My names is Antonio and i come from Italy. In this days i'm designing an fabric architecture for an important project.
My network will have one channel that represents a community of n peer. This latter can endor the transaction and to do basic operations.In that community there will be and Administrator.
is The ordere a physical peer where someone have that role? In that case i will define the Community Manager responsable for the Channel configuration, network configuration and as orderer.
The administrator will receive the reward from external national institutions. The idea is to distribute that reward to the peer in the community with a smart contract.
The Administrator, therefore orderer, will receive the reward then the smart contract automatically distribute the reward based on some parameters. The question is:
The smart contract can receive the events from orderer, therefore administrator network and channel, of reward received and automatically distribute the reward?
Antonioy
you probably misunderstand a bit how the Hyperledger Fabric works. The orderer is a separate entity and it receives transaction candidates from the peers putting them into blocks and them broadcasting these blocks in a specific order (that's why it's called "Orderer"). You can not receive events from the orderer inside the chaincode (the name of smart contracts in Fabric) and the chaincode is agnostic to what peers it is being run on, you can only work with an identity of a signer of a transaction that has been sent to a peer for endorsement.
Related
I am building one POC using Hyperledger fabric,
Is it possible to send messages from one organization admin like money details to another organization admin and he sends the (agree/denied) message?
You can work with multi organization model. Install chaincode on two organization peers and instantiate the chaincode over channel. Post Instantiation of chaincode you can invoke some transactions which will be distributed the orderer to every peer that is joined in the channel.
In the below link you can expect a basic network for two organizations with two peers each.
Please help me if my conceptualization is incorrect ---
Setup:
I am trying to understand how to achieve decentralization in Hyperledger Fabric - smart contracts. Assume Org 1 and Org 2 are in the same channel. Each of these Org have peers and endorsers. The endorsement policy is 100% of Org 1 and Org 2
Question:
In my understanding the SAME SMART CONTRACT needs to be installed in both Org 1 and Org 2 peer. In other words, So when a incoming transaction is sent to Org 1 and Org 2, the same smart contract is executed by both peers.
Is this understanding correct?
REF: https://hyperledger-fabric.readthedocs.io/en/release-1.4/developapps/smartcontract.html
In the PaperNet network, the smart contract is shared by the different network participants, such as MagnetoCorp and DigiBank. The same version of the smart contract must be used by all applications connected to the network so that they jointly implement the same shared business processes and data.
If it is correct, the smart contract code must have been written by some developer (Possible Org 1 who originated the blockchain network),How is this decentralization?
I my understanding, In a decentralized environment, should not be there a way where ORG 2 can separately create its own smart contract and install and use that to validate / commit?
If this is possible, any articles / blogs that show how to do this?
As you can see te question is nothing to do with endorsement policies etc.
thanks in advance and please feel free to correct me if my basic understanding of decentralization is incorrect
Regards
VJ
Hyperledger fabric is a DLT(decentralized ledger technology) platform. As from the word DLT, you may understand here ledger is decentralized. So, yes your basic understanding is wrong.
Smart Contract:
Its similar like to real world contract between multiple parties, on which all parties has been agreed(Like a property deed on which both parties i.e. seller and buyer will agree). Similar here in Hyperledger fabric, a smart contract is business logic, on which all parties(all participating organization, in particular channel) have to agree. So, you may say a smart contract will be written by some developer of any organization and all other organization can review the source code and will agree to use that smart contract.
How it is decentralized:
So, in every DLT, ledger is decentralized, i.e. each party will be having their own copy of transactional data.In Hyperledger fabric, each organization is having a peer that contains transactional data and world state.
Sorry for the long question but Hyperledger is a fairly complex system.
Reading the Blockchain network In the section Generating and accepting transactions
In contrast to peer nodes, which always host a copy of the ledger, we
see that there are two different kinds of peer nodes; those which host
smart contracts and those which do not. In our network, every peer
hosts a copy of the smart contract, but in larger networks, there will
be many more peer nodes that do not host a copy of the smart contract
How to design the blockchain network and to decide how many peers should have smart contracts and how many should not?, Is there any design rules or patterns ?
When we have multiple organizations, should every organization has an endorsing peer, or they all can have only one within one organization and all other can call it ?
How to design the blockchain network and to decide how many peers
should have smart contracts and how many should not?, Is there any
design rules or patterns ?
My rule of thumb is - you first think about the endorsement policy, and then you install the chaincode on peers that belong to organizations that are in the endorsement policy.
Then, you can also optionally install the chaincode for query-only transactions (that don't get into the Blockchain) on peers of organizations regardless of their involvements in the endorsement policy or not, because it makes sense that a client would want to query its own organization (since it trusts it the most).
The only corner case is that sometimes the code of the chaincode is not known and the organizations of the endorsement policy, do not want to share it.
When we have multiple organizations, should every organization have an
endorsing peer, or they all can have only one within one organization
and all other can call it ?
