Support Non-Blocking Manual Compactions (CompactRange) (#597)

Add a new option to CompactRangeOptions, a callback object. By defaut,
the callback is empty so CompactRange() will be blocking (as it is now).
If the callback is set, the callback object's callback method will be
called upon completion with the completion status.

CMakeLists.txt

@@ -743,6 +743,7 @@ set(SOURCES
         db/db_impl/db_impl_experimental.cc
         db/db_impl/db_impl_readonly.cc
         db/db_impl/db_impl_secondary.cc
+        db/db_impl/compact_range_threads_mngr.cc
         db/db_info_dumper.cc
         db/db_iter.cc
         db/dbformat.cc

HISTORY.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 ### New Features
+* Non-Blocking Manual Compaction (CompactRange()) - Support non-blocking manual compactions by setting a new CompactRangeOptions option (async_completion_cb). When set, the CompactRange() call will return control to the caller immediately. The manual compaction iteslf will be performed in an internally created thread. The manual compaction will ALWAYS call the specified callback upon completion and provide the completion status (#597).
 
 ### Enhancements
 

TARGETS

@@ -53,6 +53,7 @@ cpp_library_wrapper(name="rocksdb_lib", srcs=[
         "db/compaction/subcompaction_state.cc",
         "db/convenience.cc",
         "db/db_filesnapshot.cc",
+        "db/db_impl/compact_range_threads_mngr.cc",
         "db/db_impl/compacted_db_impl.cc",
         "db/db_impl/db_impl.cc",
         "db/db_impl/db_impl_compaction_flush.cc",
@@ -404,6 +405,7 @@ cpp_library_wrapper(name="rocksdb_whole_archive_lib", srcs=[
         "db/compaction/subcompaction_state.cc",
         "db/convenience.cc",
         "db/db_filesnapshot.cc",
+        "db/db_impl/compact_range_threads_mngr.cc",
         "db/db_impl/compacted_db_impl.cc",
         "db/db_impl/db_impl.cc",
         "db/db_impl/db_impl_compaction_flush.cc",