This tutorial describes how to prepare a development environment in order to build a business application to use a blockchain network based on Hyperledger Fabric. At a high level, a business application running on a Hyperledger Fabric network is made up of two parts: chaincode that runs in the servers (endorser nodes), and client code that runs in the Node.js application.
For chaincode development, please visit the Hyperledger Fabric chaincode tutorials.
For complete information on starting a Hyperledger Fabric network, please see the Build your first network tutorial.
The following tutorial assumes a chaincode has been developed and the focus is developing the client application.
What makes up a Hyperledger Fabric application development environment?
Below you'll find a high level summary of the Hyperledger Fabric design aimed at an introductory level of understanding, so that you can be on your way to setting up the development environment. For a comprehensive description of the concepts, the architecture, please visit the official Hyperledger Fabric documentation.
First of all, you will need an orderer. But isn't an orderer responsible for the consensus? Why start here? It's true that the main responsibility of the ordering service of a Hyperledger Fabric blockchain network is to provide consensus on a transaction among the maintainers of the ledger, a.k.a the committer nodes. However, the ordering service also maintains critical data about the overall network: what organizations are participating, what channels have been created, which organizations are part of a given channel, and last but not least what policies are in place for any kind of change to the network. In essence, the ordering service holds the network together.
Ok we've got to have an orderer node so we can add participating organizations to it and get a network started. Next you would need peers for each participating organization in order to participate in transaction endorsing and maintaining the ledger.
The peer nodes play two roles: endorser and committer. A peer's endorser role may be enabled or disabled based on the bootstrap configuration. Note that all peers are always committers. For high availability you would want more than one peer for each organization in a real deployment. For the development environment, one peer per organization is sufficient under most circumstances. This peer will be both an endorser and a committer. It will be sent transaction proposals to endorse and queries to discover information from the ledger.
Another important role that peer nodes play is broadcasting events to interested parties. Whenever a block is added to the ledger, an event is sent by the peer through a dedicated streaming port. Any application within the organization can register themselves to listen on that port to get notified.
The final piece of the puzzle is identities. Every operation in a Hyperledger Fabric network must be digitally signed for the purposes of access control, or provenance/auditing (who did what), or both. Identities are based on the Public Key Infrastructure (PKI)) standards. Every orderer node, every peer node and every user/transactor must have a key pair with the public key wrapped in a x.509 certificate signed by a Certificate Authority (CA). Since x.509 is an open standard, Hyperledger Fabric would work with any existing certificate authority. This is typically a painful process with lots of potential red tape to get real certificates, so for the development purposes it is a popular practice to use self-signed certificates locally generated. As you will see in the later section, the Hyperledger Fabric provides tools to make this less painful.
Also related to identities, you should make a decision on whether
should be part of your solution. This is a server with REST APIs that supports
dynamic identity management with registration, enrollment (getting certificates),
revocation and re-enrollment. So it is very useful in providing user identities
on the fly. Note that user identities provisioned this way are only of the
MEMBER role, which means it won't be able to perform certain operations reserved
- create/update channel
- install/instantiate chaincode
- query installed/instantiated chaincodes
For these privileged operations, the client must use an ADMIN user to submit the request.
If you choose to not use Fabric-CA, everything will still work, but the application is responsible for managing the user certificates.
You will need the following software:
- Docker and Docker Compose - see Hyperledger Fabric for details
- Nodejs v8.9.0 or higher, up to 9.0 ( Node v9.0+ is not supported )
Prepare crypto materials
As discussed above, identities are established with x.509 certificates. If you think about it, we will need a whole bunch of certificates because there are many identities involved:
- peers need identities to sign endorsements
- orderers need identities to sign proposed blocks for the committers to validate and append to the ledger
- applications need identities to sign transaction requests
- the Fabric CA themselves also need identities, so their signatures in the certificates can be validated
Luckily there is a tool for that. Follow this guide to use the cryptogen tool to generate all the required keys and certificates in one swoop.
Note that the cryptogen tool will automatically generate identities for
the Fabric CA nodes for each orderer and peer organization,
which can be used to start the Fabric-CA servers (if you choose to use
it as part of the solution as discussed above). In addition, it also
generates one admin user of the
ADMIN role with the privileges to perform
admin-level operations listed above. Finally, it also generates regular
MEMBER role) for submitting transactions.
This would get us all the crypto materials needed to start things up.
Getting things rolling for real - the genesis block
As discussed above, the orderer should be the first step to bootstrap (launch)
a network. The orderer will need the initial configurations wrapped inside
genesis block. Follow the
to use the
configtxgen tool to generate a
The output, a genesis block file for the orderer, will be used in
the next step to launch the orderer node.
Notice some features are non-backwards compatible. To enable features from a particular fabric version, the
configtx.yamlshould be updated before generate the
Start the network
Now we are ready to put it all together. The easiest way to launch the
development environment is to use docker-compose. Follow the
to start the network. To minimize the chances of a mistake,
you may wish to run the network without TLS.
The above steps give you a development environment. Now before you can ask it to process any transactions, you must first create a channel.
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