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rep_elect.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2004-2005
 *    Sleepycat Software.  All rights reserved.
 *
 * $Id: rep_elect.c,v 12.10 2005/08/23 14:18:19 sue Exp $
 */

#include "db_config.h"

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

#include "db_int.h"
#include "dbinc/db_page.h"
#include "dbinc/db_am.h"
#include "dbinc/log.h"

static void __rep_cmp_vote __P((DB_ENV *, REP *, int, DB_LSN *,
    int, u_int32_t, u_int32_t));
static int __rep_cmp_vote2 __P((DB_ENV *, REP *, int, u_int32_t));
static int __rep_elect_init
             __P((DB_ENV *, DB_LSN *, int, int, int, int *, u_int32_t *));
static int __rep_tally __P((DB_ENV *, REP *, int, int *, u_int32_t, roff_t));
static int __rep_wait __P((DB_ENV *, u_int32_t, int *, u_int32_t));

/*
 * __rep_elect --
 *    Called after master failure to hold/participate in an election for
 *    a new master.
 *
 * PUBLIC:  int __rep_elect __P((DB_ENV *, int, int, int,
 * PUBLIC:     u_int32_t, int *, u_int32_t));
 */
int
__rep_elect(dbenv, nsites, nvotes, priority, timeout, eidp, flags)
      DB_ENV *dbenv;
      int nsites, nvotes, priority;
      u_int32_t timeout;
      int *eidp;
      u_int32_t flags;
{
      DB_LOG *dblp;
      DB_LSN lsn;
      DB_REP *db_rep;
      REP *rep;
      int ack, done, in_progress, ret, send_vote;
      u_int32_t egen, orig_tally, tiebreaker, to;
#ifdef DIAGNOSTIC
      DB_MSGBUF mb;
#endif

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

      /* Error checking. */
      if (nsites <= 0) {
            __db_err(dbenv,
                "DB_ENV->rep_elect: nsites must be greater than 0");
            return (EINVAL);
      }
      if (nvotes < 0) {
            __db_err(dbenv,
                "DB_ENV->rep_elect: nvotes may not be negative");
            return (EINVAL);
      }
      if (priority < 0) {
            __db_err(dbenv,
                "DB_ENV->rep_elect: priority may not be negative");
            return (EINVAL);
      }
      if (nsites < nvotes) {
            __db_err(dbenv,
    "DB_ENV->rep_elect: nvotes (%d) is larger than nsites (%d)",
                nvotes, nsites);
            return (EINVAL);
      }

      ack = nvotes;
      /* If they give us a 0 for nvotes, default to simple majority.  */
      if (nvotes == 0)
            ack = (nsites / 2) + 1;

      /*
       * XXX
       * If users give us less than a majority, they run the risk of
       * having a network partition.  However, this also allows the
       * scenario of master/1 client to elect the client.  Allow
       * sub-majority values, but give a warning.
       */
      if (nvotes <= (nsites / 2)) {
            __db_err(dbenv,
    "DB_ENV->rep_elect:WARNING: nvotes (%d) is sub-majority with nsites (%d)",
                nvotes, nsites);
      }

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

      RPRINT(dbenv, rep,
          (dbenv, &mb, "Start election nsites %d, ack %d, priority %d",
          nsites, ack, priority));

      LOG_SYSTEM_LOCK(dbenv);
      lsn = ((LOG *)dblp->reginfo.primary)->lsn;
      LOG_SYSTEM_UNLOCK(dbenv);

      orig_tally = 0;
      to = timeout;
      if ((ret = __rep_elect_init(dbenv,
          &lsn, nsites, ack, priority, &in_progress, &orig_tally)) != 0) {
            if (ret == DB_REP_NEWMASTER) {
                  ret = 0;
                  *eidp = dbenv->rep_eid;
            }
            goto err;
      }
      /*
       * If another thread is in the middle of an election we
       * just quietly return and not interfere.
       */
      if (in_progress) {
            *eidp = rep->master_id;
            return (0);
      }
      __os_clock(dbenv, &rep->esec, &rep->eusec);
restart:
      /* Generate a randomized tiebreaker value. */
      __os_unique_id(dbenv, &tiebreaker);

