[jira] [Created] (FELIX-5621) [DS] event methods setting service properties not thread safe

[David Jencks (JIRA)]

David Jencks created FELIX-5621:
-----------------------------------

             Summary: [DS] event methods setting service properties not thread 
safe
                 Key: FELIX-5621
                 URL: https://issues.apache.org/jira/browse/FELIX-5621
             Project: Felix
          Issue Type: Bug
          Components: Declarative Services (SCR)
    Affects Versions: scr-2.0.8
            Reporter: David Jencks


Thanks to Brent Daniels for pointing this out.

Setting service properties from event methods is not thread safe and does not 
appear to be possible to make thread safe, as synchronizing will almost 
certainly produce deadlocks.  This applies to both setting the properties on 
ExtComponentContext or returning a properties map.

If ExtComponentContext reliably provided a change counter and a compareAndSet 
method then it could be used in e.g.

{code}
int cc;
Dictionary<String, Object> newProps;
do {
  cc = etc.getChangeCount();
 newProps = new Hashtable<>(ecc.getProperties());
 //update properties
} while (!ecc.compareAndSet(cc, newProps)}
{code}

I don't think this can be implemented unless ServiceRegistration provides the 
same API.  Certainly the felix ServiceRegistration implementation is not thread 
safe.



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