Corda Accounts Library

Reminder

This project is open source under an Apache 2.0 licence. That means you can submit PRs to fix bugs and add new features if they are not currently available.

What is the accounts library?

In the context of Corda, the accounts library allows a Corda node to partition the vault—a collection of state objects—into a number of subsets, where each subset represents an account. In other words, the accounts library allows a Corda node operator to split the vault into multiple "logical" sub-vaults. This is advantageous for a couple of reasons:

• Node operators can reduce costs by hosting multiple entities, as accounts, on one node
• Node operators can partition the vault on a per entity basis

Accounts are created by host nodes, which are just regular Corda nodes. Hosts can create accounts for a range of purposes such as customer accounts, balance sheets or P&L accounts, employee accounts, etc.

The accounts library takes the form of a JAR which can be dropped into the CorDapps folder. Use of it is optional. This means that some nodes will support accounts but others will not. This is intentional by design as not all nodes will need to support accounts and the optional nature of accounts reduces the learning curve for new CorDapp developers.

How to use the library?

See the docs here for how to build CorDapps using accounts.

By far the easiest way to get started with the accounts SDK is to use the "tokens template" which is a branch on the kotlin version of the "CorDapp template". You can obtain it with the following commands:

git clone http://github.com/corda/cordapp-template-kotlin
cd cordapp-template-kotlin
git checkout token-template

Once you have cloned the repository, you should open it with IntelliJ. This will give you a template repo with tokens and accounts dependencies already included.

Example Account Projects

There are three projects demonstrating how to use accounts in the examples sub-directory:

• Sweepstake
• Gold Trading
• Tokens - using tokens with accounts

Adding accounts dependencies to an existing CorDapp

First, add a variable for the accounts release group and the version you wish to use and set the corda version that should've been installed locally::

buildscript {
    ext {
        corda_release_version = '4.3-RC01'
        accounts_release_version = '1.0-RC04'
        accounts_release_group = 'com.r3.corda.lib.accounts'
        confidential_id_release_group = "com.r3.corda.lib.ci"
        confidential_id_release_version = "1.0-RC03"
    }
}

Second, you must add the accounts artifactory repository to the list of repositories for your project (if it hasn't already been added):

repositories {
    maven { url 'http://ci-artifactory.corda.r3cev.com/artifactory/corda-lib-dev' }
    maven { url 'http://ci-artifactory.corda.r3cev.com/artifactory/corda-lib' }
}

Now, you can add the accounts dependencies to the dependencies block in each module of your CorDapp. For contract modules add:

cordaCompile "$accounts_release_group:accounts-contracts:$accounts_release_version"

In your workflow build.gradle add:

cordaCompile "$confidential_id_release_group:ci-workflows:$confidential_id_release_version"
cordaCompile "$accounts_release_group:accounts-workflows:$accounts_release_version"

If you want to use the deployNodes task, you will need to add the following dependencies to your root build.gradle file:

cordapp "$confidential_id_release_group:ci-workflows:$confidential_id_release_version"
cordapp "$accounts_release_group:accounts-contracts:$accounts_release_version"
cordapp "$accounts_release_group:accounts-workflows:$accounts_release_version"

These should also be added to the deployNodes task with the following syntax:

nodeDefaults {
    projectCordapp {
        deploy = false
    }
    cordapp("$confidential_id_release_group:ci-workflows:$confidential_id_release_version")
    cordapp("$accounts_release_group:accounts-contracts:$accounts_release_version")
    cordapp("$accounts_release_group:accounts-workflows:$accounts_release_version")
}

Modifying An Existing CorDapp to Use Accounts

States should use AnonymousParty instead of Party as a Party refers to a node and the PublicKey can refer to an account.

In order to create your state you need to request the PublicKey with a flow. e.g.

val lenderKey = subFlow(RequestKeyForAccount(lenderAccountInfo.state.data)).owningKey

Once you have keys you need to have logic to determine who signs.

If your accounts are on the same node that you are running the flow on then they can all be on the signInitialTransaction, however, if one is on another node you need to use a CollectSignatureFlow

When calling the FinalityFlow you will need different sessions depending on if all the accounts are on one node or on different nodes.

If accounts are on different nodes you need to shareAccountInfoWithParty before you can transact between accounts otherwise the nodes running the flows wont be aware of the accounts on the other nodes.

Currently, if accounts are on different nodes you also need to run shareStateAndSyncAccounts after the flow to make sure that you can use all methods to look up accountInfo.

Installing the accounts library

If you wish to build the accounts library from source then do the following to publish binaries to your local maven repository:

git clone http://github.com/corda/accounts
cd accounts
./gradlew clean install

Other useful links

Contributing