Write-Ahead-Logging (WAL) is the central component in various software that require atomicity and durability, such as data management systems (DBMS). The durability and low-latency of non-volatile DIMM (NVDIMM) is a great fit for WAL. This library, libnvwal, is a handy user-space library for such software to manage WAL on NVDIMM with little effort.

The library offers the following benefits:

• Without libnvwal, individual applications must implement their own layering logics on NVDIMM and Disk (HDD/SSD) to store WAL files larger than NVDIMM.
• This would result in either 1) significant code changes on WAL, which is usually one of the most complex and critical modules, or 2) inefficiency via filesystem-level abstraction, which cannot exploit the unique access pattern of WAL.
• libnvwal solves the issue for a wide variety of DBMS.

• Install additional packages

  Debian/Ubuntu

  $ sudo apt-get install build-essential cmake doxygen valgrind
  $ sudo apt-get install libdwarf-dev libunwind-devlibunwind-dev
  

  RedHat/CentOS/Fedora

  $ sudo yum groupinstall "Development Tools"  
  $ sudo yum install cmake doxygen valgrind valgrind-devel
  $ sudo yum install libdwarf libdwarf-devel libunwind libunwind-devel
  

• Install libpmem

  You can either install [pre-built packages]((https://github.com/pmem/nvml/releases) or build from source:

  $ sudo apt-get install autoconf pkg-config doxygen graphviz
  $ git clone https://github.com/pmem/nvml.git
  $ cd nvml
  $ make
  $ sudo make install
  

To compile this project, simply build it as a CMake project. For example:

# Suppose you are at libnvwal source folder.
# We prohibit in-source build, so you have to create a build folder and compile there.
$ mkdir build
$ cd build
# You can also use Release/RelWithDebInfo just like usual CMake projects.
$ cmake ../  -DCMAKE_BUILD_TYPE=Debug
$ make

Or, import it to C++ IDE, such as kdevelop. Any IDEs that support CMake build should work.

libnvwal comes with several unittests we regularly run. We recommend you to run them in your environment to check if the compilation was successful.

Go to build folder, and:

ctest

If everything goes fine, you would see an output like the following:

[alice@dome build]$ ctest
Test project /home/alice/projects/libnvwal/build
      Start  1: test_nvwal_cursor_NoLog
1/70 Test  #1: test_nvwal_cursor_NoLog .................................   Passed    0.04 sec
      Start  2: test_nvwal_cursor_OneWriterOneEpoch
2/70 Test  #2: test_nvwal_cursor_OneWriterOneEpoch .....................   Passed    0.04 sec
.... <Snip>  .....
      Start 69: valgrind_test_nvwal_writer_TwoWritersSingleThread
69/70 Test #69: valgrind_test_nvwal_writer_TwoWritersSingleThread .......   Passed    1.71 sec
      Start 70: valgrind_test_nvwal_writer_TwoWritersConcurrent
70/70 Test #70: valgrind_test_nvwal_writer_TwoWritersConcurrent .........   Passed    2.02 sec

100% tests passed, 0 tests failed out of 70

Total Test time (real) =  42.13 sec

Take a look at the example folder for detailed examples and demonstrations. Especially, start with get_started.cpp to see the basic interface of libnvwal.

Go to build folder, and type:

make dox
google-chrome dox/html/group__LIBNVWAL.html