Merge bitcoindevkit#1670: Introduce O(n) canonicalization algorithm

956d0a9 test(chain): Update test docs to stop referencing `get_chain_position` (志宇)
1508ae3 chore: Fix typos (志宇)
af92199 refactor(wallet): Reuse chain position instead of obtaining new one (Jiri Jakes)
caa0f13 docs(wallet): Explain `.take` usage (志宇)
1196405 refactor(chain): Reorganize `TxGraph::insert_anchor` logic for clarity (志宇)
4706315 chore(chain): Address `CanonicalIter` nitpicks (志宇)
68f7b77 test(chain): Add canonicalization test (志宇)
da0c43e refactor(chain)!: Rename `LastSeenIn` to `ObservedIn` (志宇)
d4102b4 perf(chain): add benchmarks for canonicalization logic (志宇)
e34024c feat(chain): Derive `Clone` on `IndexedTxGraph` (志宇)
e985445 docs: Add ADR for `O(n)` canonicalization algorithm (志宇)
4325e2c test(chain): Add transitive anchor tests (志宇)
8fbee12 feat(chain)!: rm `get_chain_position` and associated methods (志宇)
582d6b5 feat(chain)!: `O(n)` canonicalization algorithm (志宇)
f6192a6 feat(chain)!: Add `run_until_finished` methods (志宇)
0aa39f9 feat(chain)!: `TxGraph` contain anchors in one field (志宇)

Pull request description:

  Fixes bitcoindevkit#1665
  Replaces bitcoindevkit#1659

  ### Description

  Previously, getting the canonical history of transactions/UTXOs required calling `TxGraph::get_chain_position` on each transaction. This was highly inefficient and resulted in an `O(n^2)` algorithm. The situation is especially problematic when we have many unconfirmed conflicts.

  This PR introduces an `O(n)` algorithm to determine the canonical set of transactions in `TxGraph`. The algorithm's premise is as follows:

  1. If transaction `A` is determined to be canonical, all of `A`'s ancestors must also be canonical.
  2. If transaction `B` is determined to be NOT canonical, all of `B`'s descendants must also be NOT canonical.
  3. If a transaction is anchored in the best chain, it is canonical.
  4. If a transaction conflicts with a canonical transaction, it is NOT canonical.
  5. A transaction with a higher last-seen has precedence.
  6. Last-seen values are transitive. A transaction's collective last-seen value is the max of it's last-seen value and all of it's descendants.

  We maintain two mutually-exclusive `txid` sets: `canoncial` and `not_canonical`.

  Imagine a method `mark_canonical(A)` that is based on premise 1 and 2. This method will mark transaction `A` and all of it's ancestors as canonical. For each transaction that is marked canonical, we can iterate all of it's conflicts and mark those as `non_canonical`. If a transaction already exists in `canoncial` or `not_canonical`, we can break early, avoiding duplicate work.

  This algorithm iterates transactions in 3 runs.

  1. Iterate over all transactions with anchors in descending anchor-height order. For any transaction that has an anchor pointing to the best chain, we call `mark_canonical` on it. We iterate in descending-height order to reduce the number of anchors we need to check against the `ChainOracle` (premise 1). The purpose of this run is to populate `non_canonical` with all transactions that directly conflict with anchored transactions and populate `canonical` with all anchored transactions and ancestors of anchors transactions (transitive anchors).
  2. Iterate over all transactions with last-seen values, in descending last-seen order. We can call `mark_canonical` on all of these that do not already exist in `canonical` or `not_canonical`.
  3. Iterate over remaining transactions that contains anchors (but not in the best chain) and have no last-seen value. We treat these transactions in the same way as we do in run 2.

