This commit changes the state system and database format to track the
provenance of UTXOs, in addition to the outputs themselves.
Specifically, it tracks the following additional metadata:
- the height at which the UTXO was created;
- whether or not the UTXO was created from a coinbase transaction or
not.
This metadata will allow us to:
- check the coinbase maturity consensus rule;
- check the coinbase inputs => no transparent outputs rule;
- implement lookup of transactions by utxo (using the height to find the
block and then scanning the block) for a future RPC mechanism.
Closes#1342
The UTXO query system assumes that a transaction will only request
information about UTXOs created in prior blocks. But transactions are
allowed to spend UTXOs created by prior transactions in the same block.
This doesn't fit with the existing query model, so instead of trying to
change it, allow the script verifier to take an additional set of known
UTXOs, and propagate this set from the block.
The metrics code becomes much simpler because the current version of the
metrics crate builds its own single-threaded runtime on a dedicated worker
thread, so no dependency on the main Zebra Tokio runtime is required.
This change is mostly mechanical, with the exception of the changes to the
`tower-batch` middleware. This middleware was adapted from `tower::buffer`,
and the `tower::buffer` code was changed to implement its own bounded queue,
because Tokio 0.3 removed the `mpsc::Sender::poll_send` method. See
ddc64e8d4d
for more context on the Tower changes. To match Tower as closely as possible
in order to be able to upstream `tower-batch`, those changes are copied from
`tower::Buffer` to `tower-batch`.
## Motivation
Prior to this PR we've been using `sled` as our database for storing persistent chain data on the disk between boots. We picked sled over rocksdb to minimize our c++ dependencies despite it being a less mature codebase. The theory was if it worked well enough we'd prefer to have a pure rust codebase, but if we ever ran into problems we knew we could easily swap it out with rocksdb.
Well, we ran into problems. Sled's memory usage was particularly high, and it seemed to be leaking memory. On top of all that, the performance for writes was pretty poor, causing us to become bottle-necked on sled instead of the network.
## Solution
This PR replaces `sled` with `rocksdb`. We've seen a 10x improvement in memory usage out of the box, no more leaking, and much better write performance. With this change writing chain data to disk is no longer a limiting factor in how quickly we can sync the chain.
The code in this pull request has:
- [x] Documentation Comments
- [x] Unit Tests and Property Tests
## Review
@hdevalence
The hedge middleware implements hedged requests, as described in _The
Tail At Scale_. The idea is that we auto-tune our retry logic according
to the actual network conditions, pre-emptively retrying requests that
exceed some latency percentile. This would hopefully solve the problem
where our timeouts are too long on mainnet and too slow on testnet.
This makes two changes relative to the existing download code:
1. It uses a oneshot to attempt to cancel the download task after it
has started;
2. It encapsulates the download creation and cancellation logic into a
Downloads struct.
This commit begins the process of integrating `zcash_script` with the rest of the system for verifying scripts while syncing the block chain. It does so by adding the necessary support for looking up UTXOs from the state service and implements the first parts of the `script::Verifier` for looking up the necessary UTXOs in the state and then generating the necessary call to `zcash_script` to verify the script itself.
Co-authored-by: teor <teor@riseup.net>
* implement most of the chain functions
* implement fork
* fix outpoint handling in Chain struct
* update expect for work
* split utxo into two sets
* update the Chain definition
* remove allow attribute in zebra-state/lib.rs
* merge ChainSet type into MemoryState
* Add error messages to asserts
* export proptest impls for use in downstream crates
* add testjob for disabled feature in zebra-chain
* try to fix github actions syntax
* add module doc comment
* update RFC for utxos
* add missing header
* working proptest for Chain
* propagate back results over channel
* Start updating RFC to match changes
* implement queued block pruning
* and now it syncs wooo!
* remove empty modules
* setup config for proptests
* re-enable missing_docs lint
* update RFC to match changes in impl
* add documentation
* use more explicit variable names
* Begin work on RFC5 implementation
* I think this is necessary
* holy shit supertrait implemented via subtrait
* implement most of the chain functions
* change to slightly better name
* implement fork
* fix outpoint handling in Chain struct
* update expect for work
* resolve review comment
* split utxo into two sets
* update the Chain definition
* just a little more
* update comment
* Apply suggestions from code review
Co-authored-by: teor <teor@riseup.net>
* apply changes from code review
* remove allow attribute in zebra-state/lib.rs
* Update zebra-state/src/memory_state.rs
Co-authored-by: teor <teor@riseup.net>
* merge ChainSet type into MemoryState
* rename state impl types
* Add error messages to asserts
* checkpoint so I can split off arbitrary changes into a PR
* export proptest impls for use in downstream crates
* add testjob for disabled feature in zebra-chain
* run rustfmt
* try to fix github actions syntax
* differentiate name
* prove that github action tests zebra-chain build without features
* revert change from last commit now that test is running
* remove accidentally introduced newline
* checkpoint
* add module doc comment
* update RFC for utxos
* add missing header
* working proptest for Chain
* apply change from chain impl PR
* setup config for proptests
* Update zebra-chain/src/block/arbitrary.rs
Co-authored-by: teor <teor@riseup.net>
* run rustfmt
Co-authored-by: teor <teor@riseup.net>