ex_log.c

Shows how to access the database log files.

/*-
 * Public Domain 2008-2014 WiredTiger, Inc.
 *
 * This is free and unencumbered software released into the public domain.
 *
 * Anyone is free to copy, modify, publish, use, compile, sell, or
 * distribute this software, either in source code form or as a compiled
 * binary, for any purpose, commercial or non-commercial, and by any
 * means.
 *
 * In jurisdictions that recognize copyright laws, the author or authors
 * of this software dedicate any and all copyright interest in the
 * software to the public domain. We make this dedication for the benefit
 * of the public at large and to the detriment of our heirs and
 * successors. We intend this dedication to be an overt act of
 * relinquishment in perpetuity of all present and future rights to this
 * software under copyright law.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * ex_log.c
 *      demonstrates how to logging and log cursors.
 */
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifndef _WIN32
#include <unistd.h>
#else
/* snprintf is not supported on <= VS2013 */
#define snprintf _snprintf
#endif

#include <wiredtiger.h>

static const char *home1 = "WT_HOME_LOG_1";
static const char *home2 = "WT_HOME_LOG_2";

static const char * const uri = "table:logtest";

#define CONN_CONFIG "create,cache_size=100MB,log=(archive=false,enabled=true)"
#define MAX_KEYS        10

static int
setup_copy(WT_CONNECTION **wt_connp, WT_SESSION **sessionp)
{
        int ret;

        if ((ret = wiredtiger_open(home2, NULL,
            CONN_CONFIG, wt_connp)) != 0) {
                fprintf(stderr, "Error connecting to %s: %s\n",
                    home1, wiredtiger_strerror(ret));
                return (ret);
        }

        ret = (*wt_connp)->open_session(*wt_connp, NULL, NULL, sessionp);
        ret = (*sessionp)->create(*sessionp, uri,
            "key_format=S,value_format=S");
        return (ret);
}

static int
compare_tables(WT_SESSION *session, WT_SESSION *sess_copy)
{
        WT_CURSOR *cursor, *curs_copy;
        int ret;
        const char *key, *key_copy, *value, *value_copy;

        ret = session->open_cursor(session, uri, NULL, NULL, &cursor);
        ret = sess_copy->open_cursor(sess_copy, uri, NULL, NULL, &curs_copy);

        while ((ret = cursor->next(cursor)) == 0) {
                ret = curs_copy->next(curs_copy);
                ret = cursor->get_key(cursor, &key);
                ret = cursor->get_value(cursor, &value);
                ret = curs_copy->get_key(curs_copy, &key_copy);
                ret = curs_copy->get_value(curs_copy, &value_copy);
                if (strcmp(key, key_copy) != 0 ||
                    strcmp(value, value_copy) != 0) {
                        fprintf(stderr,
                            "Mismatched: key %s, key_copy %s "
                            "value %s value_copy %s\n",
                            key, key_copy, value, value_copy);
                        return (1);
                }
        }
        if (ret != WT_NOTFOUND)
                fprintf(stderr,
                    "WT_CURSOR.next: %s\n", wiredtiger_strerror(ret));
        ret = cursor->close(cursor);

        ret = curs_copy->next(curs_copy);
        if (ret != WT_NOTFOUND)
                fprintf(stderr,
                    "copy: WT_CURSOR.next: %s\n", wiredtiger_strerror(ret));
        ret = curs_copy->close(curs_copy);

        return (ret);
}

static void
print_record(WT_LSN *lsn, uint32_t opcount,
   uint32_t rectype, uint32_t optype, uint64_t txnid, uint32_t fileid,
   WT_ITEM *key, WT_ITEM *value)
{
        printf(
            "LSN [%" PRIu32 "][%" PRIu64 "].%" PRIu32
            ": record type %" PRIu32 " optype %" PRIu32
            " txnid %" PRIu64 " fileid %" PRIu32,
            lsn->file, (uint64_t)lsn->offset, opcount,
            rectype, optype, txnid, fileid);
        printf(" key size %zu value size %zu\n", key->size, value->size);
        if (rectype == WT_LOGREC_MESSAGE)
                printf("Application Record: %s\n", (char *)value->data);
}

