feat(bloomfilter): Support more configurable items for bloom filter

apache · Apr 25, 2020 · cc54c2c · cc54c2c
1 parent fb811ba
commit cc54c2c
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Showing 2 changed files with 46 additions and 1 deletion.
diff --git a/src/server/config.ini b/src/server/config.ini
@@ -279,6 +279,18 @@
   rocksdb_disable_bloom_filter = false
   # Bloom filter type, should be either 'common' or 'prefix'
   rocksdb_filter_type = prefix
+  # rocksdb_bloom_filter_bits_per_key |           false positive rate
+  #                                   | rocksdb_format_version < 5 | rocksdb_format_version = 5
+  #        6                                 5.70953                      5.69888
+  #        8                                 2.45766                      2.29709
+  #       10                                 1.13977                      0.959254
+  #       12                                 0.662498                     0.411593
+  #       16                                 0.353023                     0.0873754
+  #       24                                 0.261552                     0.0060971
+  #       50                                 0.225453                     ~0.00003
+  rocksdb_bloom_filter_bits_per_key = 10
+  # SST file format version, should be either 2 or 5
+  rocksdb_format_version = 2
 
   # 3000, 30MB, 1000, 30s
   rocksdb_multi_get_max_iteration_count = 3000

diff --git a/src/server/pegasus_server_impl.cpp b/src/server/pegasus_server_impl.cpp
@@ -293,7 +293,40 @@ pegasus_server_impl::pegasus_server_impl(dsn::replication::replica *r)
     bool disable_bloom_filter = dsn_config_get_value_bool(
         "pegasus.server", "rocksdb_disable_bloom_filter", false, "Whether to disable bloom filter");
     if (!disable_bloom_filter) {
-        tbl_opts.filter_policy.reset(rocksdb::NewBloomFilterPolicy(10, false));
+        // average bits allocated per key in bloom filter.
+        // bits_per_key    |           false positive rate
+        //                 | format_version < 5 | format_version = 5
+        //       6                5.70953              5.69888
+        //       8                2.45766              2.29709
+        //      10                1.13977              0.959254
+        //      12                0.662498             0.411593
+        //      16                0.353023             0.0873754
+        //      24                0.261552             0.0060971
+        //      50                0.225453             ~0.00003
+        // Recommend using no more than three decimal digits after the decimal point, as in 6.667.
+        // More details: https://github.com/facebook/rocksdb/wiki/RocksDB-Bloom-Filter
+        double bits_per_key =
+            dsn_config_get_value_double("pegasus.server",
+                                        "rocksdb_bloom_filter_bits_per_key",
+                                        10,
+                                        "average bits allocated per key in bloom filter");
+        // COMPATIBILITY ATTENTION:
+        // Although old releases would see the new structure as corrupt filter data and read the
+        // table as if there's no filter, we've decided only to enable the new Bloom filter with new
+        // format_version=5. This provides a smooth path for automatic adoption over time, with an
+        // option for early opt-in.
+        // Reference from rocksdb commit:
+        // https://github.com/facebook/rocksdb/commit/f059c7d9b96300091e07429a60f4ad55dac84859
+        int format_version = (int)dsn_config_get_value_int64(
+            "pegasus.server", "rocksdb_format_version", 2, "block based table data format version, "
+                                                           "only 2 and 5 is supported in Pegasus. "
+                                                           "2 is the old version, 5 is the new "
+                                                           "version supported since rocksdb "
+                                                           "v6.6.4");
+        dassert(format_version == 2 || format_version == 5,
+                "[pegasus.server]rocksdb_format_version should be either '2' or '5'.");
+        tbl_opts.format_version = format_version;
+        tbl_opts.filter_policy.reset(rocksdb::NewBloomFilterPolicy(bits_per_key, false));
 
         std::string filter_type =
             dsn_config_get_value_string("pegasus.server",