path: root/src/cursor/cur_backup.c

/*-
 * Copyright (c) 2014-2016 MongoDB, Inc.
 * Copyright (c) 2008-2014 WiredTiger, Inc.
 *	All rights reserved.
 *
 * See the file LICENSE for redistribution information.
 */

#include "wt_internal.h"

static int __backup_all(WT_SESSION_IMPL *);
static int __backup_cleanup_handles(WT_SESSION_IMPL *, WT_CURSOR_BACKUP *);
static int __backup_list_append(
    WT_SESSION_IMPL *, WT_CURSOR_BACKUP *, const char *);
static int __backup_list_uri_append(WT_SESSION_IMPL *, const char *, bool *);
static int __backup_start(
    WT_SESSION_IMPL *, WT_CURSOR_BACKUP *, const char *[]);
static int __backup_stop(WT_SESSION_IMPL *);
static int __backup_uri(WT_SESSION_IMPL *, const char *[], bool *, bool *);

/*
 * __curbackup_next --
 *	WT_CURSOR->next method for the backup cursor type.
 */
static int
__curbackup_next(WT_CURSOR *cursor)
{
	WT_CURSOR_BACKUP *cb;
	WT_DECL_RET;
	WT_SESSION_IMPL *session;

	cb = (WT_CURSOR_BACKUP *)cursor;
	CURSOR_API_CALL(cursor, session, next, NULL);

	if (cb->list == NULL || cb->list[cb->next].name == NULL) {
		F_CLR(cursor, WT_CURSTD_KEY_SET);
		WT_ERR(WT_NOTFOUND);
	}

	cb->iface.key.data = cb->list[cb->next].name;
	cb->iface.key.size = strlen(cb->list[cb->next].name) + 1;
	++cb->next;

	F_SET(cursor, WT_CURSTD_KEY_INT);

err:	API_END_RET(session, ret);
}

/*
 * __curbackup_reset --
 *	WT_CURSOR->reset method for the backup cursor type.
 */
static int
__curbackup_reset(WT_CURSOR *cursor)
{
	WT_CURSOR_BACKUP *cb;
	WT_DECL_RET;
	WT_SESSION_IMPL *session;

	cb = (WT_CURSOR_BACKUP *)cursor;
	CURSOR_API_CALL(cursor, session, reset, NULL);

	cb->next = 0;
	F_CLR(cursor, WT_CURSTD_KEY_SET | WT_CURSTD_VALUE_SET);

err:	API_END_RET(session, ret);
}

/*
 * __curbackup_close --
 *	WT_CURSOR->close method for the backup cursor type.
 */
static int
__curbackup_close(WT_CURSOR *cursor)
{
	WT_CURSOR_BACKUP *cb;
	WT_DECL_RET;
	WT_SESSION_IMPL *session;
	int tret;

	cb = (WT_CURSOR_BACKUP *)cursor;

	CURSOR_API_CALL(cursor, session, close, NULL);

	WT_TRET(__backup_cleanup_handles(session, cb));
	WT_TRET(__wt_cursor_close(cursor));
	session->bkp_cursor = NULL;

	WT_WITH_SCHEMA_LOCK(session, tret,
	    tret = __backup_stop(session));		/* Stop the backup. */
	WT_TRET(tret);