/*
 * simple_walk_log --
 *      A simple walk of the log.
 */
static int
simple_walk_log(WT_SESSION *session)
{
        WT_CURSOR *cursor;
        WT_LSN lsn;
        WT_ITEM logrec_key, logrec_value;
        uint64_t txnid;
        uint32_t fileid, opcount, optype, rectype;
        int ret;

        ret = session->open_cursor(session, "log:", NULL, NULL, &cursor);
        while ((ret = cursor->next(cursor)) == 0) {
                ret = cursor->get_key(cursor, &lsn.file, &lsn.offset, &opcount);
                ret = cursor->get_value(cursor, &txnid,
                    &rectype, &optype, &fileid, &logrec_key, &logrec_value);
                print_record(&lsn, opcount,
                    rectype, optype, txnid, fileid, &logrec_key, &logrec_value);
        }
        if (ret == WT_NOTFOUND)
                ret = 0;
        ret = cursor->close(cursor);
        return (ret);
}
static int
walk_log(WT_SESSION *session)
{
        WT_CONNECTION *wt_conn2;
        WT_CURSOR *cursor, *cursor2;
        WT_LSN lsn, lsnsave;
        WT_ITEM logrec_key, logrec_value;
        WT_SESSION *session2;
        uint64_t txnid;
        uint32_t fileid, opcount, optype, rectype;
        int first, i, in_txn, ret;

        ret = setup_copy(&wt_conn2, &session2);
        ret = session->open_cursor(session, "log:", NULL, NULL, &cursor);
        ret = session2->open_cursor(session2, uri, NULL, "raw=true", &cursor2);
        i = 0;
        in_txn = 0;
        txnid = 0;
        memset(&lsnsave, 0, sizeof(lsnsave));
        while ((ret = cursor->next(cursor)) == 0) {
                ret = cursor->get_key(cursor, &lsn.file, &lsn.offset, &opcount);
                /*
                 * Save one of the LSNs we get back to search for it
                 * later.  Pick a later one because we want to walk from
                 * that LSN to the end (where the multi-step transaction
                 * was performed).  Just choose the record that is MAX_KEYS.
                 */
                if (++i == MAX_KEYS)
                        lsnsave = lsn;
                ret = cursor->get_value(cursor, &txnid, &rectype,
                    &optype, &fileid, &logrec_key, &logrec_value);

                print_record(&lsn, opcount,
                    rectype, optype, txnid, fileid, &logrec_key, &logrec_value);

                /*
                 * If we are in a transaction and this is a new one, end
                 * the previous one.
                 */
                if (in_txn && opcount == 0) {
                        ret = session2->commit_transaction(session2, NULL);
                        in_txn = 0;
                }

                /*
                 * If the operation is a put, replay it here on the backup
                 * connection.  Note, we cheat by looking only for fileid 1
                 * in this example.  The metadata is fileid 0.
                 */
                if (fileid == 1 && rectype == WT_LOGREC_COMMIT &&
                    optype == WT_LOGOP_ROW_PUT) {
                        if (!in_txn) {
                                ret = session2->begin_transaction(session2,
                                    NULL);
                                in_txn = 1;
                        }
                        cursor2->set_key(cursor2, &logrec_key);
                        cursor2->set_value(cursor2, &logrec_value);
                        ret = cursor2->insert(cursor2);
                }
        }
        if (in_txn)
                ret = session2->commit_transaction(session2, NULL);

        ret = cursor2->close(cursor2);
        /*
         * Compare the tables after replay.  They should be identical.
         */
        if (compare_tables(session, session2))
                printf("compare failed\n");
        ret = session2->close(session2, NULL);
        ret = wt_conn2->close(wt_conn2, NULL);

