Let's design it, because I understand myself with pictures (hahaha) (attached file) Now wait a moment, because I need to think... FM 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. http://www.odamaebrown.com.br
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