I am currently working in projects using Fabric 1.4 I am able to get a decent idea of how things seems to work out but I am quite confused with the way smart contracts and endorsement policies work together.
What i have understood is that endorsement policy is defined during chaincode instantiation where say two or three orgs will sign a transaction in order for it to be valid. This kind of an endorsement just verifies the transaction signatures right ? no data level checks.
Like say I have this kind of a scenario: I have three orgs(Org1,Org2,Org3) each with a peer. Now through a client web app each peer puts data into the blockchain. Now how do I verify if the data (the information that I submit in the blockchain) say for example the name and id are validated by another peer properly and only then added to the world state.
Example: If peer0 in org1 adds data, name and id and the ID is wrong. Org2 has a list of IDs and it should check if the ID that org1 added matches with it and validates it. If it validates then it is fine and data can be put it in the world state
How to define this kind of a transaction state level validation (more of a data level validation rather than just signature verification)? Can this be done in the Go smart contract.
Any help and suggestions would help.
Thanks
During the endorsement, each selected endorser executes (or simulates) the transaction and returns its response, read set and write set signed. The client checks signatures and that responses from different endorsers match (or at least it should do it, anyway this check is performed later again by committers), so there are data level checks (your premise is wrong). The client assembles all the endorsements into a transaction and broadcasts it so it reaches to the ordering service. The ordering service adds the transaction to a block and the block is send to every (committer) peer joined to the channel. The committers perform their checks again and commit the transaction into the state.
It is perfectly explained here: https://hyperledger-fabric.readthedocs.io/en/release-1.4/txflow.html.