corda/docs/source/shell.rst

.. highlight:: kotlin
.. raw:: html

   <script type="text/javascript" src="_static/jquery.js"></script>
   <script type="text/javascript" src="_static/codesets.js"></script>

Shell
=====

.. contents::

The Corda shell is an embedded command line that allows an administrator to control and monitor a node. It is based on
the `CRaSH`_ shell and supports many of the same features. These features include:

* Invoking any of the node's RPC methods
* Viewing a dashboard of threads, heap usage, VM properties
* Uploading and downloading attachments
* Issuing SQL queries to the underlying database
* Viewing JMX metrics and monitoring exports
* UNIX style pipes for both text and objects, an ``egrep`` command and a command for working with columnular data

The shell via the local terminal
--------------------------------

In development mode, the shell will display in the node's terminal window. It may be disabled by passing the
``--no-local-shell`` flag when running the node.

The shell via SSH
-----------------
The shell is also accessible via SSH.

Enabling SSH access
*******************

By default, the SSH server is *disabled*. To enable it, a port must be configured in the node's ``node.conf`` file:

.. code:: bash

    sshd {
        port = 2222
    }

Authentication
**************
Users log in to shell via SSH using the same credentials as for RPC. This is because the shell actually communicates
with the node using RPC calls. No RPC permissions are required to allow the connection and log in.

The host key is loaded from the ``<node root directory>/sshkey/hostkey.pem`` file. If this file does not exist, it is
generated automatically. In development mode, the seed may be specified to give the same results on the same computer
in order to avoid host-checking errors.

Connecting to the shell
***********************

Linux and MacOS
^^^^^^^^^^^^^^^

Run the following command from the terminal:

.. code:: bash

    ssh -p [portNumber] [host] -l [user]

Where:

* ``[portNumber]`` is the port number specified in the ``node.conf`` file
* ``[host]`` is the node's host (e.g. ``localhost`` if running the node locally)
* ``[user]`` is the RPC username

The RPC password will be requested after a connection is established.

:note: In development mode, restarting a node frequently may cause the host key to be regenerated. SSH usually saves
    trusted hosts and will refuse to connect in case of a change. This check can be disabled using the
    ``-o StrictHostKeyChecking=no`` flag. This option should never be used in production environment!

Windows
^^^^^^^

Windows does not provide a built-in SSH tool. An alternative such as PuTTY should be used.

Permissions
***********

When accessing the shell via SSH, some additional RPC permissions are required:

* Watching flows (``flow watch``) requires ``InvokeRpc.stateMachinesFeed``
* Starting flows requires ``InvokeRpc.startTrackedFlowDynamic`` and ``InvokeRpc.registeredFlows``, as well as a
  permission for the flow being started

Interacting with the node via the shell
---------------------------------------

The shell interacts with the node by issuing RPCs (remote procedure calls). You make an RPC from the shell by typing
``run`` followed by the name of the desired RPC method. For example, you'd see a list of the registered flows on your
node by running:

``run registeredFlows``

Some RPCs return a stream of events that will be shown on screen until you press Ctrl-C.

You can find a list of the available RPC methods
`here <https://docs.corda.net/api/kotlin/corda/net.corda.core.messaging/-corda-r-p-c-ops/index.html>`_.

Flow commands
*************

The shell also has special commands for working with flows:

* ``flow list`` lists the flows available on the node
* ``flow watch`` shows all the flows currently running on the node with result (or error) information
* ``flow start`` starts a flow. The ``flow start`` command takes the name of a flow class, or
  *any unambiguous substring* thereof, as well as the data to be passed to the flow constructor. If there are several
  matches for a given substring, the possible matches will be printed out. If a flow has multiple constructors then the
  names and types of the arguments will be used to try and automatically determine which one to use. If the match
  against available constructors is unclear, the reasons each available constructor failed to match will be printed
  out. In the case of an ambiguous match, the first applicable constructor will be used

Parameter syntax
****************

Parameters are passed to RPC or flow commands using a syntax called `Yaml`_ (yet another markup language), a
simple JSON-like language. The key features of Yaml are:

* Parameters are separated by commas
* Each parameter is specified as a ``key: value`` pair

    * There **MUST** to be a space after the colon, otherwise you'll get a syntax error

* Strings do not need to be surrounded by quotes unless they contain commas, colons or embedded quotes
* Class names must be fully-qualified (e.g. ``java.lang.String``)

.. note:: If your CorDapp is written in Java, named arguments won't work unless you compiled the node using the
   ``-parameters`` argument to javac. See :doc:`generating-a-node` for how to specify it via Gradle.

