Use READONCE io context for nrt, add MMap grouping options #774
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The
MMapDirectoryin the newer lucene versions use the new java native memory api, if available. By default, mapping files from the same segment use a ref counted memoryArena. When we open files for nrt operations, the mappings will persist until the segment is closed. This can lead to an accumulation of mappings of the same files.Opening files for nrt operations have been changed to use the
READONCEio context. This avoids use of mmap file groupings. This could not be used forRecvRawFileV2Handler, since this type of mapping can only be used by the opening thread. We will need to handle this another way in the future for acked copy.The config now exposes
mmapGroupingto set the grouping function:SEGMENT(default) - All files from the same segment are groupedSEGMENT_EXCEPT_SI- All files from the same segment are grouped, except.sifiles. The segment info file for all index segments are read on completion of an nrt point. This option may be useful to stop accumulation of these mappings on replicas.NONE- No file grouping