err:	API_END_RET(session, ret);
}

/*
 * __wt_curbackup_open --
 *	WT_SESSION->open_cursor method for the backup cursor type.
 */
int
__wt_curbackup_open(WT_SESSION_IMPL *session,
    const char *uri, const char *cfg[], WT_CURSOR **cursorp)
{
	WT_CURSOR_STATIC_INIT(iface,
	    __wt_cursor_get_key,		/* get-key */
	    __wt_cursor_get_value_notsup,	/* get-value */
	    __wt_cursor_set_key_notsup,		/* set-key */
	    __wt_cursor_set_value_notsup,	/* set-value */
	    __wt_cursor_compare_notsup,		/* compare */
	    __wt_cursor_equals_notsup,		/* equals */
	    __curbackup_next,			/* next */
	    __wt_cursor_notsup,			/* prev */
	    __curbackup_reset,			/* reset */
	    __wt_cursor_notsup,			/* search */
	    __wt_cursor_search_near_notsup,	/* search-near */
	    __wt_cursor_notsup,			/* insert */
	    __wt_cursor_notsup,			/* update */
	    __wt_cursor_notsup,			/* remove */
	    __wt_cursor_reconfigure_notsup,	/* reconfigure */
	    __curbackup_close);			/* close */
	WT_CURSOR *cursor;
	WT_CURSOR_BACKUP *cb;
	WT_DECL_RET;

	WT_STATIC_ASSERT(offsetof(WT_CURSOR_BACKUP, iface) == 0);

	cb = NULL;

	WT_RET(__wt_calloc_one(session, &cb));
	cursor = &cb->iface;
	*cursor = iface;
	cursor->session = &session->iface;
	session->bkp_cursor = cb;

	cursor->key_format = "S";	/* Return the file names as the key. */
	cursor->value_format = "";	/* No value. */

	/*
	 * Start the backup and fill in the cursor's list.  Acquire the schema
	 * lock, we need a consistent view when creating a copy.
	 */
	WT_WITH_CHECKPOINT_LOCK(session, ret,
	    WT_WITH_SCHEMA_LOCK(session, ret,
		ret = __backup_start(session, cb, cfg)));
	WT_ERR(ret);

	/* __wt_cursor_init is last so we don't have to clean up on error. */
	WT_ERR(__wt_cursor_init(cursor, uri, NULL, cfg, cursorp));

	if (0) {
err:		__wt_free(session, cb);
	}

	return (ret);
}

/*
 * __backup_log_append --
 *	Append log files needed for backup.
 */
static int
__backup_log_append(WT_SESSION_IMPL *session, WT_CURSOR_BACKUP *cb, bool active)
{
	WT_CONNECTION_IMPL *conn;
	WT_DECL_RET;
	u_int i, logcount;
	char **logfiles;

	conn = S2C(session);
	logfiles = NULL;
	logcount = 0;
	ret = 0;

	if (conn->log) {
		WT_ERR(__wt_log_get_all_files(
		    session, &logfiles, &logcount, &cb->maxid, active));
		for (i = 0; i < logcount; i++)
			WT_ERR(__backup_list_append(session, cb, logfiles[i]));
	}
err:	WT_TRET(__wt_fs_directory_list_free(session, &logfiles, logcount));
	return (ret);
}

/*
 * __backup_start --
 *	Start a backup.
 */
static int
__backup_start(
    WT_SESSION_IMPL *session, WT_CURSOR_BACKUP *cb, const char *cfg[])
{
	WT_CONNECTION_IMPL *conn;
	WT_DECL_RET;
	WT_FSTREAM *srcfs;
	const char *dest;
	bool exist, log_only, target_list;

	conn = S2C(session);
	srcfs = NULL;
	dest = NULL;

	cb->next = 0;
	cb->list = NULL;
	cb->list_next = 0;

	/*
	 * Single thread hot backups: we're holding the schema lock, so we
	 * know we'll serialize with other attempts to start a hot backup.
	 */
	if (conn->hot_backup)
		WT_RET_MSG(
		    session, EINVAL, "there is already a backup cursor open");

	/*
	 * The hot backup copy is done outside of WiredTiger, which means file
	 * blocks can't be freed and re-allocated until the backup completes.
	 * The checkpoint code checks the backup flag, and if a backup cursor
	 * is open checkpoints aren't discarded. We release the lock as soon
	 * as we've set the flag, we don't want to block checkpoints, we just
	 * want to make sure no checkpoints are deleted.  The checkpoint code
	 * holds the lock until it's finished the checkpoint, otherwise we
	 * could start a hot backup that would race with an already-started
	 * checkpoint.
	 */
	WT_RET(__wt_writelock(session, conn->hot_backup_lock));
	conn->hot_backup = true;
	WT_ERR(__wt_writeunlock(session, conn->hot_backup_lock));

