chore: add comments

.github/actions/bitcoin-int-tests/Dockerfile.bitcoin-tests

@@ -21,6 +21,7 @@ RUN cargo test -- --test-threads 1 --ignored tests::neon_integrations::bitcoind_
 RUN cargo test -- --test-threads 1 --ignored tests::neon_integrations::liquid_ustx_integration
 RUN cargo test -- --test-threads 1 --ignored tests::neon_integrations::stx_transfer_btc_integration_test
 RUN cargo test -- --test-threads 1 --ignored tests::neon_integrations::bitcoind_forking_test
+RUN cargo test -- --test-threads 1 --ignored tests::neon_integrations::should_fix_2771
 RUN cargo test -- --test-threads 1 --ignored tests::neon_integrations::pox_integration_test
 RUN cargo test -- --test-threads 1 --ignored tests::bitcoin_regtest::bitcoind_integration_test
 RUN cargo test -- --test-threads 1 --ignored tests::should_succeed_handling_malformed_and_valid_txs

src/burnchains/burnchain.rs

@@ -891,7 +891,7 @@ impl Burnchain {
     }
 
     /// Determine if there has been a chain reorg, given our current canonical burnchain tip.
-    /// Return the new chain tip
+    /// Return the new chain tip and a boolen signaling the presence of a reorg
     fn sync_reorg<I: BurnchainIndexer>(indexer: &mut I) -> Result<(u64, bool), burnchain_error> {
         let headers_path = indexer.get_headers_path();
 
@@ -1196,7 +1196,7 @@ impl Burnchain {
                     }
                 }
                 let end_height = target_block_height_opt.unwrap_or(0).max(db_height);
-                info!("Burnchain reorg happened at height {} invalidating chain tip {} but only {} headers presents on canonical chain. Retry in 1s", sync_height, db_height, end_block);
+                info!("Burnchain reorg happened at height {} invalidating chain tip {} but only {} headers presents on canonical chain. Retry in 2s", sync_height, db_height, end_block);
                 thread::sleep(Duration::from_millis(2000));
                 end_block = indexer.sync_headers(sync_height, Some(end_height))?;
             }

testnet/stacks-node/src/tests/neon_integrations.rs

@@ -1307,6 +1307,25 @@ fn bitcoind_forking_test() {
     // but we're able to keep on mining
     assert_eq!(account.nonce, 3);
 
+    // Let's create another fork, deeper
+    let burn_header_hash_to_fork = btc_regtest_controller.get_block_hash(206);
+    btc_regtest_controller.invalidate_block(&burn_header_hash_to_fork);
+    btc_regtest_controller.build_next_block(10);
+
+    thread::sleep(Duration::from_secs(5));
+    next_block_and_wait(&mut btc_regtest_controller, &blocks_processed);
+
+    let account = get_account(&http_origin, &miner_account);
+    assert_eq!(account.balance, 0);
+    assert_eq!(account.nonce, 2);
+
+    next_block_and_wait(&mut btc_regtest_controller, &blocks_processed);
+
+    let account = get_account(&http_origin, &miner_account);
+    assert_eq!(account.balance, 0);
+    // but we're able to keep on mining
+    assert_eq!(account.nonce, 3);
+
     channel.stop_chains_coordinator();
 }
 
@@ -1355,19 +1374,24 @@ fn should_fix_2771() {
         sort_height = channel.get_sortitions_processed();
         eprintln!("Sort height: {}", sort_height);
     }
-    // let's query the miner's account nonce:
-
-    eprintln!("Miner account: {}", miner_account);
 
     // okay, let's figure out the burn block we want to fork away.
-    warn!("Will trigger re-org at block {}", 208);
-    let burn_header_hash_to_fork = btc_regtest_controller.get_block_hash(208);
+    let reorg_height = 208;
+    warn!("Will trigger re-org at block {}", reorg_height);
+    let burn_header_hash_to_fork = btc_regtest_controller.get_block_hash(reorg_height);
     btc_regtest_controller.invalidate_block(&burn_header_hash_to_fork);
     btc_regtest_controller.build_next_block(1);
     thread::sleep(Duration::from_secs(5));
 
-    // We invalidated a fork 210 long, and the new one is 207 blocks long.
-    // Let's dispatch the blocks one by one, instead of mining 210-207 blocks
+    // The test here consists in producing a canonical chain with 210 blocks. 
+    // Once done, we invalidate the block 208, and instead of rebuilding directly 
+    // a longer fork with N blocks (at done in the bitcoind_forking_test) 
+    // we slowly add some more blocks.
+    // Without the patch, this behavior ends up crashing the node with errors like:
+    // WARN [1626791307.078061] [src/chainstate/coordinator/mod.rs:535] [chains-coordinator] ChainsCoordinator: could not retrieve  block burnhash=40bdbf0dda349642bdf4dd30dd31af4f0c9979ce12a7c17485245d0a6ddd970b
+    // WARN [1626791307.078098] [src/chainstate/coordinator/mod.rs:308] [chains-coordinator] Error processing new burn block: NonContiguousBurnchainBlock(UnknownBlock(40bdbf0dda349642bdf4dd30dd31af4f0c9979ce12a7c17485245d0a6ddd970b))
+    // And the burnchain db end up in the same state we ended up while investing 2771.
+    // With this patch, the node is able to entirely register this new canonical fork, and then able to make some progress.
     while sort_height < 213 {
         next_block_and_wait(&mut btc_regtest_controller, &blocks_processed);
         sort_height = channel.get_sortitions_processed();