Replication Revisited ...

varungupta_vg81

Hi all

This is regarding implementation of Replication in Mysql.

I have read the mysql manual in this regard but have not succeeded in doing

so.

This is what I did ...

1) Giving "FILE" privilege to the slave on master .

2) Making necessary changes in my.cnf files for both master and slave deamons

.(server-id,log-bin etc etc ....)
The master-host and the master password option are the ones whom i have given

privelege to ..on the master.

3) Copying the data files in server (The whole of the data directory )to

client machine.....

Running the master and the slave server.

Now when i connect to the master and make mysql queries ...(Creating

Table,Updation etc )...these changes are not reflected in the slave ....(I

being made or not ..)

Also when i check the log-position in the slave ..there is no change..clearly

reflecting that the log on the slave is not being updated ..

Kindly tell me the issues that may be involved in this failure..

Also which all data files actually need to be replicated on the server

machine (though i have copied the whole of data directory)

An kind of help would be really appreciated ....

Thnx

Varun

ultraslacker

You copy the directories containing the database(s) files to be replicated, not the whole data directory. You should take a snapshot as explained in the manual.

What does the log tell you - .err file in data dir... Check my.cnf for the appropriate options to start replication. Check the replication user permissions. Check the output of SHOW SLAVE STATUS, SHOW MASTER STATUS, SHOW PROCESSLIST.

If you need more help you will have to give more details.

varungupta_vg81

Thnx a million times for responding to the query sir ...

Now as i have listed ..

I have given the replication privelege to the slave on master.

Made a tar file of data directory on master and copied to slave .
(If not the whole data directory ...then which all files ..)

I have made the changes in my.cnf of slave ..

Now to start the slave I don't think i have to do something other than just to start the mysqld on slave machine and to check its status connect to this slave server with the client with root permissins (hope i am right in this ....).

When I run the commands on slave machine like

SHOW STATUS ---- this shows slave is running

SHOW SLAVE STATUS -- shows the correct master info like its ip etc

NOW THE BIG PROBLEM ..

Even when I stop the master server ...the slave deamon on start does not show any errors ...This means that the slave is not connnecting to the master at all .

Also giving an invalid master ip in the my.cnf at slave shows no error .

I start the slave as a normal mysql server using the command ./safe_mysqld .......

I hope there is no different meathod to start the slave ..

Plz Plz Help me out ...

Thnx

ultraslacker

You are still too vague for anyone to spot your mistake(s)...

This means that the slave is not connnecting to the master at all .

Have you tried connecting to the master as the replication user?

Made a tar file of data directory on master and copied to slave .
(If not the whole data directory ...then which all files ..)

The manual is clear on what you are to copy...and it is not the data directory.

Also giving an invalid master ip in the my.cnf at slave shows no error .

Of course, because changing master host cannot be done via my.cnf, as explained in the manual. Use CHANGE MASTER TO.

varungupta_vg81

O.k Finally got through ...

The slave server is now atleast trying to connect master server

Actually I was running the safe_mysqld deamon ..which i suppose does not support replication ..

When I used the mysqld option for both master n slave , I am atleast getting the error messages...

I now get a problem regarding the data directory. The error that i get is : Failed to open log file n some error related to the position within the log...

So I suppose this is because the naser and the slave are not in sync ...

One option to rectify this is to again copy the data files from master to slave .

Is there any other option , by which i don't need to copy it in the slave machine having copied the data files in the slave machine previously , not in sync at the moment ...

Also I tried modyfying the my.cnf file to give an invalid ip of the master just to test what happens on the slave machine .But the slave still contact the same valid ip...How is this so...

What you are saying regarding the CHANGE MASTER to COMMAND

is when i need to change the master on runtime but here i had shut down the slave server and then modified the cnf file before restarting the slave.

Do i need to manually change the master.info.....Why does the changes in my.cnf not reflected ????

varungupta_vg81

Thnx a lot Mr UltraSlacker ...I am really greatful for the help that you had provided to me regarding replication and spent your precious time..

The Good News Is that I have finally been able to implemnt Replication

Now the next problem....

NOw since I have implemented replication i want it to provide me with reliability also . i.e what if the master goes down ...

Offcourse we have to have a standby master (which is possibly one of the slave of the current master )whice takes up the work of the crashed master..

NOw to do this I feel there are two possibilities..

1.Have a bidirectional master-slave relationship between two machines .and modify the client code in such a way that it automatically connects to the 2nd master (presently the slave of master 1 ) when master1 is down ..

Have a bidirectional master-slave relationship between two machines . Use the concepts of clustering and have a floating IP between the two machines on whom the clients can connect .

Which One do you think is better.Is there any other meathod that you can suggest and have worked upon...

Are there any problems in Bidirectional master slave relationship between two machines ..
Any idea where can i get relevant info on Clustering ...

Waiting for a reply....

Thnx a lot

Varun