[infinispan-dev] CacheLoaders, Distribution mode and Interceptors

[Adrian Nistor]

Hi James,

I'm not an expert on InfinispanDirectory but I've noticed in [1] that 
the lucene-index cache is distributed with numOwners = 1. That means 
each cache entry is owned by just one cluster node and there's nowhere 
else to go in the cluster if the key is not available in local memory, 
thus it needs fetching from the cache store. This can be solved with 
numOwners > 1.
Please let me know if this solves your problem.

Cheers!

On 03/15/2013 05:03 PM, James Aley wrote:
> Hey all,
>
> <OT>
> Seeing as this is my first post, I wanted to just quickly thank you
> all for Infinispan. So far I'm really enjoying working with it - great
> product!
> </OT>
>
> I'm using the InfinispanDirectory for a Lucene project at the moment.
> We use Lucene directly to build a search product, which has high read
> requirements and likely very large indexes. I'm hoping to make use of
> a distribution mode cache to keep the whole index in memory across a
> cluster of machines (the index will be too big for one server).
>
> The problem I'm having is that after loading a filesystem-based Lucene
> directory into InfinispanDirectory via LuceneCacheLoader, no nodes are
> retrieving data from the cluster - they instead look up keys in their
> local CacheLoaders, which involves lots of disk I/O and is very slow.
> I was hoping to just use the CacheLoader to initialize the caches, but
> from there on read only from RAM (and network, of course). Is this
> supported? Maybe I've misunderstood the purpose of the CacheLoader?
>
> To explain my observations in a little more detail:
> * I start a cluster of two servers, using [1] as the cache config.
> Both have a local copy of the Lucene index that will be loaded into
> the InfinispanDirectory via the loader. This is a test configuration,
> where I've set numOwners=1 so that I only need two servers for
> distribution to happen.
> * Upon startup, things look good. I see the memory usage of the JVM
> reflect a pretty near 50/50 split of the data across both servers.
> Logging indicates both servers are in the cluster view, all seems
> fine.
> * When I send a search query to either one of the nodes, I notice the following:
>    - iotop shows huge (~100MB/s) disk I/O on that node alone from the
> JVM process.
>    - no change in network activity between nodes (~300b/s, same as when idle)
>    - memory usage on the node running the query increases dramatically,
> and stays higher even after the query is finished.
>
> So it seemed to me like each node was favouring use of the CacheLoader
> to retrieve keys that are not in memory, instead of using the cluster.
> Does that seem reasonable? Is this the expected behaviour?
>
> I started to investigate this by turning on trace logging, in this
> made me think perhaps the cause was that the CacheLoader's interceptor
> is higher priority in the chain than the the distribution interceptor?
> I'm not at all familiar with the design in any level of detail - just
> what I picked up in the last 24 hours from browsing the code, so I
> could easily be way off. I've attached the log snippets I thought
> relevant in [2].
>
> Any advice offered much appreciated.
> Thanks!
>
> James.
>
>
> [1] https://www.refheap.com/paste/12531
> [2] https://www.refheap.com/paste/12543
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