How and where does a block production take place?

Question

Like if I were to add some custom logic and checks to ensure only certain kind of blocks are produced by the validators or only those blocks that contain a certain size of data are produced then where in code should I look for or what files should I change?

I tried looking up at the BABE-pallet but it only contained logic regarding validator selection and stuff.

I want to know where this block production/building takes place in code and how I can modify that logic to allow only certain blocks to be added by validators.

Answer 1

Simply put, BABE(-pallet) provides logic which decides who, for a certain amount of blocks, is allowed to author a new block.

Authoring a block is filling the block with valid transactions from the transaction pool and sending it to other peers. But blocks are blocks, and the only way to specify what kind of blocks are allowed is specifying what kind of transactions are allowed in the blocks. This is your runtime, more specifically, the pallets you include in your runtime that provide the functionality for certain transactions on your chain. For example, again simply put, without the nft-pallet configured in your runtime you can't send nft related transactions on that particular chain. In addition, there are some constants that you could modify (e.g. block size, block length, etc) in order to specify the "size" of the blocks.