txn_region.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: txn_region.c,v 12.10 2005/10/14 21:12:18 ubell Exp $
 */

#include "db_config.h"

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.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

#include <string.h>
#endif

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

static int __txn_init __P((DB_ENV *, DB_TXNMGR *));
static size_t __txn_region_size __P((DB_ENV *));

/*
 * __txn_open --
 *      Open a transaction region.
 *
 * PUBLIC: int __txn_open __P((DB_ENV *));
 */
int
__txn_open(dbenv)
        DB_ENV *dbenv;
{
        DB_TXNMGR *mgr;
        int ret;

        /* Create/initialize the transaction manager structure. */
        if ((ret = __os_calloc(dbenv, 1, sizeof(DB_TXNMGR), &mgr)) != 0)
                return (ret);
        TAILQ_INIT(&mgr->txn_chain);
        mgr->dbenv = dbenv;

        /* Join/create the txn region. */
        mgr->reginfo.dbenv = dbenv;
        mgr->reginfo.type = REGION_TYPE_TXN;
        mgr->reginfo.id = INVALID_REGION_ID;
        mgr->reginfo.flags = REGION_JOIN_OK;
        if (F_ISSET(dbenv, DB_ENV_CREATE))
                F_SET(&mgr->reginfo, REGION_CREATE_OK);
        if ((ret = __db_r_attach(dbenv,
            &mgr->reginfo, __txn_region_size(dbenv))) != 0)
                goto err;

        /* If we created the region, initialize it. */
        if (F_ISSET(&mgr->reginfo, REGION_CREATE))
                if ((ret = __txn_init(dbenv, mgr)) != 0)
                        goto err;

        /* Set the local addresses. */
        mgr->reginfo.primary =
            R_ADDR(&mgr->reginfo, mgr->reginfo.rp->primary);

        /* If threaded, acquire a mutex to protect the active TXN list. */
        if ((ret = __mutex_alloc(
            dbenv, MTX_TXN_ACTIVE, DB_MUTEX_THREAD, &mgr->mutex)) != 0)
                goto err;

        dbenv->tx_handle = mgr;
        return (0);

err:    dbenv->tx_handle = NULL;
        if (mgr->reginfo.addr != NULL)
                (void)__db_r_detach(dbenv, &mgr->reginfo, 0);

        (void)__mutex_free(dbenv, &mgr->mutex);
        __os_free(dbenv, mgr);
        return (ret);
}

/*
 * __txn_init --
 *      Initialize a transaction region in shared memory.
 */
static int
__txn_init(dbenv, mgr)
        DB_ENV *dbenv;
        DB_TXNMGR *mgr;
{
        DB_LSN last_ckp;
        DB_TXNREGION *region;
        int ret;

        /*
         * Find the last checkpoint in the log.
         */
        ZERO_LSN(last_ckp);
        if (LOGGING_ON(dbenv)) {
                /*
                 * The log system has already walked through the last
                 * file.  Get the LSN of a checkpoint it may have found.
                 */
                if ((ret = __log_get_cached_ckp_lsn(dbenv, &last_ckp)) != 0)
                        return (ret);

                /*
                 * If that didn't work, look backwards from the beginning of
                 * the last log file until we find the last checkpoint.
                 */
                if (IS_ZERO_LSN(last_ckp) &&
                    (ret = __txn_findlastckp(dbenv, &last_ckp, NULL)) != 0)
                        return (ret);
        }

        if ((ret = __db_shalloc(&mgr->reginfo,
            sizeof(DB_TXNREGION), 0, &mgr->reginfo.primary)) != 0) {
                __db_err(dbenv,
                    "Unable to allocate memory for the transaction region");
                return (ret);
        }
        mgr->reginfo.rp->primary =
            R_OFFSET(&mgr->reginfo, mgr->reginfo.primary);
        region = mgr->reginfo.primary;
        memset(region, 0, sizeof(*region));

        if ((ret = __mutex_alloc(
            dbenv, MTX_TXN_REGION, 0, &region->mtx_region)) != 0)
                return (ret);

        region->maxtxns = dbenv->tx_max;
        region->last_txnid = TXN_MINIMUM;
        region->cur_maxid = TXN_MAXIMUM;

        if ((ret = __mutex_alloc(
            dbenv, MTX_TXN_CHKPT, 0, &region->mtx_ckp)) != 0)
                return (ret);
        region->last_ckp = last_ckp;
        region->time_ckp = time(NULL);

        memset(&region->stat, 0, sizeof(region->stat));
        region->stat.st_maxtxns = region->maxtxns;

        SH_TAILQ_INIT(&region->active_txn);
        return (ret);
}

/*
 * __txn_findlastckp --
 *      Find the last checkpoint in the log, walking backwards from the
 *      max_lsn given or the beginning of the last log file.  (The
 *      log system looked through the last log file when it started up.)
 *
 * PUBLIC: int __txn_findlastckp __P((DB_ENV *, DB_LSN *, DB_LSN *));
 */
int
__txn_findlastckp(dbenv, lsnp, max_lsn)
        DB_ENV *dbenv;
        DB_LSN *lsnp;
        DB_LSN *max_lsn;
{
        DB_LOGC *logc;
        DB_LSN lsn;
        DBT dbt;
        int ret, t_ret;
        u_int32_t rectype;

        ZERO_LSN(*lsnp);

