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|
/*-
* Copyright (c) 2014-2018 MongoDB, Inc.
* Copyright (c) 2008-2014 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
#include "wt_internal.h"
static void __checkpoint_timing_stress(WT_SESSION_IMPL *);
static int __checkpoint_lock_dirty_tree(
WT_SESSION_IMPL *, bool, bool, bool, const char *[]);
static int __checkpoint_mark_skip(WT_SESSION_IMPL *, WT_CKPT *, bool);
static int __checkpoint_presync(WT_SESSION_IMPL *, const char *[]);
static int __checkpoint_tree_helper(WT_SESSION_IMPL *, const char *[]);
/*
* __checkpoint_name_ok --
* Complain if the checkpoint name isn't acceptable.
*/
static int
__checkpoint_name_ok(WT_SESSION_IMPL *session, const char *name, size_t len)
{
/* Check for characters we don't want to see in a metadata file. */
WT_RET(__wt_name_check(session, name, len));
/*
* The internal checkpoint name is special, applications aren't allowed
* to use it. Be aggressive and disallow any matching prefix, it makes
* things easier when checking in other places.
*/
if (len < strlen(WT_CHECKPOINT))
return (0);
if (!WT_PREFIX_MATCH(name, WT_CHECKPOINT))
return (0);
WT_RET_MSG(session, EINVAL,
"the checkpoint name \"%s\" is reserved", WT_CHECKPOINT);
}
/*
* __checkpoint_name_check --
* Check for an attempt to name a checkpoint that includes anything
* other than a file object.
*/
static int
__checkpoint_name_check(WT_SESSION_IMPL *session, const char *uri)
{
WT_CURSOR *cursor;
WT_DECL_RET;
const char *fail;
cursor = NULL;
fail = NULL;
/*
* This function exists as a place for this comment: named checkpoints
* are only supported on file objects, and not on LSM trees or Helium
* devices. If a target list is configured for the checkpoint, this
* function is called with each target list entry; check the entry to
* make sure it's backed by a file. If no target list is configured,
* confirm the metadata file contains no non-file objects. Skip any
* internal system objects. We don't want spurious error messages,
* other code will skip over them and the user has no control over
* their existence.
*/
if (uri == NULL) {
WT_RET(__wt_metadata_cursor(session, &cursor));
while ((ret = cursor->next(cursor)) == 0) {
WT_ERR(cursor->get_key(cursor, &uri));
if (!WT_PREFIX_MATCH(uri, "colgroup:") &&
!WT_PREFIX_MATCH(uri, "file:") &&
!WT_PREFIX_MATCH(uri, "index:") &&
!WT_PREFIX_MATCH(uri, WT_SYSTEM_PREFIX) &&
!WT_PREFIX_MATCH(uri, "table:")) {
fail = uri;
break;
}
}
WT_ERR_NOTFOUND_OK(ret);
} else
if (!WT_PREFIX_MATCH(uri, "colgroup:") &&
!WT_PREFIX_MATCH(uri, "file:") &&
!WT_PREFIX_MATCH(uri, "index:") &&
!WT_PREFIX_MATCH(uri, "table:"))
fail = uri;
if (fail != NULL)
WT_ERR_MSG(session, EINVAL,
"%s object does not support named checkpoints", fail);
err: WT_TRET(__wt_metadata_cursor_release(session, &cursor));
return (ret);
}
/*
* __checkpoint_update_generation --
* Update the checkpoint generation of the current tree.
*
* This indicates that the tree will not be visited again by the current
* checkpoint.
*/
static void
__checkpoint_update_generation(WT_SESSION_IMPL *session)
{
WT_BTREE *btree;
btree = S2BT(session);
/*
* Updates to the metadata are made by the checkpoint transaction, so
* the metadata tree's checkpoint generation should never be updated.
*/
if (WT_IS_METADATA(session->dhandle))
return;
WT_PUBLISH(btree->checkpoint_gen, __wt_gen(session, WT_GEN_CHECKPOINT));
WT_STAT_DATA_SET(session,
btree_checkpoint_generation, btree->checkpoint_gen);
}
/*
* __checkpoint_apply_all --
* Apply an operation to all files involved in a checkpoint.
*/
static int
__checkpoint_apply_all(WT_SESSION_IMPL *session, const char *cfg[],
int (*op)(WT_SESSION_IMPL *, const char *[]))
{
WT_CONFIG targetconf;
WT_CONFIG_ITEM cval, k, v;
WT_DECL_ITEM(tmp);
WT_DECL_RET;
bool ckpt_closed, named, target_list;
target_list = false;
/* Flag if this is a named checkpoint, and check if the name is OK. */
WT_RET(__wt_config_gets(session, cfg, "name", &cval));
named = cval.len != 0;
if (named)
WT_RET(__checkpoint_name_ok(session, cval.str, cval.len));
/* Step through the targets and optionally operate on each one. */
WT_ERR(__wt_config_gets(session, cfg, "target", &cval));
__wt_config_subinit(session, &targetconf, &cval);
while ((ret = __wt_config_next(&targetconf, &k, &v)) == 0) {
if (!target_list) {
WT_ERR(__wt_scr_alloc(session, 512, &tmp));
target_list = true;
}
if (v.len != 0)
WT_ERR_MSG(session, EINVAL,
"invalid checkpoint target %.*s: URIs may require "
"quoting",
(int)cval.len, (char *)cval.str);
/* Some objects don't support named checkpoints. */
if (named)
WT_ERR(__checkpoint_name_check(session, k.str));
if (op == NULL)
continue;
WT_ERR(__wt_buf_fmt(session, tmp, "%.*s", (int)k.len, k.str));
if ((ret = __wt_schema_worker(
session, tmp->data, op, NULL, cfg, 0)) != 0)
WT_ERR_MSG(session, ret, "%s", (const char *)tmp->data);
}
WT_ERR_NOTFOUND_OK(ret);
if (!target_list && named)
/* Some objects don't support named checkpoints. */
WT_ERR(__checkpoint_name_check(session, NULL));
if (!target_list && op != NULL) {
/*
* If the checkpoint is named or we're dropping checkpoints, we
* checkpoint both open and closed files; else, only checkpoint
* open files.
*
* XXX
* We don't optimize unnamed checkpoints of a list of targets,
* we open the targets and checkpoint them even if they are
* quiescent and don't need a checkpoint, believing applications
* unlikely to checkpoint a list of closed targets.
*/
ckpt_closed = named;
if (!ckpt_closed) {
WT_ERR(__wt_config_gets(session, cfg, "drop", &cval));
ckpt_closed = cval.len != 0;
}
WT_ERR(ckpt_closed ?
__wt_meta_apply_all(session, op, NULL, cfg) :
__wt_conn_btree_apply(session, NULL, op, NULL, cfg));
}
err: __wt_scr_free(session, &tmp);
return (ret);
}
/*
* __checkpoint_apply --
* Apply an operation to all handles locked for a checkpoint.
*/
static int
__checkpoint_apply(WT_SESSION_IMPL *session, const char *cfg[],
int (*op)(WT_SESSION_IMPL *, const char *[]))
{
WT_DECL_RET;
u_int i;
/* If we have already locked the handles, apply the operation. */
for (i = 0; i < session->ckpt_handle_next; ++i) {
if (session->ckpt_handle[i] == NULL)
continue;
WT_WITH_DHANDLE(session, session->ckpt_handle[i],
ret = (*op)(session, cfg));
WT_RET(ret);
}
return (0);
}
/*
* __checkpoint_data_source --
* Checkpoint all data sources.
*/
static int
__checkpoint_data_source(WT_SESSION_IMPL *session, const char *cfg[])
{
WT_DATA_SOURCE *dsrc;
WT_NAMED_DATA_SOURCE *ndsrc;
/*
* A place-holder, to support Helium devices: we assume calling the
* underlying data-source session checkpoint function is sufficient to
* checkpoint all objects in the data source, open or closed, and we
* don't attempt to optimize the checkpoint of individual targets.
* Those assumptions is correct for the Helium device, but it's not
* necessarily going to be true for other data sources.