	/*
	 * Create a temporary backup file.  This must be opened before
	 * generating the list of targets in backup_uri.  This file will
	 * later be renamed to the correct name depending on whether or not
	 * we're doing an incremental backup.  We need a temp file so that if
	 * we fail or crash while filling it, the existence of a partial file
	 * doesn't confuse restarting in the source database.
	 */
	WT_ERR(__wt_fopen(session, WT_BACKUP_TMP,
	    WT_OPEN_CREATE, WT_STREAM_WRITE, &cb->bfs));
	/*
	 * If a list of targets was specified, work our way through them.
	 * Else, generate a list of all database objects.
	 *
	 * Include log files if doing a full backup, and copy them before
	 * copying data files to avoid rolling the metadata forward across
	 * a checkpoint that completes during the backup.
	 */
	target_list = false;
	WT_ERR(__backup_uri(session, cfg, &target_list, &log_only));

	if (!target_list) {
		WT_ERR(__backup_log_append(session, cb, true));
		WT_ERR(__backup_all(session));
	}

	/* Add the hot backup and standard WiredTiger files to the list. */
	if (log_only) {
		/*
		 * We also open an incremental backup source file so that we
		 * can detect a crash with an incremental backup existing in
		 * the source directory versus an improper destination.
		 */
		dest = WT_INCREMENTAL_BACKUP;
		WT_ERR(__wt_fopen(session, WT_INCREMENTAL_SRC,
		    WT_OPEN_CREATE, WT_STREAM_WRITE, &srcfs));
		WT_ERR(__backup_list_append(
		    session, cb, WT_INCREMENTAL_BACKUP));
	} else {
		dest = WT_METADATA_BACKUP;
		WT_ERR(__backup_list_append(session, cb, WT_METADATA_BACKUP));
		WT_ERR(__wt_fs_exist(session, WT_BASECONFIG, &exist));
		if (exist)
			WT_ERR(__backup_list_append(
			    session, cb, WT_BASECONFIG));
		WT_ERR(__wt_fs_exist(session, WT_USERCONFIG, &exist));
		if (exist)
			WT_ERR(__backup_list_append(
			    session, cb, WT_USERCONFIG));
		WT_ERR(__backup_list_append(session, cb, WT_WIREDTIGER));
	}

err:	/* Close the hot backup file. */
	WT_TRET(__wt_fclose(session, &cb->bfs));
	if (srcfs != NULL)
		WT_TRET(__wt_fclose(session, &srcfs));
	if (ret != 0) {
		WT_TRET(__backup_cleanup_handles(session, cb));
		WT_TRET(__backup_stop(session));
	} else {
		WT_ASSERT(session, dest != NULL);
		WT_TRET(__wt_fs_rename(session, WT_BACKUP_TMP, dest));
	}

	return (ret);
}

/*
 * __backup_cleanup_handles --
 *	Release and free all btree handles held by the backup. This is kept
 *	separate from __backup_stop because it can be called without the
 *	schema lock held.
 */
static int
__backup_cleanup_handles(WT_SESSION_IMPL *session, WT_CURSOR_BACKUP *cb)
{
	WT_CURSOR_BACKUP_ENTRY *p;
	WT_DECL_RET;

	if (cb->list == NULL)
		return (0);

	/* Release the handles, free the file names, free the list itself. */
	for (p = cb->list; p->name != NULL; ++p) {
		if (p->handle != NULL)
			WT_WITH_DHANDLE(session, p->handle,
			    WT_TRET(__wt_session_release_btree(session)));
		__wt_free(session, p->name);
	}