      REP_SYSTEM_LOCK(dbenv);
      F_SET(rep, REP_F_EPHASE1 | REP_F_NOARCHIVE);
      F_CLR(rep, REP_F_TALLY);

      /*
       * We are about to participate at this egen.  We must
       * write out the next egen before participating in this one
       * so that if we crash we can never participate in this egen
       * again.
       */
      if ((ret = __rep_write_egen(dbenv, rep->egen + 1)) != 0)
            goto lockdone;

      /* Tally our own vote */
      if (__rep_tally(dbenv, rep, rep->eid, &rep->sites, rep->egen,
          rep->tally_off) != 0) {
            ret = EINVAL;
            goto lockdone;
      }
      __rep_cmp_vote(dbenv, rep, rep->eid, &lsn, priority, rep->gen,
          tiebreaker);

      RPRINT(dbenv, rep, (dbenv, &mb, "Beginning an election"));

      /* Now send vote */
      send_vote = DB_EID_INVALID;
      egen = rep->egen;
      REP_SYSTEM_UNLOCK(dbenv);
      __rep_send_vote(dbenv, &lsn, nsites, ack, priority, tiebreaker, egen,
          DB_EID_BROADCAST, REP_VOTE1);
      DB_ENV_TEST_RECOVERY(dbenv, DB_TEST_ELECTVOTE1, ret, NULL);
      ret = __rep_wait(dbenv, to, eidp, REP_F_EPHASE1);
      switch (ret) {
            case 0:
                  /* Check if election complete or phase complete. */
                  if (*eidp != DB_EID_INVALID) {
                        RPRINT(dbenv, rep, (dbenv, &mb,
                            "Ended election phase 1 %d", ret));
                        goto edone;
                  }
                  goto phase2;
            case DB_REP_EGENCHG:
                  if (to > timeout)
                        to = timeout;
                  to = (to * 8) / 10;
                  RPRINT(dbenv, rep, (dbenv, &mb,
"Egen changed while waiting. Now %lu.  New timeout %lu, orig timeout %lu",
                      (u_long)rep->egen, (u_long)to, (u_long)timeout));
                  /*
                   * If the egen changed while we were sleeping, that
                   * means we're probably late to the next election,
                   * so we'll backoff our timeout so that we don't get
                   * into an out-of-phase election scenario.
                   *
                   * Backoff to 80% of the current timeout.
                   */
                  goto restart;
            case DB_TIMEOUT:
                  break;
            default:
                  goto err;
      }
      /*
       * If we got here, we haven't heard from everyone, but we've
       * run out of time, so it's time to decide if we have enough
       * votes to pick a winner and if so, to send out a vote to
       * the winner.
       */
      REP_SYSTEM_LOCK(dbenv);
      /*
       * If our egen changed while we were waiting.  We need to
       * essentially reinitialize our election.
       */
      if (egen != rep->egen) {
            REP_SYSTEM_UNLOCK(dbenv);
            RPRINT(dbenv, rep, (dbenv, &mb, "Egen changed from %lu to %lu",
                (u_long)egen, (u_long)rep->egen));
            goto restart;
      }
      if (rep->sites >= rep->nvotes) {

            /* We think we've seen enough to cast a vote. */
            send_vote = rep->winner;
            /*
             * See if we won.  This will make sure we
             * don't count ourselves twice if we're racing
             * with incoming votes.
             */
            if (rep->winner == rep->eid) {
                  (void)__rep_tally(dbenv, rep, rep->eid, &rep->votes,
                      egen, rep->v2tally_off);
                  RPRINT(dbenv, rep, (dbenv, &mb,
                      "Counted my vote %d", rep->votes));
            }
            F_SET(rep, REP_F_EPHASE2);
            F_CLR(rep, REP_F_EPHASE1);
      }
      REP_SYSTEM_UNLOCK(dbenv);
      if (send_vote == DB_EID_INVALID) {
            /* We do not have enough votes to elect. */
            RPRINT(dbenv, rep, (dbenv, &mb,
                "Not enough votes to elect: recvd %d of %d from %d sites",
                rep->sites, rep->nvotes, rep->nsites));
            ret = DB_REP_UNAVAIL;
            goto err;

