[Spread-users] Spread protocol architecture limitation?

[John Schultz]

Hi 김혁래,

The ring has been shown to be stable up to between 50 and 100 daemons on
production networks.  The problem is, beyond those numbers the timeout
mechanisms begin kicking in -- daemons not getting the token begin
executing the membership algorithm to handle perceived daemon failures,
even though none has really occurred.

In a local area network with lightly loaded machines and network, I
would think you should be able to get up to 100 daemons in a ring
without a problem.  If you intend to use this over the wide area, those
numbers will be drastically reduced.

If you really need large numbers of daemons, you might want to ask the
list how to raise the timeouts in Spread appropriately (I don't know
myself).

Another fairly simple mechanism would be to multicast the token to all
the spread daemons (currently it is unicast around the ring).  Then
modify the protocol to reset the timeout timer whenever a token is seen
-- note, however, that this approach could have large performance costs.

Other than that, I believe there is a structural limit of 128 daemons
per segment built into Spread that can't be exceeded without changing
the code.

Oh, don't forget that a single daemon can service MANY client processes,
so there is a large multiplicative factor in how many CLIENTS the system
can sustain as a whole.

I hope that answers your question.

--
John Lane Schultz
Spread Concepts LLP
Phn: 443 838 2200

김혁래 wrote:
> Hi.
> My name is H.R.Kim from south korea.
> Nice to meet you all who love spread like me.
> 
> I have urgent question about spread limitation.
> First, see the below spread user guide chapter '1.2.3 Modularity of Spread architecture'.
> 
> ------------------------------------------------------------------------------------------
> ....
> The first is called the Ring protocol and it provides high throughput 
> when used on a low latency local area network of no more then about 30 daemons.
> ....                                                          ^^^^^^^^^^^^^^^^^
> ------------------------------------------------------------------------------------------
> 
> Now here is my question.
> The number '30' has any special meaning?
> If I have more than '30' daemons, is there any serious performance degration?
> Somebody tell me about this.
> 
> Thank you anyway.
> Bye.
> 
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