I have a database myDB in the remote server (master) which has a table myTBL with some records. I want to sync the remote database with my localhost (slave) using MySQL Replication. So I have created the replication user in master and also a database with the name of myDB and the myTBL table in the localhost.
I want to use GTIDs method to syncing my databases because there is a description in MySQL website as follows:
MySQL 8.0 supports different methods of replication. The traditional
method is based on replicating events from the master's binary log,
and requires the log files and positions in them to be synchronized
between master and slave. The newer method based on global transaction
identifiers (GTIDs) is transactional and therefore does not require
working with log files or positions within these files, which greatly
simplifies many common replication tasks.
My master MySQL mysqld.cnf has:
server_id=1
enforce_gtid_consistency = on
gtid_mode = on
log_bin
log_slave_updates
and the status is:
File: ***-bin.000001
Position: 314969
Binlog_Do_DB:
Binlog_Ignore_DB:
Executed_Gtid_Set: 9a670a45-be0a-11e9-be56-52540055d8e4:1-368
and my salve mysqld.cnf has:
server-id = 2
read_only = 1
gtid_mode=ON
enforce-gtid-consistency=ON
skip-slave-start=ON
and I use the following commands to start syncing in slave:
CHANGE MASTER TO MASTER_HOST='***', MASTER_USER='***', MASTER_PASSWORD='***', MASTER_AUTO_POSITION=1;
start slave;
And every thing is OK with this status in slave:
...
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
...
So, every new record that inserted to master database is synced with my slave (localhost) database. But the records which are inserted before syncing do not placed in localhost. How can I sync them? Or in the other words, How do I start syncing from the first records? (I saw in some websites which proposed using mysqldump to dump the first data, is there a better way?)
I'm a beginner for MySQL Master-Slave .
and I have read two tutorials .
How to Setup MariaDB (Master-Slave) Replication
Setup MariaDB Master-Slave Replication
In first tutorial. It make me that
[mysqld] Master section
log-bin
server_id=1
replicate-do-db=employees
bind-address=192.168.0.18
[mysqld] SLAVE Section
server_id=2
replicate-do-db=employees
But in the second tutorial, it show me that
[mysqld] Master
server_id=1
log-basename=master
log-bin
binlog-format=row
binlog-do-db=unixmen
[mysqld] Slave
server-id = 2
replicate-do-db=unixmen
And why I should LOCK TABLES, and mysqldump sql, then import it ?
FLUSH TABLES WITH READ LOCK;
DISCLAIMER: To keep things easy and non-confusing here, I talk about a simple 1 Master - 1 Slave setup. No chains, no master-master, or whatever...
Your first tutorial is wrong, it should be binlog-do-db there.
Replication works like this.
The master writes all transactions into its binary log.
The slave reads the transactions from masters binary log and writes them to its relay log.
Only after that the slave executes the statements from its relay log.
binlog-do-db makes the master write only statements for the specified DB into its binary log.
replicate-do-db makes the slave just read statements from the relay log, that are for the specified DB.
replicate-do-db has no effect on the master, since there is no relay log to read from.
The LOCK TABLES part is there, so that the data is consistent. It prevents that the data on the master is modified while backing up the data is still in process.
You restore the database from this backup on the slave, because when you set up a slave, you don't always start from fresh. Therefore it's made so, that you just provide the same data basis on both servers, then you tell the slave at which transaction coordinates the master is and voila, you can start your replication. You can also unlock the master after having dumped the data. Just make sure, that you get the slave up in time before statements in the binary log get lost due to log rotation.
I am trying to do Master Slave Replication for MySQL. When i am typing the following command:
CHANGE MASTER TO MASTER_HOST='10.1.100.1', MASTER_USER='slave_user', MASTER_PASSWORD='slave_password', MASTER_LOG_FILE='mysql-bin.000001', MASTER_LOG_POS=451228;
mysql> START SLAVE;
it throws the following error:
ERROR 1201 (HY000): Could not
initialize master info structure; more
error messages can be found in the
MySQL error log
Any help would be greatly appreciated.