      } else {
            /*
             * We have seen enough vote1's.  Now we need to wait
             * for all the vote2's.
             */
            if (send_vote != rep->eid) {
                  RPRINT(dbenv, rep, (dbenv, &mb, "Sending vote"));
                  __rep_send_vote(dbenv, NULL, 0, 0, 0, 0, egen,
                      send_vote, REP_VOTE2);
                  /*
                   * If we are NOT the new master we want to send
                   * our vote to the winner, and wait longer.  The
                   * reason is that the winner may be "behind" us
                   * in the election waiting and if the master is
                   * down, the winner will wait the full timeout
                   * and we want to give the winner enough time to
                   * process all the votes.  Otherwise we could
                   * incorrectly return DB_REP_UNAVAIL and start a
                   * new election before the winner can declare
                   * itself.
                   */
                  to = to * 2;

            }

phase2:           ret = __rep_wait(dbenv, to, eidp, REP_F_EPHASE2);
            RPRINT(dbenv, rep, (dbenv, &mb,
                "Ended election phase 2 %d", ret));
            switch (ret) {
                  case 0:
                        goto edone;
                  case DB_REP_EGENCHG:
                        if (to > timeout)
                              to = timeout;
                        to = (to * 8) / 10;
                        RPRINT(dbenv, rep, (dbenv, &mb,
"While waiting egen changed to %lu.  Phase 2 New timeout %lu, orig timeout %lu",
                            (u_long)rep->egen,
                            (u_long)to, (u_long)timeout));
                        goto restart;
                  case DB_TIMEOUT:
                        ret = DB_REP_UNAVAIL;
                        break;
                  default:
                        goto err;
            }
            REP_SYSTEM_LOCK(dbenv);
            if (egen != rep->egen) {
                  REP_SYSTEM_UNLOCK(dbenv);
                  RPRINT(dbenv, rep, (dbenv, &mb,
                      "Egen ph2 changed from %lu to %lu",
                      (u_long)egen, (u_long)rep->egen));
                  goto restart;
            }
            done = rep->votes >= rep->nvotes;
            RPRINT(dbenv, rep, (dbenv, &mb,
                "After phase 2: done %d, votes %d, nsites %d",
                done, rep->votes, rep->nsites));
            if (send_vote == rep->eid && done) {
                  __rep_elect_master(dbenv, rep, eidp);
                  ret = 0;
                  goto lockdone;
            }
            REP_SYSTEM_UNLOCK(dbenv);
      }

err:  REP_SYSTEM_LOCK(dbenv);
lockdone:
      /*
       * If we get here because of a non-election error, then we
       * did not tally our vote.  The only non-election error is
       * from elect_init where we were unable to grow_sites.  In
       * that case we do not want to discard all known election info.
       */
      if (ret == 0 || ret == DB_REP_UNAVAIL)
            __rep_elect_done(dbenv, rep);
      else if (orig_tally)
            F_SET(rep, orig_tally);

      /*
       * If the election finished elsewhere, we need to decrement
       * the elect_th anyway.
       */
      if (0) {
edone:            REP_SYSTEM_LOCK(dbenv);
      }
      rep->elect_th = 0;

      RPRINT(dbenv, rep, (dbenv, &mb,
          "Ended election with %d, sites %d, egen %lu, flags 0x%lx",
          ret, rep->sites, (u_long)rep->egen, (u_long)rep->flags));
      REP_SYSTEM_UNLOCK(dbenv);

