Decentralized governance for smart contracts 

Hyperledger Fabric has recently launched the most major release and went from v1.4 to Fabric v2.0. It delivers important new features and changes for users and operators alike, including support for new application and privacy patterns, enhanced governance around smart contracts, and new options for operating nodes.

The ability to upgrade network components on your own terms, with support for rolling upgrades from v1.4.x, and the ability to enable the new capabilities only when member organizations are ready remains in the new update. 

Fabric v2.0 introduces a decentralized governance for smart contracts, with a new process for installing a chaincode on your peers and starting it on a channel. The new Fabric chaincode lifecycle allows multiple organizations to come to agreement on the parameters of a chaincode, such as the chaincode endorsement policy, before it can be used to interact with the ledger. The new model offers several improvements over the previous lifecycle.

  • Multiple organizations must agree to the parameters of a chaincode In the release 1.x versions of Fabric, one organization could set parameters of a chaincode (for instance the endorsement policy) for all other channel members, who only had the power to refuse to install the chaincode and therefore not take part in transactions invoking it. The new Fabric chaincode lifecycle is more flexible since it supports both centralized trust models (such as that of the previous lifecycle model) as well as decentralized models requiring a sufficient number of organizations to agree on an endorsement policy and other details before the chaincode becomes active on a channel.
  • The more deliberate chaincode upgrade process In the previous chaincode lifecycle, the upgrade transaction could be issued by a single organization, creating a risk for a channel member that had not yet installed the new chaincode. The new model allows a chaincode to be upgraded only after a sufficient number of organizations have approved the upgrade.
  • A simple endorsement policy and private data collection updates Fabric lifecycle allows you to change an endorsement policy or private data collection configuration without having to repackage or reinstall the chaincode. Users can also take advantage of a new default endorsement policy that requires endorsement from most organizations on the channel. This policy is updated automatically when organizations are added or removed from the channel.
  • Inspectable chaincode packages The Fabric lifecycle packages chaincode in easily readable tar files. This makes it easier to inspect the chaincode package and coordinate installation across multiple organizations.
  • Start multiple chaincodes on a channel using one package The previous lifecycle defined each chaincode on the channel using a name and version that was specified when the chaincode package was installed. You can now use a single chaincode package and deploy it multiple times with different names on the same channel or on different channels. For example, if you would like to track different types of assets in their own ‘copy’ of the chaincode.
  • Chaincode packages do not need to be identical across channel members Organizations can extend a chaincode for their own use case, for example to perform different validations in the interest of their organization. As long as the required number of organizations endorse chaincode transactions with matching results, the transaction will be validated and committed to the ledger. This also allows organizations to individually roll out minor fixes on their own schedules without requiring the entire network to proceed in lock-step.

 Using the new chaincode lifecycle 

For existing Fabric deployments, you can continue to use the prior chaincode lifecycle with Fabric v2.0. The new chaincode lifecycle will become effective only when the channel application capability is updated to v2.0. See the Chaincode for Operators tutorial for complete details of the new chaincode lifecycle.

New chaincode application patterns for collaboration and consensus 

The same decentralized methods of coming to agreement that underpin the new chaincode lifecycle management can also be used in your own chaincode applications to ensure organizations consent to data transactions before they are committed to the ledger.

  • Automated checks As mentioned above, organizations can add automated checks to chaincode functions to validate additional information before endorsing a transaction proposal.
  • Decentralized agreement Human decisions can be modeled into a chaincode process that spans multiple transactions. The chaincode may require actors from various organizations to indicate their terms and conditions of agreement in a ledger transaction. Then, a final chaincode proposal can verify that the conditions of all the individual transactors are met, and “settle” the business transaction with finality across all channel members. For a concrete example of indicating terms and conditions in private, see the asset transfer scenario in the Private data documentation.

 Private data enhancement.

Fabric v2.0 also enables new patterns for working with and sharing private data, without the requirement of creating private data collections for all combinations of channel members that may want to transact. Specifically, instead of sharing private data within a collection of multiple members, you may want to share private data across collections, where each collection may include a single organization, or perhaps a single organization along with a regulator or auditor.

Several enhancements in Fabric v2.0 make these new private data patterns possible:

  • Sharing and verifying private data When private data is shared with a channel member who is not a member of a collection, or shared with another private data collection that contains one or more channel members (by writing a key to that collection), the receiving parties can utilize the GetPrivateDataHash() chaincode API to verify that the private data matches the on-chain hashes that were created from private data in previous transactions.
  • Collection-level endorsement policies Private data collections can now optionally be defined with an endorsement policy that overrides the chaincode-level endorsement policy for keys within the collection. This feature can be used to restrict which organizations can write data to a collection, and is what enables the new chaincode lifecycle and chaincode application patterns mentioned earlier. For example, you may have a chaincode endorsement policy that requires most organizations to endorse, but for any given transaction, you may need two transacting organizations to endorse their agreement in their own private data collections individually.

  • Implicit per-organization collections If you would like to utilize per-organization private data patterns, you do not even need to define the collections when deploying the chaincode in Fabric v2.0. Implicit organization-specific collections can be used without any upfront definition.

 To learn more about the new private data patterns, see the Private data (conceptual documentation). For details about private data collection configuration and implicit collections, see the Private Data (reference documentation).

 External chaincode launcher

The external chaincode launcher feature empowers operators to build and launch chaincode with the technology of their choice. The use of external builders and launchers is not required as the default behavior builds and runs a chaincode in the same manner as prior releases using the Docker API.

  • Eliminate Docker daemon dependency Prior releases of Fabric required peers to have access to a Docker daemon in order to build and launch chaincode – something that may not be desirable in production environments due to the privileges required by the peer process.
  • Alternatives to containers Chaincode is no longer required to be run in Docker containers, and may be executed in the operator’s choice of environment (including containers).
  • External builder executable An operator can provide a set of external builder executable to override how the peer builds and launches chaincode.
  • Chaincode as an external service Traditionally, chaincodes are launched by the peer, and then connect back to the peer. It is now possible to run chaincode as an external service, for example in a Kubernetes pod, which a peer can connect to and utilize for chaincode execution. See Chaincode as an external service for more information.

See External Builders and Launchers to learn more about the external chaincode launcher feature.

 State database cache for improved performance on CouchDB

  • When using external CouchDB state database, read delays during endorsement and validation phases have historically been a performance bottleneck.
  • With Fabric v2.0, a new peer cache replaces many of these expensive lookup with fast local cache reads. The cache size can be configured by using the core.yaml property cacheSize.

 Alpine-based docker images

Starting with v2.0, Hyperledger Fabric Docker images will use Alpine Linux, a security-oriented, lightweight Linux distribution. This means that Docker images are now much smaller, providing faster download and startup times, as well as taking up less disk space on host systems. Alpine Linux is designed from the ground up with security in mind, and the minimalist nature of the Alpine distribution greatly reduces the risk of security vulnerabilities.

 Sample test network

The fabric-samples repository now includes a new Fabric test network. The test network is built to be a modular and user-friendly sample Fabric network that makes it easy to test your applications and smart contracts. The network also supports the ability to deploy your network using Certificate Authorities, in addition to cryptogen.