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105 lines
3.6 KiB
Markdown
105 lines
3.6 KiB
Markdown
Cuprate's blockchain database.
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This documentation is mostly for practical usage of `cuprate_blockchain`.
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For a high-level overview, see the database section in
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[Cuprate's architecture book](https://architecture.cuprate.org).
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If you're looking for a database crate, consider using the lower-level
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[`cuprate-database`](https://doc.cuprate.org/cuprate_database)
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crate that this crate is built on-top of.
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# Purpose
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This crate does 3 things:
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1. Uses [`cuprate_database`] as a base database layer
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1. Implements various `Monero` related [operations](ops), [tables], and [types]
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1. Exposes a [`tower::Service`] backed by a thread-pool
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Each layer builds on-top of the previous.
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As a user of `cuprate_blockchain`, consider using the higher-level [`service`] module,
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or at the very least the [`ops`] module instead of interacting with the `cuprate_database` traits directly.
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# `cuprate_database`
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Consider reading `cuprate_database`'s crate documentation before this crate, as it is the first layer.
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If/when this crate needs is used, be sure to use the version that this crate re-exports, e.g.:
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```rust
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use cuprate_blockchain::{
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cuprate_database::RuntimeError,
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};
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```
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This ensures the types/traits used from `cuprate_database` are the same ones used by `cuprate_blockchain` internally.
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# Feature flags
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Different database backends are enabled by the feature flags:
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- `heed` (LMDB)
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- `redb`
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The default is `heed`.
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`tracing` is always enabled and cannot be disabled via feature-flag.
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<!-- FIXME: tracing should be behind a feature flag -->
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# Invariants when not using `service`
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`cuprate_blockchain` can be used without the `service` module but
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there are some things that must be kept in mind when doing so.
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Failing to uphold these invariants may cause panics.
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1. `LMDB` requires the user to resize the memory map resizing (see [`cuprate_database::RuntimeError::ResizeNeeded`]
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1. `LMDB` has a maximum reader transaction count, currently, [it is set to `126`](https://github.com/LMDB/lmdb/blob/b8e54b4c31378932b69f1298972de54a565185b1/libraries/liblmdb/mdb.c#L794-L799)
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1. `LMDB` has [maximum key/value byte size](http://www.lmdb.tech/doc/group__internal.html#gac929399f5d93cef85f874b9e9b1d09e0) which must not be exceeded
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# Examples
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The below is an example of using `cuprate_blockchain`'s
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lowest API, i.e. using a mix of this crate and `cuprate_database`'s traits directly -
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**this is NOT recommended.**
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For examples of the higher-level APIs, see:
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- [`ops`]
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- [`service`]
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```rust
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use cuprate_blockchain::{
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cuprate_database::{
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ConcreteEnv,
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Env, EnvInner,
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DatabaseRo, DatabaseRw, TxRo, TxRw,
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},
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config::ConfigBuilder,
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tables::{Tables, TablesMut, OpenTables},
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};
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# fn main() -> Result<(), Box<dyn std::error::Error>> {
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// Create a configuration for the database environment.
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let tmp_dir = tempfile::tempdir()?;
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let db_dir = tmp_dir.path().to_owned();
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let config = ConfigBuilder::new()
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.data_directory(db_dir.into())
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.build();
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// Initialize the database environment.
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let env = cuprate_blockchain::open(config)?;
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// Open up a transaction + tables for writing.
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let env_inner = env.env_inner();
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let tx_rw = env_inner.tx_rw()?;
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let mut tables = env_inner.open_tables_mut(&tx_rw)?;
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// ⚠️ Write data to the tables directly.
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// (not recommended, use `ops` or `service`).
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const KEY_IMAGE: [u8; 32] = [88; 32];
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tables.key_images_mut().put(&KEY_IMAGE, &())?;
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// Commit the data written.
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drop(tables);
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TxRw::commit(tx_rw)?;
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// Read the data, assert it is correct.
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let tx_ro = env_inner.tx_ro()?;
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let tables = env_inner.open_tables(&tx_ro)?;
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let (key_image, _) = tables.key_images().first()?;
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assert_eq!(key_image, KEY_IMAGE);
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# Ok(()) }
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```
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