DB_TEST_RECOVERY_LABEL
      return (ret);
}

/*
 * __rep_vote1 --
 *    Handle incoming vote1 message on a client.
 *
 * PUBLIC: int __rep_vote1 __P((DB_ENV *, REP_CONTROL *, DBT *, int));
 */
int
__rep_vote1(dbenv, rp, rec, eid)
      DB_ENV *dbenv;
      REP_CONTROL *rp;
      DBT *rec;
      int eid;
{
      DB_LOG *dblp;
      DB_LSN lsn;
      DB_REP *db_rep;
      DBT data_dbt;
      LOG *lp;
      REP *rep;
      REP_VOTE_INFO *vi;
      u_int32_t egen;
      int done, master, ret;
#ifdef DIAGNOSTIC
      DB_MSGBUF mb;
#endif

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

      if (F_ISSET(rep, REP_F_MASTER)) {
            RPRINT(dbenv, rep,
                (dbenv, &mb, "Master received vote"));
            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);
            return (ret);
      }

      vi = (REP_VOTE_INFO *)rec->data;
      REP_SYSTEM_LOCK(dbenv);

      /*
       * If we get a vote from a later election gen, we
       * clear everything from the current one, and we'll
       * start over by tallying it.  If we get an old vote,
       * send an ALIVE to the old participant.
       */
      RPRINT(dbenv, rep, (dbenv, &mb,
          "Received vote1 egen %lu, egen %lu",
          (u_long)vi->egen, (u_long)rep->egen));
      if (vi->egen < rep->egen) {
            RPRINT(dbenv, rep, (dbenv, &mb,
                "Received old vote %lu, egen %lu, ignoring vote1",
                (u_long)vi->egen, (u_long)rep->egen));
            egen = rep->egen;
            REP_SYSTEM_UNLOCK(dbenv);
            data_dbt.data = &egen;
            data_dbt.size = sizeof(egen);
            (void)__rep_send_message(dbenv,
                eid, REP_ALIVE, &rp->lsn, &data_dbt, 0, 0);
            return (ret);
      }
      if (vi->egen > rep->egen) {
            RPRINT(dbenv, rep, (dbenv, &mb,
                "Received VOTE1 from egen %lu, my egen %lu; reset",
                (u_long)vi->egen, (u_long)rep->egen));
            __rep_elect_done(dbenv, rep);
            rep->egen = vi->egen;
      }
      if (!IN_ELECTION(rep))
            F_SET(rep, REP_F_TALLY);

      /* Check if this site knows about more sites than we do. */
      if (vi->nsites > rep->nsites)
            rep->nsites = vi->nsites;

      /* Check if this site requires more votes than we do. */
      if (vi->nvotes > rep->nvotes)
            rep->nvotes = vi->nvotes;

      /*
       * We are keeping the vote, let's see if that changes our
       * count of the number of sites.
       */
      if (rep->sites + 1 > rep->nsites)
            rep->nsites = rep->sites + 1;
      if (rep->nsites > rep->asites &&
          (ret = __rep_grow_sites(dbenv, rep->nsites)) != 0) {
            RPRINT(dbenv, rep, (dbenv, &mb,
                "Grow sites returned error %d", ret));
            goto err;
      }

      /*
       * Ignore vote1's if we're in phase 2.
       */
      if (F_ISSET(rep, REP_F_EPHASE2)) {
            RPRINT(dbenv, rep, (dbenv, &mb,
                "In phase 2, ignoring vote1"));
            goto err;
      }

