CODEWITHSUNDEEP
hyperledger-fabric
the_lost_one
the_lost_one

Reputation: 127

hyperledger fabric: read query and communicating amoung peers within a channel

I'm aware that read query is a chaincode invocation which reads the ledger current state but does not write to the ledger. The client app can choose to submit the read-only transaction for ordering, validation, and commit (for auditing purpose)

Question:

  1. Is it possible to read the ledger db without going via the chaincode ? What prevents someone on channel from directly reading CouchDB (assuming that is the underlying DB used) without using contracts and avoiding recording of reads

  2. Fundamentally, we use an async communication in fabric. The node initiating transaction talks only with the peers synchronously and after that ordering service is initiated which will commit the txn to ledger after all verification check..

Is the following possible ? node A submits a data to the ledger request for an operation -> which needs to be done by node B.

Is this possible for node A to notify B to check ledger and perform operation and B upon completion notify A to check the updated ledger ?

Upvotes: 0

Views: 428

Answers (1)

yacovm
yacovm

Reputation: 5140

Is it possible to read the ledger db without going via the chaincode ? What prevents someone on channel from directly reading CouchDB (assuming that is the underlying DB used) without using contracts and avoiding recording of reads

Nothing prevents you from doing it, if you have access to the database itself. However, the clients usually don't have access to the database and thus the peer (through the chaincode) may enforce selective logic on which clients and what data can be read. Think of an application server, a servlet container, etc. The user that browses from the browser doesn't have access to the database the application server uses, right? A similar thing takes place here.

Fundamentally, we use an async communication in fabric. The node initiating transaction talks only with the peers synchronously and after that ordering service is initiated which will commit the txn to ledger after all verification check..

Strictly speaking, the ordering service does not commit the txn to the ledger, as the ordering service has no ledger. It packages transactions into blocks, then sends the blocks to peers. It is the peers that then validate and commit the block to their own ledgers.

Is this possible for node A to notify B to check ledger and perform operation and B upon completion notify A to check the updated ledger ?

You need the client SDK to orchestrate all of these. User Chaincodes only run in the context of a client's request. So, you can have a client perform an operation that submits a transaction, and then the client sends another transaction in which the chaincode checks the current ledger, etc.

Upvotes: 2

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