Round ingress_expiry to the minute

ic-agent/src/agent/builder.rs

@@ -83,6 +83,10 @@ impl AgentBuilder {
     /// Provides a _default_ ingress expiry. This is the delta that will be applied
     /// at the time an update or query is made. The default expiry cannot be a
     /// fixed system time.
+    ///
+    /// This duration may be rounded in order to reduce cache misses. The current
+    /// implementation rounds to the nearest minute if the expiry is more than a minute,
+    /// but this is not guaranteed.
     pub fn with_ingress_expiry(mut self, ingress_expiry: Option<std::time::Duration>) -> Self {
         self.config.ingress_expiry = ingress_expiry;
         self

ic-agent/src/agent/mod.rs

@@ -330,12 +330,21 @@ impl Agent {
     }
 
     fn get_expiry_date(&self) -> u64 {
-        // TODO(hansl): evaluate if we need this on the agent side (my hunch is we don't).
-        let permitted_drift = Duration::from_secs(60);
-        self.ingress_expiry
-            .as_nanos()
-            .saturating_add(OffsetDateTime::now_utc().unix_timestamp_nanos() as u128)
-            .saturating_sub(permitted_drift.as_nanos()) as u64
+        let expiry_raw = OffsetDateTime::now_utc() + self.ingress_expiry;
+        let rounded = if self.ingress_expiry.as_secs() > 60 {
+            let mut rounded_minute = expiry_raw
+                .replace_second(0)
+                .unwrap()
+                .replace_nanosecond(0)
+                .unwrap();
+            if expiry_raw.second() >= 30 {
+                rounded_minute += Duration::from_secs(60);
+            }
+            rounded_minute
+        } else {
+            expiry_raw.replace_nanosecond(0).unwrap()
+        };
+        rounded.unix_timestamp_nanos() as u64
     }
 
     /// Return the principal of the identity.
@@ -1275,3 +1284,31 @@ impl<'agent> UpdateBuilder<'agent> {
         })
     }
 }
+
+#[cfg(test)]
+mod offline_tests {
+    use super::*;
+    // Any tests that involve the network should go in agent_test, not here.
+
+    #[test]
+    fn rounded_expiry() {
+        let agent = Agent::builder()
+            .with_url("http://not-a-real-url")
+            .build()
+            .unwrap();
+        let mut prev_expiry = None;
+        let mut num_timestamps = 0;
+        for _ in 0..6 {
+            let update = agent
+                .update(&Principal::management_canister(), "not_a_method")
+                .sign()
+                .unwrap();
+            if prev_expiry < Some(update.ingress_expiry) {
+                prev_expiry = Some(update.ingress_expiry);
+                num_timestamps += 1;
+            }
+        }
+        // in six requests, there should be no more than two timestamps
+        assert!(num_timestamps <= 2, "num_timestamps:{num_timestamps} > 2");
+    }
+}