Run Example

Build the nodes

In the previous chapter, you looked at the example Cordapp code, here you are going to run it and get a feel of what is going on. You are going to run it all on your computer, in what can be described as a development network.

Running the project in a test and development context is a 3 step process. You will:

1. Declare the configuration.
2. Create the nodes' configuration files.
3. Launch the executables.

Here is a screencast of what comes ahead. You can always come back to it when you hit difficulties doing it on your own.

Declare the configuration

The configuration is already declared with the help of deployNodes. Each node task statically declares a new node and its configuration. Together, these nodes represent a small, though whole, network, complete with a notary. Indeed, however small, a network needs a network map service to help each node connect to the other nodes it will interact with. The deployNodes task, among other things, distributes the network information on all declared nodes.

Since all nodes will run on a single machine, all ports need to be unique and assigned. If you did not assign ports, the nodes would all use the default of 10002 and that would create a port conflict on a single machine. The p2p address is not mentioned so it will default to localhost. Now, if you wanted to run your services on different machines, you would update the configuration with externally resolvable names or IPs under the label p2pAddress:, like so p2pAddress "192.168.0.15:10006".

Build the configuration files

Be sure you are in your cordapp-example working directory. Let us run this build task with:

$ ./gradlew deployNodes

as explained by the Corda team.

This task takes a long time, so this is a good time to refill your cup. Not only does the task take time on its own, but you are running 2 of them - one for workflows-java and the other for workflows-kotlin.

In the future, to save time, run only the task for workflows-java, like so:

Copy

$ ./gradlew --build-file workflows-java/build.gradle deployNodes

With the nodes built, as seen in ./workflows-java/build/nodes. Inside this folder you will find the different nodes and their node.conf files, with their expected parameters. Also, helpfully, certificates have been created.

Run the nodes

Now that your nodes have been deployed, do as per what the documentation says and run this command:

$ ./workflows-java/build/nodes/runnodes

You should get 4 pop-up windows; do not move focus away from them until all 4 show the welcome message:

   ______               __
  / ____/     _________/ /___ _
 / /     __  / ___/ __  / __ `/         I had an account with a bank in the
/ /___  /_/ / /  / /_/ / /_/ /          North Pole, but they froze all my assets
\____/     /_/   \__,_/\__,_/

--- Corda Open Source 4.3 (d679784) -------------------------------------------------------------


Logs can be found in                    : /home/user/corda/r3/samples/cordapp-example/workflows-java/build/nodes/Notary/logs
! ATTENTION: This node is running in development mode!  This is not safe for production deployment.
Advertised P2P messaging addresses      : localhost:10000
RPC connection address                  : localhost:10001
RPC admin connection address            : localhost:10002
Loaded 0 CorDapp(s)                     :
Node for "Notary" started up and registered in 17.03 sec


Welcome to the Corda interactive shell.
Useful commands include 'help' to see what is available, and 'bye' to shut down the node.

Wed Mar 11 12:10:00 CDT 2020>>>

Notice:

• The Node for "Notary" mention.
• The quips data bank.

Interact with the nodes

You are going to create your first IOU where PartyB owes 50 to PartyA. Because of how the flows are coded:

1. You need to initiate the flow from the lender, i.e. PartyA.
2. PartyB will receive it.
3. PartyC will be oblivious.

To show points 2 and 3, let's prepare PartyB and PartyC with an IOUState tracker. On the interactive shells of both nodes of PartyB and PartyC, run:

>>> run vaultTrack contractStateType: com.example.state.IOUState
Snapshot:
states: []
statesMetadata: []
totalStatesAvailable: -1
stateTypes: "UNCONSUMED"
otherResults: []

Updates:
Waiting for completion or Ctrl-C ...

Then head to the interactive shell of PartyA and launch the flow as per the docs:

# In PartyA
>>> flow start ExampleFlow$Initiator iouValue: 50, otherParty: "O=PartyB,L=New York,C=US"

It takes a few seconds because the processes are started lazily. Notice the last line, that looks like:

Flow completed with result: SignedTransaction(id=EC06EA903314BE02610032933FBA2392151732CFD87408A4681C3AFEA83C53B1)

Head over to PartyC and see that the tracker has not seen anything, but on PartyB, you should see something like:

Observation 1: consumed: []
produced:
- state:
    data: !<com.example.state.IOUState>
      value: 50
      lender: "O=PartyA, L=London, C=GB"
      borrower: "O=PartyB, L=New York, C=US"
      linearId:
        externalId: null
        id: "0c0dd4e2-dc4e-4810-aa59-97f6bbe69567"
    contract: "com.example.contract.IOUContract"
    notary: "O=Notary, L=London, C=GB"
    encumbrance: null
    constraint: !<net.corda.core.contracts.SignatureAttachmentConstraint>
      key: "aSq9DsNNvGhYxYyqA9wd2eduEAZ5AXWgJTbTEw3G5d2maAq8vtLE4kZHgCs5jcB1N31cx1hpsLeqG2ngSysVHqcXhbNts6SkRWDaV7xNcr6MtcbufGUchxredBb6"
  ref:
    txhash: "EC06EA903314BE02610032933FBA2392151732CFD87408A4681C3AFEA83C53B1"
    index: 0
flowId: null
type: "GENERAL"
references: []

Nice, it worked as expected:

• Nothing was consumed: Observation 1: consumed: [].
• A single state was created, or produced, with the expected values. This concludes your first interaction with a flow from the command line.

In the next chapter, you will do the same but look deeper into the database.