  #### Benchmarks

  Thank you to @ValuedMammal for working on this.

  ```sh
  $ cargo bench -p bdk_chain --bench canonicalization
  ```

  Benchmark results (this PR):

  ```
  many_conflicting_unconfirmed::list_canonical_txs
                          time:   [709.46 us 710.36 us 711.35 us]
  many_conflicting_unconfirmed::filter_chain_txouts
                          time:   [712.59 us 713.23 us 713.90 us]
  many_conflicting_unconfirmed::filter_chain_unspents
                          time:   [709.95 us 711.16 us 712.45 us]
  many_chained_unconfirmed::list_canonical_txs
                          time:   [2.2604 ms 2.2641 ms 2.2680 ms]
  many_chained_unconfirmed::filter_chain_txouts
                          time:   [3.5763 ms 3.5869 ms 3.5979 ms]
  many_chained_unconfirmed::filter_chain_unspents
                          time:   [3.5540 ms 3.5596 ms 3.5652 ms]
  nested_conflicts_unconfirmed::list_canonical_txs
                          time:   [660.06 us 661.75 us 663.60 us]
  nested_conflicts_unconfirmed::filter_chain_txouts
                          time:   [650.15 us 651.36 us 652.71 us]
  nested_conflicts_unconfirmed::filter_chain_unspents
                          time:   [658.37 us 661.54 us 664.81 us]
  ```

  Benchmark results (master): https://github.com/evanlinjin/bdk/tree/fix/1665-master-bench

  ```
  many_conflicting_unconfirmed::list_canonical_txs
                          time:   [94.618 ms 94.966 ms 95.338 ms]
  many_conflicting_unconfirmed::filter_chain_txouts
                          time:   [159.31 ms 159.76 ms 160.22 ms]
  many_conflicting_unconfirmed::filter_chain_unspents
                          time:   [163.29 ms 163.61 ms 163.96 ms]

  # I gave up running the rest of the benchmarks since they were taking too long.
  ```

  ### Notes to the reviewers

  * ***PLEASE MERGE bitcoindevkit#1733 BEFORE THIS PR!*** We had to change the signature of `ChainPosition` to account for transitive anchors and unconfirmed transactions with no `last-seen` value.

  * The canonicalization algorithm is contained in `/crates/chain/src/canonical_iter.rs`.

  * Since the algorithm requires traversing transactions ordered by anchor height, and then last-seen values, we introduce two index fields in `TxGraph`; `txs_by_anchor` and `txs_by_last_seen`. Methods `insert_anchor` and `insert_seen_at` are changed to populate these index fields.

  * An ADR is added: `docs/adr/0003_canonicalization_algorithm.md`. This is based on the work in bitcoindevkit#1592.

  ### Changelog notice

  * Added: Introduce an `O(n)` canonicalization algorithm. This logic is contained in `/crates/chain/src/canonical_iter.rs`.
  * Added: Indexing fields in `TxGraph`; `txs_by_anchor_height` and `txs_by_last_seen`. Pre-indexing allows us to construct the canonical history more efficiently.
  * Removed: `TxGraph` methods: `try_get_chain_position` and `get_chain_position`. This is superseded by the new canonicalization algorithm.

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

  #### New Features:

  * [x] I've added tests for the new feature
  * [x] I've added docs for the new feature

  #### Bugfixes:

  * [x] This pull request breaks the existing API
  * [x] I've added tests to reproduce the issue which are now passing
  * [x] I'm linking the issue being fixed by this PR

ACKs for top commit:
  ValuedMammal:
    ACK 956d0a9
  nymius:
    ACK 956d0a9
  oleonardolima:
    utACK 956d0a9
  jirijakes:
    ACK 956d0a9

Tree-SHA512: 44963224abf1aefb3510c59d0eb27e3a572cd16f46106fd92e8da2e6e12f0671dcc1cd5ffdc4cc80683bc9e89fa990eba044d9c64d9ce02abc29a08f4859b69e

.github/workflows/cont_integration.yml

@@ -51,6 +51,8 @@ jobs:
           cargo update -p tokio-util --precise "0.7.11"
           cargo update -p indexmap --precise "2.5.0"
           cargo update -p security-framework-sys --precise "2.11.1"
+          cargo update -p csv --precise "1.3.0"
+          cargo update -p unicode-width --precise "0.1.13"
       - name: Build
         run: cargo build --workspace --exclude 'example_*' ${{ matrix.features }}
       - name: Test

