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Learn about Collators

Introduction

A collator plays an essential role in our network and is responsible for crucial tasks, including block production and transaction confirmation. A collator needs to maintain a high communication response capability to ensure the seamless operation of the Astar ecosystem.

Role of collators in the Astar ecosystem

Collators maintain our ecosystem by collecting transactions from users and producing state transition proofs for Relay Chain validators. In other words, collators maintain the network by aggregating parachain transactions into parachain block candidates and producing state transition proofs for validators based on those blocks.

Unlike validators, collator nodes do not secure the network. If a parachain block is invalid, it will get rejected by validators. Therefore the assumption that having more collators is better or more secure is not correct. On the contrary, too many collators may slow down the network. The only nefarious power collators have transaction censorship. To prevent censorship, a parachain only needs to ensure some neutral collators - but not necessarily a majority. Theoretically, the censorship problem is solved by having just one honest collator (reference: https://wiki.polkadot.network/docs/learn-collator).

Performance of the network depends directly on collators. To ensure optimal performance of the network, a slashing mechanism is implemented.

XCMP

Collators are a key element of XCMP (Cross-Chain Message Passing). By being full-nodes of the Relay Chain, they are all aware of each other as peers. This makes it possible for them to send messages from parachain A to parachain B.


Aura PoS Consensus

Aura PoS consist of 2 pallets:

The first phase in making PoS was by deploying the Aura pallet. Aura PoA Collator Phase - permissioned block authoring and collator session key setup for Astar ecosystem. After extended testing, we have deployed the PoS pallet and switched to Aura PoS. We have enabled permissionless collator staking, network inflation, and rewards.

Let’s break down the latest phase:

  • Collator staking: collators can now start with securing the network. This will be with a minimum bond of a fixed amount of tokens.
  • Network inflation: Astar mainnets has a 10% inflation. This 10% is based on a perfect block production every 12 seconds.
  • Rewards: a fixed amount will be created at each block and divided between treasury, collators, and dApp staking.

A collator (block producer) gets a reward for each block it’s produced. The reward is a fixed amount for each block.


Collator election mechanism

Election process

When your node fits the parameters and checks all the boxes to become a collator, you will be added to the chain. After registering for a collator and bonded the tokens. Note: if your collator doesn’t produce blocks during one session (1h) it will be kicked out.


Collator reward distribution mechanism

At every block you produced as a collator, rewards will automatically be transferred to your account. The reward includes block reward + fees.


Slash mechanism

Starting April 2022, a slashing mechanism is implemented on Astar and Shiden network: a collator who doesn't produce any block during one session (1 hour) will get slashed by 1% of his total stake and kick out from active collator set. This slashing aims to ensure the best block rate for the network and prevent malicious actors to harm it without financial consequences.


FAQ

What about NPoS?

Our first intention was to activate NPoS to Shiden Network. After internal testing, this would use a lot of Shiden collator resources. NPoS is not designed for collators in the Polkadot ecosystem (reference: role of collators). Astar ecosystem is build to be a dApp hub in the Polkadot ecosystem for smart contracts with a unique incentive reward mechanism for developers, dApp staking.