Become a baker (create blocks)

This section explains what a baker is, its role in the network and how to become one.

By reading this section you will learn:

• What is a baker and the concepts related to it.

• How to upgrade your node to become a baker.

The process of becoming a baker can be summarized in the following steps:

1. Get an account and some GTUs.

2. Get a set of baker keys.

3. Register the baker keys with the account.

4. Start the node with the baker keys.

After completing these steps, the baker node will bake blocks. If a baked block is added to the chain the node’s baker will receive a reward.

Note

In this section we will use the name bakerAccount as the name of the account that will be used to register and manage a baker.

Definitions

Baker

A node is a baker (or is baking) when it actively participates in the network by creating new blocks that are added to the chain. A baker collects, orders and validates the transactions that are included in a block to maintain the integrity of the blockchain. The baker signs each block that they bake so that the block can be checked and executed by the rest of the participants of the network.

Baker keys

Each baker has a set of cryptographic keys called baker keys. The node uses these keys to sign the blocks that it bakes. In order to bake blocks signed by a specific baker the node has to be running with its set of baker keys loaded.

Baker account

Each account can use a set of baker keys to register a baker.

Whenever a baker bakes a valid block that gets included in the chain, after some time a reward is paid to the associated account.

Stake and lottery

The account can stake part of its GTU balance into the baker stake and can later manually release all or part of the staked amount. The staked amount cannot be moved or transferred until it is released by the baker.

Note

If an account owns an amount that was transferred with a release schedule, the amount can be staked even if not released yet.

In order to be chosen for baking a block, the baker must participate in a lottery in which the probability of getting a winning ticket is roughly proportional to the staked amount.

The same stake is used when calculating whether a baker is included in the finalization committee or not. See Finalization.

Epochs and slots

In the Concordium blockchain, time is subdivided into slots. Slots have a time duration fixed at the Genesis block. On any given branch, each slot can have at most one block, but multiple blocks on different branches can be produced in the same slot.

When considering the rewards and other baking-related concepts, we use the concept of an epoch as a unit of time that defines a period in which the set of current bakers and stakes are fixed. Epochs have a time duration fixed at the Genesis block. In the testnet, epochs have a duration of 1 hour.

Start baking

Managing accounts

This section provides a brief recap of the relevant steps for importing an account. For a complete description, see Accounts.

Accounts are created using the Concordium ID app. Once an account has been successfully created, navigating to the More tab and selecting Export allows you to get a JSON file containing the account information.

To import an account into the toolchain run

$concordium-client config account import <path/to/exported/file> --name bakerAccount

concordium-client will ask for a password to decrypt the exported file and import all accounts. The same password will be used for encrypting the transaction signing keys and the encrypted transfers key.

Creating keys for a baker and registering it

Note

For this process the account needs to own some GTU so make sure to request the 100 GTU drop for the account in the mobile app.

Each account has a unique baker ID that is used when registering its baker. This ID has to be provided by the network and currently cannot be precomputed. This ID must be given inside the baker keys file to the node so that it can use the baker keys to create blocks. The concordium-client will automatically fill this field when performing the following operations.

To create a fresh set of keys run:

$concordium-client baker generate-keys <keys-file>.json

where you can choose an arbitrary name for the keys file. To register the keys in the network you need to be running a node and send a baker add transaction to the network:

$concordium-client baker add <keys-file>.json --sender bakerAccount --stake <amountToStake> --out <concordium-data-dir>/baker-credentials.json

replacing

• <amountToStake> with the GTU amount for the baker’s initial stake

• <concordium-data-dir> with the following data directory:

  • on Linux and MacOS: ~/.local/share/concordium

  • on Windows: %LOCALAPPDATA%\\concordium.

(The output file name should remain baker-credentials.json).

Provide a --no-restake flag to avoid automatically adding the rewards to the staked amount on the baker. This behavior is described on the section Restaking the earnings.

In order to start the node with these baker keys and start producing blocks you first need to shut down the current running node (either by pressing Ctrl + C on the terminal where the node is running or using the concordium-node-stop executable).

After placing the file in the appropriate directory (already done in the previous command when specifying the output file), start the node again using concordium-node. The node will automatically start baking when the baker gets included in the bakers for the current epoch.

This change will be executed immediately and will take effect when finishing the epoch after the one in which the transaction for adding the baker was included in a block.

Timeline: adding a baker

	When transaction is included in a block	After 2 epochs
Change is visible by querying the node	✓
Baker is included in the baking committee		✓

Note

If the transaction for adding the baker was included in a block during epoch E, the baker will be considered as part of the baking committee when epoch E+2 starts.

Managing the baker

Checking the status of the baker and its lottery power

In order to see if the node is baking, you can check various sources that offer different degrees of precision in the information displayed.

• In the network dashboard, your node will show its baker ID in the Baker column.

• Using the concordium-client you can check the list of current bakers and the relative staked amount that they hold, i.e. their lottery power. The lottery power will determine how likely it is that a given baker will win the lottery and bake a block.

  $concordium-client consensus show-parameters --include-bakers
  Election nonce:      07fe0e6c73d1fff4ec8ea910ffd42eb58d5a8ecd58d9f871d8f7c71e60faf0b0
  Election difficulty: 4.0e-2
  Bakers:
                               Account                       Lottery power
          ----------------------------------------------------------------
      ...
      34: 4p2n8QQn5akq3XqAAJt2a5CsnGhDvUon6HExd2szrfkZCTD4FX   <0.0001
      ...
  