README.md

@@ -78,6 +78,8 @@ cargo update -p tokio --precise "1.38.1"
 cargo update -p tokio-util --precise "0.7.11"
 cargo update -p indexmap --precise "2.5.0"
 cargo update -p security-framework-sys --precise "2.11.1"
+cargo update -p csv --precise "1.3.0"
+cargo update -p unicode-width --precise "0.1.13"
 ```
 
 ## License

crates/bitcoind_rpc/tests/test_emitter.rs

@@ -389,6 +389,7 @@ fn tx_can_become_unconfirmed_after_reorg() -> anyhow::Result<()> {
         assert_eq!(
             get_balance(&recv_chain, &recv_graph)?,
             Balance {
+                trusted_pending: SEND_AMOUNT * reorg_count as u64,
                 confirmed: SEND_AMOUNT * (ADDITIONAL_COUNT - reorg_count) as u64,
                 ..Balance::default()
             },

crates/chain/Cargo.toml

@@ -28,11 +28,15 @@ rusqlite = { version = "0.31.0", features = ["bundled"], optional = true }
 rand = "0.8"
 proptest = "1.2.0"
 bdk_testenv = { path = "../testenv", default-features = false }
-
+criterion = { version = "0.2" }
 
 [features]
 default = ["std", "miniscript"]
 std = ["bitcoin/std", "miniscript?/std", "bdk_core/std"]
 serde = ["dep:serde", "bitcoin/serde", "miniscript?/serde", "bdk_core/serde"]
 hashbrown = ["bdk_core/hashbrown"]
 rusqlite = ["std", "dep:rusqlite", "serde"]
+
+[[bench]]
+name = "canonicalization"
+harness = false

crates/chain/benches/canonicalization.rs

@@ -0,0 +1,250 @@
+use bdk_chain::{keychain_txout::KeychainTxOutIndex, local_chain::LocalChain, IndexedTxGraph};
+use bdk_core::{BlockId, CheckPoint};
+use bdk_core::{ConfirmationBlockTime, TxUpdate};
+use bdk_testenv::hash;
+use bitcoin::{
+    absolute, constants, hashes::Hash, key::Secp256k1, transaction, Amount, BlockHash, Network,
+    OutPoint, ScriptBuf, Transaction, TxIn, TxOut,
+};
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use miniscript::{Descriptor, DescriptorPublicKey};
+use std::sync::Arc;
+
+type Keychain = ();
+type KeychainTxGraph = IndexedTxGraph<ConfirmationBlockTime, KeychainTxOutIndex<Keychain>>;
+
+/// New tx guaranteed to have at least one output
+fn new_tx(lt: u32) -> Transaction {
+    Transaction {
+        version: transaction::Version::TWO,
+        lock_time: absolute::LockTime::from_consensus(lt),
+        input: vec![],
+        output: vec![TxOut::NULL],
+    }
+}
+
+fn spk_at_index(txout_index: &KeychainTxOutIndex<Keychain>, index: u32) -> ScriptBuf {
+    txout_index
+        .get_descriptor(())
+        .unwrap()
+        .at_derivation_index(index)
+        .unwrap()
+        .script_pubkey()
+}
+
+fn genesis_block_id() -> BlockId {
+    BlockId {
+        height: 0,
+        hash: constants::genesis_block(Network::Regtest).block_hash(),
+    }
+}
+
+fn tip_block_id() -> BlockId {
+    BlockId {
+        height: 100,
+        hash: BlockHash::all_zeros(),
+    }
+}
+
+/// Add ancestor tx confirmed at `block_id` with `locktime` (used for uniqueness).
+/// The transaction always pays 1 BTC to SPK 0.
+fn add_ancestor_tx(graph: &mut KeychainTxGraph, block_id: BlockId, locktime: u32) -> OutPoint {
+    let spk_0 = spk_at_index(&graph.index, 0);
+    let tx = Transaction {
+        input: vec![TxIn {
+            previous_output: OutPoint::new(hash!("bogus"), locktime),
+            ..Default::default()
+        }],
+        output: vec![TxOut {
+            value: Amount::ONE_BTC,
+            script_pubkey: spk_0,
+        }],
+        ..new_tx(locktime)
+    };
+    let txid = tx.compute_txid();
+    let _ = graph.insert_tx(tx);
+    let _ = graph.insert_anchor(
+        txid,
+        ConfirmationBlockTime {
+            block_id,
+            confirmation_time: 100,
+        },
+    );
+    OutPoint { txid, vout: 0 }
+}
+
+fn setup<F: Fn(&mut KeychainTxGraph, &LocalChain)>(f: F) -> (KeychainTxGraph, LocalChain) {
