CODEWITHSUNDEEP
hyperledger-fabricblockchain
Shajal Ahamed
Shajal Ahamed

Reputation: 141

Definition of ledger

I was reading the documentation of hyperledger fabric. In the transaction flow page I found this line 

The chaincode (containing a set of key value pairs representing 
the initial state of the radish market) is installed on the peers and
instantiated on the channel.

This line confused me. I think it is the definition of ledger .But here it is written as chaincode.

Is my perception correct ?

Can anyone explain me ?

Upvotes: 1

Views: 130

Answers (2)

Aniket Chile
Aniket Chile

Reputation: 31

A chaincode is programmatic code deployed on the network, where it is executed and validated by chain validators together during the consensus process. Developers can use chaincodes to develop business contracts, asset definitions, and collectively-managed decentralized applications. more about chaincode click here

How ledger and chaincode relate in Fabric?

Chaincode is a program (smart contract) that is written to read and update the ledger state.

Upvotes: 0

Isaac Wong
Isaac Wong

Reputation: 298

Chaincode (or the more commonly-known term smart-contract) defines a set of business models, transaction definitions and logics which the application (SDK) could utilize to create transactions. For the sentence you show above, this does not refer to the definition of the chaincode. I believe it merely conveys the idea that a list of radishes (in key and value pair) has been defined in the chaincode already, so once it is instantiated (or a initRadish function, if it exists in the chaincode is being called), that list of radishes will become part of the world state in the ledger.

How ledger and chaincode relate in Fabric?

Ledger consists of two components, namely world state and blockchain. World state stores the latest values of the key, whereas the blockchain stores all the transaction log that leads to the world state.

As I said above, chaincode defines the transaction logics in terms of functions such that the application could call to create transaction, which triggers state transition or state retrieval.

For example, you have a function called buyRadish(radishID, newOwner) defined in the chaincode. Suppose there is a radish with key R1001 with value {"owner": FarmerA, "status": OnSale}. This is the key-value pair before any transaction occurs. Once the function in the chaincode is invoked with the argument radishID = R1001, newOwner = Ken, a transaction is created and the state of radish with key R1001 will become {"owner": Ken, "status": Sold}. Note that this latest state of the radish will be seen at the world state.

With the example above, you can think in this way: The ledger stores the latest key-value pairs (or to be precise latest value of the key). The chaincode may have some key-value pairs for initialization purpose; however, the point is that we are passing a new set of key-value pairs (radishID = R1001, newOwner = Ken) as argument to the function in chaincode, so as to update the values of the same key (radishID = R1001) in the world state of the ledger.

Hope it helps.

Upvotes: 2

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