# Prepare fail, Is it mysql slave? Waiting for change buffer merge to complete number of bytes of change buffer **URL:** \ **Category:** Percona XtraBackup\ **Tags:** mysql, percona\ **Created:** [July 30, 2024, 10:08am UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902 "2024-07-30T10:08:27Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![javaPope](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/javapope/32/16986_2.png) [@javaPope](https://forums.percona.com/u/javaPope)\ **Post date:** [July 30, 2024, 10:08am UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/1 "2024-07-30T10:08:27Z")
My backup was made on the MySQL slave database. When I was preparing the backup file, it prompted “start shutdown”, and then it has been showing “Waiting for change buffer merge to complete number of bytes of change buffer”, but this number keeps increasing and decreasing. I suspect whether it is still synchronizing with the master database during the prepare process. Here are note info: 2024-07-30T17:43:28.535402+08:00 0 [Note] [MY-013072] [InnoDB] Starting shutdown… 2024-07-30T17:44:28.536153+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 26059 2024-07-30T17:45:02.912677+08:00 0 [Note] [MY-013073] [InnoDB] Waiting for master to exit. 2024-07-30T17:45:28.536472+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 25672 2024-07-30T17:46:28.536851+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 25046 2024-07-30T17:46:37.242152+08:00 0 [Note] [MY-013073] [InnoDB] Waiting for master to exit. 2024-07-30T17:47:28.537042+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 24800 2024-07-30T17:48:11.466264+08:00 0 [Note] [MY-013073] [InnoDB] Waiting for master to exit. 2024-07-30T17:48:28.537710+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 26506 2024-07-30T17:49:28.537857+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 26222 2024-07-30T17:49:45.659260+08:00 0 [Note] [MY-013073] [InnoDB] Waiting for master to exit. 2024-07-30T17:50:28.538629+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 26147 2024-07-30T17:51:19.890650+08:00 0 [Note] [MY-013073] [InnoDB] Waiting for master to exit. 2024-07-30T17:51:28.539107+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 24990 2024-07-30T17:52:28.539204+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 26118 2024-07-30T17:52:54.088733+08:00 0 [Note] [MY-013073] [InnoDB] Waiting for master to exit. 2024-07-30T17:53:28.539744+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 26763 2024-07-30T17:54:28.304980+08:00 0 [Note] [MY-013073] [InnoDB] Waiting for master to exit. 2024-07-30T17:54:28.540255+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 25321 2024-07-30T17:55:28.540414+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 26119 2024-07-30T17:56:02.526305+08:00 0 [Note] [MY-013073] [InnoDB] Waiting for master to exit. 2024-07-30T17:56:28.541092+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 26168 2024-07-30T17:57:28.541436+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 24441 2024-07-30T17:57:36.744417+08:00 0 [Note] [MY-013073] [InnoDB] Waiting for master to exit. 2024-07-30T17:58:28.541860+08:00 0 [Note] [MY-012874] [InnoDB] Waiting for change buffer merge to complete number of bytes of change buffer just merged: 25650 ---
**Author:** ![matthewb](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/matthewb/32/34_2.png) [@matthewb](https://forums.percona.com/u/matthewb)\ **Post date:** [July 30, 2024, 2:26pm UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/2 "2024-07-30T14:26:57Z")
> [@javaPope](#): > > My backup was made on the MySQL slave database. When I was preparing the backup file, it prompted “start shutdown” You do not need to shut down MySQL to take a backup. What tool are you using? ---
**Author:** ![javaPope](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/javapope/32/16986_2.png) [@javaPope](https://forums.percona.com/u/javaPope)\ **Post date:** [July 31, 2024, 11:44am UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/3 "2024-07-31T11:44:10Z")
When the prepare operation is executed, master-slave data synchronization will be performed with the MySQL master node. Is there a command to prohibit master-slave synchronization during the prepare process? ---
**Author:** ![matthewb](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/matthewb/32/34_2.png) [@matthewb](https://forums.percona.com/u/matthewb)\ **Post date:** [July 31, 2024, 2:58pm UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/4 "2024-07-31T14:58:18Z")
> [@javaPope](#): > > When the prepare operation is executed, master-slave data synchronization will be performed with the MySQL master node That’s not correct. When you run `xtrabackup --prepare`, MySQL should not be running at all because you are about to restore this backup to this server, so MySQL must be stopped. You cannot restore a backup to a running MySQL server. You can take a backup with running MySQL, you cannot restore a backup with running MySQL. ---
**Author:** ![javaPope](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/javapope/32/16986_2.png) [@javaPope](https://forums.percona.com/u/javaPope)\ **Post date:** [August 1, 2024, 12:32pm UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/5 "2024-08-01T12:32:45Z")
When I execute `xtrabackup --prepare --export --apply-log-only`, it keeps showing as follows ![image](https://us1.discourse-cdn.com/flex019/uploads/percona1/original/3X/f/c/fcebc98afef5b23d5230fdf7a9bf68335dd7963b.png) The data volume behind “this change buffer just merged:” will decrease and increase from time to time. If I reset the master-slave synchronization information of the current MySQL when performing --backup again, the problem of “Waiting for change buffer merge to complete number of bytes of change buffer just merged” will not occur during the subsequent --prepare. ---
