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-Have cache persist a little longer to improve concurrent NodeRange expansion rather that slow it down

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git-svn-id: https://svn.code.sf.net/p/xcat/code/xcat-core/trunk@4086 8638fb3e-16cb-4fca-ae20-7b5d299a9bcd
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jbjohnso 2009-09-02 17:20:28 +00:00
parent 0e14b4f481
commit b2789bdede
1 changed files with 28 additions and 0 deletions
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28
perl-xCAT/xCAT/Table.pm
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@ -1,4 +1,15 @@
# IBM(c) 2007 EPL license http://www.eclipse.org/legal/epl-v10.html
#TODO:
# just enough notes to remind me of the design that I think would allow for
# -cache to persist so long as '_build_cache' calls concurrently stack (for NodeRange interpretation mainly) (done)
# -Allow plugins to define a staleness threshold for getNodesAttribs freshness (complicated enough to postpone...)
# so that actions requested by disparate managed nodes may aggregate in SQL calls
# reference count managed cache lifetime, if clear_cache is called, and build_chache has been called twice, decrement the counter
# if called again, decrement again and clear cache
# for getNodesAttribs, we can put a parameter to request allowable staleneess
# if the cachestamp is too old, build_cache is called
# in this mode, 'use_cache' is temporarily set to 1, regardless of
# potential other consumers (notably, NodeRange)
#perl errors/and warnings are not currently wrapped.
# This probably will be cleaned
#up
@ -1382,20 +1393,37 @@ sub getNodesAttribs {
sub _clear_cache { #PRIVATE FUNCTION TO EXPIRE CACHED DATA EXPLICITLY
#This is no longer sufficient to do at destructor time, as Table objects actually live an indeterminite amount of time now
#TODO: only clear cache if ref count mentioned in build_cache is 1, otherwise decrement ref count
my $self = shift;
if ($dbworkerpid) {
return dbc_call($self,'_clear_cache',$_);
}
if ($self->{_cache_ref} > 1) { #don't clear the cache if there are still live references
$self->{_cache_ref} -= 1;
return;
} elsif ($self->{_cache_ref} == 1) { #If it is 1, decrement to zero and carry on
$self->{_cache_ref} = 0;
}
#it shouldn't have been zero, but whether it was 0 or 1, ensure that the cache is gone
$self->{_use_cache}=0; # Signal slow operation to any in-flight operations that may fail with empty cache
undef $self->{_tablecache};
undef $self->{_nodecache};
}
sub _build_cache { #PRIVATE FUNCTION, PLEASE DON'T CALL DIRECTLY
#TODO: increment a reference counter type thing to preserve current cache
#Also, if ref count is 1 or greater, and the current cache is less than 3 seconds old, reuse the cache?
my $self = shift;
if ($dbworkerpid) {
return dbc_call($self,'_build_cache',@_);
}
if ($self->{_cache_ref}) { #we have active cache reference, increment counter and return
#TODO: ensure that the cache isn't somehow still ludirously old
$self->{_cache_ref} += 1;
return;
}
#If here, _cache_ref indicates no cache
$self->{_cache_ref} = 1;
my $oldusecache = $self->{_use_cache}; #save previous 'use_cache' setting
$self->{_use_cache} = 0; #This function must disable cache
#to function