ceph/src/rocksdb/docs/_posts/2015-02-24-reading-rocksdb-options-from-a-file.markdown

   1 ---
   2 title: Reading RocksDB options from a file
   3 layout: post
   4 author: lgalanis
   5 category: blog
   6 redirect_from:
   7   - /blog/1883/reading-rocksdb-options-from-a-file/
   8 ---
   9
  10 RocksDB options can be provided using a file or any string to RocksDB. The format is straightforward: `write_buffer_size=1024;max_write_buffer_number=2`. Any whitespace around `=` and `;` is OK. Moreover, options can be nested as necessary. For example `BlockBasedTableOptions` can be nested as follows: `write_buffer_size=1024; max_write_buffer_number=2; block_based_table_factory={block_size=4k};`. Similarly any white space around `{` or `}` is ok. Here is what it looks like in code:
  11
  12 <!--truncate-->
  13
  14 ```c++
  15 #include <string>
  16 #include "rocksdb/db.h"
  17 #include "rocksdb/table.h"
  18 #include "rocksdb/utilities/convenience.h"
  19
  20 using namespace rocksdb;
  21
  22 int main(int argc, char** argv) {
  23   DB *db;
  24
  25   Options opt;
  26
  27   std::string options_string =
  28     "create_if_missing=true;max_open_files=1000;"
  29     "block_based_table_factory={block_size=4096}";
  30
  31   Status s = GetDBOptionsFromString(opt, options_string, &opt);
  32
  33   s = DB::Open(opt, "/tmp/mydb_rocks", &db);
  34
  35   // use db
  36
  37   delete db;
  38 }
  39 ```
  40
  41 Using `GetDBOptionsFromString` is a convenient way of changing options for your RocksDB application without needing to resort to recompilation or tedious command line parsing.