*
* It's not difficult to support data-source checkpoints of individual
* targets (__wt_schema_worker is the underlying function that will do
* the work, and it's already written to support data-sources, although
* we'd probably need to pass the URI of the object to the data source
* checkpoint function which we don't currently do). However, doing a
* full data checkpoint is trickier: currently, the connection code is
* written to ignore all objects other than "file:", and that code will
* require significant changes to work with data sources.
*/
TAILQ_FOREACH(ndsrc, &S2C(session)->dsrcqh, q) {
dsrc = ndsrc->dsrc;
if (dsrc->checkpoint != NULL)
WT_RET(dsrc->checkpoint(dsrc,
(WT_SESSION *)session, (WT_CONFIG_ARG *)cfg));
}
return (0);
}
/*
* __wt_checkpoint_get_handles --
* Get a list of handles to flush.
*/
int
__wt_checkpoint_get_handles(WT_SESSION_IMPL *session, const char *cfg[])
{
WT_BTREE *btree;
WT_CONFIG_ITEM cval;
WT_DECL_RET;
const char *name;
bool force;
/* Find out if we have to force a checkpoint. */
WT_RET(__wt_config_gets_def(session, cfg, "force", 0, &cval));
force = cval.val != 0;
if (!force) {
WT_RET(__wt_config_gets_def(session, cfg, "name", 0, &cval));
force = cval.len != 0;
}
/* Should not be called with anything other than a live btree handle. */
WT_ASSERT(session, session->dhandle->type == WT_DHANDLE_TYPE_BTREE &&
session->dhandle->checkpoint == NULL);
btree = S2BT(session);
/* Skip files that are never involved in a checkpoint. */
if (F_ISSET(btree, WT_BTREE_NO_CHECKPOINT))
return (0);
/*
* We may have raced between starting the checkpoint transaction and
* some operation completing on the handle that updated the metadata
* (e.g., closing a bulk load cursor). All such operations either have
* exclusive access to the handle or hold the schema lock. We are now
* holding the schema lock and have an open btree handle, so if we
* can't update the metadata, then there has been some state change
* invisible to the checkpoint transaction.
*/
if (!WT_IS_METADATA(session->dhandle)) {
WT_CURSOR *meta_cursor;
WT_ASSERT(session, !F_ISSET(&session->txn, WT_TXN_ERROR));
WT_RET(__wt_metadata_cursor(session, &meta_cursor));
meta_cursor->set_key(meta_cursor, session->dhandle->name);
ret = __wt_curfile_insert_check(meta_cursor);
if (ret == WT_ROLLBACK) {
/*
* If create or drop or any schema operation of a table
* is with in an user transaction then checkpoint can
* see the dhandle before the commit, which will lead
* to the rollback error. We will ignore this dhandle as
* part of this checkpoint by returning from here.
*/
WT_TRET(__wt_metadata_cursor_release(session,
&meta_cursor));
return (0);
}
WT_TRET(__wt_metadata_cursor_release(session, &meta_cursor));
WT_RET(ret);
}
/*
* Decide whether the tree needs to be included in the checkpoint and
* if so, acquire the necessary locks.
*/
WT_SAVE_DHANDLE(session, ret = __checkpoint_lock_dirty_tree(
session, true, force, true, cfg));
WT_RET(ret);
if (F_ISSET(btree, WT_BTREE_SKIP_CKPT)) {
WT_ASSERT(session, btree->ckpt == NULL);
__checkpoint_update_generation(session);
return (0);
}
/*
* Make sure there is space for the new entry: do this before getting
* the handle to avoid cleanup if we can't allocate the memory.
*/
WT_RET(__wt_realloc_def(session, &session->ckpt_handle_allocated,
session->ckpt_handle_next + 1, &session->ckpt_handle));
/*
* The current tree will be included: get it again because the handle
* we have is only valid for the duration of this function.
*/
name = session->dhandle->name;
session->dhandle = NULL;
if ((ret = __wt_session_get_dhandle(session, name, NULL, NULL, 0)) != 0)
return (ret == EBUSY ? 0 : ret);
/*
* Save the current eviction walk setting: checkpoint can interfere
* with eviction and we don't want to unfairly penalize (or promote)
* eviction in trees due to checkpoints.
*/
btree->evict_walk_saved = btree->evict_walk_period;
session->ckpt_handle[session->ckpt_handle_next++] = session->dhandle;
return (0);
}
/*
* __checkpoint_reduce_dirty_cache --
* Release clean trees from the list cached for checkpoints.
*/
static void
__checkpoint_reduce_dirty_cache(WT_SESSION_IMPL *session)
{
WT_CACHE *cache;
WT_CONNECTION_IMPL *conn;
double current_dirty, prev_dirty;
uint64_t bytes_written_start, bytes_written_total;
uint64_t cache_size, max_write;
uint64_t time_start, time_stop;
uint64_t total_ms;
conn = S2C(session);
cache = conn->cache;
/*
* Give up if scrubbing is disabled, including when checkpointing with
* a timestamp on close (we can't evict dirty pages in that case, so
* scrubbing cannot help).
*/
if (F_ISSET(conn, WT_CONN_CLOSING_TIMESTAMP) ||
cache->eviction_checkpoint_target < DBL_EPSILON)
return;
time_start = __wt_clock(session);
bytes_written_start = cache->bytes_written;
/*
* If the cache size is zero or very small, we're done. The cache
* size can briefly become zero if we're transitioning to a shared
* cache via reconfigure. This avoids potential divide by zero.
*/
if ((cache_size = conn->cache_size) < 10 * WT_MEGABYTE)
return;
current_dirty =
(100.0 * __wt_cache_dirty_leaf_inuse(cache)) / cache_size;
if (current_dirty <= cache->eviction_checkpoint_target)
return;
/* Stop if we write as much dirty data as is currently in cache. */
max_write = __wt_cache_dirty_leaf_inuse(cache);
/* Set the dirty trigger to the target value. */
cache->eviction_scrub_target = cache->eviction_checkpoint_target;
WT_STAT_CONN_SET(session, txn_checkpoint_scrub_target, 0);
/* Wait while the dirty level is going down. */
for (;;) {
__wt_sleep(0, 100 * WT_THOUSAND);
prev_dirty = current_dirty;
current_dirty =
(100.0 * __wt_cache_dirty_leaf_inuse(cache)) / cache_size;
if (current_dirty <= cache->eviction_checkpoint_target ||
current_dirty >= prev_dirty)
break;
/*
* Don't scrub when the lookaside table is in use: scrubbing is
* counter-productive in that case.
*/
if (F_ISSET(cache, WT_CACHE_EVICT_LOOKASIDE))
break;
/*
* We haven't reached the current target.
*
* Don't wait indefinitely: there might be dirty pages
* that can't be evicted. If we can't meet the target,
* give up and start the checkpoint for real.
*/
bytes_written_total =
cache->bytes_written - bytes_written_start;
if (bytes_written_total > max_write)
break;
}
time_stop = __wt_clock(session);
total_ms = WT_CLOCKDIFF_MS(time_stop, time_start);
WT_STAT_CONN_SET(session, txn_checkpoint_scrub_time, total_ms);
}
/*
* __wt_checkpoint_progress --
* Output a checkpoint progress message.
*/
void
__wt_checkpoint_progress(WT_SESSION_IMPL *session, bool closing)
{
struct timespec cur_time;
WT_CONNECTION_IMPL *conn;
uint64_t time_diff;
conn = S2C(session);
__wt_epoch(session, &cur_time);
/* Time since the full database checkpoint started */
time_diff = WT_TIMEDIFF_SEC(cur_time,
conn->ckpt_timer_start);
if (closing || (time_diff / 20) > conn->ckpt_progress_msg_count) {
__wt_verbose(session, WT_VERB_CHECKPOINT_PROGRESS,
"Checkpoint %s for %" PRIu64
" seconds and wrote: %" PRIu64 " pages (%" PRIu64 " MB)",
closing ? "ran" : "has been running",
time_diff, conn->ckpt_write_pages,
conn->ckpt_write_bytes / WT_MEGABYTE);
conn->ckpt_progress_msg_count++;
}
}
/*
* __checkpoint_stats --
* Update checkpoint timer stats.
