On Saturday 19 January 2008 05:51, Robert Hailey wrote:
>
> Requests equi-distant from each other can create dead-lock loops
> because the uid changes. Without disabling request coalescing
> altogether I could not think of a better solution, but this solves 90%
> of the problem.
Are you quite sure? We send the UID of the request we coalesce with back along
the chain, so a request can't indirectly coalesce with itself, can it?
>
> There is another deadlock condition regarding probablisticHtl
> decrementing which is much less likely (requires at least a 5-node
> race condition) as follows:
>
> B
> A C
> D
> E
>
> C, D, & E each respectively probabilistically don't decrement
>
> (1) Node A (2/11) & B(2/22) both start/route a request (htl/uid)
> (2) D routes to E (1/11)
> (3) C routes to D (1/22), where the request is coalesced with (1/11)
> (4) E routes to C where the request is coalesced with (1/22).
>
> Without this patch even if it were only two nodes starting (for
> example, a USK fetch) at the same time, they would each ask the other
> and each request would be coalesced onto the other.
That sort of thing we expect, but IIRC we deal with the problem, don't we?
>
> --
> Robert Hailey
>
> On Jan 18, 2008, at 11:02 PM, robert at freenetproject.org wrote:
>
> > Author: robert
> > Date: 2008-01-19 05:02:58 +0000 (Sat, 19 Jan 2008)
> > New Revision: 17164
> >
> > Modified:
> > trunk/freenet/src/freenet/node/Node.java
> > trunk/freenet/src/freenet/node/RequestSender.java
> > Log:
> > fix fatal timeout
> >
> >
> > Modified: trunk/freenet/src/freenet/node/Node.java
> > ===================================================================
> > --- trunk/freenet/src/freenet/node/Node.java 2008-01-19 03:33:18 UTC
> >
> > (rev 17163)
> > +++ trunk/freenet/src/freenet/node/Node.java 2008-01-19 05:02:58 UTC
> >
> > (rev 17164)
> > @@ -1779,7 +1779,7 @@
> > // Request coalescing
> > KeyHTLPair kh = new KeyHTLPair(key, htl);
> > sender = (RequestSender) requestSenders.get(kh);
> > - if(sender != null) {
> > + if(sender != null && !sender.isLocalRequestSearch()) {
> > if(logMINOR) Logger.minor(this, "Found sender:
> > "+sender+" for
> > "+uid);
> > return sender;
> > }
> >
> > Modified: trunk/freenet/src/freenet/node/RequestSender.java
> > ===================================================================
> > --- trunk/freenet/src/freenet/node/RequestSender.java 2008-01-19
> > 03:33:18 UTC (rev 17163)
> > +++ trunk/freenet/src/freenet/node/RequestSender.java 2008-01-19
> > 05:02:58 UTC (rev 17164)
> > @@ -851,4 +851,8 @@
> > synchronized int getRecentlyFailedTimeLeft() {
> > return recentlyFailedTimeLeft;
> > }
> > +
> > + public boolean isLocalRequestSearch() {
> > + return (source==null);
> > + }
> > }
> >
> > _______________________________________________
> > cvs mailing list
> > cvs at freenetproject.org
> > http://emu.freenetproject.org/cgi-bin/mailman/listinfo/cvs
> >
>
>
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