[infinispan-dev] Stream operations under lock

[Tristan Tarrant]

On 21/03/17 16:37, William Burns wrote:
> Some users have expressed the need to have some sort of forEach 
> operation that is performed where the Consumer is called while holding 
> the lock for the given key and subsequently released after the Consumer 
> operation completes.
> 
> Due to the nature of how streams work with retries and performing the 
> operation on the primary owner, this works out quite well with forEach 
> 1. AdvancedCache.forEachWithLock(BiConsumer<Cache, CacheEntry<K, V>> 
> consumer)
> 
> This require the least amount of changes, however the user can't 
> customize certain parameters that CacheStream currently provides (listed 
> below - big one being filterKeys).
> 
> 2. CacheStream.forEachWithLock(BiConsumer<Cache, CacheEntry<K, V>> consumer)
> 
> This method would only be allowed to be invoked on the Stream if no 
> other intermediate operations were invoked, otherwise an exception would 
> be thrown. This still gives us access to all of the CacheStream methods 
> that aren't on the Stream interface (ie. sequentialDistribution, 
> parallelDistribution, parallel, sequential, filterKeys, 
> filterKeySegments, distributedBatchSize, disableRehashAware, timeout).
> 
> 3. LockedStream<CacheEntry<K, V>> AdvancedCache.lockedStream()
> 
> This requires the most changes, however the API would be the most 
> explicit. In this case the LockedStream would only have the methods on 
> it that are able to be invoked as noted above and forEach.
> 
> I personally feel that #3 might be the cleanest, but obviously requires 
> adding more classes. Let me know what you guys think and if you think 
> the optimistic exclusion is acceptable.

I prefer option 3, because I don't like UnsupportedOperationExceptions 
lurking until you hit runtime. Can you quantify the amount of extra 
effort here ?

Tristan

-- 
Tristan Tarrant
Infinispan Lead
JBoss, a division of Red Hat