TRY TO RESET IT, IT DOES MAGIC! ON SLAVE THE SLAVE MYSQL COMMAND TYPE:
RESET SLAVE;
THEN TRY AGAIN:
CHANGE MASTER TO MASTER_HOST='10.1.100.1', MASTER_USER='slave_user', MASTER_PASSWORD='slave_password', MASTER_LOG_FILE='mysql-bin.000001', MASTER_LOG_POS=451228;
mysql> START SLAVE;
Please check several things:
1) Make sure the Master's /etc/my.cnf has server_id actually set
Here is why: Replication relies on the server_id. Whenever a query is executed and is recorded in the master's binary log, the server_id of the master is recorded with it. By default, if a server_id is not defined in /etc/my.cnf, the server_id is defaulted to 1. However, the rules MySQL Replication demand that a server_id be explicitly defined in the master's /etc/my.cnf. In addition, for any given slave, mysqld checks the server_id of the SQL statement as it reads it from the relay log and makes sure it is different from the slave's server_id. That is how MySQL Replication knows it is safe to execute that SQL statement. This rule is necessary in the event Circular (Master-Master,MultiMaster) Replication is implemented.
use select ##server_id; in sql command line to check config really on server.
2) Make sure the Slave's /etc/my.cnf has server_id actually set
Here is why: Same reason as in #1
3) Make sure the server_id in the Master's /etc/my.cnf is different from the server_id in the Slave's /etc/my.cnf
Here is why: Same reason as in #1
As a side note : If you setup multiple slaves, please make sure each slave has a different server_id from its master and its sibling slaves.
Here is why : Example
A master with 2 slaves
MASTER has server_id 1
SLAVE1 has server_id 2
SLAVE2 has server_id 2
Replication will become agressively sluggish on SLAVE2 because a sibling slave has the same server_id. In fact, it will steadily fall behind, catch a break, process a few SQL statements. This is the master's fault for having one or more slaves with identical server_ids. This is a gotcha that is not really documented anywhere.
I've seen this dozens of times in my life time.
I had something very close to that and got same error messages.
Replication run fine, mariadb restart -> "cannot open relay log"
Solution from Neo helped in the first place.
But the root cause it seems were to small open file limits.
Try a lsof | wc and increase DefaultLimitNOFILE to 65535 in /etc/systemd/system.conf and /etc/systemd/user.conf
If nothing else helps and you are convinced everything is set correctly you will have to remove this file:
/var/lib/mysql/<relay_logname>-<connection>.info
after that perform the 'CHANGE MASTER' command as stated above
Mysql Server1 is running as MASTER.
Mysql Server2 is running as SLAVE.
Now DB replication is happening from MASTER to SLAVE.
Server2 is removed from network and re-connect it back after 1 day. After this there is mismatch in database in master and slave.
How to re-sync the DB again as after restoring DB taken from Master to Slave also doesn't solve the problem ?
This is the full step-by-step procedure to resync a master-slave replication from scratch:
At the master:
RESET MASTER;
FLUSH TABLES WITH READ LOCK;
SHOW MASTER STATUS;
And copy the values of the result of the last command somewhere.
Without closing the connection to the client (because it would release the read lock) issue the command to get a dump of the master:
mysqldump -u root -p --all-databases > /a/path/mysqldump.sql
Now you can release the lock, even if the dump hasn't ended yet. To do it, perform the following command in the MySQL client:
UNLOCK TABLES;
Now copy the dump file to the slave using scp or your preferred tool.
At the slave:
Open a connection to mysql and type:
STOP SLAVE;
Load master's data dump with this console command:
mysql -uroot -p < mysqldump.sql
Sync slave and master logs:
RESET SLAVE;
CHANGE MASTER TO MASTER_LOG_FILE='mysql-bin.000001', MASTER_LOG_POS=98;
Where the values of the above fields are the ones you copied before.
Finally, type:
START SLAVE;
To check that everything is working again, after typing:
SHOW SLAVE STATUS;
you should see:
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
That's it!
The documentation for this at the MySQL site is woefully out of date and riddled with foot-guns (such as interactive_timeout). Issuing FLUSH TABLES WITH READ LOCK as part of your export of the master generally only makes sense when coordinated with a storage/filesystem snapshot such as LVM or zfs.
If you are going to use mysqldump, you should rely instead on the --master-data option to guard against human error and release the locks on the master as quickly as possible.