It depends on the use case. Some organizations have clients only, and some organizations have peers only, or only orderers.
Whether an organization is an endorser for a chaincode, usually depends on the endorsement policy.
Below is my understanding of a Hyperledger Fabric system. Do let me know if any of it is incorrect.
1) So we have peers (endorser, anchor, general (who has the ledger), orderer). Also when we setup the fabric, let's say we registered two organizations. let's call them Company A and Company B. Now what I should do is use cryptogen to generate their certificates which go to specific folder.(in crypto folder, what I'll have at this stage is keystore and signcerts for Company A and Company B).
Now for these companies, A and B, I also make the peers for them. Let's say I give peer0 (anchor) to Company A and peer1 (anchor) to Company B and also
I give peer2 (general) to Company A and peer3 (general) to Company B and also I give peer4 (endorser) to Company A and peer5 (endorser) to Company B. As my understanding each organization must have at least 1 endorser peer (who receives requests from client), at least 1 general peer (who has the ledger) and at least 1 anchor peer who gets blocks from orderer to give it to general peers in the same organization.
So this is the setup. Let's say I give these peers to company A and B and I also setup orderer peer (let's leave it as SOLO). before I run the network, I also need to have genesis block and channel. Let's create global channel and call it EveryoneChannel and put all peers in it.
I will go on. Now when I want to have chaincode, which node should have this written chaincode? My understanding is that chaincode must be owned by endorser, because as I read it's the one who executes chaincode to simulate proposal to return it to user. So endorsers have chaincodes? General peers have ledgers. anchors get blocks and give it to general peers in the same organization. I know what orderer does.
Who are the clients? I have read many times that clients make transaction requests to network. So my guess is in each organization, for example Company A, Company A can register employees that will be binded to Company A's Organization. Let's say Company A has registered three employees, employee1, employee2,employee3. so what will happen is 3 certificates will be created for these employees and they will also be saved in crypto folder.
Now what can happen is employe1 can make a transaction request to the endorser peer that is in the same organization as is employee1. employee1 already has the certificate as I mentioned so request and response and transaction will be valid. Company A's endorser will take care of it.
Now I also have read about endorsement policy. so it means transaction will be valid if it will be validated by n-th times of number peers from organizations and it's said that this endorsement policy is written
in chaincode. if we have Company A and Company B, and their endorsers have chaincodes, should I put endorsement policy in both of them? I guess when client makes transaction request, he can only make this request to his only organization, not other organizations. so Company A's endorser will have this chaincode and endorsement policy. so what will happen? Company'As endorser also throws this request to Company B's endorser and waits its response and returns two responses to client?
First, I would refer you to the answer for this question. It explains the different peer types, as well as linking to the relevant Hyperledger Fabric documentation. The documentation explains everything much better than I could, with some nice diagrams :)
You have the right general idea about how the network is configured and operates, but to pick up on a couple of points in your question:
Anchor peers do not have any special responsibility for distributing blocks, they merely act as initial connection endpoints to allow other organizations to discover all other peers in the network. See here for more details on how this works.
The endorsement policy is defined when the chaincode is instantiated. If an endorsement policy requires endorsement from multiple organisations, the client initiating the transaction must send the transaction proposal to an endorsing peer for each organisation required by the endorsement policy. Once all necessary peers have returned a properly signed transaction response, these are then sent to the orderer for packaging into a block, and transmission to all peers. On receipt of a block from the orderer, each peer then performs it's own validation against the endorsement policy, before committing the block to its copy of the ledger.
In Fabric, we know the term of peers, according to the docs, as
a fundamental element of the network because they host ledgers and
smart contracts
Based on that, I assume that peers are some kind of hardware servers that organization assign.
But I'm not so sure about that, so I ask:
What exactly is the physical representation of peers in real-case organization?
Is it a computer that must always be online? Is it operated by some person in the related organizations?
It is also said in this paper on page 6 about the consensus process, that
In particular, this requires all endorsers
as determined by the policy to produce the same execution result
(i.e., identical readset and writeset). Then, the client proceeds to
create the transaction and passes it to the ordering service
This leaves me to the next question:
In real life usage, if the endorsing peers failed temporarily (say, due to electricity issue), does it mean that the blockchain transactions can't happen in that time?
A peer is a software service. An organization can have multiple peers running for resilience. When a peer fails, for whatever reason, when it is restarted, it will catch up with the other peers in an organization's cluster either by receiving missing transaction blocks from the orderer, or by gossiping with other peers.
If an endorsing peer fails, it does not necessarily mean that the transaction processing will be blocked. Again, an org can have multiple redundant endorsing peers, and depending on the endorsement policy chosen for the channel, propose the transaction to other endorsing peers for that channel in order to receive the requisite number of endorsements to satisfy the policy.
Of course, if you ran a single endorsing peer for a channel/network... then yes, if it failed then transaction processing would be blocked. That would not be a wise deployment choice;-) Fabric was designed for resilience.