	__wt_free(session, cb->list);
	return (ret);
}

/*
 * __backup_stop --
 *	Stop a backup.
 */
static int
__backup_stop(WT_SESSION_IMPL *session)
{
	WT_CONNECTION_IMPL *conn;
	WT_DECL_RET;

	conn = S2C(session);

	/* Remove any backup specific file. */
	ret = __wt_backup_file_remove(session);

	/* Checkpoint deletion can proceed, as can the next hot backup. */
	WT_TRET(__wt_writelock(session, conn->hot_backup_lock));
	conn->hot_backup = false;
	WT_TRET(__wt_writeunlock(session, conn->hot_backup_lock));

	return (ret);
}

/*
 * __backup_all --
 *	Backup all objects in the database.
 */
static int
__backup_all(WT_SESSION_IMPL *session)
{
	WT_DECL_RET;

	/* Build a list of the file objects that need to be copied. */
	WT_WITH_HANDLE_LIST_LOCK(session, ret =
	    __wt_meta_apply_all(session, NULL, __backup_list_uri_append, NULL));

	return (ret);
}

/*
 * __backup_uri --
 *	Backup a list of objects.
 */
static int
__backup_uri(WT_SESSION_IMPL *session,
    const char *cfg[], bool *foundp, bool *log_only)
{
	WT_CONFIG targetconf;
	WT_CONFIG_ITEM cval, k, v;
	WT_DECL_ITEM(tmp);
	WT_DECL_RET;
	bool target_list;
	const char *uri;

	*foundp = *log_only = false;

	/*
	 * If we find a non-empty target configuration string, we have a job,
	 * otherwise it's not our problem.
	 */
	WT_RET(__wt_config_gets(session, cfg, "target", &cval));
	WT_RET(__wt_config_subinit(session, &targetconf, &cval));
	for (target_list = false;
	    (ret = __wt_config_next(&targetconf, &k, &v)) == 0;
	    target_list = true) {
		/* If it is our first time through, allocate. */
		if (!target_list) {
			*foundp = true;
			WT_ERR(__wt_scr_alloc(session, 512, &tmp));
		}

		WT_ERR(__wt_buf_fmt(session, tmp, "%.*s", (int)k.len, k.str));
		uri = tmp->data;
		if (v.len != 0)
			WT_ERR_MSG(session, EINVAL,
			    "%s: invalid backup target: URIs may need quoting",
			    uri);

		/*
		 * Handle log targets. We do not need to go through the schema
		 * worker, just call the function to append them. Set log_only
		 * only if it is our only URI target.
		 */
		if (WT_PREFIX_MATCH(uri, "log:")) {
			/*
			 * Log archive cannot mix with incremental backup, don't
			 * let that happen.
			 */
			if (FLD_ISSET(
			    S2C(session)->log_flags, WT_CONN_LOG_ARCHIVE))
				WT_ERR_MSG(session, EINVAL,
				    "incremental backup not possible when "
				    "automatic log archival configured");
			*log_only = !target_list;
			WT_ERR(__backup_log_append(
			    session, session->bkp_cursor, false));
		} else {
			*log_only = false;
			WT_ERR(__wt_schema_worker(session,
			    uri, NULL, __backup_list_uri_append, cfg, 0));
		}
	}
	WT_ERR_NOTFOUND_OK(ret);

err:	__wt_scr_free(session, &tmp);
	return (ret);
}

/*
 * __wt_backup_file_remove --
 *	Remove the incremental and meta-data backup files.
 */
int
__wt_backup_file_remove(WT_SESSION_IMPL *session)
{
	WT_DECL_RET;

	/*
	 * Note that order matters for removing the incremental files.  We must
	 * remove the backup file before removing the source file so that we
	 * always know we were a source directory while there's any chance of
	 * an incremental backup file existing.
	 */
	WT_TRET(__wt_remove_if_exists(session, WT_BACKUP_TMP));
	WT_TRET(__wt_remove_if_exists(session, WT_INCREMENTAL_BACKUP));
	WT_TRET(__wt_remove_if_exists(session, WT_INCREMENTAL_SRC));
	WT_TRET(__wt_remove_if_exists(session, WT_METADATA_BACKUP));
	return (ret);
}