Assume the master is 192.168.100.50 and the slave is 192.168.100.51, each server has a distinct server-id configured, the master has binary logging on and the slave has read-only=1 in my.cnf
To stage the slave to be able to start replication just after importing the dump, issue a CHANGE MASTER command but omit the log file name and position:
slaveserver> CHANGE MASTER TO MASTER_HOST='192.168.100.50', MASTER_USER='replica', MASTER_PASSWORD='asdmk3qwdq1';
Issue the GRANT on the master for the slave to use:
masterserver> GRANT REPLICATION SLAVE ON *.* TO 'replica'#'192.168.100.51' IDENTIFIED BY 'asdmk3qwdq1';
Export the master (in screen) using compression and automatically capturing the correct binary log coordinates:
mysqldump --master-data --all-databases --flush-privileges | gzip -1 > replication.sql.gz
Copy the replication.sql.gz file to the slave and then import it with zcat to the instance of MySQL running on the slave:
zcat replication.sql.gz | mysql
Start replication by issuing the command to the slave:
slaveserver> START SLAVE;
Optionally update the /root/.my.cnf on the slave to store the same root password as the master.
If you are on 5.1+, it is best to first set the master's binlog_format to MIXED or ROW. Beware that row logged events are slow for tables which lack a primary key. This is usually better than the alternative (and default) configuration of binlog_format=statement (on master), since it is less likely to produce the wrong data on the slave.
If you must (but probably shouldn't) filter replication, do so with slave options replicate-wild-do-table=dbname.% or replicate-wild-ignore-table=badDB.% and use only binlog_format=row
This process will hold a global lock on the master for the duration of the mysqldump command but will not otherwise impact the master.
If you are tempted to use mysqldump --master-data --all-databases --single-transaction (because you only using InnoDB tables), you are perhaps better served using MySQL Enterprise Backup or the open source implementation called xtrabackup (courtesy of Percona)
Unless you are writing directly to the slave (Server2) the only problem should be that Server2 is missing any updates that have happened since it was disconnected. Simply restarting the slave with "START SLAVE;" should get everything back up to speed.
I am very late to this question, however I did encounter this problem and, after much searching, I found this information from Bryan Kennedy: http://plusbryan.com/mysql-replication-without-downtime
On Master take a backup like this:
mysqldump --skip-lock-tables --single-transaction --flush-logs --hex-blob --master-data=2 -A > ~/dump.sql
Now, examine the head of the file and jot down the values for MASTER_LOG_FILE and MASTER_LOG_POS. You will need them later:
head dump.sql -n80 | grep "MASTER_LOG"
Copy the "dump.sql" file over to Slave and restore it:
mysql -u mysql-user -p < ~/dump.sql
Connect to Slave mysql and run a command like this:
CHANGE MASTER TO MASTER_HOST='master-server-ip', MASTER_USER='replication-user', MASTER_PASSWORD='slave-server-password', MASTER_LOG_FILE='value from above', MASTER_LOG_POS=value from above; START SLAVE;
To check the progress of Slave:
SHOW SLAVE STATUS;
If all is well, Last_Error will be blank, and Slave_IO_State will report “Waiting for master to send event”.
Look for Seconds_Behind_Master which indicates how far behind it is.
YMMV. :)
I think, Maatkit utilits helps for you! You can use mk-table-sync. Please see this link: http://www.maatkit.org/doc/mk-table-sync.html
Here is what I typically do when a mysql slave gets out of sync. I have looked at mk-table-sync but thought the Risks section was scary looking.
On Master:
SHOW MASTER STATUS
The outputted columns (File, Position) will be of use to us in a bit.
On Slave:
STOP SLAVE
Then dump the master db and import it to the slave db.
Then run the following:
CHANGE MASTER TO
MASTER_LOG_FILE='[File]',
MASTER_LOG_POS=[Position];
START SLAVE;
Where [File] and [Position] are the values outputted from the "SHOW MASTER STATUS" ran above.
Hope this helps!
Following up on David's answer...
Using SHOW SLAVE STATUS\G will give human-readable output.
Master:
mysqldump -u root -p --all-databases --master-data | gzip > /tmp/dump.sql.gz
scp master:/tmp/dump.sql.gz slave:/tmp/ Move dump file to slave server
Slave:
STOP SLAVE;
zcat /tmp/dump.sql.gz | mysql -u root -p
START SLAVE;
SHOW SLAVE STATUS;
NOTE:
On master you can run SET GLOBAL expire_logs_days = 3 to keep binlogs for 3 days in case of slave issues.