*/
static void
__checkpoint_stats(WT_SESSION_IMPL *session)
{
struct timespec stop;
WT_CONNECTION_IMPL *conn;
uint64_t msec;
conn = S2C(session);
/* Output a verbose progress message for long running checkpoints */
if (conn->ckpt_progress_msg_count > 0)
__wt_checkpoint_progress(session, true);
__wt_epoch(session, &stop);
msec = WT_TIMEDIFF_MS(stop, conn->ckpt_timer_scrub_end);
if (msec > conn->ckpt_time_max)
conn->ckpt_time_max = msec;
if (conn->ckpt_time_min == 0 || msec < conn->ckpt_time_min)
conn->ckpt_time_min = msec;
conn->ckpt_time_recent = msec;
conn->ckpt_time_total += msec;
}
/*
* __checkpoint_verbose_track --
* Output a verbose message with timing information
*/
static void
__checkpoint_verbose_track(WT_SESSION_IMPL *session, const char *msg)
{
struct timespec stop;
WT_CONNECTION_IMPL *conn;
uint64_t msec;
if (!WT_VERBOSE_ISSET(session, WT_VERB_CHECKPOINT))
return;
conn = S2C(session);
__wt_epoch(session, &stop);
/* Get time diff in milliseconds. */
msec = WT_TIMEDIFF_MS(stop, conn->ckpt_timer_start);
__wt_verbose(session,
WT_VERB_CHECKPOINT, "time: %" PRIu64 " ms, gen: %" PRIu64
": Full database checkpoint %s",
msec, __wt_gen(session, WT_GEN_CHECKPOINT), msg);
}
/*
* __checkpoint_fail_reset --
* Reset fields when a failure occurs.
*/
static void
__checkpoint_fail_reset(WT_SESSION_IMPL *session)
{
WT_BTREE *btree;
btree = S2BT(session);
btree->modified = true;
__wt_meta_ckptlist_free(session, &btree->ckpt);
}
/*
* __checkpoint_prepare --
* Start the transaction for a checkpoint and gather handles.
*/
static int
__checkpoint_prepare(
WT_SESSION_IMPL *session, bool *trackingp, const char *cfg[])
{
WT_CONFIG_ITEM cval;
WT_CONNECTION_IMPL *conn;
WT_DECL_RET;
WT_TXN *txn;
WT_TXN_GLOBAL *txn_global;
WT_TXN_STATE *txn_state;
const char *txn_cfg[] = { WT_CONFIG_BASE(session,
WT_SESSION_begin_transaction), "isolation=snapshot", NULL };
bool use_timestamp;
conn = S2C(session);
txn = &session->txn;
txn_global = &conn->txn_global;
txn_state = WT_SESSION_TXN_STATE(session);
WT_RET(__wt_config_gets(session, cfg, "use_timestamp", &cval));
use_timestamp = (cval.val != 0);
/*
* Start a snapshot transaction for the checkpoint.
*
* Note: we don't go through the public API calls because they have
* side effects on cursors, which applications can hold open across
* calls to checkpoint.
*/
WT_RET(__wt_txn_begin(session, txn_cfg));
WT_DIAGNOSTIC_YIELD;
/* Ensure a transaction ID is allocated prior to sharing it globally */
WT_RET(__wt_txn_id_check(session));
/* Keep track of handles acquired for locking. */
WT_RET(__wt_meta_track_on(session));
*trackingp = true;
/*
* Mark the connection as clean. If some data gets modified after
* generating checkpoint transaction id, connection will be reset to
* dirty when reconciliation marks the btree dirty on encountering the
* dirty page.
*/
conn->modified = false;
/*
* Save the checkpoint session ID.
*
* We never do checkpoints in the default session (with id zero).
*/
WT_ASSERT(session, session->id != 0 && txn_global->checkpoint_id == 0);
txn_global->checkpoint_id = session->id;
/*
* Remove the checkpoint transaction from the global table.
*
* This allows ordinary visibility checks to move forward because
* checkpoints often take a long time and only write to the metadata.
*/
__wt_writelock(session, &txn_global->rwlock);
txn_global->checkpoint_state = *txn_state;
txn_global->checkpoint_state.pinned_id = txn->snap_min;
/*
* Sanity check that the oldest ID hasn't moved on before we have
* cleared our entry.
*/
WT_ASSERT(session,
WT_TXNID_LE(txn_global->oldest_id, txn_state->id) &&
WT_TXNID_LE(txn_global->oldest_id, txn_state->pinned_id));
/*
* Clear our entry from the global transaction session table. Any
* operation that needs to know about the ID for this checkpoint will
* consider the checkpoint ID in the global structure. Most operations
* can safely ignore the checkpoint ID (see the visible all check for
* details).
*/
txn_state->id = txn_state->pinned_id =
txn_state->metadata_pinned = WT_TXN_NONE;
#ifdef HAVE_TIMESTAMPS
/*
* Set the checkpoint transaction's timestamp, if requested.
*
* We rely on having the global transaction data locked so the oldest
* timestamp can't move past the stable timestamp.
*/
WT_ASSERT(session, !F_ISSET(txn,
WT_TXN_HAS_TS_COMMIT | WT_TXN_HAS_TS_READ |
WT_TXN_PUBLIC_TS_COMMIT | WT_TXN_PUBLIC_TS_READ));
if (use_timestamp) {
/*
* If the user wants timestamps then set the metadata
* checkpoint timestamp based on whether or not a stable
* timestamp is actually in use. Only set it when we're not
* running recovery because recovery doesn't set the recovery
* timestamp until its checkpoint is complete.
*/
if (txn_global->has_stable_timestamp) {
__wt_timestamp_set(&txn->read_timestamp,
&txn_global->stable_timestamp);
__wt_timestamp_set(&txn_global->checkpoint_timestamp,
&txn->read_timestamp);
F_SET(txn, WT_TXN_HAS_TS_READ);
if (!F_ISSET(conn, WT_CONN_RECOVERING))
__wt_timestamp_set(
&txn_global->meta_ckpt_timestamp,
&txn->read_timestamp);
} else if (!F_ISSET(conn, WT_CONN_RECOVERING))
__wt_timestamp_set(&txn_global->meta_ckpt_timestamp,
&txn_global->recovery_timestamp);
} else if (!F_ISSET(conn, WT_CONN_RECOVERING))
__wt_timestamp_set_zero(&txn_global->meta_ckpt_timestamp);
#else
WT_UNUSED(use_timestamp);
#endif
__wt_writeunlock(session, &txn_global->rwlock);
#ifdef HAVE_TIMESTAMPS
if (F_ISSET(txn, WT_TXN_HAS_TS_READ)) {
__wt_verbose_timestamp(session, &txn->read_timestamp,
"Checkpoint requested at stable timestamp");
/*
* The snapshot we established when the transaction started may
* be too early to match the timestamp we just read.
*
* Get a new one.
*/
__wt_txn_get_snapshot(session);
}
#endif
/*
* Get a list of handles we want to flush; for named checkpoints this
* may pull closed objects into the session cache.
*
* First, gather all handles, then start the checkpoint transaction,
* then release any clean handles.
*/
WT_ASSERT(session, session->ckpt_handle_next == 0);
WT_WITH_TABLE_READ_LOCK(session, ret =
__checkpoint_apply_all(session, cfg, __wt_checkpoint_get_handles));
return (ret);
}
/*
* __txn_checkpoint_can_skip --
* Determine whether it's safe to skip taking a checkpoint.
*/
static int
__txn_checkpoint_can_skip(WT_SESSION_IMPL *session,
const char *cfg[], bool *fullp, bool *use_timestampp, bool *can_skipp)
{
WT_CONFIG targetconf;
WT_CONFIG_ITEM cval, k, v;
WT_CONNECTION_IMPL *conn;
WT_TXN_GLOBAL *txn_global;
bool full, use_timestamp;
/*
* Default to not skipping - also initialize the other output
* parameters - even though they will always be initialized unless
* there is an error and callers need to ignore the results on error.
*/
*can_skipp = *fullp = *use_timestampp = false;
conn = S2C(session);
txn_global = &conn->txn_global;
/*
* This function also parses out some configuration options and hands
* them back to the caller - make sure it does that parsing regardless
* of the result.
*
* Determine if this is going to be a full checkpoint, that is a
* checkpoint that applies to all data tables in a database.
