dist_ac question

Per Bergqvist <>
Sun Apr 21 10:23:46 CEST 2002


Investigating dist_ac a bit more exposed some serious deadlocks.      
                                                                      
1) During startup it almost certain that introduce will cause         
a deadlock if nodes are started at the same time.                     
2) weight negotiation will cause a lock-up if a app is not yet        
loaded on a remote node.                                              
                                                                      
Fixed in the attached patch. Apply with patch -p0                     
                                                                      
The problem is present in previous releases as well.                  
                                                                      
The weight negotiation is somewhat changed so that dist_ac will       
respond with weight = undefined if there are some kind of problem.    
Weight = undefined will later on be excluded from selection of node.  
                                                                      
Has anybody ever successfully used distributed applications ???       
                                                                      
/Per                                                                  
                                                                      
>                                                                     
> Quite some time since I tried this. I think though, that you have to
> set sync_nodes_timeout (to something finite) as well.               
>                                                                     
> /Peter                                                              
>                                                                     
> On Thu, 18 Apr 2002, Per Bergqvist wrote:                           
>                                                                     
> > I have problems with dist_ac in R8B-1.                            
                                                                      
> > The dist_ac procress is blocking for ever even though             
                                                                      
> > all nodes are defined in sync_nodes_optional.                     
                                                                      
> >                                                                   
                                                                      
> > In the readme for bug OTP-3509 it says that sync_nodes            
functionality                                                         
> > must be used.                                                     
                                                                      
> >                                                                   
                                                                      
> > My question is : is sync_nodes_optional enough.                   
                                                                      
> >                                                                   
                                                                      
> > Can somebody please elaborate a bit on the topic ?                
                                                                      
> >                                                                   
                                                                      
> > BR                                                                
                                                                      
> > /Per                                                              
                                                                      
> >                                                                   
                                                                      
> > =========================================================         
                                                                      
> > Per Bergqvist                                                     
                                                                      
> > Synapse Systems AB                                                
                                                                      
> > Phone: +46 709 686 685                                            
                                                                      
> > Email:                                                
                                                                      
> >                                                                   
>                                                                     
=========================================================             
Per Bergqvist                                                         
Synapse Systems AB                                                    
Phone: +46 709 686 685                                                
Email:                                                    
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