        ret = cursor->reset(cursor);
        cursor->set_key(cursor, lsnsave.file, lsnsave.offset, 0);
        ret = cursor->search(cursor);
        printf("Reset to saved...\n");
        /*
         * Walk all records starting with this key.
         */
        first = 1;
        while ((ret = cursor->get_key(cursor,
            &lsn.file, &lsn.offset, &opcount)) == 0) {
                if (first) {
                        first = 0;
                        if (lsnsave.file != lsn.file ||
                            lsnsave.offset != lsn.offset) {
                                fprintf(stderr,
                                    "search returned the wrong LSN\n");
                                exit (1);
                        }
                }
                ret = cursor->get_value(cursor, &txnid, &rectype,
                    &optype, &fileid, &logrec_key, &logrec_value);

                print_record(&lsn, opcount,
                    rectype, optype, txnid, fileid, &logrec_key, &logrec_value);

                ret = cursor->next(cursor);
                if (ret != 0)
                        break;
        }
        ret = cursor->close(cursor);
        return (ret);
}

int
main(void)
{
        WT_CONNECTION *wt_conn;
        WT_CURSOR *cursor;
        WT_SESSION *session;
        int i, record_count, ret;
        char cmd_buf[256], k[16], v[16];

        snprintf(cmd_buf, sizeof(cmd_buf), "rm -rf %s %s && mkdir %s %s",
            home1, home2, home1, home2);
        if ((ret = system(cmd_buf)) != 0) {
                fprintf(stderr, "%s: failed ret %d\n", cmd_buf, ret);
                return (ret);
        }
        if ((ret = wiredtiger_open(home1, NULL,
            CONN_CONFIG, &wt_conn)) != 0) {
                fprintf(stderr, "Error connecting to %s: %s\n",
                    home1, wiredtiger_strerror(ret));
                return (ret);
        }

        ret = wt_conn->open_session(wt_conn, NULL, NULL, &session);
        ret = session->create(session, uri, "key_format=S,value_format=S");

        ret = session->open_cursor(session, uri, NULL, NULL, &cursor);
        /*
         * Perform some operations with individual auto-commit transactions.
         */
        for (record_count = 0, i = 0; i < MAX_KEYS; i++, record_count++) {
                snprintf(k, sizeof(k), "key%d", i);
                snprintf(v, sizeof(v), "value%d", i);
                cursor->set_key(cursor, k);
                cursor->set_value(cursor, v);
                ret = cursor->insert(cursor);
        }
        ret = session->begin_transaction(session, NULL);
        /*
         * Perform some operations within a single transaction.
         */
        for (i = MAX_KEYS; i < MAX_KEYS+5; i++, record_count++) {
                snprintf(k, sizeof(k), "key%d", i);
                snprintf(v, sizeof(v), "value%d", i);
                cursor->set_key(cursor, k);
                cursor->set_value(cursor, v);
                ret = cursor->insert(cursor);
        }
        ret = session->commit_transaction(session, NULL);
        ret = cursor->close(cursor);

        ret = session->log_printf(session, "Wrote %d records", record_count);
        /*
         * Close and reopen the connection so that the log ends up with
         * a variety of records such as file sync and checkpoint.  We
         * have archiving turned off.
         */
        ret = wt_conn->close(wt_conn, NULL);
        if ((ret = wiredtiger_open(home1, NULL,
            CONN_CONFIG, &wt_conn)) != 0) {
                fprintf(stderr, "Error connecting to %s: %s\n",
                    home1, wiredtiger_strerror(ret));
                return (ret);
        }

        ret = wt_conn->open_session(wt_conn, NULL, NULL, &session);
        ret = simple_walk_log(session);
        ret = walk_log(session);
        ret = wt_conn->close(wt_conn, NULL);
        return (ret);
}