[mysql-dde] Re: Connection Fail

  • From: Fabricio Mota <fabricio.mota@xxxxxxxxx>
  • To: mysql-dde@xxxxxxxxxxxxx
  • Date: Thu, 8 Dec 2005 20:53:30 -0300

Let's design it, because I understand myself with pictures (hahaha)

(attached file)

Now wait a moment, because I need to think...


2005/12/8, Peter B. Volk <peter.benjamin.volk@xxxxxxxxxxxxxxxxx>:
> Hey,
>  ----- Original Message -----
> *From:* Fabricio Mota <fabricio.oliveira@xxxxxxxxxxxxxxxx>
> *To:* Peter B. Volk <peter.benjamin.volk@xxxxxxxxxxxxxxxxx> ; 
> mim<fabricio.mota@xxxxxxxxx>
> *Sent:* Tuesday, December 06, 2005 2:44 PM
> *Subject:* Connection Fail
> Hey Peter,
> I was thinking a bit more about connection liveness and server liveness
> management, and I've got another problem: visibility is a *bidiretional 
> *property.
> That is: suppose a cluster with 3 servers, S1, S2 and S3. At the first
> moment, everybody sees everybody.
> But in a second moment, due a network transient, S1 stops to see S2,
> although S2 still sees S1. That means, only connection from S1 (as
> client) to S2 (as server) failed. So, I think that there are no Islands
> here, only a non-complete graph will be found.
> Of course, S3 will not be prohibited to perform any operation, because it
> completely sees everybody.
> But what about S1 and S2?
> Well, if we (eventually) consider to use any billateral management, so S2
> will be also able to perform operations origined by it. That's because it
> also sees everybody.
> But S1 will try perform active-cluster operations under
> late-synchronization proceeding. So, it will do that is needed communicating
> with S3, and could save a buffer to inform modifications to S2 later.
> It could be dangerous if we imagine a RDD updating example, as above:
> *1.* S1 updates MyRDDTable, because it is protected under
> majority-criteria law.
> *  1.1 *S1 updates itself;
> *  1.2 *S1 sends update command to S3;
> *  1.3 *S1 creates a buffer (late sync) for when S2 come active again;
>  *2.* And a little after, S2 try to update MyRDDTable, since it is
> protected under majority-criteria law, too.
> *  1.1 *S2 updates itself (before to receive buffered command from S1,
> it's very bad!);
> *  1.2 *S2 sends update command to S3;
> *  1.3 *S2 sends update command to S1 (ishhhh);
> How do you suggest to solve it?
> [Peter] Hmmm good question. Once S1 doesnt see S2 anymore S2 is suspected
> by S1 to be down and communicates this to S3 since S3 can see all of them
> ther is a classification of this error -> networkerror. Then S1-3 should
> decide on who should be taken out of the cluster S1 or S2.
> How does that sound?
> Peter


Sem mais,

Fabricio Mota
Oda Mae Brown - Aprecie sem moderação.

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