      /*
       * Record this vote.  If we get back non-zero, we
       * ignore the vote.
       */
      if ((ret = __rep_tally(dbenv, rep, eid, &rep->sites,
          vi->egen, rep->tally_off)) != 0) {
            RPRINT(dbenv, rep, (dbenv, &mb,
                "Tally returned %d, sites %d",
                ret, rep->sites));
            ret = 0;
            goto err;
      }
      RPRINT(dbenv, rep, (dbenv, &mb,
          "Incoming vote: (eid)%d (pri)%d (gen)%lu (egen)%lu [%lu,%lu]",
          eid, vi->priority,
          (u_long)rp->gen, (u_long)vi->egen,
          (u_long)rp->lsn.file, (u_long)rp->lsn.offset));
#ifdef DIAGNOSTIC
      if (rep->sites > 1)
            RPRINT(dbenv, rep, (dbenv, &mb,
    "Existing vote: (eid)%d (pri)%d (gen)%lu (sites)%d [%lu,%lu]",
                rep->winner, rep->w_priority,
                (u_long)rep->w_gen, rep->sites,
                (u_long)rep->w_lsn.file,
                (u_long)rep->w_lsn.offset));
#endif
      __rep_cmp_vote(dbenv, rep, eid, &rp->lsn, vi->priority,
          rp->gen, vi->tiebreaker);
      /*
       * If you get a vote and you're not in an election, we've
       * already recorded this vote.  But that is all we need
       * to do.
       */
      if (!IN_ELECTION(rep)) {
            RPRINT(dbenv, rep, (dbenv, &mb,
                "Not in election, but received vote1 0x%x",
                rep->flags));
            ret = DB_REP_HOLDELECTION;
            goto err;
      }

      master = rep->winner;
      lsn = rep->w_lsn;
      /*
       * We need to check sites == nsites, not more than half
       * like we do in __rep_elect and the VOTE2 code below.  The
       * reason is that we want to process all the incoming votes
       * and not short-circuit once we reach more than half.  The
       * real winner's vote may be in the last half.
       */
      done = rep->sites >= rep->nsites && rep->w_priority != 0;
      if (done) {
            RPRINT(dbenv, rep,
                (dbenv, &mb, "Phase1 election done"));
            RPRINT(dbenv, rep, (dbenv, &mb, "Voting for %d%s",
                master, master == rep->eid ? "(self)" : ""));
            egen = rep->egen;
            F_SET(rep, REP_F_EPHASE2);
            F_CLR(rep, REP_F_EPHASE1);
            if (master == rep->eid) {
                  (void)__rep_tally(dbenv, rep, rep->eid,
                      &rep->votes, egen, rep->v2tally_off);
                  goto err;
            }
            REP_SYSTEM_UNLOCK(dbenv);

            /* Vote for someone else. */
            __rep_send_vote(dbenv, NULL, 0, 0, 0, 0, egen,
                master, REP_VOTE2);
      } else
err:        REP_SYSTEM_UNLOCK(dbenv);
      return (ret);
}

/*
 * __rep_vote2 --
 *    Handle incoming vote1 message on a client.
 *
 * PUBLIC: int __rep_vote2 __P((DB_ENV *, DBT *, int *));
 */
int
__rep_vote2(dbenv, rec, eidp)
      DB_ENV *dbenv;
      DBT *rec;
      int *eidp;
{
      DB_LOG *dblp;
      DB_LSN lsn;
      DB_REP *db_rep;
      LOG *lp;
      REP *rep;
      REP_VOTE_INFO *vi;
      int done, ret;
#ifdef DIAGNOSTIC
      DB_MSGBUF mb;
#endif

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

      RPRINT(dbenv, rep, (dbenv, &mb, "We received a vote%s",
          F_ISSET(rep, REP_F_MASTER) ? " (master)" : ""));
      if (F_ISSET(rep, REP_F_MASTER)) {
            LOG_SYSTEM_LOCK(dbenv);
            lsn = lp->lsn;
            LOG_SYSTEM_UNLOCK(dbenv);
            rep->stat.st_elections_won++;
            (void)__rep_send_message(dbenv,
                DB_EID_BROADCAST, REP_NEWMASTER, &lsn, NULL, 0, 0);
            return (ret);
      }

      REP_SYSTEM_LOCK(dbenv);

      /* If we have priority 0, we should never get a vote. */
      DB_ASSERT(rep->priority != 0);

