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36 lines
1.3 KiB
Markdown
36 lines
1.3 KiB
Markdown
# Observer - P2P network crawler
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Observer crawls the Ethereum network and collects information about the nodes.
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### Build
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make observer
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### Run
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observer --datadir ... --nat extip:<IP> --port <PORT>
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Where `IP` is your public IP, and `PORT` has to be open for incoming UDP traffic.
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See `observer --help` for available options.
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### Report
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To get the report about the currently known network state run:
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observer report --datadir ...
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## Description
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Observer uses [discv4](https://github.com/ethereum/devp2p/blob/master/discv4.md) protocol to discover new nodes.
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Starting from a list of preconfigured "bootnodes" it uses FindNode
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to obtain their "neighbor" nodes, and then recursively crawls neighbors of neighbors and so on.
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Each found node is re-crawled again a few times.
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If the node fails to be pinged after maximum attempts, it is considered "dead", but still re-crawled less often.
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A separate "diplomacy" process is doing "handshakes" to obtain information about the discovered nodes.
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It tries to get [RLPx Hello](https://github.com/ethereum/devp2p/blob/master/rlpx.md#hello-0x00)
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and [Eth Status](https://github.com/ethereum/devp2p/blob/master/caps/eth.md#status-0x00)
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from each node.
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The handshake repeats a few times according to the configured delays.
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