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

        /* Get the last LSN. */
        memset(&dbt, 0, sizeof(dbt));
        if (max_lsn != NULL) {
                lsn = *max_lsn;
                if ((ret = __log_c_get(logc, &lsn, &dbt, DB_SET)) != 0)
                        goto err;
        } else {
                if ((ret = __log_c_get(logc, &lsn, &dbt, DB_LAST)) != 0)
                        goto err;
                /*
                 * Twiddle the last LSN so it points to the beginning of the
                 * last file; we know there's no checkpoint after that, since
                 * the log system already looked there.
                 */
                lsn.offset = 0;
        }

        /* Read backwards, looking for checkpoints. */
        while ((ret = __log_c_get(logc, &lsn, &dbt, DB_PREV)) == 0) {
                if (dbt.size < sizeof(u_int32_t))
                        continue;
                memcpy(&rectype, dbt.data, sizeof(u_int32_t));
                if (rectype == DB___txn_ckp) {
                        *lsnp = lsn;
                        break;
                }
        }

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

        /*
         * Not finding a checkpoint is not an error;  there may not exist
         * one in the log.
         */
        return ((ret == 0 || ret == DB_NOTFOUND) ? 0 : ret);
}

/*
 * __txn_dbenv_refresh --
 *      Clean up after the transaction system on a close or failed open.
 *
 * PUBLIC: int __txn_dbenv_refresh __P((DB_ENV *));
 */
int
__txn_dbenv_refresh(dbenv)
        DB_ENV *dbenv;
{
        DB_TXN *txn;
        DB_TXNMGR *mgr;
        REGINFO *reginfo;
        u_int32_t txnid;
        int aborted, ret, t_ret;

        ret = 0;
        mgr = dbenv->tx_handle;
        reginfo = &mgr->reginfo;

        /*
         * This function can only be called once per process (i.e., not
         * once per thread), so no synchronization is required.
         *
         * The caller is probably doing something wrong if close is called with
         * active transactions.  Try and abort any active transactions that are
         * not prepared, but it's quite likely the aborts will fail because
         * recovery won't find open files.  If we can't abort any of the
         * unprepared transaction, panic, we have to run recovery to get back
         * to a known state.
         */
        aborted = 0;
        if (TAILQ_FIRST(&mgr->txn_chain) != NULL) {
                while ((txn = TAILQ_FIRST(&mgr->txn_chain)) != NULL) {
                        /* Prepared transactions are OK. */
                        txnid = txn->txnid;
                        if (((TXN_DETAIL *)txn->td)->status == TXN_PREPARED) {
                                if ((ret = __txn_discard_int(txn, 0)) != 0) {
                                        __db_err(dbenv,
                                            "Unable to discard txn 0x%x: %s",
                                            txnid, db_strerror(ret));
                                        break;
                                }
                                continue;
                        }
                        aborted = 1;
                        if ((t_ret = __txn_abort(txn)) != 0) {
                                __db_err(dbenv,
                                    "Unable to abort transaction 0x%x: %s",
                                    txnid, db_strerror(t_ret));
                                ret = __db_panic(dbenv, t_ret);
                                break;
                        }
                }
                if (aborted) {
                        __db_err(dbenv,
        "Error: closing the transaction region with active transactions");
                        if (ret == 0)
                                ret = EINVAL;
                }
        }

        /* Flush the log. */
        if (LOGGING_ON(dbenv) &&
            (t_ret = __log_flush(dbenv, NULL)) != 0 && ret == 0)
                ret = t_ret;

        /* Discard the per-thread lock. */
        if ((t_ret = __mutex_free(dbenv, &mgr->mutex)) != 0 && ret == 0)
                ret = t_ret;

        /* Detach from the region. */
        if ((t_ret = __db_r_detach(dbenv, reginfo, 0)) != 0 && ret == 0)
                ret = t_ret;

        __os_free(dbenv, mgr);

        dbenv->tx_handle = NULL;
        return (ret);
}

/*
 * __txn_region_size --
 *       Return the amount of space needed for the txn region.  Make the
 *       region large enough to hold txn_max transaction detail structures
 *       plus some space to hold thread handles and the beginning of the
 *       shalloc region and anything we need for mutex system resource
 *       recording.
 */
static size_t
__txn_region_size(dbenv)
        DB_ENV *dbenv;
{
        size_t s;

        s = sizeof(DB_TXNREGION) +
            dbenv->tx_max * sizeof(TXN_DETAIL) + 10 * 1024;
        return (s);
}

/*
 * __txn_id_set --
 *      Set the current transaction ID and current maximum unused ID (for
 *      testing purposes only).
 *
 * PUBLIC: int __txn_id_set __P((DB_ENV *, u_int32_t, u_int32_t));
 */
int
__txn_id_set(dbenv, cur_txnid, max_txnid)
        DB_ENV *dbenv;
        u_int32_t cur_txnid, max_txnid;
{
        DB_TXNMGR *mgr;
        DB_TXNREGION *region;
        int ret;

        ENV_REQUIRES_CONFIG(dbenv, dbenv->tx_handle, "txn_id_set", DB_INIT_TXN);

        mgr = dbenv->tx_handle;
        region = mgr->reginfo.primary;
        region->last_txnid = cur_txnid;
        region->cur_maxid = max_txnid;

        ret = 0;
        if (cur_txnid < TXN_MINIMUM) {
                __db_err(dbenv, "Current ID value %lu below minimum",
                    (u_long)cur_txnid);
                ret = EINVAL;
        }
        if (max_txnid < TXN_MINIMUM) {
                __db_err(dbenv, "Maximum ID value %lu below minimum",
                    (u_long)max_txnid);
                ret = EINVAL;
        }
        return (ret);
}

---