Interacting with the Staking Precompile¶

Introduction¶

Moonbeam uses a Delegated Proof of Stake system through the Parachain Staking Pallet, allowing token holders (delegators) to express exactly which collator candidates they would like to support and with what quantity of stake. The design of the Parachain Staking Pallet is such that it enforces shared risk/reward on chain between delegators and candidates. For general information on staking, such as general terminology, staking variables, and more, please refer to the Staking on Moonbeam page.

The staking module is coded in Rust and it is part of a pallet that is normally not accessible from the Ethereum side of Moonbeam. However, a staking precompile allows developers to access the staking features using the Ethereum API in a precompiled contract located at address:

0x0000000000000000000000000000000000000800

0x0000000000000000000000000000000000000800

0x0000000000000000000000000000000000000800

This guide will cover the available methods in the staking precompile interface. In addition, it will show you how to interact with the Parachain Staking Pallet through the staking precompile and the Ethereum API. The examples in this guide are done on Moonbase Alpha, but they can be adapted for Moonbeam or Moonriver.

Exit Delays¶

Some of the Parachain Staking Pallet extrinsics include exit delays that you must wait before the request can be executed. The exit delays to note are as follows:

Parachain Staking Solidity Interface¶

StakingInterface.sol is an interface through which Solidity contracts can interact with parachain-staking. The beauty is that Solidity developers don’t have to learn the Substrate API. Instead, they can interact with staking functions using the Ethereum interface they are familiar with.

The Solidity interface includes the following functions:

As of runtime 2400, the following methods are deprecated:

As of runtime 1800, the following methods are deprecated and, as of runtime 2500, have been removed:

As of runtime 1001, the following methods are deprecated and, as of runtime 1800, have been removed:

Interact with the Solidity Interface¶

Checking Prerequisites¶

The below example is demonstrated on Moonbase Alpha, however, similar steps can be taken for Moonbeam and Moonriver.

• Have MetaMask installed and connected to Moonbase Alpha
• Have an account with at least 1 token. You can get DEV tokens for testing on Moonbase Alpha once every 24 hours from the Moonbase Alpha Faucet

Remix Set Up¶

1. Click on the File explorer tab
2. Get a copy of StakingInterface.sol and paste the file contents into a Remix file named StakingInterface.sol

Compile the Contract¶

1. Click on the Compile tab, second from top
2. Then to compile the interface, click on Compile StakingInterface.sol

Access the Contract¶

1. Click on the Deploy and Run tab, directly below the Compile tab in Remix. Note: you are not deploying a contract here, instead you are accessing a precompiled contract that is already deployed
2. Make sure Injected Provider - Metamask is selected in the ENVIRONMENT drop down
3. Ensure ParachainStaking - StakingInterface.sol is selected in the CONTRACT dropdown. Since this is a precompiled contract there is no need to deploy, instead you are going to provide the address of the precompile in the At Address field
4. Provide the address of the staking precompile for Moonbase Alpha: 0x0000000000000000000000000000000000000800 and click At Address
5. The Parachain Staking precompile will appear in the list of Deployed Contracts

Delegate a Collator with Auto-Compounding¶

For this example, you are going to be delegating a collator and setting up the percentage of rewards to auto-compound on Moonbase Alpha. Delegators are token holders who stake tokens, vouching for specific candidates. Any user that holds a minimum amount of 1 token in their free balance can become a delegator. When delegating a candidate, you can simultaneously set up auto-compounding. You'll be able to specify a percentage of your rewards that will automatically be applied to your total delegation. You don't have to set up auto-compounding right away, you can always do it at a later time.

You can do your own research and select the candidate you desire. For this guide, the following candidate address will be used: 0x12E7BCCA9b1B15f33585b5fc898B967149BDb9a5.

In order to delegate a candidate, you'll need to determine the candidate's current delegation count, their auto-compounding delegation count, and your own delegation count.

The candidate delegation count is the number of delegations backing a specific candidate. To obtain the candidate delegator count, you can call a function that the staking precompile provides. Expand the PARACHAINSTAKING contract found under the Deployed Contracts list, then:

1. Find and expand the candidateDelegationCount function
2. Enter the candidate address (0x12E7BCCA9b1B15f33585b5fc898B967149BDb9a5)
3. Click call
4. After the call is complete, the results will be displayed

The auto-compounding delegation count is the amount of delegations that have auto-compounding configured. To determine the number of delegations that have auto-compounding set up, you can

1. Find and expand the candidateAutoCompoundingDelegationCount function
2. Enter the candidate address (0x12E7BCCA9b1B15f33585b5fc898B967149BDb9a5)
3. Click call
4. After the call is complete, the results will be displayed

The last item you'll need to retrieve is your delegation count. If you don't know your existing number of delegations, you can easily get them by following these steps:

