Version 3.0.1
ex_log.c

Shows how to access the database log files.

/*-
* Public Domain 2014-2018 MongoDB, Inc.
* 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 use logging and log cursors.
*/
#include <test_util.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 void
setup_copy(WT_CONNECTION **wt_connp, WT_SESSION **sessionp)
{
error_check(wiredtiger_open(home2, NULL, CONN_CONFIG, wt_connp));
error_check((*wt_connp)->open_session(*wt_connp, NULL, NULL, sessionp));
error_check((*sessionp)->create(
*sessionp, uri, "key_format=S,value_format=S"));
}
static void
compare_tables(WT_SESSION *session, WT_SESSION *sess_copy)
{
WT_CURSOR *cursor, *curs_copy;
int ret;
const char *key, *key_copy, *value, *value_copy;
error_check(session->open_cursor(session, uri, NULL, NULL, &cursor));
error_check(
sess_copy->open_cursor(sess_copy, uri, NULL, NULL, &curs_copy));
while ((ret = cursor->next(cursor)) == 0) {
error_check(curs_copy->next(curs_copy));
error_check(cursor->get_key(cursor, &key));
error_check(cursor->get_value(cursor, &value));
error_check(curs_copy->get_key(curs_copy, &key_copy));
error_check(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);
exit (1);
}
}
scan_end_check(ret == WT_NOTFOUND);
error_check(cursor->close(cursor));
ret = curs_copy->next(curs_copy);
scan_end_check(ret == WT_NOTFOUND);
error_check(curs_copy->close(curs_copy));
}
static void
print_record(uint32_t log_file, uint32_t log_offset, uint32_t opcount,
uint32_t rectype, uint32_t optype, uint64_t txnid, uint32_t fileid,
WT_ITEM *key, WT_ITEM *value)
{
printf(
"LSN [%" PRIu32 "][%" PRIu32 "].%" PRIu32
": record type %" PRIu32 " optype %" PRIu32
" txnid %" PRIu64 " fileid %" PRIu32,
log_file, log_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 void
simple_walk_log(WT_SESSION *session, int count_min)
{
WT_CURSOR *cursor;
WT_ITEM logrec_key, logrec_value;
uint64_t txnid;
uint32_t fileid, log_file, log_offset, opcount, optype, rectype;
int count, ret;
error_check(session->open_cursor(session, "log:", NULL, NULL, &cursor));
count = 0;
while ((ret = cursor->next(cursor)) == 0) {
count++;
error_check(cursor->get_key(
cursor, &log_file, &log_offset, &opcount));
error_check(cursor->get_value(cursor, &txnid,
&rectype, &optype, &fileid, &logrec_key, &logrec_value));
print_record(log_file, log_offset, opcount,
rectype, optype, txnid, fileid, &logrec_key, &logrec_value);
}
scan_end_check(ret == WT_NOTFOUND);
error_check(cursor->close(cursor));
if (count < count_min) {
fprintf(stderr,
"Expected minimum %d records, found %d\n",
count_min, count);
exit (1);
}
}
static void
walk_log(WT_SESSION *session)
{
WT_CONNECTION *wt_conn2;
WT_CURSOR *cursor, *cursor2;
WT_ITEM logrec_key, logrec_value;
WT_SESSION *session2;
uint64_t txnid;
uint32_t fileid, opcount, optype, rectype;
uint32_t log_file, log_offset, save_file, save_offset;
int first, i, in_txn, ret;
setup_copy(&wt_conn2, &session2);
error_check(session->open_cursor(session, "log:", NULL, NULL, &cursor));
error_check(session2->open_cursor(
session2, uri, NULL, "raw=true", &cursor2));
i = 0;
in_txn = 0;
txnid = 0;
save_file = save_offset = 0;
while ((ret = cursor->next(cursor)) == 0) {
error_check(cursor->get_key(
cursor, &log_file, &log_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) {
save_file = log_file;
save_offset = log_offset;
}
error_check(cursor->get_value(cursor, &txnid, &rectype,
&optype, &fileid, &logrec_key, &logrec_value));
print_record(log_file, log_offset, 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) {
error_check(
session2->commit_transaction(session2, NULL));
in_txn = 0;
}
/*
* If the operation is a put, replay it here on the backup
* connection.
