What's new in Hyperledger Fabric v2.x
=====================================

What's New in Hyperledger Fabric v2.3
-------------------------------------

Hyperledger Fabric v2.3 introduces two new features for improved orderer and peer operations.

Orderer channel management without a system channel
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

To simplify the channel creation process and enhance the privacy and scalability of channels,
it is now possible to create application channels without first creating a “system channel” managed by the ordering service.
This process allows ordering nodes to join (or leave) any number of channels as needed, similar to how peers can participate in multiple channels.

Benefits of the new process:

* **Increased privacy:** Because all ordering nodes used to be joined to the system channel,
  every ordering node in a network knew about the existence of every channel on that ordering service.
  Now, an ordering node only knows about the channels it is joined to.
* **Scalability:** When there is a large number of ordering nodes and channels defined on the system channel,
  it can take a long time for ordering nodes to reach consensus on the membership of all the channels.
  Now, an ordering service can scale horizontally in a decentralized fashion by independently joining ordering nodes to specific channels.
* **Operational benefits**
   * Simple process to join an ordering node to a channel.
   * Ability to list the channels that the ordering node is a consenter on.
   * Simple process to remove a channel from an ordering node, which automatically cleans up the blocks associated with that channel.
   * Peer organizations do not need to coordinate with an admin of the system channel to create or update its MSP.

For more information, see the :doc:`create_channel/create_channel_participation` topic.

Ledger snapshot
^^^^^^^^^^^^^^^

It is now possible to take a snapshot of a peer's channel information, including its state database,
and join new peers (in the same organization or different organizations) to the channel based on the snapshot.

Using ledger snapshots has the following advantages:

* **Peers don't need to process all blocks since genesis block:** Peers can join a channel without processing all
  previous blocks since the genesis block, greatly reducing the time it takes to join a peer to an existing channel.
* **Peers can join channels using latest channel configuration:** Because snapshots include the latest channel configuration,
  peers can now join a channel using the latest channel configuration.
  This is especially important if critical channel configuration such as orderer endpoints or TLS CA certificates have been updated since the genesis block.
* **Reduced storage costs:** Peers that join by snapshot do not incur the storage cost of maintaining all blocks since the genesis block.
* **State checkpoints:** Peer administrators can snapshot current channel state and compare with other peers,
  in the same organization or different organizations, to verify the consistency and integrity of the ledger on each peer.
  Agreed upon snapshots can be used as a checkpoint and basis for newly joining peers.

For more information, see the :doc:`peer_ledger_snapshot` topic.

.. note::

   While Fabric v2.3.0 introduces new features, Fabric v2.2.x remains the current long-term support release until the next LTS release is announced.

What's New in Hyperledger Fabric v2.0, v2.1, v2.2
-------------------------------------------------

The first Hyperledger Fabric major release since v1.0, Fabric v2.0
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.

v2.1 and v2.2 build on the v2.0 release with minor features,
improvements, and bug fixes, with v2.2 being the first long-term support (LTS) release of Fabric v2.x.
Fixes will be provided on the v2.2.x release stream until after the next LTS release is announced.

Let's take a look at some of the highlights of the Fabric v2.0 release...

Decentralized governance for smart contracts
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Fabric v2.0 introduces 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 had the ability to
  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.

* **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 for a chaincode to be upgraded only after
  a sufficient number of organizations have approved the upgrade.

* **Simpler 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 a majority of 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’d
  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.

For existing Fabric deployments, you can continue to use the prior chaincode
lifecycle with Fabric v2.x. The new chaincode lifecycle will become effective
only when the channel application capability is updated to v2.0.
See the :doc:`chaincode_lifecycle` concept topic for an overview 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 from 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 :doc:`private-data/private-data` documentation.

Private data enhancements
^^^^^^^^^^^^^^^^^^^^^^^^^

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.x 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 a majority of organizations to endorse,
  but for any given transaction, you may need two transacting organizations
  to individually endorse their agreement in their own private data collections.

* **Implicit per-organization collections:** If you’d like to utilize
  per-organization private data patterns, you don’t even need to define the
  collections when deploying chaincode in Fabric v2.x.  Implicit
  organization-specific collections can be used without any upfront definition.

To learn more about the new private data patterns, see the :doc:`private-data/private-data` (conceptual
documentation). For details about private data collection configuration and
implicit collections, see the :doc:`private-data-arch` (reference documentation).

External chaincode launcher
^^^^^^^^^^^^^^^^^^^^^^^^^^^

The external chaincode launcher feature empowers operators to build and launch
chaincode with the technology of their choice. Use of external builders and launchers
is not required as the default behavior builds and runs 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 executables:** An operator can provide a set of external
  builder executables 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 :doc:`cc_service` for more
  information.

See :doc:`cc_launcher` 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 lookups
  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.

For more information about this network, check out :doc:`test_network`.

Upgrading to Fabric v2.x
^^^^^^^^^^^^^^^^^^^^^^^^

A major new release brings some additional upgrade considerations. Rest assured
though, that rolling upgrades from v1.4.x to v2.0 are supported, so that network
components can be upgraded one at a time with no downtime. You can also upgrade
directly from the v1.4.x LTS release to the v2.2.x LTS release.

The upgrade docs have been significantly expanded and reworked, and now have a
standalone home in the documentation: :doc:`upgrade`. Here you'll find documentation on
:doc:`upgrading_your_components` and :doc:`updating_capabilities`, as well as a
specific look  at the considerations for upgrading to v2.x, :doc:`upgrade_to_newest_version`.

Release notes
=============

The release notes provide more details for users moving to the new release.
Specifically, take a look at the changes and deprecations
announced in each of the v2.x releases.

* `Fabric v2.0.0 release notes <https://github.com/hyperledger/fabric/releases/tag/v2.0.0>`_.
* `Fabric v2.0.1 release notes <https://github.com/hyperledger/fabric/releases/tag/v2.0.1>`_.
* `Fabric v2.1.0 release notes <https://github.com/hyperledger/fabric/releases/tag/v2.1.0>`_.
* `Fabric v2.1.1 release notes <https://github.com/hyperledger/fabric/releases/tag/v2.1.1>`_.
* `Fabric v2.2.0 release notes <https://github.com/hyperledger/fabric/releases/tag/v2.2.0>`_.
* `Fabric v2.2.1 release notes <https://github.com/hyperledger/fabric/releases/tag/v2.2.1>`_.
* `Fabric v2.2.2 release notes <https://github.com/hyperledger/fabric/releases/tag/v2.2.2>`_.
* `Fabric v2.3.0 release notes <https://github.com/hyperledger/fabric/releases/tag/v2.3.0>`_.
* `Fabric v2.3.1 release notes <https://github.com/hyperledger/fabric/releases/tag/v2.3.1>`_.
* `Fabric v2.3.2 release notes <https://github.com/hyperledger/fabric/releases/tag/v2.3.2>`_.

.. Licensed under Creative Commons Attribution 4.0 International License
   https://creativecommons.org/licenses/by/4.0/
