PXB-3269 Reduce the time the Server is locked by xtrabackup #1603
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satya-bodapati
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Aug 29, 2024
storage/innobase/xtrabackup/test/suites/binlog/ib_slave_info.sh
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satya-bodapati
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satya-bodapati
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| db_name = db_name.substr(last_separator_pos + 1); | ||
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| return db_name + '/' + space_name + EXT_NEW; |
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satya-bodapati
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Oct 11, 2024
https://jira.percona.com/browse/PXB-3034 Changed lock-ddl option to be an enum. Possible Values are: ON - Same as True OFF - Same as False REDUCED - Enable REDUCED lock mode. The first attempt to copy IBD files are done without locking and changed tables (Affected by DDL) are recopied (if needed) under DDL.
https://jira.percona.com/browse/PXB-3034 Add DDL tracking to xtrabackup. This new object is responsible for tracking DDL's while the backup is running. Later those changes will be handled in the end of backup and during prepare.
https://jira.percona.com/browse/PXB-3034 Adjusted DDL tracking to produce correct files at the end of backup and handle those files during prepare.
https://jira.percona.com/browse/PXB-3034 Added parallel copy capability to the second phase copy of .ibd files.
https://jira.percona.com/browse/PXB-3034 Added test cases under suite/lockless Fixed test cases using --lock-ddl=false/true
Adjusted fil_open_for_xtrabackup to tolerate file been gone and re-attempt to open the file 10 times.
2. PXB-3220 Allow deleted tables between disovery and file open, save them in missing tables list 3. PXB-3227: Rename table and then drop table, make sure that original table was deleted
…ed and loaded to cache; moving ddl_tracker->add_table to the correct spot
…ume threads https://perconadev.atlassian.net/browse/PXB-3113 The current debug-sync option in PXB completely suspends PXB process and user can resume by sending SIGCONT signal This is useful for scenarios where PXB is paused and do certain operations on server and then resume PXB to complete. But many bugs we found during testing, involves multiple threads in PXB. The goal of this work is to be able to pause and resume the thread. Since many tests use the existing debug-sync option, I dont want to disturb these tests. We can convert them to the new mechanism later. How to use? ----------- The new mechanism is used with option --debug-sync-thread="sync_point_name" In the code place a debug_sync_thread(“debug_point_1”) to stop thread at this place. You can pass the debug_sync point via commandline --debug-sync-thread=”debug_sync_point1” PXB will create a file of the debug_sync point name in the backup directory. It is suffixed with a threadnumber. Please ensure that no two debug_sync points use same name (it doesn’t make sense to have two sync points with same name) ``` 2024-03-28T15:58:23.310386-00:00 0 [Note] [MY-011825] [Xtrabackup] DEBUG_SYNC_THREAD: sleeping 1sec. Resume this thread by deleting file /home/satya/WORK/pxb/bld/backup//xb_before_file_copy_4860396430306702017 ``` In the test, after activating syncpoint, you can use wait_for_debug_sync_thread_point <syncpoint_name> Do some stuff now. This thread is sleeping. Once you are done, and if you want the thread to resume, you can do so by deleting the file 'rm backup_dir/sync_point_name_*` Please use resume_debug_sync_thread_point <syncpoint_name> <backup_dir>. It dletes the syncpoint file and additionally checks that syncpoint is indeed resumed. More common/complicated scenario: ---------------------------------- The scenario is to signal another thread to stop after reaching the first sync point. To achieve this. Do steps 1 to 3 (above) Echo the debug_sync point name into a file named “xb_debug_sync_thread”. Example: 4. echo "xtrabackup_copy_logfile_pause" > backup/xb_debug_sync_thread 5. send SIGUSR1 signal to PXB process. kill -SIGUSR1 496102 6. Wait for syncpoint to be reached. wait_for_debug_sync_thread <syncpoint_name> PXB acknowledges it 2024-03-28T16:05:07.849926-00:00 0 [Note] [MY-011825] [Xtrabackup] SIGUSR1 received. Reading debug_sync point from xb_debug_sync_thread file in backup directory 2024-03-28T16:05:07.850004-00:00 0 [Note] [MY-011825] [Xtrabackup] DEBUG_SYNC_THREAD: Deleting file/home/satya/WORK/pxb/bld/backup//xb_debug_sync_thread and then prints this once the sync point is reached. 2024-03-28T16:05:08.508830-00:00 1 [Note] [MY-011825] [Xtrabackup] DEBUG_SYNC_THREAD: sleeping 1sec. Resume this thread by deleting file /home/satya/WORK/pxb/bld/backup//xb_xtrabackup_copy_logfile_pause_10389933572825668634 At this point, we have two threads sleeping at two sync points. Either of them can be resumed by deleting the filenames mentioned in the error log. (Or use resume_debug_sync_thread())