Here is a complete answer that will hopefully help others...
I want to setup mysql replication using master and slave, and since the only thing I knew was that it uses log file(s) to synchronize, if the slave goes offline and gets out of sync, in theory it should only need to connect back to its master and keep reading the log file from where it left off, as user malonso mentioned.
So here are the test result after configuring the master and slave as mentioned by: http://dev.mysql.com/doc/refman/5.0/en/replication-howto.html ...
Provided you use the recommended master/slave configuration and don't write to the slave, he and I where right (as far as mysql-server 5.x is concerned). I didn't even need to use "START SLAVE;", it just caught up to its master. But there is a default 88000 something retries every 60 second so I guess if you exhaust that you might have to start or restart the slave. Anyways, for those like me who wanted to know if having a slave going offline and back up again requires manual intervention.. no, it doesn't.
Maybe the original poster had corruption in the log-file(s)? But most probably not just a server going off-line for a day.
pulled from /usr/share/doc/mysql-server-5.1/README.Debian.gz which probably makes sense to non debian servers as well:
* FURTHER NOTES ON REPLICATION
===============================
If the MySQL server is acting as a replication slave, you should not
set --tmpdir to point to a directory on a memory-based filesystem or to
a directory that is cleared when the server host restarts. A replication
slave needs some of its temporary files to survive a machine restart so
that it can replicate temporary tables or LOAD DATA INFILE operations. If
files in the temporary file directory are lost when the server restarts,
replication fails.
you can use something sql like: show variables like 'tmpdir'; to find out.
Adding to the popular answer to include this error:
"ERROR 1200 (HY000): The server is not configured as slave; fix in config file or with CHANGE MASTER TO",
Replication from slave in one shot:
In one terminal window:
mysql -h <Master_IP_Address> -uroot -p
After connecting,
RESET MASTER;
FLUSH TABLES WITH READ LOCK;
SHOW MASTER STATUS;
The status appears as below: Note that position number varies!
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000001 | 98 | your_DB | |
+------------------+----------+--------------+------------------+
Export the dump similar to how he described "using another terminal"!
Exit and connect to your own DB(which is the slave):
mysql -u root -p
The type the below commands:
STOP SLAVE;
Import the Dump as mentioned (in another terminal, of course!) and type the below commands:
RESET SLAVE;
CHANGE MASTER TO
MASTER_HOST = 'Master_IP_Address',
MASTER_USER = 'your_Master_user', // usually the "root" user
MASTER_PASSWORD = 'Your_MasterDB_Password',
MASTER_PORT = 3306,
MASTER_LOG_FILE = 'mysql-bin.000001',
MASTER_LOG_POS = 98; // In this case
Once logged, set the server_id parameter (usually, for new / non-replicated DBs, this is not set by default),
set global server_id=4000;
Now, start the slave.
START SLAVE;
SHOW SLAVE STATUS\G;
The output should be the same as he described.
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Note: Once replicated, the master and slave share the same password!
Rebuilding the slave using LVM
Here is the method we use to rebuild MySQL slaves using Linux LVM. This guarantees a consistent snapshot while requiring very minimal downtime on your master.
Set innodb max dirty pages percent to zero on the master MySQL server. This will force MySQL to write all the pages to the disk which will significantly speed up the restart.
set global innodb_max_dirty_pages_pct = 0;
To monitor the number of dirty pages run the command
mysqladmin ext -i10 | grep dirty
Once the number stop decreasing you have reach the point to continue. Next reset the master to clear the old bin logs / relay logs:
RESET MASTER;
Execute lvdisplay to get LV Path
lvdisplay
Output will look like this
--- Logical volume ---
LV Path /dev/vg_mysql/lv_data
LV Name lv_data
VG Name vg_mysql
Shutdown the master database with command
service mysql stop
Next take a snaphot, mysql_snapshot will be the new logical volume name. If binlogs are place on the OS drive those need to be snapshot as well.
