Write-Behind Caching and Re-entrant Calls

Question

Support Team -
     The Coherence User Guide states that:
     "The CacheStore implementation must not call back into the hosting cache service. This includes OR/M solutions that may internally reference Coherence cache services. Note that calling into another cache service instance is allowed, though care should be taken to avoid deeply nested calls (as each call will "consume" a cache service thread and could result in deadlock if a cache service threadpool is exhausted)."
     I have Load-tested a use case wherein I have two caches: ABCache and BACache. ABCache is accessed by the application for write operation, BACache is accessed by the application for read operation. ABCache is a write-behind cache whose CacheStore populates BACache by reversing key and value of each cache entry stored in the ABCache.
     The solution worked under load with no issues.
     But can I use it? Or is it too dangerous?
     My write-behind thread-count setting is left at default (0). The documentation states that
     "If zero, all relevant tasks are performed on the service thread."
     What does this mean? Can I re-enter the caching service if my thread-count is zero?
     Thank you,
     Denis.

Answer 1

Dimitri -
     I am not sure I fully understand your answer:
     1. "Your test worked because write-behing backing map invokes CacheStore methods asynchronously, on a write-behind thread." In my configuration, I have default value for thread-count, which is zero. According to the documentation, that means that CacheStore methods would be executed by the service thread and not by the write-behind thread. Do I understand this correctly?
     2. "If will fail if CacheStore method will need to be invoked synchronously on a service thread." I am not sure what is the purpose of the "service thread". In which scenarios the "CacheStore method will need to be invoked synchronously on a service thread"?
     Thank you,
     Denis.