mirror of https://github.com/poanetwork/quorum.git
32 lines
4.0 KiB
Markdown
32 lines
4.0 KiB
Markdown
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# How a block gets added to the chain in quorum
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A code walkthrough showing the making of a new block and how nodes receive and vote for it.
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## Pre-requisites for all nodes:
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The [BlockVoting service has been started](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/cmd/geth/main.go#L332) with a [block maker strategy in place](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/eth/block_voting.go#L11-L13)
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## On the block maker
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1. BlockMaker reaches its deadline waiting for a new block from others and [fires an event to trigger the creation of a new one itself](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/quorum/vote_strategy.go#L91)
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2. The event is [picked up by the BlockVoting loop](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/quorum/block_voting.go#L261)
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3. A new block is [constructed, inserted into the chain](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/quorum/block_voting.go#L348-L349)
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4. A [ChainHeadEvent is published on BlockChain.chainEvents](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/blockchain.go#L1239)
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5. A [NewMinedBlockEvent is published](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/quorum/block_voting.go#L353)
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6. The NewMinedBlockEvent will eventually cause the ProtocolManager to [broadcast the new block](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/eth/handler.go#L759-L761)
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7. Finally, the ChainHeadEvent will cause the node to [reset its pending state and vote for its own block](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/quorum/block_voting.go#L232-L236)
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## On other nodes
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1. Node [receives a message notifying about new block](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/eth/handler.go#L653)
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2. [Enqueues it for import](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/eth/handler.go#L664)
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3. The fetcher [detects a new import has been queued](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/eth/fetcher/fetcher.go#L293)
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4. And [imports it](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/eth/fetcher/fetcher.go#L313) by [calling ProtocolManager.insertChain()](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/eth/handler.go#L178)
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5. Which in turn calls BlockChain.InsertChain(), which checks that [the block was created by a block maker](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/block_validator.go#L334) (via [BlockValidator.ValidateBlock()](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/blockchain.go#L879) -> [ValidateHeader()](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/block_validator.go#L97) -> [ValidateExtraData()](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/block_validator.go#L329)),
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and [call BlockValidator.ValidateState()](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/blockchain.go#L945)
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to check that [its parent is the current head](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/block_validator.go#L172)
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6. It will then send a [ChainHeadEvent on BlockChain.chainEvents](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/blockchain.go#L1239)
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6. Which is processed in BlockVoting.run(), causing the Node's [pending state to be reset and the node to vote for the new block](https://github.com/jpmorganchase/quorum/blob/856c9fe43e3eb675678c55ceda7eb4d298a7ca7d/core/quorum/block_voting.go#L232-L236)
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