*
* !!!
* Minor cheat: the metadata is fileid 0, skip its records.
*/
if (fileid != 0 &&
rectype == WT_LOGREC_COMMIT && optype == WT_LOGOP_ROW_PUT) {
if (!in_txn) {
error_check(session2->begin_transaction(
session2, NULL));
in_txn = 1;
}
cursor2->set_key(cursor2, &logrec_key);
cursor2->set_value(cursor2, &logrec_value);
error_check(cursor2->insert(cursor2));
}
}
if (in_txn)
error_check(session2->commit_transaction(session2, NULL));
error_check(cursor2->close(cursor2));
/*
* Compare the tables after replay. They should be identical.
*/
compare_tables(session, session2);
error_check(session2->close(session2, NULL));
error_check(wt_conn2->close(wt_conn2, NULL));
error_check(cursor->reset(cursor));
cursor->set_key(cursor, save_file, save_offset, 0);
error_check(cursor->search(cursor));
printf("Reset to saved...\n");
/*
* Walk all records starting with this key.
*/
for (first = 1;;) {
error_check(cursor->get_key(
cursor, &log_file, &log_offset, &opcount));
if (first) {
first = 0;
if (save_file != log_file ||
save_offset != log_offset) {
fprintf(stderr,
"search returned the wrong LSN\n");
exit (1);
}
}
error_check(cursor->get_value(cursor, &txnid, &rectype,
&optype, &fileid, &logrec_key, &logrec_value));
print_record(log_file, log_offset, opcount,
rectype, optype, txnid, fileid, &logrec_key, &logrec_value);
ret = cursor->next(cursor);
if (ret != 0)
break;
}
scan_end_check(ret == WT_NOTFOUND);
error_check(cursor->close(cursor));
}
int
main(int argc, char *argv[])
{
WT_CONNECTION *wt_conn;
WT_CURSOR *cursor;
WT_SESSION *session;
int count_min, i, record_count;
char cmd_buf[256], k[32], v[32];
(void)argc; /* Unused variable */
(void)testutil_set_progname(argv);
count_min = 0;
(void)snprintf(cmd_buf, sizeof(cmd_buf),
"rm -rf %s %s && mkdir %s %s", home1, home2, home1, home2);
error_check(system(cmd_buf));
error_check(wiredtiger_open(home1, NULL, CONN_CONFIG, &wt_conn));
error_check(wt_conn->open_session(wt_conn, NULL, NULL, &session));
error_check(
session->create(session, uri, "key_format=S,value_format=S"));
count_min++;
error_check(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++) {
(void)snprintf(k, sizeof(k), "key%d", i);
(void)snprintf(v, sizeof(v), "value%d", i);
cursor->set_key(cursor, k);
cursor->set_value(cursor, v);
error_check(cursor->insert(cursor));
count_min++;
}
error_check(session->begin_transaction(session, NULL));
/*
* Perform some operations within a single transaction.
*/
for (i = MAX_KEYS; i < MAX_KEYS+5; i++, record_count++) {
(void)snprintf(k, sizeof(k), "key%d", i);
(void)snprintf(v, sizeof(v), "value%d", i);
cursor->set_key(cursor, k);
cursor->set_value(cursor, v);
error_check(cursor->insert(cursor));
}
error_check(session->commit_transaction(session, NULL));
count_min++;
error_check(cursor->close(cursor));
error_check(
session->log_printf(session, "Wrote %d records", record_count));
count_min++;
/*
* 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.
*/
error_check(wt_conn->close(wt_conn, NULL));
error_check(wiredtiger_open(home1, NULL, CONN_CONFIG, &wt_conn));
error_check(wt_conn->open_session(wt_conn, NULL, NULL, &session));
simple_walk_log(session, count_min);
walk_log(session);
error_check(wt_conn->close(wt_conn, NULL));
return (EXIT_SUCCESS);
}