141 lines
4.6 KiB
Markdown
141 lines
4.6 KiB
Markdown
# Premix
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> Premix is **pre**mium gasoline **mix**ed with lubricant oil and it is
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used in two-stroke internal combustion engines. It tends to produce a lot of
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smoke.
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This Premix is a block validation debugging tool for the Nimbus Ethereum
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client. Premix will query transaction execution steps from other Ethereum
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clients and compare them with those generated by Nimbus. It will then produce a
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web page to present comparison results that can be inspected by the developer
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to pinpoint the faulty instruction.
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Premix will also produce a test case for the specific problematic transaction,
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complete with a database snapshot to execute transaction validation in
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isolation. This test case can then be integrated with the Nimbus project's test
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suite.
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## Requirements
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Before you can use the Premix debugging tool there are several things you need
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to prepare. The first requirement is a recent version of `geth` installed from
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[source](https://github.com/ethereum/go-ethereum/releases) or
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[binary](https://ethereum.github.io/go-ethereum/downloads/). The minimum
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required version is 1.8.18. Afterwards, 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 fully syncs past the problematic block you want to
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debug (you might need to do it on an empty db, because some geth versions will
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keep on doing a fast sync if that's what was done before). After that, you can
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stop it by pressing `CTRL-C` and rerun it with the additional flag `--maxpeers
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0` if you want it to stop syncing
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- or just let it run as is if you want to keep syncing.
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The next requirement is building Nimbus and Premix:
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```bash
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# in the top-level directory:
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make
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```
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After that, you can run Nimbus with this command:
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```bash
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./build/nimbus --prune:archive --port:30304
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```
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Nimbus will try to sync up to the problematic block, then stop and execute
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Premix which will then load a report page in your default browser. If it fails
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to do that, you can see the report page by manually opening
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`premix/index.html`.
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In your browser, you can explore the tracing result and find where the problem is.
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## Tools
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### Premix
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Premix is the main debugging tool. It produces reports that can be viewed in
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a browser and serialised debug data that can be consumed by the `debug` tool.
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Premix consumes data produced by either `nimbus`, `persist`, or `dumper`.
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You can run it manually using this command:
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```bash
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./build/premix debug*.json
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```
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### Persist
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Because the Nimbus P2P layer still contains bugs, you may become impatient when
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trying to sync blocks. In the `./premix` directory, you can find a `persist`
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tool. It will help you sync relatively quicker because it will bypass the P2P
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layer and download blocks from `geth` via `rpc-api`.
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When it encounters a problematic block during syncing, it will stop and produce
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debugging data just like Nimbus does.
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```bash
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./build/persist [--dataDir:your_database_directory] [--head: blockNumber] [--maxBlocks: number] [--numCommits: number]
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```
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### Debug
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In the same `./premix` directory you'll find the `debug` tool that you can use
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to process previously generated debugging info in order to work with one block
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and one transaction at a time instead of multiple confusing blocks and
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transactions.
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```bash
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./build/debug block*.json
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```
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where `block*.json` contains the database snapshot needed to debug a single
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block produced by the Premix tool.
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### Dumper
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Dumper was designed specifically to produce debugging data that can be further
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processed by Premix from information already stored in database. It will create
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tracing information for a single block if that block has been already
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persisted.
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If you want to generate debugging data, it's better to use the Persist tool.
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The data generated by Dumper is usually used to debug Premix features in
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general and the report page logic in particular.
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```bash
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# usage:
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./build/dumper [--datadir:your_path] --head:blockNumber
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```
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### Hunter
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Hunter's purpose is to track down problematic blocks and create debugging info
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associated with them. It will not access your on-disk database, because it has
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its own prestate construction code.
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Hunter will download all it needs from geth, just make sure your geth version
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is at least 1.8.18.
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Hunter depends on
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`eth_getProof`[(EIP1186)](https://github.com/ethereum/EIPs/issues/1186). Make
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sure your installed `geth` supports this functionality (older versions don't
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have this implemented).
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```bash
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# usage:
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./build/hunter --head:blockNumber --maxBlocks:number
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```
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`blockNumber` is the starting block where the hunt begins.
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`maxBlocks` is the number of problematic blocks you want to capture before
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stopping the hunt.
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