+    const DESC: &str = "tr([ab28dc00/86h/1h/0h]tpubDCdDtzAMZZrkwKBxwNcGCqe4FRydeD9rfMisoi7qLdraG79YohRfPW4YgdKQhpgASdvh612xXNY5xYzoqnyCgPbkpK4LSVcH5Xv4cK7johH/0/*)";
+    let cp = CheckPoint::from_block_ids([genesis_block_id(), tip_block_id()])
+        .expect("blocks must be chronological");
+    let chain = LocalChain::from_tip(cp).unwrap();
+
+    let (desc, _) =
+        <Descriptor<DescriptorPublicKey>>::parse_descriptor(&Secp256k1::new(), DESC).unwrap();
+    let mut index = KeychainTxOutIndex::new(10);
+    index.insert_descriptor((), desc).unwrap();
+    let mut tx_graph = KeychainTxGraph::new(index);
+
+    f(&mut tx_graph, &chain);
+    (tx_graph, chain)
+}
+
+fn run_list_canonical_txs(tx_graph: &KeychainTxGraph, chain: &LocalChain, exp_txs: usize) {
+    let txs = tx_graph
+        .graph()
+        .list_canonical_txs(chain, chain.tip().block_id());
+    assert_eq!(txs.count(), exp_txs);
+}
+
+fn run_filter_chain_txouts(tx_graph: &KeychainTxGraph, chain: &LocalChain, exp_txos: usize) {
+    let utxos = tx_graph.graph().filter_chain_txouts(
+        chain,
+        chain.tip().block_id(),
+        tx_graph.index.outpoints().clone(),
+    );
+    assert_eq!(utxos.count(), exp_txos);
+}
+
+fn run_filter_chain_unspents(tx_graph: &KeychainTxGraph, chain: &LocalChain, exp_utxos: usize) {
+    let utxos = tx_graph.graph().filter_chain_unspents(
+        chain,
+        chain.tip().block_id(),
+        tx_graph.index.outpoints().clone(),
+    );
+    assert_eq!(utxos.count(), exp_utxos);
+}
+
+pub fn many_conflicting_unconfirmed(c: &mut Criterion) {
+    const CONFLICTING_TX_COUNT: u32 = 2100;
+    let (tx_graph, chain) = black_box(setup(|tx_graph, _chain| {
+        let previous_output = add_ancestor_tx(tx_graph, tip_block_id(), 0);
+        // Create conflicting txs that spend from `previous_output`.
+        let spk_1 = spk_at_index(&tx_graph.index, 1);
+        for i in 1..=CONFLICTING_TX_COUNT {
+            let tx = Transaction {
+                input: vec![TxIn {
+                    previous_output,
+                    ..Default::default()
+                }],
+                output: vec![TxOut {
+                    value: Amount::ONE_BTC - Amount::from_sat(i as u64 * 10),
+                    script_pubkey: spk_1.clone(),
+                }],
+                ..new_tx(i)
+            };
+            let update = TxUpdate {
+                txs: vec![Arc::new(tx)],
+                ..Default::default()
+            };
+            let _ = tx_graph.apply_update_at(update, Some(i as u64));
+        }
+    }));
+    c.bench_function("many_conflicting_unconfirmed::list_canonical_txs", {
+        let (tx_graph, chain) = (tx_graph.clone(), chain.clone());
+        move |b| b.iter(|| run_list_canonical_txs(&tx_graph, &chain, 2))
+    });
+    c.bench_function("many_conflicting_unconfirmed::filter_chain_txouts", {
+        let (tx_graph, chain) = (tx_graph.clone(), chain.clone());
+        move |b| b.iter(|| run_filter_chain_txouts(&tx_graph, &chain, 2))
+    });
+    c.bench_function("many_conflicting_unconfirmed::filter_chain_unspents", {
+        let (tx_graph, chain) = (tx_graph.clone(), chain.clone());
+        move |b| b.iter(|| run_filter_chain_unspents(&tx_graph, &chain, 1))
+    });
+}
+
+pub fn many_chained_unconfirmed(c: &mut Criterion) {
+    const TX_CHAIN_COUNT: u32 = 2100;
+    let (tx_graph, chain) = black_box(setup(|tx_graph, _chain| {
+        let mut previous_output = add_ancestor_tx(tx_graph, tip_block_id(), 0);
+        // Create a chain of unconfirmed txs where each subsequent tx spends the output of the
+        // previous one.
+        for i in 0..TX_CHAIN_COUNT {
+            // Create tx.
