cuprate/storage/txpool/README.md

Cuprate's tx-pool database.

This documentation is mostly for practical usage of cuprate_txpool.

For a high-level overview, see the database section in Cuprate's architecture book.

If you're looking for a database crate, consider using the lower-level cuprate-database crate that this crate is built on-top of.

Purpose

This crate does 3 things:

1. Uses [cuprate_database] as a base database layer
2. Implements various transaction pool related operations, [tables], and [types]
3. Exposes a [tower::Service] backed by a thread-pool

Each layer builds on-top of the previous.

As a user of cuprate_txpool, consider using the higher-level [service] module, or at the very least the [ops] module instead of interacting with the cuprate_database traits directly.

cuprate_database

Consider reading cuprate_database's crate documentation before this crate, as it is the first layer.

If/when this crate needs is used, be sure to use the version that this crate re-exports, e.g.:

use cuprate_txpool::{
    cuprate_database::RuntimeError,
};

This ensures the types/traits used from cuprate_database are the same ones used by cuprate_txpool internally.

Feature flags

Different database backends are enabled by the feature flags:

• heed (LMDB)
• redb

The default is heed.

tracing is always enabled and cannot be disabled via feature-flag.

Invariants when not using service

See cuprate_blockchain, the invariants are the same.

Examples

The below is an example of using cuprate_txpool's lowest API, i.e. using a mix of this crate and cuprate_database's traits directly - this is NOT recommended.

For examples of the higher-level APIs, see:

• [ops]
• [service]

use cuprate_txpool::{
    cuprate_database::{
        ConcreteEnv,
        Env, EnvInner,
        DatabaseRo, DatabaseRw, TxRo, TxRw,
    },
    config::ConfigBuilder,
    tables::{Tables, TablesMut, OpenTables},
};

# fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Create a configuration for the database environment.
    let tmp_dir = tempfile::tempdir()?;
    let db_dir = tmp_dir.path().to_owned();
    let config = ConfigBuilder::new()
        .data_directory(db_dir.into())
        .build();

    // Initialize the database environment.
    let env = cuprate_txpool::open(config)?;

    // Open up a transaction + tables for writing.
    let env_inner = env.env_inner();
    let tx_rw = env_inner.tx_rw()?;
    let mut tables = env_inner.open_tables_mut(&tx_rw)?;

    // ⚠️ Write data to the tables directly.
    // (not recommended, use `ops` or `service`).
    const KEY_IMAGE: [u8; 32] = [88; 32];
    const TX_HASH: [u8; 32] = [88; 32];
    tables.spent_key_images_mut().put(&KEY_IMAGE, &TX_HASH)?;

    // Commit the data written.
    drop(tables);
    TxRw::commit(tx_rw)?;

    // Read the data, assert it is correct.
    let tx_ro = env_inner.tx_ro()?;
    let tables = env_inner.open_tables(&tx_ro)?;
    let (key_image, tx_hash) = tables.spent_key_images().first()?;
    assert_eq!(key_image, KEY_IMAGE);
    assert_eq!(tx_hash, TX_HASH);
    # Ok(())
}