BLKCached

Intro

BLKCached was created in response to IBM Research's Paper "Reaping the performance of fast NVM storage with uDepot". The goal of this project was to, like uDepot, create a drop-in replacement for memcached, but to simplify the API, and to tune for performance. Unlike uDepot the goal of BLKCached is to provide a proof-of-concept for the use of block-addressable DRAM in the in-memory database sector. The hope is that, in time, block-addressable DRAM (accessible via either PCIe, DIMM or other northbridge ports) will provide more affordable, reliable and fast storage solutions.

Installation

git clone http://github.com/ztipnis/BLKCached
cd BLKCached
mkdir build
cd build
cmake ..
make

Usage

Usage: BLKCached [options]

General:
-v [ –version ] Print version string
-h [ –help ] Print command line help

Configuration:
-s [ –poolSize ] Size of Block Pool Stored on Disk (Defines maximum data stored to disk)
-f [ –path ] Path to pool file
-j [ –threads ] Maximum number of concurrent threads handling socket i/o
-i [ –ip ] IP Address on which to listen
-p [ –port ] Port on which to listen

Command Line:
-c [ –cfg ] Path to config file

BLKCached
- Intro
- Installation
- Usage
- Table of Contents
- Files

Files

Block.h

Class for managing in-memory blocks of data (as well as for fetching those blocks from some block addressable storage medium)

Class Block

Function	Args	Effect	Return
getInst	None	Calls default contructor on first call, after that returns atomic pointer to shared instance	`std::atomic<Store*>&`
get	`std::string key`	Fetches reference to block/offset stored for given key, then dereferences to find value	`std::string`
put	`std::string key, std::string value`	Inserts value into the block with the lowest free space that is able to accomodate the string, then associates the key with the ref to that value	N/A
del	`std::string key`	Fetches reference to block/offset for key, deletes te value from the block, and returns the old value	`std::string`
containsKey	std::string key	Checks if store contains a certain key	`bool`
forKeys	`<typename F> cb`	Calls the function pointer (or lambda function, etc.) cb, for each key.	N/A

Struct RawMemory

Bridges malloc (allocate raw memory of certain size) to C++'s internal

Store.h

Singleton class which serves as a coordinator for blocks, and a storage for key/value ref pairs.

Class Store

Function	Args	Effect	Return
Constructor	`long long block, void (&_getter)(long long, void)`, `void (&_setter)(long long, void)`	Creates a new Block Object at Block offset # (block), with function (_getter) to fetch data from the disk, and (_setter) to save to disk	N/A
get	`size_t offset`	fetches null-terminated or RS- terminated char array starting at (offset)	`std::string`
put	`std::string s`	Inserts string (s) into block (if fits), returns offset of new char array	`ssize_t`
del	`size_t offset`	Deletes string at (offset) and returns its old value	`std::string`
getFreeSpace	None	Returns remaining space in block	`size_t`

Struct ref

Reference to block/offset. Contains a few helpful functions for dereferencing etc.

Struct bref

Shim for pointer to block, with operators for comparing blocks based on free space.

configParser.h

Defines static unordered map with k/v pairs for config options and values.

memory_*.h

Debug (memory-only), and Production (Persistent Memory [aka. on disk]) getters and setters used to emulate block-addressable mediums.

bds.conf

Options used to configure k/v store and server daemon

Option	Values	Desc.
poolSize	(int) 1+	Size of pool (pre-allocated) in GB
path	(string) [any]	Path to persistent memory store. Can be relative or absolute.
threads	(int) 0+	0 => let system choose # of threads. 1+ => specific max number of threads (not yet implemented)
ip	(ipaddr) [any]	The ip on which to listen for connections (not yet implemented)
port	(int)[any]	The port on which to listen for connections

Documentation

Full documentation is available on GitHub Pages

ztipnis / BLKCached