+            let tx = Transaction {
+                input: vec![TxIn {
+                    previous_output,
+                    ..Default::default()
+                }],
+                ..new_tx(i)
+            };
+            let txid = tx.compute_txid();
+            let update = TxUpdate {
+                txs: vec![Arc::new(tx)],
+                ..Default::default()
+            };
+            let _ = tx_graph.apply_update_at(update, Some(i as u64));
+            // Store the next prevout.
+            previous_output = OutPoint::new(txid, 0);
+        }
+    }));
+    c.bench_function("many_chained_unconfirmed::list_canonical_txs", {
+        let (tx_graph, chain) = (tx_graph.clone(), chain.clone());
+        move |b| b.iter(|| run_list_canonical_txs(&tx_graph, &chain, 2101))
+    });
+    c.bench_function("many_chained_unconfirmed::filter_chain_txouts", {
+        let (tx_graph, chain) = (tx_graph.clone(), chain.clone());
+        move |b| b.iter(|| run_filter_chain_txouts(&tx_graph, &chain, 1))
+    });
+    c.bench_function("many_chained_unconfirmed::filter_chain_unspents", {
+        let (tx_graph, chain) = (tx_graph.clone(), chain.clone());
+        move |b| b.iter(|| run_filter_chain_unspents(&tx_graph, &chain, 0))
+    });
+}
+
+pub fn nested_conflicts(c: &mut Criterion) {
+    const CONFLICTS_PER_OUTPUT: usize = 3;
+    const GRAPH_DEPTH: usize = 7;
+    let (tx_graph, chain) = black_box(setup(|tx_graph, _chain| {
+        let mut prev_ops = core::iter::once(add_ancestor_tx(tx_graph, tip_block_id(), 0))
+            .collect::<Vec<OutPoint>>();
+        for depth in 1..GRAPH_DEPTH {
+            for previous_output in core::mem::take(&mut prev_ops) {
+                for conflict_i in 1..=CONFLICTS_PER_OUTPUT {
+                    let mut last_seen = depth * conflict_i;
+                    if last_seen % 2 == 0 {
+                        last_seen /= 2;
+                    }
+                    let ((_, script_pubkey), _) = tx_graph.index.next_unused_spk(()).unwrap();
+                    let value =
+                        Amount::ONE_BTC - Amount::from_sat(depth as u64 * 200 - conflict_i as u64);
+                    let tx = Transaction {
+                        input: vec![TxIn {
+                            previous_output,
+                            ..Default::default()
+                        }],
+                        output: vec![TxOut {
+                            value,
+                            script_pubkey,
+                        }],
+                        ..new_tx(conflict_i as _)
+                    };
+                    let txid = tx.compute_txid();
+                    prev_ops.push(OutPoint::new(txid, 0));
+                    let _ = tx_graph.insert_seen_at(txid, last_seen as _);
+                    let _ = tx_graph.insert_tx(tx);
+                }
+            }
+        }
+    }));
+    c.bench_function("nested_conflicts_unconfirmed::list_canonical_txs", {
+        let (tx_graph, chain) = (tx_graph.clone(), chain.clone());
+        move |b| b.iter(|| run_list_canonical_txs(&tx_graph, &chain, GRAPH_DEPTH))
+    });
+    c.bench_function("nested_conflicts_unconfirmed::filter_chain_txouts", {
+        let (tx_graph, chain) = (tx_graph.clone(), chain.clone());
+        move |b| b.iter(|| run_filter_chain_txouts(&tx_graph, &chain, GRAPH_DEPTH))
+    });
+    c.bench_function("nested_conflicts_unconfirmed::filter_chain_unspents", {
+        let (tx_graph, chain) = (tx_graph.clone(), chain.clone());
+        move |b| b.iter(|| run_filter_chain_unspents(&tx_graph, &chain, 1))
+    });
+}
+
+criterion_group!(
+    benches,
+    many_conflicting_unconfirmed,
+    many_chained_unconfirmed,
+    nested_conflicts,
+);
+criterion_main!(benches);