lvcreate --size 10G --snapshot --name mysql_snapshot /dev/vg_mysql/lv_data
Start master again with command
service mysql start
Restore dirty pages setting to the default
set global innodb_max_dirty_pages_pct = 75;
Run lvdisplay again to make sure the snapshot is there and visible
lvdisplay
Output:
--- Logical volume ---
LV Path /dev/vg_mysql/mysql_snapshot
LV Name mysql_snapshot
VG Name vg_mysql
Mount the snapshot
mkdir /mnt/mysql_snapshot
mount /dev/vg_mysql/mysql_snapshot /mnt/mysql_snapshot
If you have an existing MySQL slave running you need to stop it
service mysql stop
Next you need to clear MySQL data folder
cd /var/lib/mysql
rm -fr *
Back to master. Now rsync the snapshot to the MySQL slave
rsync --progress -harz /mnt/mysql_snapshot/ targethostname:/var/lib/mysql/
Once rsync has completed you may unmount and remove the snapshot
umount /mnt/mysql_snapshot
lvremove -f /dev/vg_mysql/mysql_snapshot
Create replication user on the master if the old replication user doesn't exist or password is unknown
GRANT REPLICATION SLAVE on *.* to 'replication'#'[SLAVE IP]' identified by 'YourPass';
Verify that /var/lib/mysql data files are owned by the mysql user, if so you can omit the following command:
chown -R mysql:mysql /var/lib/mysql
Next record the binlog position
ls -laF | grep mysql-bin
You will see something like
..
-rw-rw---- 1 mysql mysql 1073750329 Aug 28 03:33 mysql-bin.000017
-rw-rw---- 1 mysql mysql 1073741932 Aug 28 08:32 mysql-bin.000018
-rw-rw---- 1 mysql mysql 963333441 Aug 28 15:37 mysql-bin.000019
-rw-rw---- 1 mysql mysql 65657162 Aug 28 16:44 mysql-bin.000020
Here the master log file is the highest file number in sequence and bin log position is the file size. Record these values:
master_log_file=mysql-bin.000020
master_log_post=65657162
Next start the slave MySQL
service mysql start
Execute change master command on the slave by executing the following:
CHANGE MASTER TO
master_host="10.0.0.12",
master_user="replication",
master_password="YourPass",
master_log_file="mysql-bin.000020",
master_log_pos=65657162;
Finally start the slave
SLAVE START;
Check slave status:
SHOW SLAVE STATUS;
Make sure Slave IO is running and there are no connection errors. Good luck!
I recently wrote this on my blog which is found here... There are few more details there but the story is the same.
http://www.juhavehnia.com/2015/05/rebuilding-mysql-slave-using-linux-lvm.html
I created a GitHub repo with an script to solve this problem quickly. Just change a couple variables and run it (First, the script creates a backup of your database).
I hope this help you (and others people too).
How to Reset (Re-Sync) MySQL Master-Slave Replication
sometimes you just need to give the slave a kick too
try
stop slave;
reset slave;
start slave;
show slave status;
quite often, slaves, they just get stuck guys :)
We are using master-master replication technique of MySQL and if one MySQL server say 1 is removed from the network it reconnects itself after the connection are restored and all the records that were committed in the in the server 2 which was in the network are transferred to the server 1 which has lost the connection after restoration.
Slave thread in the MySQL retries to connect to its master after every 60 sec by default. This property can be changed as MySQL ha a flag "master_connect_retry=5" where 5 is in sec. This means that we want a retry after every 5 sec.
But you need to make sure that the server which lost the connection show not make any commit in the database as you get duplicate Key error Error code: 1062
I'm setting up replication for a server which runs a bunch of databases (one per client) and plan on adding more all the time, on my.cnf, Instead of having:
binlog-do-db = databasename 1
binlog-do-db = databasename 2
binlog-do-db = databasename 3
...
binlog-do-db = databasename n
can I rather just have
binlog-ignore-db = mysql
binlog-ignore-db = informationschema
(and no database to log specified) and assume that everything else is logged?
EDIT: actually if I remove all my binlog-do-db entries, it seemingly logs everything (as you see the binary log file change position when you move the database), but on the slave server, nothing gets picked up! (perhaps, this is the case to use replicate-do-db? this would kill the idea; i guess I cant have MySQL automagically detect which databases to replicate).
That looks correct: http://dev.mysql.com/doc/refman/5.0/en/binary-log.html#option_mysqld_binlog-ignore-db.
According to that reference:
There are some --binlog-ignore-db
rules. Does the default database match
any of the --binlog-ignore-db rules?
Yes: Do not write the statement, and exit.
No: Write the query and exit.
Since you only have ignore commands, all queries will be written to the log as long as the default (active) database doesn't match one of the ignored databases.