database,node.js,sockets , What type of database is the best for storing array or object like data [on hold]


What type of database is the best for storing array or object like data [on hold]

Question:

Tag: database,node.js,sockets

I'm just curious what the best method would be if I'm trying to have a bot running on my Node server that I could play Blackjack against.

But for multiple connected clients via sockets, each connected socket will have their own bot to play against but I need some way to keep the bots available cards for each time they send a POST request with whatever card they pull out of their deck.

I figured MySQL would get messy really quickly because I cannot just store an array or an object and splice out each card as it gets used, but I'm not really familiar with which database would specialize in this kind of use.

If I didn't make any sense, basically:

I need to store cards for the bot (but for each connected users session) not just 1 deck for 1 person but multiple decks for multiple people.

I'm not asking you to write any code for me, just point me in the direction of which database would be ideal for this kind of setup.

I was thinking maybe Redis or MongoDB?


Answer:

Redis would probably be fastest, especially if you don't need a durability guarantee - most of the game can be played out using Redis' in-memory datastore, which is probably gonna be faster than writing to any disk in the world. Perhaps periodically, you can write the "entire game" to disk. If the project is not meant for commercial purposes, i.e. computer errors aren't gonna cause players to lose money, this is definitely an enticing choice.

MongoDB is popular, especially easy to get started with Node, and is definitely faster than most relational SQL solutions, but transactions may be a problem. For a prototype or proof-of-concept projec, it should do fine. But you may also want to look at other "NoSQL" solutions as well.

Cassandra is another popular document-oriented DB, and many people prefer it over MongoDB, for various reasons - most notably, for better scalability.

The choice really highly depends on how you model your data. In your current scenario, I know you want to simply store an object/array, which sounds like you are basically going the way of the aggregated document (MongoDB). You are, in effect, "denormalizing" the entire DB into an aggregate, and performing reads/writes on the entire object every single time in order to achieve consistency. This is a prevalent technique in MongoDB and other document-oriented DBs. But do note that this solution only works because you are not operating across partitions. Think about what happens when you have multiple servers serving the application writing to a separate DB cluster.

You've really got to analyze and decide for yourself what is the best way to model data, if scalability is a concern. Would it be a better model to NOT continually write to this array? For example, generate the sequence of cards once, store it in DB as a Game, and only do reads on it to draw cards? Then, each player's move can be stored as a very succinct data structure Hit referencing a card from the Game. Although the data becomes very relational (back to old school SQL), but the writes are much smaller, and your server never gets into a lock state waiting for players to release the Game object. It may or may not work for your use case, but think about how to model the data for maximum reads and minimum independent writes.

Personally (IMO), if this project is for fun, I'd go with Redis as an in-memory cache layer where most reads/writes happens, and write the game logs into Cassandra. But if this is serious business and I need some real consistency guarantees, I'd probably go back to relational DBs, with a Redis cache layer to speed up reads.

Because there is no one correct answer, the only advice anyone can give is to weigh your application's persistence needs against the strengths/weaknesses of each DB solution, and do a hell lot of research before making an important decision like "which technology to use for persistence". For example, there may be long-term problems with MongoDB that you overlooked - if you'd just Google "MongoDB problems" or "MongoDB sucks". Hell, there may even be long-term problems with all current NoSQL offerings with regards to transactions or consistency.


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