dstore

dstore is a distributed storage framework inspired from the FAASM project.

Database

Built as an in-memory datastore with dual layer architecture that enables the storage of Key-Value pairs on nodes in coherence with a single ‘Global’ datastore for synchronization purposes. Keys are UIDs and should technically only be associated with a Value for eternity. Hopefully that will be implemented with the hash of said Value being used for the same.

Architecture

The two layer architecture consists of an in-memory datastore on each node called ‘Local’, which stores copies of data-objects as Key-Value pairs where the Key acts as a UID and enables the user to have a single copy of the data on each node, thus decreasing network access to access the same.

Demo

To demo the working of Dstore, we have created a CLI based Key-Value database that isn’t fully featured, to try it out, follow the steps given below:

Download the code:

git clone https://github.com/vyuham/dstore

Run the server(ensure cargo is installed with rustup):
```
cargo run --example global
```
Ensure the following is showing on the terminal:
```
Dstore server listening on 127.0.0.1:50051
```

On another terminal, start a client:

cargo run --example local

Ensure the following is showing on the terminal:

dstore v0.1.0 (addr: 127.0.0.1:50052)
This is an experimental database, do contribute to further developments at https://github.com/vyuham/dstore. 
Use `.exit` to exit the repl
db > 

Now you know some of the workings of dstore :D

REPL Commands

The demo’s REPL uses commands similar to KVDB, you may use the following to interact with it:

SET: The user/process can store data on the system using the SET/PUT command word, as shown below:
```
db> SET key value
```
The output Database updated implies that key now maps to value within dstore. When you try to SET a key that already exists in ‘Local’, expect to get the output:
```
Key occupied!
```
When a key exists only on ‘Global’ it is updated on local and the SET operation is abandoned, with the message:
```
(Updated local) Key occupied!
```
GET: The user/process can access data from the system using the GET/OUT command word, as shown below:
```
db> GET key
```
This will output:
```
db: key -> value
```
The above output implies that key is mapped to value within dstore. If you try to GET a random key which isn’t mapped to any value in the system, you will recieve the output:
```
Key-Value mapping doesn't exist
```
When you try to GET a key(say hi) that isn’t available in ‘Local’ but exists in ‘Global’(associated with a value hello), expect to receve the output:
```
global: hi -> hello     (Updating Local)
```
DEL: The user/process can removes local as well as global copies of a Key-Value pair with the DEL/REM keyword as shown below:
```
db> DEL key
```
This might only remove the key-value mapping from within the current ‘Local’ and ‘Global’ while other ‘Local’s may still maintain a copy as currently the REPL thread blocks the update() thread leading to a possible lack of support for invalidating KEYs that aren’t unique, at all times. Discussion on how to reflect changes across all ‘Local’s needs to take place. To test these claims, please change the port number of local_addr in ‘example/local.rs` and try opening a few ‘Local’ clients, with a unique port assigned to each and do different order of tasks relating to deleting key-value pairs.

Contribution

Please consider opening an issue to discuss possible feature additions and use cases for the framework. We would love to review genuine PRs to fix bugs, solve issues and add feature, so do consider opening some!

As always, maintain decorum and follow the rust-lang code of conduct. Thank you!

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