77 lines
3.0 KiB
Markdown
77 lines
3.0 KiB
Markdown
# Premix
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> Premix was **pre**mium(subsidized gasoline) **mix**ed [with lubricant oil]
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used for two stroke internal combustion engines and it tends to produce a lot
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of smoke.
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Today premix is a block validation debugging tool targeting at nimbus ethereum
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client. Premix will query transaction execution steps from other ethereum
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clients and compare it with nimbus'.
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Premix then will produce a web page to present comparison result that can be
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inspected by developer to pinpoint where the faulty instruction located.
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Premix will also produce a test case for the specific problematic transaction
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complete with snapshot database to execute transaction validation in isolation.
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This test case then can be integrated with nimbus project test suite.
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## Requirements
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Before you start to use premix debugging tool there are several things you need to prepare.
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The first one is you need to install `geth` from [source](https://github.com/ethereum/go-ethereum/releases)
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or [binary](https://ethereum.github.io/go-ethereum/downloads/). Then you can run it with this command:
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```bash
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geth --rpc --rpcapi eth,debug --syncmode full --gcmode=archive
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```
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You need to run it until it synced past the problematic block you want to debug.
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After that you can stop it by pressing `CTRL-C` and rerun it with additional
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flags `--maxpeers 0` if you want it to stop syncing or let it run as is if you want keep syncing.
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The next requirement is you should build Nimbus and Premix with latest dependencies:
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```bash
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nim c nimbus/nimbus
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nim c premix/premix
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```
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After you successfully build nimbus and premix, you can run nimbus with this command.
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```bash
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nimbus --prune:archive
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```
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Nimbus will try to sync up to problematic block then it will stop and execute Premix.
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Premix then will launch browser to display a report page. If premix failed to open your default browser,
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you can see the report page by opening `premix/index.html`.
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In the browser, you can try to navigate tracing result and find where the problem/bug is.
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## Helper tools
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* Persist Tool
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Because nimbus p2p layer still contains bugs, you may become impatient when try to syncing blocks.
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In `/premix` directory, you can find a `persist.nim` tool.
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It will help you to sync relative quicker because it will bypass p2p layer and download blocks from `geth` via `rpc-api`.
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```bash
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nim c -r premix/persist [--dataDir:your_database_directory] [--head: blockNumber] [--maxBlocks: number] [--numCommits: number]
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```
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* Debug Tool
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Premix debugging tool also produce a set of debugging meta data that you can use to quickly
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find the bug without the need to run p2p layer or any other unnecessary code.
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In `/premix` directory you'll find `debug.nim` tool that you can use to execute
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this debug meta data and you'll only need to work with one block and one transaction
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at a time instead of multiple confusing blocks or transactions.
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```bash
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nim c -r premix/debug blockxxx.json
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```
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`blockxxx.json` contains database snapshot needed to debug a single block produced by Premix tool.
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