*/
WT_RET(__wt_config_gets(session, cfg, "target", &cval));
__wt_config_subinit(session, &targetconf, &cval);
*fullp = full = __wt_config_next(&targetconf, &k, &v) != 0;
WT_RET(__wt_config_gets(session, cfg, "use_timestamp", &cval));
*use_timestampp = use_timestamp = cval.val != 0;
/* Never skip non-full checkpoints */
if (!full)
return (0);
/* Never skip if force is configured. */
WT_RET(__wt_config_gets_def(session, cfg, "force", 0, &cval));
if (cval.val != 0)
return (0);
/* Never skip named checkpoints. */
WT_RET(__wt_config_gets(session, cfg, "name", &cval));
if (cval.val != 0)
return (0);
/*
* Skip checkpointing the database if nothing has been dirtied since
* the last checkpoint. That said there can be short instances when a
* btree gets marked dirty and the connection is yet to be. We might
* skip a checkpoint in that short instance, which is okay because by
* the next time we get to checkpoint, the connection would have been
* marked dirty and hence the checkpoint will not be skipped again.
*/
if (!conn->modified) {
*can_skipp = true;
return (0);
}
#ifdef HAVE_TIMESTAMPS
/*
* If the checkpoint is using timestamps, and the stable timestamp
* hasn't been updated since the last checkpoint there is nothing
* more that could be written.
*/
if (use_timestamp && txn_global->has_stable_timestamp &&
!__wt_timestamp_iszero(&txn_global->last_ckpt_timestamp) &&
__wt_timestamp_cmp(&txn_global->last_ckpt_timestamp,
&txn_global->stable_timestamp) == 0) {
*can_skipp = true;
return (0);
}
#else
WT_UNUSED(txn_global);
#endif
return (0);
}
/*
* __txn_checkpoint --
* Checkpoint a database or a list of objects in the database.
*/
static int
__txn_checkpoint(WT_SESSION_IMPL *session, const char *cfg[])
{
WT_CACHE *cache;
WT_CONNECTION_IMPL *conn;
WT_DECL_RET;
WT_DECL_TIMESTAMP(ckpt_tmp_ts)
WT_TXN *txn;
WT_TXN_GLOBAL *txn_global;
WT_TXN_ISOLATION saved_isolation;
uint64_t fsync_duration_usecs, generation, time_start, time_stop;
u_int i;
bool can_skip, failed, full, idle, logging, tracking, use_timestamp;
void *saved_meta_next;
conn = S2C(session);
cache = conn->cache;
txn = &session->txn;
txn_global = &conn->txn_global;
saved_isolation = session->isolation;
full = idle = logging = tracking = use_timestamp = false;
/* Avoid doing work if possible. */
WT_RET(__txn_checkpoint_can_skip(session,
cfg, &full, &use_timestamp, &can_skip));
if (can_skip) {
WT_STAT_CONN_INCR(session, txn_checkpoint_skipped);
return (0);
}
/*
* Do a pass over the configuration arguments and figure out what kind
* of checkpoint this is.
*/
WT_RET(__checkpoint_apply_all(session, cfg, NULL));
logging = FLD_ISSET(conn->log_flags, WT_CONN_LOG_ENABLED);
/* Reset the maximum page size seen by eviction. */
conn->cache->evict_max_page_size = 0;
/* Initialize the verbose tracking timer */
__wt_epoch(session, &conn->ckpt_timer_start);
/* Initialize the checkpoint progress tracking data */
conn->ckpt_progress_msg_count = 0;
conn->ckpt_write_bytes = 0;
conn->ckpt_write_pages = 0;
/*
* Update the global oldest ID so we do all possible cleanup.
*
* This is particularly important for compact, so that all dirty pages
* can be fully written.
*/
WT_ERR(__wt_txn_update_oldest(
session, WT_TXN_OLDEST_STRICT | WT_TXN_OLDEST_WAIT));
/* Flush data-sources before we start the checkpoint. */
WT_ERR(__checkpoint_data_source(session, cfg));
/*
* Try to reduce the amount of dirty data in cache so there is less
* work do during the critical section of the checkpoint.
*/
__checkpoint_reduce_dirty_cache(session);
/* Tell logging that we are about to start a database checkpoint. */
if (full && logging)
WT_ERR(__wt_txn_checkpoint_log(
session, full, WT_TXN_LOG_CKPT_PREPARE, NULL));
__checkpoint_verbose_track(session, "starting transaction");
if (full)
__wt_epoch(session, &conn->ckpt_timer_scrub_end);
/*
* Start the checkpoint for real.
*
* Bump the global checkpoint generation, used to figure out whether
* checkpoint has visited a tree. Use an atomic increment even though
* we are single-threaded because readers of the checkpoint generation
* don't hold the checkpoint lock.
*
* We do need to update it before clearing the checkpoint's entry out
* of the transaction table, or a thread evicting in a tree could
* ignore the checkpoint's transaction.
*/
generation = __wt_gen_next(session, WT_GEN_CHECKPOINT);
WT_STAT_CONN_SET(session, txn_checkpoint_generation, generation);
/*
* We want to skip checkpointing clean handles whenever possible. That
* is, when the checkpoint is not named or forced. However, we need to
* take care about ordering with respect to the checkpoint transaction.
*
* We can't skip clean handles before starting the transaction or the
* checkpoint can miss updates in trees that become dirty as the
* checkpoint is starting. If we wait until the transaction has
* started before locking a handle, there could be a metadata-changing
* operation in between (e.g., salvage) that will cause a write
* conflict when the checkpoint goes to write the metadata.
*
* Hold the schema lock while starting the transaction and gathering
* handles so the set we get is complete and correct.
*/
WT_WITH_SCHEMA_LOCK(session,
ret = __checkpoint_prepare(session, &tracking, cfg));
WT_ERR(ret);
WT_ASSERT(session, txn->isolation == WT_ISO_SNAPSHOT);
/*
* Unblock updates -- we can figure out that any updates to clean pages
* after this point are too new to be written in the checkpoint.
*/
cache->eviction_scrub_target = 0.0;
WT_STAT_CONN_SET(session, txn_checkpoint_scrub_target, 0);
/* Tell logging that we have started a database checkpoint. */
if (full && logging)
WT_ERR(__wt_txn_checkpoint_log(
session, full, WT_TXN_LOG_CKPT_START, NULL));
__checkpoint_timing_stress(session);
WT_ERR(__checkpoint_apply(session, cfg, __checkpoint_tree_helper));
/*
* Clear the dhandle so the visibility check doesn't get confused about
* the snap min. Don't bother restoring the handle since it doesn't
* make sense to carry a handle across a checkpoint.
*/
session->dhandle = NULL;
#ifdef HAVE_TIMESTAMPS
/*
* Record the timestamp from the transaction if we were successful.
* Store it in a temp variable now because it will be invalidated during
* commit but we don't want to set it until we know the checkpoint
* is successful. We have to set the system information before we
* release the snapshot.
*/
__wt_timestamp_set_zero(&ckpt_tmp_ts);
if (full) {
WT_ERR(__wt_meta_sysinfo_set(session));
__wt_timestamp_set(&ckpt_tmp_ts, &txn->read_timestamp);
}
#endif
/* Release the snapshot so we aren't pinning updates in cache. */
__wt_txn_release_snapshot(session);
/* Mark all trees as open for business (particularly eviction). */
WT_ERR(__checkpoint_apply(session, cfg, __checkpoint_presync));
__wt_evict_server_wake(session);
__checkpoint_verbose_track(session, "committing transaction");
/*
* Checkpoints have to hit disk (it would be reasonable to configure for
* lazy checkpoints, but we don't support them yet).
*/
time_start = __wt_clock(session);
WT_ERR(__checkpoint_apply(session, cfg, __wt_checkpoint_sync));
time_stop = __wt_clock(session);
fsync_duration_usecs = WT_CLOCKDIFF_US(time_stop, time_start);
WT_STAT_CONN_INCR(session, txn_checkpoint_fsync_post);
WT_STAT_CONN_SET(session,
txn_checkpoint_fsync_post_duration, fsync_duration_usecs);
__checkpoint_verbose_track(session, "sync completed");
/*
* Commit the transaction now that we are sure that all files in the
* checkpoint have been flushed to disk. It's OK to commit before
* checkpointing the metadata since we know that all files in the
* checkpoint are now in a consistent state.
