mirror of
https://github.com/corda/corda.git
synced 2024-12-30 17:57:02 +00:00
93 lines
3.6 KiB
ReStructuredText
93 lines
3.6 KiB
ReStructuredText
Nodes
|
|
=====
|
|
|
|
.. topic:: Summary
|
|
|
|
* *A node is JVM run-time with a unique network identity running the Corda software*
|
|
* *The node has two interfaces with the outside world:*
|
|
|
|
* *A network layer, for interacting with other nodes*
|
|
* *RPC, for interacting with the node's owner*
|
|
|
|
* *The node's functionality is extended by installing CorDapps in the plugin registry*
|
|
|
|
Video
|
|
-----
|
|
.. raw:: html
|
|
|
|
<p><a href="https://vimeo.com/214168860">Corda Node, CorDapps and Network</a></p>
|
|
<iframe src="https://player.vimeo.com/video/214168860" width="640" height="360" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe>
|
|
<p></p>
|
|
|
|
Node architecture
|
|
-----------------
|
|
A Corda node is a JVM run-time environment with a unique identity on the network that hosts Corda services and
|
|
CorDapps.
|
|
|
|
We can visualize the node's internal architecture as follows:
|
|
|
|
.. image:: resources/node-architecture.png
|
|
:scale: 25%
|
|
:align: center
|
|
|
|
The core elements of the architecture are:
|
|
|
|
* A persistence layer for storing data
|
|
* A network interface for interacting with other nodes
|
|
* An RPC interface for interacting with the node's owner
|
|
* A service hub for allowing the node's flows to call upon the node's other services
|
|
* A cordapp interface and provider for extending the node by installing CorDapps
|
|
|
|
Persistence layer
|
|
-----------------
|
|
The persistence layer has two parts:
|
|
|
|
* The **vault**, where the node stores any relevant current and historic states
|
|
* The **storage service**, where it stores transactions, attachments and flow checkpoints
|
|
|
|
The node's owner can query the node's storage using the RPC interface (see below).
|
|
|
|
Network interface
|
|
-----------------
|
|
All communication with other nodes on the network is handled by the node itself, as part of running a flow. The
|
|
node's owner does not interact with other network nodes directly.
|
|
|
|
RPC interface
|
|
-------------
|
|
The node's owner interacts with the node via remote procedure calls (RPC). The key RPC operations the node exposes
|
|
are documented in :doc:`api-rpc`.
|
|
|
|
The service hub
|
|
---------------
|
|
Internally, the node has access to a rich set of services that are used during flow execution to coordinate ledger
|
|
updates. The key services provided are:
|
|
|
|
* Information on other nodes on the network and the services they offer
|
|
* Access to the contents of the vault and the storage service
|
|
* Access to, and generation of, the node's public-private keypairs
|
|
* Information about the node itself
|
|
* The current time, as tracked by the node
|
|
|
|
The CorDapp provider
|
|
--------------------
|
|
The CorDapp provider is where new CorDapps are installed to extend the behavior of the node.
|
|
|
|
The node also has several CorDapps installed by default to handle common tasks such as:
|
|
|
|
* Retrieving transactions and attachments from counterparties
|
|
* Upgrading contracts
|
|
* Broadcasting agreed ledger updates for recording by counterparties
|
|
|
|
Draining mode
|
|
^^^^^^^^^^^^^
|
|
|
|
In order to operate a clean shutdown of a node, it is important than no flows are in-flight, meaning no checkpoints should
|
|
be persisted. The node is able to be put in a Flows Draining Mode, during which:
|
|
|
|
* Commands requiring to start new flows through RPC will be rejected.
|
|
* Scheduled flows due will be ignored.
|
|
* Initial P2P session messages will not be processed, meaning peers will not be able to initiate new flows involving the node.
|
|
* All other activities will proceed as usual, ensuring that the number of in-flight flows will strictly diminish.
|
|
|
|
As their number - which can be monitored through RPC - reaches zero, it is safe to shut the node down.
|
|
This property is durable, meaning that restarting the node will not reset it to its default value and that a RPC command is required. |