Creating an instance of a class
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Class instances are created using curly-bracket syntax. For example, if we have a ``Campaign`` class with the following
constructor:

``data class Campaign(val name: String, val target: Int)``

Then we could create an instance of this class to pass as a parameter as follows:

``newCampaign: { name: Roger, target: 1000 }``

Where ``newCampaign`` is a parameter of type ``Campaign``.

Mappings from strings to types
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Several parameter types can automatically be mapped from strings. See the `defined parsers`_ for more information. We
cover the most common types here.

Amount
~~~~~~
A parameter of type ``Amount<Currency>`` can be written as either:

* A dollar ($), pound (£) or euro (€) symbol followed by the amount as a decimal
* The amount as a decimal followed by the ISO currency code (e.g. "100.12 CHF")

OpaqueBytes
~~~~~~~~~~~
A parameter of type ``OpaqueBytes`` can be provided as a string, which will be automatically converted to
``OpaqueBytes``.

Party
~~~~~
A parameter of type ``Party`` can be written in several ways:

* By using the node's full name: ``"O=Monogram Bank,L=Sao Paulo,C=GB"``
* By specifying the organisation name only: ``"Monogram Bank"``
* By specifying any other non-ambiguous part of the name: ``"Sao Paulo"`` (if only one network node is located in Sao
  Paulo)

Instant
~~~~~~~
A parameter of type ``Instant`` can be written as follows: ``"2017-12-22T00:00:00Z"``.

Examples
^^^^^^^^

Starting a flow
~~~~~~~~~~~~~~~

We would start the ``CashIssue`` flow as follows:

``flow start CashIssue amount: $1000, issueRef: 1234, recipient: "O=Bank A,L=London,C=GB", notary: "O=Notary Service,OU=corda,L=London,C=GB"``

This breaks down as follows:

* ``flow start`` is a shell command for starting a flow
* ``CashIssue`` is the flow we want to start
* Each ``name: value`` pair after that is a flow constructor argument

This command invokes the following ``CashIssue`` constructor:

.. container:: codeset

   .. sourcecode:: kotlin

      class CashIssueFlow(val amount: Amount<Currency>,
                          val issueRef: OpaqueBytes,
                          val recipient: Party,
                          val notary: Party) : AbstractCashFlow(progressTracker)

Querying the vault
~~~~~~~~~~~~~~~~~~

We would query the vault for ``IOUState`` states as follows:

``run vaultQuery contractStateType: com.template.IOUState``

This breaks down as follows:

* ``run`` is a shell command for making an RPC call
* ``vaultQuery`` is the RPC call we want to make
* ``contractStateType: com.template.IOUState`` is the fully-qualified name of the state type we are querying for

Attachments
***********

The shell can be used to upload and download attachments from the node. To learn more, see the tutorial
":doc:`tutorial-attachments`".

Getting help
************

You can type ``help`` in the shell to list the available commands, and ``man`` to get interactive help on many
commands. You can also pass the ``--help`` or ``-h`` flags to a command to get info about what switches it supports.

Commands may have subcommands, in the same style as ``git``. In that case, running the command by itself will
list the supported subcommands.

Extending the shell
-------------------

The shell can be extended using commands written in either Java or `Groovy`_ (a Java-compatible scripting language).
These commands have full access to the node's internal APIs and thus can be used to achieve almost anything.

A full tutorial on how to write such commands is out of scope for this documentation. To learn more, please refer to
the `CRaSH`_ documentation. New commands are placed in the ``shell-commands`` subdirectory in the node directory. Edits
to existing commands will be used automatically, but currently commands added after the node has started won't be
automatically detected. Commands must have names all in lower-case with either a ``.java`` or ``.groovy`` extension.

.. warning:: Commands written in Groovy ignore Java security checks, so have unrestricted access to node and JVM
   internals regardless of any sandboxing that may be in place. Don't allow untrusted users to edit files in the
   shell-commands directory!

Limitations
-----------

The shell will be enhanced over time. The currently known limitations include:

* There is no command completion for flows or RPCs
* Command history is not preserved across restarts
* The ``jdbc`` command requires you to explicitly log into the database first
* Commands placed in the ``shell-commands`` directory are only noticed after the node is restarted
* The ``jul`` command advertises access to logs, but it doesn't work with the logging framework we're using

.. _Yaml: http://www.yaml.org/spec/1.2/spec.html
.. _defined parsers: api/kotlin/corda/net.corda.client.jackson/-jackson-support/index.html
.. _Groovy: http://groovy-lang.org/
.. _CRaSH: http://www.crashub.org/