…sql.ibd seems to be corrupted. https://perconadev.atlassian.net/browse/PXB-3252 Problem: -------- With lock-ddl=REDUCED, ALTER ENCRYPTION='Y'/'N' happens. On general tablespaces, this is done inplace. ie the space_id of tablespace will not change and the pages are encrypted or decrypted. For file per table tablespaces, a new tablespace is created with encryption key and data is copied from old tablespace to new tablespace. In xtrabackup, the files are discovered and then they are copied. Between these two operations, the encrypted tablespace can change. For example, PXB saw that ts1.ibd is encrypted with key1, loaded into cache. Then server did ENCRYPTION='N' and then back to ENCRYPTION='Y', now the tablspace is encrypted with a different key. Now PXB copy threads tries to copy this tablespce and cannot decrypt a page. Page 0 is always unencrypted. So the problem typically detected at Page 1. It can happen on any page. Since PXB cannot decrypt the page, it reports corruption and aborts the backup. Fix: ---- On decryption errors, we track such tablespaces with separate corrupted list. We also them to the recopy tables list. Under lock, these tablespaces are copied again. A .new extension is used. Then we process the corrupted list under lock. Create .corrupt files for the tablespaces from the corrupted list. For example, if the tablespace encrypted is ts1.ibd, the file will be ts1.ibd.corrupted. On prepare, we delete the corresponding ts1.ibd if the ts1.ibd.corrupted is present. This has to be done before the *.ibd scan becuase tablespace loading aborts on processing such half-written tablespaces. If the .corrupted is present in incremental directory, delete the ts1.ibd.meta and ts.ibd.delta files from the incremental backup directory.
…_is_index(page_type) Problem: -------- Unable to apply redo log record entry because page is in wrong state. It was observed that tablespace is created by incremental backup How did this happen? -------------------- lets say tablespace is t1.ibd and happily in fullbackup before incremental, this gets renamed to t2.ibd incremental backup creates t2.ibd.delta and t2.ibd.meta files in incremental backup directory later there is drop t2.ibd, we have space_id.del file in incremental backup directory also some redo generated on this table before it is dropped. During prepare of incremental backup, when we process a space_id.del file, we check the tablespace if tablespace is found. Lets say, it 2.del. To process 2.del, we first check, the tabespace that is with space_id 2. Since the tablespace name is t1.ibd in the full backup directory, we delete it. Additionally, we delete the .ibd and .meta files, so we try to delete t1.ibd.meta and t1.ibd.delta files. They never existed, so we ignore the errors to delete them. But in the inc backup directory, we still have t2.ibd.delta and t2.ibd.meta files. So inc backup prepare creates a tablespace with space_id 2 and apply the delta file changes. This tablespace is wrong because, we are creating a dropped tablespace and we dont have all the changes. incremental backup creates this tablespace with all-zero 7 pages. Later when we do MLOG_INSERT into the index page, we find out the page is NOT in correct state. Fix: ---- We have to delete the right incremental files based on space_id. So we build metamap by scanning *.meta files and with the key as space_id (found in meta file). Later, when we process the space_id.del file, after removing the tablespace with space_id, we will now ask aka meta map cache to give the .delta and .meta file belonging to deleted space_id. By deleting the un-necessary .meta file and .delta, the tablespace is considred as dropped by redo and corresponding redo entries are not applied.
… 2 in a file operation https://perconadev.atlassian.net/browse/PXB-3253 Problem: -------- Files disappear during backup with --lockd-ddl=reduced Analysis: --------- PXB open server files using os_file_create_simple_no_error_handling() via Fil_shard::open_file(), Fil_shard::get_file_size(), Datafile::open_read_only. This API doesn't tolerate file open errors. This particular bug occurs when the file disappeared after get_file_size() in Fil_shard::open_file(). (See the testcase for more details). Fix: ---- If lock ddl is reduced and if we have not yet acquired/entered the copy under lock phase ie is_server_locked() is false, we can tolerate the file open errors. So we use the function/API os_file_create() instead of other variants. Within this, based on lock_ddl reduced mode, we tolerate file opening errors.