      /*
       * We might be the last to the party and we haven't had
       * time to tally all the vote1's, but others have and
       * decided we're the winner.  So, if we're in the process
       * of tallying sites, keep the vote so that when our
       * election thread catches up we'll have the votes we
       * already received.
       */
      vi = (REP_VOTE_INFO *)rec->data;
      if (!IN_ELECTION_TALLY(rep) && vi->egen >= rep->egen) {
            RPRINT(dbenv, rep, (dbenv, &mb,
                "Not in election gen %lu, at %lu, got vote",
                (u_long)vi->egen, (u_long)rep->egen));
            ret = DB_REP_HOLDELECTION;
            goto err;
      }

      /*
       * Record this vote.  In a VOTE2, the only valid entry
       * in the REP_VOTE_INFO is the election generation.
       *
       * There are several things which can go wrong that we
       * need to account for:
       * 1. If we receive a latent VOTE2 from an earlier election,
       * we want to ignore it.
       * 2. If we receive a VOTE2 from a site from which we never
       * received a VOTE1, we want to ignore it.
       * 3. If we have received a duplicate VOTE2 from this election
       * from the same site we want to ignore it.
       * 4. If this is from the current election and someone is
       * really voting for us, then we finally get to record it.
       */
      /*
       * __rep_cmp_vote2 checks for cases 1 and 2.
       */
      if ((ret = __rep_cmp_vote2(dbenv, rep, *eidp, vi->egen)) != 0) {
            ret = 0;
            goto err;
      }
      /*
       * __rep_tally takes care of cases 3 and 4.
       */
      if ((ret = __rep_tally(dbenv, rep, *eidp, &rep->votes,
          vi->egen, rep->v2tally_off)) != 0) {
            ret = 0;
            goto err;
      }
      done = rep->votes >= rep->nvotes;
      RPRINT(dbenv, rep, (dbenv, &mb, "Counted vote %d of %d",
          rep->votes, rep->nvotes));
      if (done) {
            __rep_elect_master(dbenv, rep, eidp);
            ret = DB_REP_NEWMASTER;
      }

err:  REP_SYSTEM_UNLOCK(dbenv);
      return (ret);
}

/*
 * __rep_tally --
 *    Handle incoming vote1 message on a client.  Called with the db_rep
 *    mutex held.  This function will return 0 if we successfully tally
 *    the vote and non-zero if the vote is ignored.  This will record
 *    both VOTE1 and VOTE2 records, depending on which region offset the
 *    caller passed in.
 */
static int
__rep_tally(dbenv, rep, eid, countp, egen, vtoff)
      DB_ENV *dbenv;
      REP *rep;
      int eid, *countp;
      u_int32_t egen;
      roff_t vtoff;
{
      REP_VTALLY *tally, *vtp;
      int i;
#ifdef DIAGNOSTIC
      DB_MSGBUF mb;
#else
      COMPQUIET(rep, NULL);
#endif

      tally = R_ADDR((REGINFO *)dbenv->reginfo, vtoff);
      i = 0;
      vtp = &tally[i];
      while (i < *countp) {
            /*
             * Ignore votes from earlier elections (i.e. we've heard
             * from this site in this election, but its vote from an
             * earlier election got delayed and we received it now).
             * However, if we happened to hear from an earlier vote
             * and we recorded it and we're now hearing from a later
             * election we want to keep the updated one.  Note that
             * updating the entry will not increase the count.
             * Also ignore votes that are duplicates.
             */
            if (vtp->eid == eid) {
                  RPRINT(dbenv, rep, (dbenv, &mb,
                      "Tally found[%d] (%d, %lu), this vote (%d, %lu)",
                            i, vtp->eid, (u_long)vtp->egen,
                            eid, (u_long)egen));
                  if (vtp->egen >= egen)
                        return (1);
                  else {
                        vtp->egen = egen;
                        return (0);
                  }
            }
            i++;
            vtp = &tally[i];
      }
      /*
       * If we get here, we have a new voter we haven't
       * seen before.  Tally this vote.
       */
#ifdef DIAGNOSTIC
      if (vtoff == rep->tally_off)
            RPRINT(dbenv, rep, (dbenv, &mb, "Tallying VOTE1[%d] (%d, %lu)",
                i, eid, (u_long)egen));
      else
            RPRINT(dbenv, rep, (dbenv, &mb, "Tallying VOTE2[%d] (%d, %lu)",
                i, eid, (u_long)egen));
#endif
      vtp->eid = eid;
      vtp->egen = egen;
      (*countp)++;
      return (0);
}

