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34 lines
1.4 KiB
34 lines
1.4 KiB
Fast Sync
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=========
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Background
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----------
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In a proof of work blockchain, syncing with the chain is the same
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process as staying up-to-date with the consensus: download blocks, and
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look for the one with the most total work. In proof-of-stake, the
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consensus process is more complex, as it involves rounds of
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communication between the nodes to determine what block should be
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committed next. Using this process to sync up with the blockchain from
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scratch can take a very long time. It's much faster to just download
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blocks and check the merkle tree of validators than to run the real-time
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consensus gossip protocol.
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Fast Sync
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---------
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To support faster syncing, tendermint offers a ``fast-sync`` mode, which
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is enabled by default, and can be toggled in the ``config.toml`` or via
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``--fast_sync=false``.
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In this mode, the tendermint daemon will sync hundreds of times faster
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than if it used the real-time consensus process. Once caught up, the
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daemon will switch out of fast sync and into the normal consensus mode.
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After running for some time, the node is considered ``caught up`` if it
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has at least one peer and it's height is at least as high as the max
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reported peer height. See `the IsCaughtUp
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method <https://github.com/tendermint/tendermint/blob/b467515719e686e4678e6da4e102f32a491b85a0/blockchain/pool.go#L128>`__.
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If we're lagging sufficiently, we should go back to fast syncing, but
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this is an open issue:
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https://github.com/tendermint/tendermint/issues/129
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