This is an in-memory datastore that mirrors the functionality and interface of redis. However, the similarities end there – internally we take advantage of lock free data structures and parallelism to achieve significantly higher throughput on a single instance than redis would be capable of on multicore machines, and comparable performance on single core machines.
> git clone https://github.com/thesecretmaster/predis
> make
> bin/server
The build on master may show some warnings but should always be functional. This will also build bin/server_dbg which compiles without optimizations for easier debugging with gdb.
Predis implements the RESP protocol which is also used by redis, so you can interact with predis using the redis-cli interface provided by redis.
Currently this project is fully functional on get and set commands and can be benchmarked with redis-benchmark. The engine and type/command support could use a lot of work and those are the main focuses at the moment.
There are two main directions that can be worked on in this project:
- Adding new types and commands to work towards feature parity with redis
- Engine improvements and performance optimizations
The engine lives in network_parser.c and uses many of the resources in lib/. General improvements in this area will come from things like reducing system calls, restructuring code for better cache locality, redesigning interfaces and algorithms.
Additionally, this is where the interface that commands and types use lives (in addition to parts in commands.c), and many optimizations in that area are certainly possible.
If this sounds interesting to you, check out the issues tagged engine orcommand-interface in the issue tracker!
Commands and types live in commands/ and types/ respectively. Their interfaces aren't formally documented (it's on the to do list!) but should be fairly intuitive from the headers in the public/ directory and from looking at the string or hash types which have some basic work done.
To add new commands and types, you simply add the files to the correct directories. To load a command or type by default, you can add a line to the main function in network_parser.c of the form load_structures(&ctx, NULL, &((char*){"<types or commands>/my_type_or_command.so"}), NULL, 1);, or you can call load <filename> at runtime to load an arbitrary module into predis.
Generally, anything that's in redis is fair game to add, but if there's something else you're interested in feel free to try it out! Just remember that your type and command has to be thread safe and ideally lock free.