… enabled Problem: ------- We cannot allow pagetracking with lock-ddl=REDUCED. This is because page-tracking gives us a set of page_ids (space_id, page_nos). PXB should copy these pages and while we copy these pages, tablespace disappear, get renamed, encrypted etc. We will enable it if there is need or usecase for this. For now, we will disable it. Fix: ---- Disable the combination of --page-tracking and --lock-ddl=REDUCED
Problem: -------- InnoDB assumes directories or files do not disappear. It is true for the engine because, it is in the startup mode and no opeartions are allowed at this point of time. Analysis: --------- With lock-ddl=RECUCED, tables can be dropped concurrently when pxb does *.ibd scan or subdirectories can disappear too. Fix: ---- Handle walk_posix() for missing files/directories. The scan should continue and skip these deleted files or directories.
…=REDUCED Problem: -------- ddl_tracker_t::backup_file_op assumes the required redo bytes are always present. see the assertion len < 6. But it may happen we sometimes receive redo less than that. In such cases, we return nullptr and let the caller read more read and retry Fix: ---- fil_tablespace_redo_create()/rename()/delete() variants handle this problem by returning nullptr and reading more redo and retry. Moved ddl tracker calls to track after the validation is done.
… are not thread safe Problem: ------- xtrabackup uses multiple threads to scan the *.ibd files. With lock-ddl=reduced, we use several STL maps to track of missing, dropped or renamed tables. Multiple threads are used only when number of IBDs are more than 8K Unsafe calls: ddl_tracker->add_missing_table(phy_filename); ddl_tracker->add_renamed_table(space_id, path); These calls from multiple threads operate on std::map/unordered_map and can cause race conditions. Fix: ---- 1. stream line mutex usage for entire ddl_tracker class. Currently used only for corrupted STL map. 2. Use space id instead of table id in messages 3. Rename add_table() since the name is confusing. Actual map elements should be renamed. it will be done later
…ckups with lock-ddl=REDUCED Problem: -------- Backups taken with lock-ddl=reduced, prepare failed to complete. Analysis: --------- When handling .ren files, the destination file name already exists and this causes assertion failure. See the below backup log ``` 102: 2024-02-28T12:15:49.061631-00:00 1 [Note] [MY-011825] [Xtrabackup] DDL tracking : LSN: 73749548 create table ID: 788 Name: test/#sql-1fc79d_13#p#p3.ibd 423: 2024-02-28T12:15:50.121767-00:00 1 [Note] [MY-011825] [Xtrabackup] DDL tracking : LSN: 74312497 rename table ID: 425 From: test/tt_28_p#p#p3.ibd To: test/#sql2-1fc79d-13#p#p3.ibd 870: 2024-02-28T12:15:50.609015-00:00 2 [Note] [MY-011825] [Xtrabackup] Copying ./test/#sql-1fc79d_13#p#p3.ibd to /home/mohit.joshi/dbbackup_28_02_2024/full/test/#sql-1fc79d_13#p#p3.ibd 1337 2024-02-28T12:15:51.183699-00:00 1 [Note] [MY-011825] [Xtrabackup] DDL tracking : LSN: 74967007 rename table ID: 788 From: test/#sql-1fc79d_13#p#p3.ibd To: test/tt_28_p#p#p3.ibd 1491: 2024-02-28T12:15:51.398615-00:00 2 [Note] [MY-011825] [Xtrabackup] Copying ./test/tt_28_p#p#p3.ibd to /home/mohit.joshi/dbbackup_28_02_2024/full/test/tt_28_p#p#p3.ibd 2115: 2024-02-28T12:15:52.209645-00:00 1 [Note] [MY-011825] [Xtrabackup] DDL tracking : LSN: 75267178 delete table ID: 425 Name: test/#sql2-1fc79d-13#p#p3.ibd ``` Whats going on here? Lets say we have partition p3 with space id 425. This is being altered. So partition algorithm does this: 1. create new copy of space_id: 788 (#sql1). 2. rename the existing table 425 to some temp taname (#sql2) 3. we copied the new copy space_id 788 (#sql1) to backup. 4. we also copied the space_id 425 with original name (p3). 5. Later we saw a rename file for the copied tablespace 788. (788.ren created with destination name as tt_28_p#p#p3.ibd The rename file for space_id 425 is skipped, because we knowthat it is dropped. So only a .del file. Final state of backup is: === 788 in backup with name #sql1 425 in backup with name p3 788.ren file-> 788 From: test/#sql-1fc79d_13#p#p3.ibd To: test/tt_28_p#p#p3.ibd 425.drop file === Now prepare starts to process .ren files it tries to rename 788 from #sql1 to p3. but p3 already exists.. Fix: ---- we skip rename and other operations if we know that tablespace is going to be dropped. In the above example, we skipped 425.ren file. So while preparing, we should handle the .del files first. Then we are applying all the consolidated operations in a way. Then .ren can be processed
… during incremental backup with lock-ddl=REDUCED Problem: -------- File deleted between PXB discovery and opening the file. This time at Fil_shard::create_node. It insists the file to be found. Fix: ---- 1. Tolerate the file missing error 2. Use different error code to track in missing files 3. free the tablespace object on error (otherwise, if fil_space_t remians in cache, pxb will try to copy the file)
…lock Problem: ------- With lock-ddl=reduced and Concurrent undo truncations, xtrabackup fails with an assertion Analysis: --------- After truncation, the tablespace id of an undo tablespace id might change and xtrabackup returns error instead of crash. But higher layers of undo discovery do not tolerate missing files or errors. Fix: --- Tolerate file deletions during undo discovery
1. On prepare phase when handling ddl files some of the data files were not loaded to cache because of the first page validation therefore were left without applying ddls on them.