/*
 * __rep_cmp_vote --
 *    Compare incoming vote1 message on a client.  Called with the db_rep
 *    mutex held.
 *
 */
static void
__rep_cmp_vote(dbenv, rep, eid, lsnp, priority, gen, tiebreaker)
      DB_ENV *dbenv;
      REP *rep;
      int eid;
      DB_LSN *lsnp;
      int priority;
      u_int32_t gen, tiebreaker;
{
      int cmp;

#ifdef DIAGNOSTIC
      DB_MSGBUF mb;
#else
      COMPQUIET(dbenv, NULL);
#endif
      cmp = log_compare(lsnp, &rep->w_lsn);
      /*
       * If we've seen more than one, compare us to the best so far.
       * If we're the first, make ourselves the winner to start.
       */
      if (rep->sites > 1 && priority != 0) {
            /*
             * LSN is primary determinant. Then priority if LSNs
             * are equal, then tiebreaker if both are equal.
             */
            if (cmp > 0 ||
                (cmp == 0 && (priority > rep->w_priority ||
                (priority == rep->w_priority &&
                (tiebreaker > rep->w_tiebreaker))))) {
                  RPRINT(dbenv, rep, (dbenv, &mb, "Accepting new vote"));
                  rep->winner = eid;
                  rep->w_priority = priority;
                  rep->w_lsn = *lsnp;
                  rep->w_gen = gen;
                  rep->w_tiebreaker = tiebreaker;
            }
      } else if (rep->sites == 1) {
            if (priority != 0) {
                  /* Make ourselves the winner to start. */
                  rep->winner = eid;
                  rep->w_priority = priority;
                  rep->w_gen = gen;
                  rep->w_lsn = *lsnp;
                  rep->w_tiebreaker = tiebreaker;
            } else {
                  rep->winner = DB_EID_INVALID;
                  rep->w_priority = 0;
                  rep->w_gen = 0;
                  ZERO_LSN(rep->w_lsn);
                  rep->w_tiebreaker = 0;
            }
      }
      return;
}

/*
 * __rep_cmp_vote2 --
 *    Compare incoming vote2 message with vote1's we've recorded.  Called
 *    with the db_rep mutex held.  We return 0 if the VOTE2 is from a
 *    site we've heard from and it is from this election.  Otherwise return 1.
 *
 */
static int
__rep_cmp_vote2(dbenv, rep, eid, egen)
      DB_ENV *dbenv;
      REP *rep;
      int eid;
      u_int32_t egen;
{
      int i;
      REP_VTALLY *tally, *vtp;
#ifdef DIAGNOSTIC
      DB_MSGBUF mb;
#endif

      tally = R_ADDR((REGINFO *)dbenv->reginfo, rep->tally_off);
      i = 0;
      vtp = &tally[i];
      for (i = 0; i < rep->sites; i++) {
            vtp = &tally[i];
            if (vtp->eid == eid && vtp->egen == egen) {
                  RPRINT(dbenv, rep, (dbenv, &mb,
                      "Found matching vote1 (%d, %lu), at %d of %d",
                      eid, (u_long)egen, i, rep->sites));
                  return (0);
            }
      }
      RPRINT(dbenv, rep,
          (dbenv, &mb, "Didn't find vote1 for eid %d, egen %lu",
          eid, (u_long)egen));
      return (1);
}

