corda/docs/source/network-simulator.rst

Network Simulator
=================

A network simulator is provided which shows traffic between nodes through the lifecycle of an interest rate swap
contract. It can optionally also show network setup, during which nodes register themselves with the network
map service and are notified of the changes to the map. The network simulator is run from the command line via Gradle:

**Windows**::

    gradlew.bat :samples:network-visualiser:run

**Other**::

    ./gradlew :samples:network-visualiser:run

You can produce a standalone JAR of the tool by using the ``:samples:network-visualiser:deployVisualiser`` target
and then using the ``samples/network-visualiser/build/libs/network-visualiser-*-capsule.jar`` file, where * is
whatever the current Corda version is.

What it is and is not
---------------------

The simulator currently exists as an illustrative tool to help with explaining how Corda works in an example scenario.
It utilises the ``Simulator`` tools that support creating a simulated Corda network and the nodes running in it within
a single JVM, as an extension of the ``MockNetwork`` testing framework.  See more about the ``MockNetwork`` and
testing flows here: :doc:`flow-testing`.

Whilst it is not yet fully generic or full featured, the intention is for the simulator to mature into the following,
which it presently cannot do without writing more code:

1. A tool for visualising new CorDapps and their flows to help with debugging, presentations, explanations and tutorials,
   but still running as a simulation in a single JVM.
2. A tool to visualise the activity on a real Corda network deployment, with activity streams being fed from each node
   running in its own JVM, most likely on remote hosts.

Both of these scenarios would be fed by the standard observables in the RPC framework, rather than the local binding
that the simulator uses currently.  The ability to step through a flow one step at a time would obviously be restricted
to single JVM simulations.

Interface
---------

.. image:: resources/network-simulator.png

The network simulator can be run automatically, or stepped manually through each step of the interest rate swap. The
options on the simulator window are:

Simulate initialisation
  If checked, the nodes registering with the network map is shown. Normally this setup step
  is not shown, but may be of interest to understand the details of node discovery.
Run
  Runs the network simulation in automatic mode, in which it progresses each step on a timed basis. Once running,
  the simulation can be paused in order to manually progress it, or reset.
Next
  Manually progress the simulation to the next step.
Reset
  Reset the simulation (only available when paused).
Map/Circle
  How the nodes are shown, by default nodes are rendered on a world map, but alternatively they can rendered
  in a circle layout.

While the simulation runs, details of the steps currently being executed are shown in a sidebar on the left hand side
of the window.

.. TODO: Add documentation on how to use with different contracts for testing/debugging