mirror of
https://github.com/corda/corda.git
synced 2024-12-28 08:48:57 +00:00
73 lines
4.6 KiB
ReStructuredText
73 lines
4.6 KiB
ReStructuredText
Versioning
|
|
==========
|
|
|
|
As the Corda platform evolves and new features are added it becomes important to have a versioning system which allows
|
|
its users to easily compare versions and know what feature are available to them. Each Corda release uses the standard
|
|
semantic versioning scheme of ``major.minor.patch``. This is useful when making releases in the public domain but is not
|
|
friendly for a developer working on the platform. It first has to be parsed and then they have three separate segments on
|
|
which to determine API differences. The release version is still useful and every MQ message the node sends attaches it
|
|
to the ``release-version`` header property for debugging purposes.
|
|
|
|
Platform Version
|
|
----------------
|
|
|
|
It is much easier to use a single incrementing integer value to represent the API version of the Corda platform, which
|
|
is called the Platform Version. It is similar to Android's `API Level <https://developer.android.com/guide/topics/manifest/uses-sdk-element.html>`_.
|
|
It starts at 1 and will increment by exactly 1 for each release which changes any of the publicly exposed APIs in the
|
|
entire platform. This includes public APIs on the node itself, the RPC system, messaging, serialisation, etc. API backwards
|
|
compatibility will always be maintained, with the use of deprecation to migrate away from old APIs. In rare situations
|
|
APIs may have to be removed, for example due to security issues. There is no relationship between the Platform Version
|
|
and the release version - a change in the major, minor or patch values may or may not increase the Platform Version.
|
|
|
|
The Platform Version is part of the node's ``NodeInfo`` object, which is available from the ``ServiceHub``. This enables
|
|
a CorDapp to find out which version it's running on and determine whether a desired feature is available. When a node
|
|
registers with the Network Map Service it will use the node's Platform Version to enforce a minimum version requirement
|
|
for the network.
|
|
|
|
.. note:: A future release may introduce the concept of a target platform version, which would be similar to Android's
|
|
``targetSdkVersion``, and would provide a means of maintaining behavioural compatibility for the cases where the
|
|
platform's behaviour has changed.
|
|
|
|
Flow versioning
|
|
---------------
|
|
|
|
In addition to the evolution of the platform, flows that run on top of the platform can also evolve. It may be that the
|
|
flow protocol between an initiating flow and it's intiated flow changes from one CorDapp release to the next in such as
|
|
way to be backwards incompatible with existing flows. For example, if a sequence of sends and receives needs to change
|
|
or if the semantics of a particular receive changes.
|
|
|
|
The ``InitiatingFlow`` annotation (see :doc:`flow-state-machine` for more information on the flow annotations) has a ``version``
|
|
property, which if not specified defaults to 1. This flow version is included in the flow session handshake and exposed
|
|
to both parties in the communication via ``FlowLogic.getFlowContext``. This takes in a ``Party`` and will return a
|
|
``FlowContext`` object which describes the flow running on the other side. In particular it has the ``flowVersion`` property
|
|
which can be used to programmatically evolve flows across versions.
|
|
|
|
.. container:: codeset
|
|
|
|
.. sourcecode:: kotlin
|
|
|
|
@Suspendable
|
|
override fun call() {
|
|
val flowVersionOfOtherParty = getFlowContext(otherParty).flowVersion
|
|
val receivedString = if (flowVersionOfOtherParty == 1) {
|
|
receive<Int>(otherParty).unwrap { it.toString() }
|
|
} else {
|
|
receive<String>(otherParty).unwrap { it }
|
|
}
|
|
}
|
|
|
|
The above shows an example evolution of a flow which in the first version was expecting to receive an Int, but then
|
|
in subsequent versions was relaxed to receive a String. This flow is still able to communicate with parties which are
|
|
running the older flow (or rather older CorDapps containing the older flow).
|
|
|
|
.. warning:: It's important that ``InitiatingFlow.version`` be incremented each time the flow protocol changes in an
|
|
incompatible way.
|
|
|
|
``FlowContext`` also has ``appName`` which is the name of the CorDapp hosting the flow. This can be used to determine
|
|
implementation details of the CorDapp. See :doc:`cordapp-build-systems` for more information on the CorDapp filename.
|
|
|
|
.. note:: Currently changing any of the properties of a ``CordaSerializable`` type is also backwards incompatible and
|
|
requires incrementing of ``InitiatingFlow.version``. This will be relaxed somewhat once the AMQP wire serialisation
|
|
format is implemented as it will automatically handle a lot of the data type migration cases.
|
|
|