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53 lines
2.5 KiB
53 lines
2.5 KiB
/*
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Package evidence handles all evidence storage and gossiping from detection to block proposal.
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For the different types of evidence refer to the `evidence.go` file in the types package
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or https://github.com/tendermint/spec/blob/master/spec/consensus/light-client/accountability.md.
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Gossiping
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The core functionality begins with the evidence reactor (see reactor.
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go) which operates both the sending and receiving of evidence.
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The `Receive` function takes a list of evidence and does the following:
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1. Checks that it does not already have the evidence stored
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2. Verifies the evidence against the node's state (see state/validation.go#VerifyEvidence)
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3. Stores the evidence to a db and a concurrent list
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The gossiping of evidence is initiated when a peer is added which starts a go routine to broadcast currently
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uncommitted evidence at intervals of 60 seconds (set by the by broadcastEvidenceIntervalS).
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It uses a concurrent list to store the evidence and before sending verifies that each evidence is still valid in the
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sense that it has not exceeded the max evidence age and height (see types/params.go#EvidenceParams).
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There are two buckets that evidence can be stored in: Pending & Committed.
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1. Pending is awaiting to be committed (evidence is usually broadcasted then)
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2. Committed is for those already on the block and is to ensure that evidence isn't submitted twice
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All evidence is proto encoded to disk.
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Proposing
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When a new block is being proposed (in state/execution.go#CreateProposalBlock),
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`PendingEvidence(maxNum)` is called to send up to the maxNum number of uncommitted evidence, from the evidence store,
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prioritized in order of age. All evidence is checked for expiration.
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When a node receives evidence in a block it will use the evidence module as a cache first to see if it has
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already verified the evidence before trying to verify it again.
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Once the proposed evidence is submitted,
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the evidence is marked as committed and is moved from the broadcasted set to the committed set.
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As a result it is also removed from the concurrent list so that it is no longer gossiped.
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Minor Functionality
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As all evidence (including POLC's) are bounded by an expiration date, those that exceed this are no longer needed
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and hence pruned. Currently, only committed evidence in which a marker to the height that the evidence was committed
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and hence very small is saved. All updates are made from the `Update(block, state)` function which should be called
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when a new block is committed.
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*/
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package evidence
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