*/
WT_ERR(__wt_txn_commit(session, NULL));
/*
* Ensure that the metadata changes are durable before the checkpoint
* is resolved. Do this by either checkpointing the metadata or syncing
* the log file.
* Recovery relies on the checkpoint LSN in the metadata only being
* updated by full checkpoints so only checkpoint the metadata for
* full or non-logged checkpoints.
*
* This is very similar to __wt_meta_track_off, ideally they would be
* merged.
*/
if (full || !logging) {
session->isolation = txn->isolation = WT_ISO_READ_UNCOMMITTED;
/* Disable metadata tracking during the metadata checkpoint. */
saved_meta_next = session->meta_track_next;
session->meta_track_next = NULL;
WT_WITH_DHANDLE(session, WT_SESSION_META_DHANDLE(session),
WT_WITH_METADATA_LOCK(session,
ret = __wt_checkpoint(session, cfg)));
session->meta_track_next = saved_meta_next;
WT_ERR(ret);
WT_WITH_DHANDLE(session,
WT_SESSION_META_DHANDLE(session),
ret = __wt_checkpoint_sync(session, NULL));
WT_ERR(ret);
__checkpoint_verbose_track(session, "metadata sync completed");
} else
WT_WITH_DHANDLE(session,
WT_SESSION_META_DHANDLE(session),
ret = __wt_txn_checkpoint_log(
session, false, WT_TXN_LOG_CKPT_SYNC, NULL));
/*
* Now that the metadata is stable, re-open the metadata file for
* regular eviction by clearing the checkpoint_pinned flag.
*/
txn_global->checkpoint_state.pinned_id = WT_TXN_NONE;
if (full) {
__checkpoint_stats(session);
#ifdef HAVE_TIMESTAMPS
/*
* If timestamps were used to define the content of the
* checkpoint update the saved last checkpoint timestamp,
* otherwise leave it alone. If a checkpoint is taken without
* timestamps, it's likely a bug, but we don't want to clear
* the saved last checkpoint timestamp regardless.
*/
if (use_timestamp)
__wt_timestamp_set(
&conn->txn_global.last_ckpt_timestamp,
&ckpt_tmp_ts);
#endif
}
err: /*
* Reset the timer so that next checkpoint tracks the progress only if
* configured.
*/
conn->ckpt_timer_start.tv_sec = 0;
/*
* XXX
* Rolling back the changes here is problematic.
*
* If we unroll here, we need a way to roll back changes to the avail
* list for each tree that was successfully synced before the error
* occurred. Otherwise, the next time we try this operation, we will
* try to free an old checkpoint again.
*
* OTOH, if we commit the changes after a failure, we have partially
* overwritten the checkpoint, so what ends up on disk is not
* consistent.
*/
failed = ret != 0;
if (failed)
conn->modified = true;
session->isolation = txn->isolation = WT_ISO_READ_UNCOMMITTED;
if (tracking)
WT_TRET(__wt_meta_track_off(session, false, failed));
cache->eviction_scrub_target = 0.0;
WT_STAT_CONN_SET(session, txn_checkpoint_scrub_target, 0);
if (F_ISSET(txn, WT_TXN_RUNNING)) {
/*
* Clear the dhandle so the visibility check doesn't get
* confused about the snap min. Don't bother restoring the
* handle since it doesn't make sense to carry a handle across
* a checkpoint.
*/
session->dhandle = NULL;
WT_TRET(__wt_txn_rollback(session, NULL));
}
/*
* Tell logging that we have finished a database checkpoint. Do not
* write a log record if the database was idle.
*/
if (full && logging) {
if (ret == 0 &&
F_ISSET(((WT_CURSOR_BTREE *)
session->meta_cursor)->btree, WT_BTREE_SKIP_CKPT))
idle = true;
WT_TRET(__wt_txn_checkpoint_log(session, full,
(ret == 0 && !idle) ?
WT_TXN_LOG_CKPT_STOP : WT_TXN_LOG_CKPT_CLEANUP, NULL));
}
for (i = 0; i < session->ckpt_handle_next; ++i) {
if (session->ckpt_handle[i] == NULL)
continue;
/*
* If the operation failed, mark all trees dirty so they are
* included if a future checkpoint can succeed.
*/
if (failed)
WT_WITH_DHANDLE(session, session->ckpt_handle[i],
__checkpoint_fail_reset(session));
WT_WITH_DHANDLE(session, session->ckpt_handle[i],
WT_TRET(__wt_session_release_dhandle(session)));
}
__wt_free(session, session->ckpt_handle);
session->ckpt_handle_allocated = session->ckpt_handle_next = 0;
session->isolation = txn->isolation = saved_isolation;
return (ret);
}
/*
* __txn_checkpoint_wrapper --
* Checkpoint wrapper.
*/
static int
__txn_checkpoint_wrapper(WT_SESSION_IMPL *session, const char *cfg[])
{
WT_DECL_RET;
WT_TXN_GLOBAL *txn_global;
txn_global = &S2C(session)->txn_global;
WT_STAT_CONN_SET(session, txn_checkpoint_running, 1);
txn_global->checkpoint_running = true;
ret = __txn_checkpoint(session, cfg);
WT_STAT_CONN_SET(session, txn_checkpoint_running, 0);
txn_global->checkpoint_running = false;
return (ret);
}
/*
* __wt_txn_checkpoint --
* Checkpoint a database or a list of objects in the database.
*/
int
__wt_txn_checkpoint(WT_SESSION_IMPL *session, const char *cfg[], bool waiting)
{
WT_DECL_RET;
uint32_t orig_flags;
/*
* Reset open cursors. Do this explicitly, even though it will happen
* implicitly in the call to begin_transaction for the checkpoint, the
* checkpoint code will acquire the schema lock before we do that, and
* some implementation of WT_CURSOR::reset might need the schema lock.
*/
WT_RET(__wt_session_reset_cursors(session, false));
/* Ensure the metadata table is open before taking any locks. */
WT_RET(__wt_metadata_cursor(session, NULL));
/*
* Don't highjack the session checkpoint thread for eviction.
*
* Application threads are not generally available for potentially slow
* operations, but checkpoint does enough I/O it may be called upon to
* perform slow operations for the block manager.
*
* Application checkpoints wait until the checkpoint lock is available,
* compaction checkpoints don't.
*
* Checkpoints should always use a separate session for lookaside
* updates, otherwise those updates are pinned until the checkpoint
* commits. Also, there are unfortunate interactions between the
* special rules for lookaside eviction and the special handling of the
* checkpoint transaction.
*/
#undef WT_CHECKPOINT_SESSION_FLAGS
#define WT_CHECKPOINT_SESSION_FLAGS \
(WT_SESSION_CAN_WAIT | WT_SESSION_IGNORE_CACHE_SIZE)
#undef WT_CHECKPOINT_SESSION_FLAGS_OFF
#define WT_CHECKPOINT_SESSION_FLAGS_OFF \
(WT_SESSION_LOOKASIDE_CURSOR)
orig_flags = F_MASK(session,
WT_CHECKPOINT_SESSION_FLAGS | WT_CHECKPOINT_SESSION_FLAGS_OFF);
F_SET(session, WT_CHECKPOINT_SESSION_FLAGS);
F_CLR(session, WT_CHECKPOINT_SESSION_FLAGS_OFF);
/*
* Only one checkpoint can be active at a time, and checkpoints must run
* in the same order as they update the metadata. It's probably a bad
* idea to run checkpoints out of multiple threads, but as compaction
* calls checkpoint directly, it can be tough to avoid. Serialize here
* to ensure we don't get into trouble.
*/
if (waiting)
WT_WITH_CHECKPOINT_LOCK(session,
ret = __txn_checkpoint_wrapper(session, cfg));
else
WT_WITH_CHECKPOINT_LOCK_NOWAIT(session, ret,
ret = __txn_checkpoint_wrapper(session, cfg));
F_CLR(session, WT_CHECKPOINT_SESSION_FLAGS);
F_SET(session, orig_flags);
return (ret);
}
/*
* __drop --
* Drop all checkpoints with a specific name.
*/
static void
__drop(WT_CKPT *ckptbase, const char *name, size_t len)
{
WT_CKPT *ckpt;
/*
* If we're dropping internal checkpoints, match to the '.' separating
* the checkpoint name from the generational number, and take all that
* we can find. Applications aren't allowed to use any variant of this
* name, so the test is still pretty simple, if the leading bytes match,
* it's one we want to drop.
