###What is KingDB?
KingDB is a fast on-disk persistent key-value store. You can embed it or use it as a library in your C++ applications.
KingServer is a server application that embeds KingDB and implements the Memcached protocol. It allows you to access your data through a network interface using whatever programming language you want. KingServer is not a distributed system: the data lives in a single machine.
WARNING: This is still alpha code. Even though unit-tests are covering the core components, make sure you run tests for your environment before using KingDB in production.
###Why use KingDB?
- Fast for heavy write workloads and random reads.
- The architecture, code, and data format are simple.
- Multipart API to read and write large entries in smaller parts.
- Multiple threads can access the same database safely.
- Crash-proof: nothing ever gets overwritten.
- Iterators and read-only consistent snapshots.
- Compaction happens in a background thread, and does not block reads or writes.
- The data format allows hot backups to be made.
- Covered by unit tests.
###How fast is KingDB?
KingDB was benchmarked using the same test suite as LevelDB. On a Linux CentOS 6.5, for entries with 16-byte keys and 100-byte values (50 bytes after compression), the performance was:
| Workload | Operations per second |
|---|---|
| Sequential reads | 104k |
| Random reads | 203k |
| Sequential writes | 233k |
| Random writes | 251k |
| Overwrite | 250k |
For more details and a comparison with LevelDB, you can refer to the full KingDB benchmarks.
###Where is the documentation?
You can learn more in the KingDB documentation and the KingServer documentation.
###How to install KingDB?
You can find installation instructions in the installation section of the documentation.
KingDB has no external dependencies and has been tested on:
- Mac OS X 10.9.5 with Apple LLVM version 6.0 (clang-600.0.51)
- Linux Ubuntu 14.04 x64 with GCC 4.9.2
- Linux Ubuntu 15.04 x64 with GCC 4.9.2-10ubuntu13
- Linux CentOS 6.5 x86_64 with GCC 4.9.2
If you are using GCC, update the Makefile and add -fno-builtin-memcmp in the CFLAGS, and if you have tcmalloc on your system, add -ltcmalloc to the LDFLAGS. This will give you a nice performance speed-up.
###Where to get help?
You can get help on the KingDB mailing list. To ask a question, simply join the list.