**Author:** ![matthewb](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/matthewb/32/34_2.png) [@matthewb](https://forums.percona.com/u/matthewb)\ **Post date:** [August 1, 2024, 1:21pm UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/6 "2024-08-01T13:21:29Z")
- Why are you using `--export`? Are you trying to restore a single table? If not, remove that flag. - Why are you using `--apply-log-only`? Is this an incremental backup you are merging into a full? If not, remove this flag. - I would not use 8.3.0-Innovation. This version is a “public beta”. You should be using 8.0.\* for anything production until Percona 8.4 is released. ---
**Author:** ![javaPope](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/javapope/32/16986_2.png) [@javaPope](https://forums.percona.com/u/javaPope)\ **Post date:** [August 1, 2024, 3:28pm UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/7 "2024-08-01T15:28:32Z")
yes,i want to get cfg file and ibd file to restore a table yes,incremental backup my mysql version is 8.3.0 ---
**Author:** ![javaPope](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/javapope/32/16986_2.png) [@javaPope](https://forums.percona.com/u/javaPope)\ **Post date:** [August 1, 2024, 3:34pm UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/8 "2024-08-01T15:34:03Z")
I tried to wait for the merge to end, but as described in my problem log, the change buffer kept growing repeatedly. When I cleared the master-slave information before executing the backup, this problem did not occur. Therefore, I am not sure if the key point is that during the preparation process, the xtrabackup tool synchronized data with my master database, which caused the change buffer to remain unable to merge successfully ---
**Author:** ![matthewb](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/matthewb/32/34_2.png) [@matthewb](https://forums.percona.com/u/matthewb)\ **Post date:** [August 1, 2024, 3:37pm UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/9 "2024-08-01T15:37:06Z")
> [@javaPope](#): > > the xtrabackup tool synchronized data with my master database Xtrabackup does not make any connections to any MySQL databases during the prepare phase. It only operates on the local data. Can you try without `--export` and `--apply-log-only` just as a test? ---
**Author:** ![javaPope](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/javapope/32/16986_2.png) [@javaPope](https://forums.percona.com/u/javaPope)\ **Post date:** [August 1, 2024, 3:38pm UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/10 "2024-08-01T15:38:34Z")
I tried to reproduce this issue in the testing environment, but I was not successful. The testing environment can successfully prepare using these three parameters ---
**Author:** ![javaPope](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/javapope/32/16986_2.png) [@javaPope](https://forums.percona.com/u/javaPope)\ **Post date:** [August 1, 2024, 3:40pm UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/11 "2024-08-01T15:40:38Z")
Is it possible that this problem occurred because there were too many data changes during the backup period in the official environment, but why does the quantity after the merge repeatedly increase and decrease? Shouldn’t it be decreasing ---
**Author:** ![javaPope](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/javapope/32/16986_2.png) [@javaPope](https://forums.percona.com/u/javaPope)\ **Post date:** [August 2, 2024, 3:03am UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/12 "2024-08-02T03:03:23Z")
When I use --apply-log-only, this problem occurs. Is this “Waiting for change buffer merge to complete number of bytes of change buffer just merged” a normal phenomenon? What I don’t understand is that if this merge capacity shows the already merged capacity, then it should keep increasing until the merge is completed. If it shows the unmerged capacity, then it should keep decreasing until the merge is completed. Why does it increase and decrease sometimes? ---
**Author:** ![matthewb](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/matthewb/32/34_2.png) [@matthewb](https://forums.percona.com/u/matthewb)\ **Post date:** [August 2, 2024, 3:44am UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/13 "2024-08-02T03:44:47Z")
`--apply-log-only` should only be used when you have multiple intermediate incrementals. If you take Full/Sunday, Incr/Mon, Incr/Tues, Incr/Wed, then you would need to use `--apply-log-only` when preparing Mon, and Tues, but not on Wed. If you do not have this situation of multiple incrementals, you should not be using this flag. ---
**Author:** ![javaPope](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/javapope/32/16986_2.png) [@javaPope](https://forums.percona.com/u/javaPope)\ **Post date:** [August 2, 2024, 4:36am UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/14 "2024-08-02T04:36:17Z")
> [@matthewb](#): > > have multiple intermediate incrementals i have multiple intermediate incrementals ---
**Author:** ![javaPope](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/javapope/32/16986_2.png) [@javaPope](https://forums.percona.com/u/javaPope)\ **Post date:** [August 2, 2024, 4:37am UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/15 "2024-08-02T04:37:49Z")
so, how to resolve my problem ---
**Author:** ![javaPope](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/javapope/32/16986_2.png) [@javaPope](https://forums.percona.com/u/javaPope)\ **Post date:** [August 2, 2024, 5:08am UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/16 "2024-08-02T05:08:02Z")
![image](https://us1.discourse-cdn.com/flex019/uploads/percona1/original/3X/1/0/10f8afb1da877b2bc4c34c0dee0e8c7cb09dc5cf.png) I tried to wait for it to end, but after half an hour, the number of this merge kept changing repeatedly. Is this a normal phenomenon? ---
**Author:** ![javaPope](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/javapope/32/16986_2.png) [@javaPope](https://forums.percona.com/u/javaPope)\ **Post date:** [August 20, 2024, 2:32am UTC](https://forums.percona.com/t/prepare-fail-is-it-mysql-slave-waiting-for-change-buffer-merge-to-complete-number-of-bytes-of-change-buffer/31902/17 "2024-08-20T02:32:13Z")
Sir, have you found a solution to this problem?