*/
if (strncmp(WT_CHECKPOINT, name, len) == 0) {
WT_CKPT_FOREACH(ckptbase, ckpt)
if (WT_PREFIX_MATCH(ckpt->name, WT_CHECKPOINT))
F_SET(ckpt, WT_CKPT_DELETE);
} else
WT_CKPT_FOREACH(ckptbase, ckpt)
if (WT_STRING_MATCH(ckpt->name, name, len))
F_SET(ckpt, WT_CKPT_DELETE);
}
/*
* __drop_from --
* Drop all checkpoints after, and including, the named checkpoint.
*/
static void
__drop_from(WT_CKPT *ckptbase, const char *name, size_t len)
{
WT_CKPT *ckpt;
bool matched;
/*
* There's a special case -- if the name is "all", then we delete all
* of the checkpoints.
*/
if (WT_STRING_MATCH("all", name, len)) {
WT_CKPT_FOREACH(ckptbase, ckpt)
F_SET(ckpt, WT_CKPT_DELETE);
return;
}
/*
* We use the first checkpoint we can find, that is, if there are two
* checkpoints with the same name in the list, we'll delete from the
* first match to the end.
*/
matched = false;
WT_CKPT_FOREACH(ckptbase, ckpt) {
if (!matched && !WT_STRING_MATCH(ckpt->name, name, len))
continue;
matched = true;
F_SET(ckpt, WT_CKPT_DELETE);
}
}
/*
* __drop_to --
* Drop all checkpoints before, and including, the named checkpoint.
*/
static void
__drop_to(WT_CKPT *ckptbase, const char *name, size_t len)
{
WT_CKPT *ckpt, *mark;
/*
* We use the last checkpoint we can find, that is, if there are two
* checkpoints with the same name in the list, we'll delete from the
* beginning to the second match, not the first.
*/
mark = NULL;
WT_CKPT_FOREACH(ckptbase, ckpt)
if (WT_STRING_MATCH(ckpt->name, name, len))
mark = ckpt;
if (mark == NULL)
return;
WT_CKPT_FOREACH(ckptbase, ckpt) {
F_SET(ckpt, WT_CKPT_DELETE);
if (ckpt == mark)
break;
}
}
/*
* __checkpoint_lock_dirty_tree --
* Decide whether the tree needs to be included in the checkpoint and if
* so, acquire the necessary locks.
*/
static int
__checkpoint_lock_dirty_tree(WT_SESSION_IMPL *session,
bool is_checkpoint, bool force, bool need_tracking, const char *cfg[])
{
WT_BTREE *btree;
WT_CKPT *ckpt, *ckptbase;
WT_CONFIG dropconf;
WT_CONFIG_ITEM cval, k, v;
WT_CONNECTION_IMPL *conn;
WT_DATA_HANDLE *dhandle;
WT_DECL_RET;
const char *name;
char *name_alloc;
bool hot_backup_locked;
btree = S2BT(session);
conn = S2C(session);
ckpt = ckptbase = NULL;
dhandle = session->dhandle;
hot_backup_locked = false;
name_alloc = NULL;
/* Only referenced in diagnostic builds. */
WT_UNUSED(is_checkpoint);
/*
* Only referenced in diagnostic builds and gcc 5.1 isn't satisfied
* with wrapping the entire assert condition in the unused macro.
*/
WT_UNUSED(need_tracking);
/*
* Most callers need meta tracking to be on here, otherwise it is
* possible for this checkpoint to cleanup handles that are still in
* use. The exceptions are:
* - Checkpointing the metadata handle itself.
* - On connection close when we know there can't be any races.
*/
WT_ASSERT(session, !need_tracking ||
WT_IS_METADATA(dhandle) || WT_META_TRACKING(session));
/* Get the list of checkpoints for this file. */
WT_RET(__wt_meta_ckptlist_get(session, dhandle->name, &ckptbase));
/* This may be a named checkpoint, check the configuration. */
cval.len = 0;
if (cfg != NULL)
WT_ERR(__wt_config_gets(session, cfg, "name", &cval));
if (cval.len == 0)
name = WT_CHECKPOINT;
else {
WT_ERR(__checkpoint_name_ok(session, cval.str, cval.len));
WT_ERR(__wt_strndup(session, cval.str, cval.len, &name_alloc));
name = name_alloc;
}
/* We may be dropping specific checkpoints, check the configuration. */
if (cfg != NULL) {
cval.len = 0;
WT_ERR(__wt_config_gets(session, cfg, "drop", &cval));
if (cval.len != 0) {
__wt_config_subinit(session, &dropconf, &cval);
while ((ret =
__wt_config_next(&dropconf, &k, &v)) == 0) {
/* Disallow unsafe checkpoint names. */
if (v.len == 0)
WT_ERR(__checkpoint_name_ok(
session, k.str, k.len));
else
WT_ERR(__checkpoint_name_ok(
session, v.str, v.len));
if (v.len == 0)
__drop(ckptbase, k.str, k.len);
else if (WT_STRING_MATCH("from", k.str, k.len))
__drop_from(ckptbase, v.str, v.len);
else if (WT_STRING_MATCH("to", k.str, k.len))
__drop_to(ckptbase, v.str, v.len);
else
WT_ERR_MSG(session, EINVAL,
"unexpected value for checkpoint "
"key: %.*s",
(int)k.len, k.str);
}
WT_ERR_NOTFOUND_OK(ret);
}
}
/* Drop checkpoints with the same name as the one we're taking. */
__drop(ckptbase, name, strlen(name));
/* Add a new checkpoint entry at the end of the list. */
WT_CKPT_FOREACH(ckptbase, ckpt)
;
WT_ERR(__wt_strdup(session, name, &ckpt->name));
/*
* We are now done with the local use of the name. Free the local
* allocation, if needed.
*/
__wt_free(session, name_alloc);
F_SET(ckpt, WT_CKPT_ADD);
/*
* We can't delete checkpoints if a backup cursor is open. WiredTiger
* checkpoints are uniquely named and it's OK to have multiple of them
* in the system: clear the delete flag for them, and otherwise fail.
* Hold the lock until we're done (blocking hot backups from starting),
* we don't want to race with a future hot backup.
*/
__wt_readlock(session, &conn->hot_backup_lock);
hot_backup_locked = true;
if (conn->hot_backup)
WT_CKPT_FOREACH(ckptbase, ckpt) {
if (!F_ISSET(ckpt, WT_CKPT_DELETE))
continue;
if (WT_PREFIX_MATCH(ckpt->name, WT_CHECKPOINT)) {
F_CLR(ckpt, WT_CKPT_DELETE);
continue;
}
WT_ERR_MSG(session, EBUSY,
"checkpoint %s blocked by hot backup: it would "
"delete an existing checkpoint, and checkpoints "
"cannot be deleted during a hot backup",
ckpt->name);
}
/*
* Mark old checkpoints that are being deleted and figure out which
* trees we can skip in this checkpoint.
*/
WT_ERR(__checkpoint_mark_skip(session, ckptbase, force));
if (F_ISSET(btree, WT_BTREE_SKIP_CKPT))
goto err;
/*
* Lock the checkpoints that will be deleted.
*
* Checkpoints are only locked when tracking is enabled, which covers
* checkpoint and drop operations, but not close. The reasoning is
* there should be no access to a checkpoint during close, because any
* thread accessing a checkpoint will also have the current file handle
* open.
*/
if (WT_META_TRACKING(session))
WT_CKPT_FOREACH(ckptbase, ckpt) {
if (!F_ISSET(ckpt, WT_CKPT_DELETE))
continue;
/*
* We can't delete checkpoints referenced by a cursor.
* WiredTiger checkpoints are uniquely named and it's
* OK to have multiple in the system: clear the delete
* flag for them, and otherwise fail.
*/
ret = __wt_session_lock_checkpoint(session, ckpt->name);
if (ret == 0)
continue;
if (ret == EBUSY &&
WT_PREFIX_MATCH(ckpt->name, WT_CHECKPOINT)) {
F_CLR(ckpt, WT_CKPT_DELETE);
continue;
}
WT_ERR_MSG(session, ret,
"checkpoints cannot be dropped when in-use");
}
/*
* There are special tree: those being bulk-loaded, salvaged, upgraded
* or verified during the checkpoint. They should never be part of a
* checkpoint: we will fail to lock them because the operations have
* exclusive access to the handles. Named checkpoints will fail in that
* case, ordinary checkpoints will skip files that cannot be opened
* normally.
