn;
      DB_REP *db_rep;
      LOG *lp;
      REP *rep;
      int ret;
      u_int32_t gapflags, repflags;

      db_rep = dbenv->rep_handle;
      rep = db_rep->region;
      dblp = dbenv->lg_handle;
      lp = dblp->reginfo.primary;
      ret = 0;

      repflags = rep->flags;
      /*
       * If we are delayed we do not rerequest anything.
       */
      if (FLD_ISSET(repflags, REP_F_DELAY))
            return (ret);
      gapflags = rereq ? REP_GAP_REREQUEST : 0;

      if (FLD_ISSET(repflags, REP_F_RECOVER_VERIFY)) {
            MUTEX_LOCK(dbenv, rep->mtx_clientdb);
            lsn = lp->verify_lsn;
            MUTEX_UNLOCK(dbenv, rep->mtx_clientdb);
            if (!IS_ZERO_LSN(lsn))
                  (void)__rep_send_message(dbenv, rep->master_id,
                      REP_VERIFY_REQ, &lsn, NULL, 0, DB_REP_REREQUEST);
      } else if (FLD_ISSET(repflags, REP_F_RECOVER_UPDATE)) {
            /*
             * UPDATE_REQ only goes to the master.
             */
            (void)__rep_send_message(dbenv, rep->master_id,
                REP_UPDATE_REQ, NULL, NULL, 0, 0);
      } else if (FLD_ISSET(repflags, REP_F_RECOVER_PAGE)) {
            REP_SYSTEM_LOCK(dbenv);
            ret = __rep_pggap_req(dbenv, rep, NULL, gapflags);
            REP_SYSTEM_UNLOCK(dbenv);
      } else {
            MUTEX_LOCK(dbenv, rep->mtx_clientdb);
            ret = __rep_loggap_req(dbenv, rep, NULL, gapflags);
            MUTEX_UNLOCK(dbenv, rep->mtx_clientdb);
      }

      return (ret);
}

/*
 * __rep_check_doreq --
 * PUBLIC: int __rep_check_doreq __P((DB_ENV *, REP *));
 *
 * Check if we need to send another request.  If so, compare with
 * the request limits the user might have set.  This assumes the
 * caller holds the REP->mtx_clientdb mutex.  Returns 1 if a request
 * needs to be made, and 0 if it does not.
 */
int
__rep_check_doreq(dbenv, rep)
      DB_ENV *dbenv;
      REP *rep;
{

      DB_LOG *dblp;
      LOG *lp;
      int req;

      dblp = dbenv->lg_handle;
      lp = dblp->reginfo.primary;
      req = ++lp->rcvd_recs >= lp->wait_recs;
      if (req) {
            lp->wait_recs *= 2;
            if (lp->wait_recs > rep->max_gap)
                  lp->wait_recs = rep->max_gap;
            lp->rcvd_recs = 0;
      }
      return (req);
}

/*
 * __rep_skip_msg -
 *
 *    If we're in recovery we want to skip/ignore the message, but
 *    we also need to see if we need to re-request any retransmissions.
 */
static int
__rep_skip_msg(dbenv, rep, eid, rectype)
      DB_ENV *dbenv;
      REP *rep;
      int eid;
      u_int32_t rectype;
{
      int do_req, ret;

      ret = 0;
      /*
       * If we have a request message from a client then immediately
       * send a REP_REREQUEST back to that client since we're skipping it.
       */
      if (rep->master_id != DB_EID_INVALID && eid != rep->master_id)
            do_req = 1;
      else {
            /* Check for need to retransmit. */
            MUTEX_LOCK(dbenv, rep->mtx_clientdb);
            do_req = __rep_check_doreq(dbenv, rep);
            MUTEX_UNLOCK(dbenv, rep->mtx_clientdb);
      }
      /*
       * Don't respond to a MASTER_REQ with
       * a MASTER_REQ or REREQUEST.
       */
      if (do_req && rectype != REP_MASTER_REQ) {
            /*
             * There are three cases:
             * 1.  If we don't know who the master is, then send MASTER_REQ.
             * 2.  If the message we're skipping came from the master,
             * then we need to rerequest.
             * 3.  If the message didn't come from a master (i.e. client
             * to client), then send a rerequest back to the sender so
             * the sender can rerequest it elsewhere.
             */
            if (rep->master_id == DB_EID_INVALID)     /* Case 1. */
                  (void)__rep_send_message(dbenv,
                      DB_EID_BROADCAST, REP_MASTER_REQ, NULL, NULL, 0, 0);
            else if (eid == rep->master_id)           /* Case 2. */
                  ret = __rep_resend_req(dbenv, 0);
            else                          /* Case 3. */
                  (void)__rep_send_message(dbenv,
                      eid, REP_REREQUEST, NULL, NULL, 0, 0);
      }
      return (ret);
}

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