• Using the concordium-client you can check that the account has registered a baker and the current amount that is staked by that baker.

  $./concordium-client account show bakerAccount
  ...
  
  Baker: #22
   - Staked amount: 10.000000 GTU
   - Restake earnings: yes
  ...
  

• If the staked amount is big enough and there is a node running with the baker keys loaded, that baker should eventually produce blocks and you can see in your mobile wallet that baking rewards are being received by the account, as seen in this image:

  

Updating the staked amount

To update the baker stake run

$concordium-client baker update-stake --stake <newAmount> --sender bakerAccount

Modifying the staked amount modifies the probability that a baker gets elected to bake blocks.

When a baker adds stake for the first time or increases their stake, that change is executed on the chain and becomes visible as soon as the transaction is included in a block (can be seen through concordium-client account show bakerAccount) and takes effect 2 epochs after that.

Timeline: increasing the stake

	When transaction is included in a block	After 2 epochs
Change is visible by querying the node	✓
Baker uses the new stake		✓

When a baker decreases the staked amount, the change will need 2 + bakerCooldownEpochs epochs to take effect. The change becomes visible on the chain as soon as the transaction is included in a block, it can be consulted through concordium-client account show bakerAccount:

$concordium-client account show bakerAccount
...

Baker: #22
 - Staked amount: 50.000000 GTU to be updated to 20.000000 GTU at epoch 261  (2020-12-24 12:56:26 UTC)
 - Restake earnings: yes

...

Timeline: decreasing the stake

	When transaction is included in a block	After 2 + bakerCooldownEpochs epochs
Change is visible by querying the node	✓
Baker uses the new stake		✓
Stake can be decreased again or baker can be removed	✗	✓

Note

In the testnet, bakerCooldownEpochs is set initially to 168 epochs. This value can be checked as follows:

$concordium-client raw GetBlockSummary
...
        "bakerCooldownEpochs": 168
...

Warning

As noted in the Definitions section, the staked amount is locked, i.e. it cannot be transferred or used for payment. You should take this into account and consider staking an amount that will not be needed in the short term. In particular, to deregister a baker or to modify the staked amount you need to own some non-staked GTU to cover the transaction costs.

Restaking the earnings

When participating as a baker in the network and baking blocks, the account receives rewards on each baked block. These rewards are automatically added to the staked amount by default.

You can choose to modify this behavior and instead receive the rewards in the account balance without staking them automatically. This switch can be changed through concordium-client:

$concordium-client baker update-restake False --sender bakerAccount
$concordium-client baker update-restake True --sender bakerAccount

Changes to the restake flag will take effect immediately; however, the changes start affecting baking and finalizing power in the epoch after next. The current value of the switch can be seen in the account information which can be queried using concordium-client:

$concordium-client account show bakerAccount
...

Baker: #22
 - Staked amount: 50.000000 GTU
 - Restake earnings: yes

...

Timeline: updating restake

	When transaction is included in a block	2 epochs after being rewarded
Change is visible by querying the node	✓
Earnings will [not] be restaked automatically	✓
If restaking automatically, the gained stake affects the lottery power		✓

When the baker is registered, it will automatically re-stake the earnings, but as mentioned above, this can be changed by providing the --no-restake flag to the baker add command as shown here:

$concordium-client baker add baker-keys.json --sender bakerAccount --stake <amountToStake> --out baker-credentials.json --no-restake

Finalization

Finalization is the voting process performed by nodes in the finalization committee that finalizes a block when a sufficiently big number of members of the committee have received the block and agree on its outcome. Newer blocks must have the finalized block as an ancestor to ensure the integrity of the chain. For more information about this process, see the finalization section.

The finalization committee is formed by the bakers that have a certain staked amount. This specifically implies that in order to participate in the finalization committee you will probably have to modify the staked amount to reach said threshold. In the testnet, the staked amount needed to participate in the finalization committee is 0.1% of the total amount of existing GTU.

Participating in the finalization committee produces rewards on each block that is finalized. The rewards are paid to the baker account some time after the block is finalized.

Removing a baker

The controlling account can choose to de-register its baker on the chain. To do so you have to execute the concordium-client:

$concordium-client baker remove --sender bakerAccount

This will remove the baker from the baker list and unlock the staked amount on the baker so that it can be transferred or moved freely.

When removing the baker, the change has the same timeline as decreasing the staked amount. The change will need 2 + bakerCooldownEpochs epochs to take effect. The change becomes visible on the chain as soon as the transaction is included in a block and you can check when this change will be take effect by querying the account information with concordium-client as usual:

$concordium-client account show bakerAccount
...

Baker #22 to be removed at epoch 275 (2020-12-24 13:56:26 UTC)
 - Staked amount: 20.000000 GTU
 - Restake earnings: yes

...

Timeline: removing a baker

	When transaction is included in a block	After 2 + bakerCooldownEpochs epochs
Change is visible by querying the node	✓
Baker is removed from the baking committee		✓

Warning

Decreasing the staked amount and removing the baker cannot be done simultaneously. During the cooldown period produced by decreasing the staked amount, the baker cannot be removed and vice versa.

Support & Feedback

If you run into any issues or have suggestions, post your question or feedback on Discord, or contact us at testnet@concordium.com.