*/
WT_ASSERT(session,
!is_checkpoint || !F_ISSET(btree, WT_BTREE_SPECIAL_FLAGS));
__wt_readunlock(session, &conn->hot_backup_lock);
WT_ASSERT(session, btree->ckpt == NULL &&
!F_ISSET(btree, WT_BTREE_SKIP_CKPT));
btree->ckpt = ckptbase;
return (0);
err: if (hot_backup_locked)
__wt_readunlock(session, &conn->hot_backup_lock);
__wt_meta_ckptlist_free(session, &ckptbase);
__wt_free(session, name_alloc);
return (ret);
}
/*
* __checkpoint_mark_skip --
* Figure out whether the checkpoint can be skipped for a tree.
*/
static int
__checkpoint_mark_skip(
WT_SESSION_IMPL *session, WT_CKPT *ckptbase, bool force)
{
WT_BTREE *btree;
WT_CKPT *ckpt;
int deleted;
const char *name;
btree = S2BT(session);
/*
* Check for clean objects not requiring a checkpoint.
*
* If we're closing a handle, and the object is clean, we can skip the
* checkpoint, whatever checkpoints we have are sufficient. (We might
* not have any checkpoints if the object was never modified, and that's
* OK: the object creation code doesn't mark the tree modified so we can
* skip newly created trees here.)
*
* If the application repeatedly checkpoints an object (imagine hourly
* checkpoints using the same explicit or internal name), there's no
* reason to repeat the checkpoint for clean objects. The test is if
* the only checkpoint we're deleting is the last one in the list and
* it has the same name as the checkpoint we're about to take, skip the
* work. (We can't skip checkpoints that delete more than the last
* checkpoint because deleting those checkpoints might free up space in
* the file.) This means an application toggling between two (or more)
* checkpoint names will repeatedly take empty checkpoints, but that's
* not likely enough to make detection worthwhile.
*
* Checkpoint read-only objects otherwise: the application must be able
* to open the checkpoint in a cursor after taking any checkpoint, which
* means it must exist.
*/
F_CLR(btree, WT_BTREE_SKIP_CKPT);
if (!btree->modified && !force) {
deleted = 0;
WT_CKPT_FOREACH(ckptbase, ckpt)
if (F_ISSET(ckpt, WT_CKPT_DELETE))
++deleted;
/*
* Complicated test: if the tree is clean and last two
* checkpoints have the same name (correcting for internal
* checkpoint names with their generational suffix numbers), we
* can skip the checkpoint, there's nothing to do. The
* exception is if we're deleting two or more checkpoints: then
* we may save space.
*/
name = (ckpt - 1)->name;
if (ckpt > ckptbase + 1 && deleted < 2 &&
(strcmp(name, (ckpt - 2)->name) == 0 ||
(WT_PREFIX_MATCH(name, WT_CHECKPOINT) &&
WT_PREFIX_MATCH((ckpt - 2)->name, WT_CHECKPOINT)))) {
F_SET(btree, WT_BTREE_SKIP_CKPT);
return (0);
}
}
return (0);
}
/*
* __checkpoint_tree --
* Checkpoint a single tree.
* Assumes all necessary locks have been acquired by the caller.
*/
static int
__checkpoint_tree(
WT_SESSION_IMPL *session, bool is_checkpoint, const char *cfg[])
{
WT_BM *bm;
WT_BTREE *btree;
WT_CKPT *ckpt, *ckptbase;
WT_CONNECTION_IMPL *conn;
WT_DATA_HANDLE *dhandle;
WT_DECL_RET;
WT_LSN ckptlsn;
bool fake_ckpt, resolve_bm;
WT_UNUSED(cfg);
btree = S2BT(session);
bm = btree->bm;
ckptbase = btree->ckpt;
conn = S2C(session);
dhandle = session->dhandle;
fake_ckpt = resolve_bm = false;
/*
* Set the checkpoint LSN to the maximum LSN so that if logging is
* disabled, recovery will never roll old changes forward over the
* non-logged changes in this checkpoint. If logging is enabled, a
* real checkpoint LSN will be assigned for this checkpoint and
* overwrite this.
*/
WT_MAX_LSN(&ckptlsn);
/*
* If an object has never been used (in other words, if it could become
* a bulk-loaded file), then we must fake the checkpoint. This is good
* because we don't write physical checkpoint blocks for just-created
* files, but it's not just a good idea. The reason is because deleting
* a physical checkpoint requires writing the file, and fake checkpoints
* can't write the file. If you (1) create a physical checkpoint for an
* empty file which writes blocks, (2) start bulk-loading records into
* the file, (3) during the bulk-load perform another checkpoint with
* the same name; in order to keep from having two checkpoints with the
* same name you would have to use the bulk-load's fake checkpoint to
* delete a physical checkpoint, and that will end in tears.
*/
if (is_checkpoint)
if (btree->original) {
fake_ckpt = true;
goto fake;
}
/*
* Mark the root page dirty to ensure something gets written. (If the
* tree is modified, we must write the root page anyway, this doesn't
* add additional writes to the process. If the tree is not modified,
* we have to dirty the root page to ensure something gets written.)
* This is really about paranoia: if the tree modification value gets
* out of sync with the set of dirty pages (modify is set, but there
* are no dirty pages), we perform a checkpoint without any writes, no
* checkpoint is created, and then things get bad.
* While marking the root page as dirty, we do not want to dirty the
* btree because we are marking the btree as clean just after this call.
* Also, marking the btree dirty at this stage will unnecessarily mark
* the connection as dirty causing checkpoint-skip code to fail.
*/
WT_ERR(__wt_page_modify_init(session, btree->root.page));
__wt_page_only_modify_set(session, btree->root.page);
/*
* Clear the tree's modified flag; any changes before we clear the flag
* are guaranteed to be part of this checkpoint (unless reconciliation
* skips updates for transactional reasons), and changes subsequent to
* the checkpoint start, which might not be included, will re-set the
* modified flag. The "unless reconciliation skips updates" problem is
* handled in the reconciliation code: if reconciliation skips updates,
* it sets the modified flag itself.
*/
btree->modified = false;
WT_FULL_BARRIER();
/* Tell logging that a file checkpoint is starting. */
if (FLD_ISSET(conn->log_flags, WT_CONN_LOG_ENABLED))
WT_ERR(__wt_txn_checkpoint_log(
session, false, WT_TXN_LOG_CKPT_START, &ckptlsn));
/* Tell the block manager that a file checkpoint is starting. */
WT_ERR(bm->checkpoint_start(bm, session));
resolve_bm = true;
/* Flush the file from the cache, creating the checkpoint. */
if (is_checkpoint)
WT_ERR(__wt_cache_op(session, WT_SYNC_CHECKPOINT));
else
WT_ERR(__wt_cache_op(session, WT_SYNC_CLOSE));
/*
* All blocks being written have been written; set the object's write
* generation.
*/
WT_CKPT_FOREACH(ckptbase, ckpt)
if (F_ISSET(ckpt, WT_CKPT_ADD))
ckpt->write_gen = btree->write_gen;
fake: /*
* If we're faking a checkpoint and logging is enabled, recovery should
* roll forward any changes made between now and the next checkpoint,
* so set the checkpoint LSN to the beginning of time.
*/
if (fake_ckpt && FLD_ISSET(conn->log_flags, WT_CONN_LOG_ENABLED))
WT_INIT_LSN(&ckptlsn);
/*
* Update the object's metadata.
*
* If the object is the metadata, the call to __wt_meta_ckptlist_set
* will update the turtle file and swap the new one into place. We
* need to make sure the metadata is on disk before the turtle file is
* updated.
*
* If we are doing a checkpoint in a file without a transaction (e.g.,
* closing a dirty tree before an exclusive operation like verify),
* the metadata update will be auto-committed. In that case, we need to
* sync the file here or we could roll forward the metadata in
* recovery and open a checkpoint that isn't yet durable.
