[389-devel] Please review: [389 Project] #47347: Simple paged results should support async search

[Noriko Hosoi]

https://fedorahosted.org/389/ticket/47347

https://fedorahosted.org/389/attachment/ticket/47347/0001-Ticket-47347-Si...

  Bug description: Simple paged results serialized the request
  even for a series of asynchronous search requests, and it
  returned error 53 (unwilling to perform) if the second request
  comes in while the first one is being processed.

  Fix description: This patch implements the asynchronous support
  for the Simple paged results search.
  - Removed pagedresults_check_or_set_processing which was
    used to Simple paged results requests exclusive.  Instead,
    pagedresults_lock is introduced to protect the PagedResults
    object from the other threads sharing the same cookie.
  - If any error including hitting the sizelimit or timelimit,
    search result set was released immediately in ldbm_back_
    next_search_entry_ext, which could cause the race condition
    among multiple asynchronous search requests.  To prevent it,
    the search result set is untouched if the operation is a
    Simple paged result search, and let its clean up function
    to handle it.
  - Sizelimit was evaluated in the accumulative way instead of
    on the each page size.  For instance, if the sizelimit was
    101 AND the page size is 100, as soon as getting the 2nd page,
    it hit the sizelimit and the search failed.  This patch fixes
    it so that as long as the requested page size is less than 101,
    the requests successfully continue without getting an error 4
    (LDAP_SIZELIMIT_EXCEEDED).  To fulfill the requirement, the
    current size needs to be managed per operation instead of the
    search result set or PagedResults object. For the purpose,
    introduced o_pagedresults_sizelimit to Slapi_Operation.
  - When shutting down, connection_table_free could use backend
    callback (e.g., be_search_results_release). Therefore, moved
    be_cleanupall after connection_table_free.
  - Each Simple paged results helper functions checks if the
    operation is really a Simple paged result request control is
    associated with to prevent any unexpected behaviour.