1. Find and expand the delegatorDelegationCount function
2. Enter your address
3. Click call
4. After the call is complete, the results will be displayed

Now that you have obtained the candidate delegator count, the auto-compounding delegation count, and your number of existing delegations, you have all of the information you need to delegate a candidate and set up auto-compounding. To get started:

1. Find and expand the delegateWithAutoCompound function
2. Enter the candidate address you would like to delegate. For this example you can use 0x12E7BCCA9b1B15f33585b5fc898B967149BDb9a5
3. Provide the amount to delegate in Wei. There is a minimum of 1 token to delegate, so the lowest amount in Wei is 1000000000000000000
4. Enter an integer (no decimals) between 0-100 to represent the percentage of rewards to auto-compound
5. Enter the delegation count for the candidate
6. Enter the auto-compounding delegation count for the candidate
7. Enter your delegation count
8. Press transact
9. MetaMask will pop-up, you can review the details and confirm the transaction

If you want to delegate without setting up auto-compounding, you can follow the previous steps, but instead of using delegateWithAutoCompound, you can use the delegate extrinsic.

Verify Delegation¶

To verify your delegation was successful, you can check the chain state in Polkadot.js Apps. First, add your MetaMask address to the address book in Polkadot.js Apps.

Navigate to Accounts and then Address Book, click on Add contact, and enter the following information:

1. Add your MetaMask address
2. Provide a nickname for the account
3. Click Save

To verify your delegation was successful, head to Polkadot.js Apps and navigate to Developer and then Chain State

1. Select the parachainStaking pallet
2. Select the delegatorState query
3. Enter your address
4. Optionally, you can enable the include option slider if you want to provide a specific blockhash to query
5. Click the + button to return the results and verify your delegation

Confirm Auto-Compounding Percentage¶

You can confirm the percentage of rewards you've set to auto-compound in Remix using the delegationAutoCompound function of the Solidity interface:

1. Find and expand the delegationAutoCompound function
2. Enter your account you used to delegate with
3. Enter the candidate you've delegated
4. Click call
5. The response will appear below the call button

Set or Change the Auto-Compounding Percentage¶

If you initially set up your delegation without auto-compounding or if you want to update the percentage on an existing delegation with auto-compounding set up, you can use the setAutoCompound function of the Solidity interface.

You'll need to get the number of delegations with auto-compounding set up for the candidate you want to set or update auto-compounding for. You'll also need to retrieve your own delegation count. You can follow the instructions in the Delegate a Collator with Auto-Compounding section to get both of these items.

Once you have the necessary information, you can take the following steps in Remix:

1. Find and expand the setAutoCompound function
2. Enter the candidate's account you want to set or update auto-compounding for
3. Enter a number 0-100 to represent the percentage of rewards you want to auto-compound
4. Enter the auto-compounding delegation count for the candidate
5. Enter your delegation count
6. Press transact
7. MetaMask will pop-up, you can review the details and confirm the transaction

Revoke a Delegation¶

As of runtime version 1001, there have been significant changes to the way users can interact with various staking features. Including the way staking exits are handled.

Exits now require you to schedule a request to exit or revoke a delegation, wait a delay period, and then execute the request.

To revoke a delegation for a specific candidate and receive your tokens back, you can use the scheduleRevokeDelegation extrinsic. Scheduling a request does not automatically revoke your delegation, you must wait an exit delay, and then execute the request by using the executeDelegationRequest method.

To revoke a delegation and receive your tokens back, head back over to Remix, then:

1. Find and expand the scheduleRevokeDelegation function
2. Enter the candidate address you would like to revoke the delegation for
3. Click transact
4. MetaMask will pop, you can review the transaction details, and click Confirm

Once the transaction is confirmed, you must wait the duration of the exit delay before you can execute and revoke the delegation request. If you try to revoke it before the exit delay is up, your extrinsic will fail.

After the exit delay has passed, you can go back to Remix and follow these steps to execute the due request:

1. Find and expand the executeDelegationRequest function
2. Enter the address of the delegator you would like to revoke the delegation for
3. Enter the candidate address you would like to revoke the delegation from
4. Click transact
5. MetaMask will pop, you can review the transaction details, and click Confirm

After the call is complete, the results will be displayed and the delegation will be revoked for the given delegator and from the specified candidate. You can also check your delegator state again on Polkadot.js Apps to confirm.

If for any reason you need to cancel a pending scheduled request to revoke a delegation, you can do so by following these steps in Remix:

1. Find and expand the cancelDelegationRequest function
2. Enter the candidate address you would like to cancel the pending request for
3. Click transact
4. MetaMask will pop, you can review the transaction details, and click Confirm

You can check your delegator state again on Polkadot.js Apps to confirm that your delegation is still intact.