/*
 * __backup_list_uri_append --
 *	Append a new file name to the list, allocate space as necessary.
 *	Called via the schema_worker function.
 */
static int
__backup_list_uri_append(
    WT_SESSION_IMPL *session, const char *name, bool *skip)
{
	WT_CURSOR_BACKUP *cb;
	WT_DECL_RET;
	char *value;

	cb = session->bkp_cursor;
	WT_UNUSED(skip);

	/*
	 * While reading the metadata file, check there are no data sources
	 * that can't support hot backup.  This checks for a data source that's
	 * non-standard, which can't be backed up, but is also sanity checking:
	 * if there's an entry backed by anything other than a file or lsm
	 * entry, we're confused.
	 */
	if (!WT_PREFIX_MATCH(name, "file:") &&
	    !WT_PREFIX_MATCH(name, "colgroup:") &&
	    !WT_PREFIX_MATCH(name, "index:") &&
	    !WT_PREFIX_MATCH(name, "lsm:") &&
	    !WT_PREFIX_MATCH(name, "table:"))
		WT_RET_MSG(session, ENOTSUP,
		    "hot backup is not supported for objects of type %s",
		    name);

	/* Ignore the lookaside table. */
	if (strcmp(name, WT_LAS_URI) == 0)
		return (0);

	/* Add the metadata entry to the backup file. */
	WT_RET(__wt_metadata_search(session, name, &value));
	ret = __wt_fprintf(session, cb->bfs, "%s\n%s\n", name, value);
	__wt_free(session, value);
	WT_RET(ret);

	/* Add file type objects to the list of files to be copied. */
	if (WT_PREFIX_MATCH(name, "file:"))
		WT_RET(__backup_list_append(session, cb, name));

	return (0);
}

/*
 * __backup_list_append --
 *	Append a new file name to the list, allocate space as necessary.
 */
static int
__backup_list_append(
    WT_SESSION_IMPL *session, WT_CURSOR_BACKUP *cb, const char *uri)
{
	WT_CURSOR_BACKUP_ENTRY *p;
	WT_DATA_HANDLE *old_dhandle;
	WT_DECL_RET;
	const char *name;

	/* Leave a NULL at the end to mark the end of the list. */
	WT_RET(__wt_realloc_def(session, &cb->list_allocated,
	    cb->list_next + 2, &cb->list));
	p = &cb->list[cb->list_next];
	p[0].name = p[1].name = NULL;
	p[0].handle = p[1].handle = NULL;

	name = uri;

	/*
	 * If it's a file in the database, get a handle for the underlying
	 * object (this handle blocks schema level operations, for example
	 * WT_SESSION.drop or an LSM file discard after level merging).
	 *
	 * If the handle is busy (e.g., it is being bulk-loaded), silently skip
	 * it.  We have a special fake checkpoint in the metadata, and recovery
	 * will recreate an empty file.
	 */
	if (WT_PREFIX_MATCH(uri, "file:")) {
		name += strlen("file:");

		old_dhandle = session->dhandle;
		ret = __wt_session_get_btree(session, uri, NULL, NULL, 0);
		p->handle = session->dhandle;
		session->dhandle = old_dhandle;
		if (ret != 0)
			return (ret == EBUSY ? 0 : ret);
	}

	/*
	 * !!!
	 * Assumes metadata file entries map one-to-one to physical files.
	 * To support a block manager where that's not the case, we'd need
	 * to call into the block manager and get a list of physical files
	 * that map to this logical "file".  I'm not going to worry about
	 * that for now, that block manager might not even support physical
	 * copying of files by applications.
	 */
	WT_RET(__wt_strdup(session, name, &p->name));

	++cb->list_next;
	return (0);
}