Backup

[Ivan Smahin]

Hello Mr.,

Wednesday, February 13, 2008, 11:47:16 PM, you wrote:

> Hi Ivan,
> On 13-feb-08, at 22:26, Ivan Smahin wrote:

>> Hello Mr.,
>>
>> Wednesday, February 13, 2008, 10:56:04 PM, you wrote:
>>
>>> Hi List,Ruslan,
>>
>>> Does anybody care to explain to me what exactly happens when a  
>>> VServer
>>> is making a backup. I have a VServer on an interval of 1 hour. This  
>>> is
>>> working flawless.
>>
>>> However I'm wondering what is happening while the VServer is making a
>>> backup. Does it become unresponsive for clients making an attempt to
>>> talk to the database?
>>
>> Well, obviously you mean not backup but scheduler - right?
>> Just the most wanted command to run by schedule is backup.
> right

>>
>>
>> One of the service thread inside the server is for scheduler purpose.
>> You    are   preparing   event  via  SQL  and  then  vServer scheduler
>> calculates the nearest time to wake up and perform the task defined in
>> that event. So most of the time scheduler thread sleeps.
>> Awaking, it performs the task very similar to regular client - so  
>> during
>> task execution  kernel is locked out (but server is still able to  
>> accept commands
>> from  another clients. The deal is - almost any command goes to kernel
>> -  so  most  of  the  client requests will be waiting for kernel  
>> mutex.).
>>

> This is what I mean. The scheduler takes the mutex when performing the
> backup. So when , while the backup is being created (may take a few  
> seconds), ANOTHER client (in this case vPHP) wants to acces the kernel
> (perform an insert let's say) what will happen ?

> Insert will fail ? Is there an error thrown ?

No - another client with its insert command will be just blocked on mutex.


-- 
Best regards,
Ivan Smahin 
Senior Software Engineer
Paradigma Software, Inc
Valentina - The Ultra-Fast Database
http://www.valentina-db.com