To tolerate this issue we should open and load data files to cache without validation, to do so we are using fil_tablespace_open_for_recovery() function instead of fil_open_for_xtrabackup().
2. Remove macro checks for debug_sync_thread() temporarily, for QA testing
removed argument `prep_handle_ddls` from all using functions, using xtrabackup_prepare instead
Add error handling for prepare_handle_rename() and prepare_handle_del() operations and some minor code refactoring
Add ifdef XTRABACKUP for the code introduced in innobase codebase. (100% not possible though for places that are heavily refactored)
Setting handle_ddl_ops variable to false initially
It is possible that a space_id.ren with content of desired filename, the destination file name could already exist. If the source and desitnation to be renamed is same, skip rename.
Fix keyring test failures by replacing keyring_file to keyring_component
… from 65536 Problem: -------- A regression introduced by 6c9aa00 caused extra opening of files. Fix: ---- remove extra file open
With lock-ddl=REDUCED, the following sequence can happen (Not possible
with lock-ddl=ON)
1. first an IBD with all zero(invalid) encryption is found
2. so this is added to invalid encryption ids
3. the same IBD is found again (because of concurrent DDL, they are both found with different names)
4. this time IBD has proper encryption, so fil_space_t is created
5. encryption info from redo is parsed. fil_tablespace_redo_encryption()
6. because the fil_space_t exists, encryption key is not added to the recovery encryption keys map
7. later at the end of the backup, we check if we have found a valid encryption key for the invalid encryption space_ids.
8. we haven’t (remember at step 6, we skipped it)
9. backup is aborted
Fix:
----
Store keys in recv_sys->keys map even if there exists a tablespace
…es is not same as number of files in datadir 1. Verifies the ulimit -Sn , ulimit -Hn, current --open-files-limit parameter and increases the limit if possible, else throws an error early. 2. Despite the limit increase, backup may still fail because if there are new files that appear, we may need more handles than we first calculated.
…do files Fixed the path for .del/.ren/.new files. Removed extra scan of external tablespaces during prepare
Problem: -------- Undo tablespaces are encrypted during the backup. Their key is in redo but not on the file yet. During recopy phase, xtrabackup was not able to decrypt the pages and wants to add to list of corrupted tablespaces. But this is too late as we are at handling DDL operations. Fix: ---- Read encryption keys of undo tablespaces from redo and use it for decryption.
…tside data directory when lock-ddl=REDUCED Problem: ------- When external general tablespaces are present, with reduced mode, xtrabackup created the .crpt files in the external dir instead of the backup dir. Fix: --- Always create files within backupdir.
…blespace Problem: ======== For every IBD file, we open the file twice. Datafile::open Fil_shard::get_file_size Between these two operations, a general tablespace may become ENCRYPTION Y->N or N->Y So the tablespace flags can mismatch. This should be tolerated because Fix: ---- we track this encryption change and recopy them under lock anyway
1. Dumple tablespace key has two parts. Saving the keys during the backup and using them during prepare. We should use keys from dump file during prepare only 2. Free the memory allocated by fil_path_to_space_name() using a scope guard
…tside data directory when lock-ddl=REDUCED
Problem:
When using backup with lock-ddl=REDUCED and backing up general tablesapce in an external data directory, external directory is assumed as schema of
the general tablspace. For example: Delete DDL for `ext_dir/ext_subdir/gen_tbs.ibd` creates `backup/ext_subdir/space_id.del` file, instead of `backup/space_id.del`
Fix:
---
Check tablespace type and strip the leading path in case of general tablesapces and undo tablespaces
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