/*
 * __rep_elect_init
 *    Initialize an election.  Sets beginp non-zero if the election is
 * already in progress; makes it 0 otherwise.
 */
static int
__rep_elect_init(dbenv, lsnp, nsites, nvotes, priority, beginp, otally)
      DB_ENV *dbenv;
      DB_LSN *lsnp;
      int nsites, nvotes, priority;
      int *beginp;
      u_int32_t *otally;
{
      DB_REP *db_rep;
      REP *rep;
      int ret;

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

      ret = 0;

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

      /* If we are already a master; simply broadcast that fact and return. */
      if (F_ISSET(rep, REP_F_MASTER)) {
            (void)__rep_send_message(dbenv,
                DB_EID_BROADCAST, REP_NEWMASTER, lsnp, NULL, 0, 0);
            rep->stat.st_elections_won++;
            return (DB_REP_NEWMASTER);
      }

      REP_SYSTEM_LOCK(dbenv);
      if (otally != NULL)
            *otally = F_ISSET(rep, REP_F_TALLY);
      *beginp = IN_ELECTION(rep) || rep->elect_th;
      if (!*beginp) {
            /*
             * Make sure that we always initialize all the election fields
             * before putting ourselves in an election state.  That means
             * issuing calls that can fail (allocation) before setting all
             * the variables.
             */
            if (nsites > rep->asites &&
                (ret = __rep_grow_sites(dbenv, nsites)) != 0)
                  goto err;
            DB_ENV_TEST_RECOVERY(dbenv, DB_TEST_ELECTINIT, ret, NULL);
            rep->elect_th = 1;
            rep->nsites = nsites;
            rep->nvotes = nvotes;
            rep->priority = priority;
            rep->master_id = DB_EID_INVALID;
      }
DB_TEST_RECOVERY_LABEL
err:  REP_SYSTEM_UNLOCK(dbenv);
      return (ret);
}

/*
 * __rep_elect_master
 *    Set up for new master from election.  Must be called with
 *    the replication region mutex held.
 *
 * PUBLIC: void __rep_elect_master __P((DB_ENV *, REP *, int *));
 */
void
__rep_elect_master(dbenv, rep, eidp)
      DB_ENV *dbenv;
      REP *rep;
      int *eidp;
{
#ifdef DIAGNOSTIC
      DB_MSGBUF mb;
#else
      COMPQUIET(dbenv, NULL);
#endif
      rep->master_id = rep->eid;
      F_SET(rep, REP_F_MASTERELECT);
      if (eidp != NULL)
            *eidp = rep->master_id;
      rep->stat.st_elections_won++;
      RPRINT(dbenv, rep, (dbenv, &mb,
          "Got enough votes to win; election done; winner is %d, gen %lu",
          rep->master_id, (u_long)rep->gen));
}

static int
__rep_wait(dbenv, timeout, eidp, flags)
      DB_ENV *dbenv;
      u_int32_t timeout;
      int *eidp;
      u_int32_t flags;
{
      DB_REP *db_rep;
      REP *rep;
      int done, echg;
      u_int32_t egen, sleeptime;

      done = echg = 0;
      db_rep = dbenv->rep_handle;
      rep = db_rep->region;
      egen = rep->egen;

      /*
       * The user specifies an overall timeout function, but checking
       * is cheap and the timeout may be a generous upper bound.
       * Sleep repeatedly for the smaller of .5s and timeout/10.
       */
      sleeptime = (timeout > 5000000) ? 500000 : timeout / 10;
      if (sleeptime == 0)
            sleeptime++;
      while (timeout > 0) {
            __os_sleep(dbenv, 0, sleeptime);
            REP_SYSTEM_LOCK(dbenv);
            echg = egen != rep->egen;
            done = !F_ISSET(rep, flags) && rep->master_id != DB_EID_INVALID;

            *eidp = rep->master_id;
            REP_SYSTEM_UNLOCK(dbenv);

            if (done)
                  return (0);

            if (echg)
                  return (DB_REP_EGENCHG);

            if (timeout > sleeptime)
                  timeout -= sleeptime;
            else
                  timeout = 0;
      }
      return (DB_TIMEOUT);
}

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