*/
if (WT_IS_METADATA(dhandle) ||
!F_ISSET(&session->txn, WT_TXN_RUNNING))
WT_ERR(__wt_checkpoint_sync(session, NULL));
WT_ERR(__wt_meta_ckptlist_set(
session, dhandle->name, ckptbase, &ckptlsn));
/*
* If we wrote a checkpoint (rather than faking one), we have to resolve
* it. Normally, tracking is enabled and resolution deferred until
* transaction end. The exception is if the handle is being discarded,
* in which case the handle will be gone by the time we try to apply or
* unroll the meta tracking event.
*/
if (!fake_ckpt) {
resolve_bm = false;
if (WT_META_TRACKING(session) && is_checkpoint)
WT_ERR(__wt_meta_track_checkpoint(session));
else
WT_ERR(bm->checkpoint_resolve(bm, session, false));
}
/* Tell logging that the checkpoint is complete. */
if (FLD_ISSET(conn->log_flags, WT_CONN_LOG_ENABLED))
WT_ERR(__wt_txn_checkpoint_log(
session, false, WT_TXN_LOG_CKPT_STOP, NULL));
err: /* Resolved the checkpoint for the block manager in the error path. */
if (resolve_bm)
WT_TRET(bm->checkpoint_resolve(bm, session, ret != 0));
/*
* If the checkpoint didn't complete successfully, make sure the
* tree is marked dirty.
*/
if (ret != 0) {
btree->modified = true;
conn->modified = true;
}
__wt_meta_ckptlist_free(session, &btree->ckpt);
return (ret);
}
/*
* __checkpoint_presync --
* Visit all handles after the checkpoint writes are complete and before
* syncing. At this point, all trees should be completely open for
* business.
*/
static int
__checkpoint_presync(WT_SESSION_IMPL *session, const char *cfg[])
{
WT_BTREE *btree;
WT_UNUSED(cfg);
btree = S2BT(session);
WT_ASSERT(session,
btree->checkpoint_gen == __wt_gen(session, WT_GEN_CHECKPOINT));
btree->evict_walk_period = btree->evict_walk_saved;
return (0);
}
/*
* __checkpoint_tree_helper --
* Checkpoint a tree (suitable for use in *_apply functions).
*/
static int
__checkpoint_tree_helper(WT_SESSION_IMPL *session, const char *cfg[])
{
WT_BTREE *btree;
WT_DECL_RET;
WT_TXN *txn;
bool with_timestamp;
btree = S2BT(session);
txn = &session->txn;
/* Are we using a read timestamp for this checkpoint transaction? */
with_timestamp = F_ISSET(txn, WT_TXN_HAS_TS_READ);
/*
* For tables with immediate durability (indicated by having logging
* enabled), ignore any read timestamp configured for the checkpoint.
*/
if (__wt_btree_immediately_durable(session))
F_CLR(txn, WT_TXN_HAS_TS_READ);
ret = __checkpoint_tree(session, true, cfg);
/* Restore the use of the timestamp for other tables. */
if (with_timestamp)
F_SET(txn, WT_TXN_HAS_TS_READ);
/*
* Whatever happened, we aren't visiting this tree again in this
* checkpoint. Don't keep updates pinned any longer.
*/
__checkpoint_update_generation(session);
/*
* In case this tree was being skipped by the eviction server
* during the checkpoint, restore the previous state.
*/
btree->evict_walk_period = btree->evict_walk_saved;
/*
* Wake the eviction server, in case application threads have
* stalled while the eviction server decided it couldn't make
* progress. Without this, application threads will be stalled
* until the eviction server next wakes.
*/
__wt_evict_server_wake(session);
return (ret);
}
/*
* __wt_checkpoint --
* Checkpoint a file.
*/
int
__wt_checkpoint(WT_SESSION_IMPL *session, const char *cfg[])
{
WT_CONFIG_ITEM cval;
WT_DECL_RET;
bool force;
/* Should not be called with a checkpoint handle. */
WT_ASSERT(session, session->dhandle->checkpoint == NULL);
/* We must hold the metadata lock if checkpointing the metadata. */
WT_ASSERT(session, !WT_IS_METADATA(session->dhandle) ||
F_ISSET(session, WT_SESSION_LOCKED_METADATA));
WT_RET(__wt_config_gets_def(session, cfg, "force", 0, &cval));
force = cval.val != 0;
WT_SAVE_DHANDLE(session, ret = __checkpoint_lock_dirty_tree(
session, true, force, true, cfg));
WT_RET(ret);
if (F_ISSET(S2BT(session), WT_BTREE_SKIP_CKPT))
return (0);
return (__checkpoint_tree(session, true, cfg));
}
/*
* __wt_checkpoint_sync --
* Sync a file that has been checkpointed, and wait for the result.
*/
int
__wt_checkpoint_sync(WT_SESSION_IMPL *session, const char *cfg[])
{
WT_BM *bm;
WT_UNUSED(cfg);
bm = S2BT(session)->bm;
/* Should not be called with a checkpoint handle. */
WT_ASSERT(session, session->dhandle->checkpoint == NULL);
/* Unnecessary if checkpoint_sync has been configured "off". */
if (!F_ISSET(S2C(session), WT_CONN_CKPT_SYNC))
return (0);
return (bm->sync(bm, session, true));
}
/*
* __wt_checkpoint_close --
* Checkpoint a single file as part of closing the handle.
*/
int
__wt_checkpoint_close(WT_SESSION_IMPL *session, bool final)
{
WT_BTREE *btree;
WT_DECL_RET;
bool bulk, need_tracking;
btree = S2BT(session);
bulk = F_ISSET(btree, WT_BTREE_BULK);
/*
* We've done the final checkpoint before the final close, subsequent
* writes to normal objects are wasted effort. Discard the objects to
* validate exit accounting.
*/
if (final && !WT_IS_METADATA(session->dhandle))
return (__wt_cache_op(session, WT_SYNC_DISCARD));
/*
* If closing an unmodified file, check that no update is required
* for active readers.
*/
if (!btree->modified && !bulk) {
WT_RET(__wt_txn_update_oldest(
session, WT_TXN_OLDEST_STRICT | WT_TXN_OLDEST_WAIT));
return (__wt_txn_visible_all(session, btree->rec_max_txn,
WT_TIMESTAMP_NULL(&btree->rec_max_timestamp)) ?
__wt_cache_op(session, WT_SYNC_DISCARD) : EBUSY);
}
/*
* Don't flush data from trees when there is a stable timestamp set:
* that can lead to files that are inconsistent on disk after a crash.
*/
if (btree->modified && !bulk &&
S2C(session)->txn_global.has_stable_timestamp &&
!__wt_btree_immediately_durable(session))
return (__wt_set_return(session, EBUSY));
/*
* Turn on metadata tracking if:
* - The session is not already doing metadata tracking.
* - The file was not bulk loaded.
* - The close is not during connection close.
*/
need_tracking = !WT_META_TRACKING(session) && !bulk && !final;
if (need_tracking)
WT_RET(__wt_meta_track_on(session));
WT_SAVE_DHANDLE(session, ret = __checkpoint_lock_dirty_tree(
session, false, false, need_tracking, NULL));
WT_ASSERT(session, ret == 0);
if (ret == 0 && !F_ISSET(btree, WT_BTREE_SKIP_CKPT))
ret = __checkpoint_tree(session, false, NULL);
if (need_tracking)
WT_TRET(__wt_meta_track_off(session, true, ret != 0));
return (ret);
}
/*
* __checkpoint_timing_stress --
* Optionally add a 10 second delay to a checkpoint to simulate a long
* running checkpoint for debug purposes. The reason for this option is
* finding operations that can block while waiting for a checkpoint to
* complete.
*/
static void
__checkpoint_timing_stress(WT_SESSION_IMPL *session)
{
WT_CONNECTION_IMPL *conn;
conn = S2C(session);
/*
* We only want to sleep if the flag is set and the checkpoint comes
* from the API, so check if the session used is either of the two
* sessions set aside for internal checkpoints.
*/
if (conn->ckpt_session != session &&
conn->meta_ckpt_session != session &&
FLD_ISSET(conn->timing_stress_flags,
WT_TIMING_STRESS_CHECKPOINT_SLOW))
__wt_sleep(10, 0);
}
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