"Yet Another In-Memory Cache"
This application implements a basic in-memory key-value store (conceptually similar to Memcached), with support for transactions.
For a quick and easy way to demo YAIMC, visit https://glitch.com/edit/console.html?yaimc, type node app.js, and hit Enter. This will start you right up in the application, where you can run commands immediately. When you are done, simply close the window.
Glitch is a quick and easy way to prototype web applications, with or without Node.js.
Visit https://glitch.com/edit/#!/yaimc to view or remix the code. Note that, while Glitch will reload web apps as they are changed, console apps must be restarted manually (by issuing the END command and then restarting with node app.js).
If you prefer to run YAIMC locally, you will first need to install Node.js.
Visit https://nodejs.org/en/download/current/ to download and install the latest version of Node.
After installing Node, download the file app.js to anywhere on your computer. Then open a command prompt in that location, type node app.js, and hit Enter to start up YAIMC.
YAIMC is very laconic. It won't really give you any feedback as you enter commands, except to let you know if it doesn't recognize a command, or in response to commands like GET. Generally speaking, as they say, no news is good news.
| Command | Example | Purpose | Notes |
|---|---|---|---|
| SET key value | SET foo bar |
Set the variable key to value. | Neither key nor value should contain spaces. If value contains spaces, only the first word will be saved. |
| GET key | GET foo |
Print the value associated to key. | Prints NULL when key is not set. |
| UNSET key | UNSET foo |
Remove key (and its associated value) from the cache. | |
| NUMEQUALTO value | NUMEQUALTO bar |
Print the number of variables that are currently set to value. | Prints 0 if no variables are set to value. |
| END | END |
Exit the program. |
YAIMC supports the notion of transactions -- in short, commands can be grouped into blocks in order to ensure that related updates all happen in a single consistent action.
| Command | Purpose | Notes |
|---|---|---|
| BEGIN | Open a new transaction block. | Transaction blocks can be nested: a BEGIN can be issued within an existing block. |
| ROLLBACK | Undo all of the data commands issued within the most recent transaction block and close that block. | Prints NO TRANSACTION if no transaction is in progress. |
| COMMIT | Close all open transaction blocks, permanently applying all data commands made within them. | Prints NO TRANSACTION if no transaction is in progress. |
Any command executed outside of a transaction block will be committed immediately.
How could this application be improved?
- This application has not been tested for concurrent use.
- Interaction is through stdin/stdout, which is not necessarily the most flexible or performant.
- For that matter, refactoring to use another I/O method won't be as easy as it could have been, as I/O was not done through a generic interface.
- Isolation levels for transactions.