feat: add tenure_extend_buffer_secs miner config option

This allows the miner to specify a buffer (in seconds) that it should
wait after it has reached a time when it thinks 70% of signers should
approve a time-based tenure extend. The goal is to provide a little
buffer for clock skew, since we have seen, live on mainnet, cases where
<70% of signers approve a tenure-extend.

This is item 2 in #5757.

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to the versioning scheme outlined in the [README.md](RE
 ### Added
 
 - Add `vrf_seed` to the `/v3/sortitions` rpc endpoint
+- Add miner configuration option `tenure_extend_buffer_secs` to specify the number of seconds of buffer the miner should wait, after reaching the 70% threshold for tenure extension time, before issuing a tenure extension, to allow for clock skew between the miner and signers
 
 ### Changed
 

stackslib/src/config/mod.rs

@@ -121,6 +121,10 @@ const DEFAULT_TENURE_TIMEOUT_SECS: u64 = 180;
 /// Default percentage of block budget that must be used before attempting a
 /// time-based tenure extend
 const DEFAULT_TENURE_EXTEND_COST_THRESHOLD: u64 = 50;
+/// Default number of seconds to wait after reaching a time when 70% of signers
+/// would allow a time-based tenure extend before actually attempting to
+/// extend, to allow for clock skew.
+const DEFAULT_TENURE_EXTEND_BUFFER_SECS: u64 = 2;
 
 static HELIUM_DEFAULT_CONNECTION_OPTIONS: LazyLock<ConnectionOptions> =
     LazyLock::new(|| ConnectionOptions {
@@ -2169,6 +2173,8 @@ pub struct MinerConfig {
     pub tenure_timeout: Duration,
     /// Percentage of block budget that must be used before attempting a time-based tenure extend
     pub tenure_extend_cost_threshold: u64,
+    /// Duration defining a buffer period to wait before submitting a time-based tenure extend after reaching the 70% approval time
+    pub tenure_extend_buffer_secs: u64,
     /// Define the timeout to apply while waiting for signers responses, based on the amount of rejections
     pub block_rejection_timeout_steps: HashMap<u32, Duration>,
 }
@@ -2210,6 +2216,7 @@ impl Default for MinerConfig {
             tenure_extend_poll_secs: Duration::from_secs(DEFAULT_TENURE_EXTEND_POLL_SECS),
             tenure_timeout: Duration::from_secs(DEFAULT_TENURE_TIMEOUT_SECS),
             tenure_extend_cost_threshold: DEFAULT_TENURE_EXTEND_COST_THRESHOLD,
+            tenure_extend_buffer_secs: DEFAULT_TENURE_EXTEND_BUFFER_SECS,
 
             block_rejection_timeout_steps: {
                 let mut rejections_timeouts_default_map = HashMap::<u32, Duration>::new();
@@ -2616,6 +2623,7 @@ pub struct MinerConfigFile {
     pub tenure_extend_poll_secs: Option<u64>,
     pub tenure_timeout_secs: Option<u64>,
     pub tenure_extend_cost_threshold: Option<u64>,
+    pub tenure_extend_buffer_secs: Option<u64>,
     pub block_rejection_timeout_steps: Option<HashMap<String, u64>>,
 }
 
@@ -2760,6 +2768,7 @@ impl MinerConfigFile {
             tenure_extend_poll_secs: self.tenure_extend_poll_secs.map(Duration::from_secs).unwrap_or(miner_default_config.tenure_extend_poll_secs),
             tenure_timeout: self.tenure_timeout_secs.map(Duration::from_secs).unwrap_or(miner_default_config.tenure_timeout),
             tenure_extend_cost_threshold: self.tenure_extend_cost_threshold.unwrap_or(miner_default_config.tenure_extend_cost_threshold),
+            tenure_extend_buffer_secs: self.tenure_extend_buffer_secs.unwrap_or(miner_default_config.tenure_extend_buffer_secs),
 
             block_rejection_timeout_steps: {
                 if let Some(block_rejection_timeout_items) = self.block_rejection_timeout_steps {

testnet/stacks-node/src/nakamoto_node/miner.rs

@@ -1352,7 +1352,8 @@ impl BlockMinerThread {
                 });
             }
 
-            let tenure_extend_timestamp = coordinator.get_tenure_extend_timestamp();
+            let tenure_extend_timestamp = coordinator.get_tenure_extend_timestamp()
+                + self.config.miner.tenure_extend_buffer_secs;
             if get_epoch_time_secs() <= tenure_extend_timestamp
                 && self.tenure_change_time.elapsed() <= self.config.miner.tenure_timeout
             {

testnet/stacks-node/src/tests/signer/v0.rs

@@ -13500,3 +13500,55 @@ fn interrupt_miner_on_new_stacks_tip() {
     info!("------------------------- Shutdown -------------------------");
     signer_test.shutdown();
 }
+
+#[test]
+#[ignore]
+/// This test verifies that a miner will produce a TenureExtend transaction
+/// after the signers' idle timeout, plus buffer, is reached.
+fn tenure_extend_after_idle_signers_with_buffer() {
+    if env::var("BITCOIND_TEST") != Ok("1".into()) {
+        return;
+    }
+
+    tracing_subscriber::registry()
+        .with(fmt::layer())
+        .with(EnvFilter::from_default_env())
+        .init();
+
+    info!("------------------------- Test Setup -------------------------");
+    let num_signers = 5;
+    let idle_timeout = Duration::from_secs(1);
+    let buffer_secs = 20;
+    let mut signer_test: SignerTest<SpawnedSigner> = SignerTest::new_with_config_modifications(
+        num_signers,
+        vec![],
+        |config| {
+            config.tenure_idle_timeout = idle_timeout;
+        },
+        |config| {
+            config.miner.tenure_extend_cost_threshold = 0;
+            config.miner.tenure_extend_buffer_secs = buffer_secs;
+        },
+        None,
+        None,
+    );
+
+    signer_test.boot_to_epoch_3();
+
+    info!("---- Nakamoto booted, starting test ----");
+    signer_test.mine_nakamoto_block(Duration::from_secs(30), true);
+
+    info!("---- Waiting for a tenure extend ----");
+
+    // Now, wait for a block with a tenure extend
+    wait_for(idle_timeout.as_secs() + buffer_secs / 2, || {
+        Ok(last_block_contains_tenure_change_tx(
+            TenureChangeCause::Extended,
+        ))
+    })
+    .expect_err(
+        "Received a tenure extend before idle timeout plus buffer should have been reached",
+    );
+
+    signer_test.shutdown();
+}