x:Metric: say which node wrote each sample

Each node stores histograms as running totals since it started. A sample
didn't say which node wrote it (the node was only in the id's low bits),
so a reader couldn't diff totals per node, and the console diffed across
nodes: on the three-node production cluster the delivery attempt time
read 14.7 s over the last hour against 0.7 s from the nodes' own figures.

x:Metric/get now returns nodeId alongside timestamp, both from the id.
The telemetry suite checks every sample carries it.

crates/common/src/telemetry/metrics/store.rs

@@ -104,6 +104,12 @@ impl StoredMetric {
     pub fn timestamp(&self) -> u64 {
         SnowflakeIdGenerator::to_timestamp(self.id)
     }
+
+    /// The node that wrote the sample. Histogram totals are per node, so a
+    /// reader diffs them per node.
+    pub fn node_id(&self) -> u64 {
+        SnowflakeIdGenerator::to_node_id(self.id)
+    }
 }
 
 /// What the node wrote last, so counters and histograms are written as

crates/jmap/src/inbuxa/telemetry.rs

@@ -6,7 +6,7 @@
 
 //! `x:Metric/get` and `/query` over the stored history (monitoring spec,
 //! "Interfaces"). Samples are server-level (MON-31) and read-only (MON-32).
-//! A sample's `timestamp` comes from its id.
+//! A sample's `timestamp` and `nodeId` come from its id.
 
 use crate::{
     api::query::QueryResponseBuilder,
@@ -54,12 +54,16 @@ fn metric_type(metric: &Metric) -> MetricType {
 
 fn to_value(sample: StoredMetric) -> JmapValue<'static> {
     let timestamp = sample.timestamp();
+    let node_id = sample.node_id();
     let mut value = sample.metric.into_value();
     if let JmapValue::Object(obj) = &mut value {
         obj.insert_unchecked(
             Property::Timestamp,
             JmapValue::Str(UTCDateTime::from_timestamp(timestamp as i64).to_string().into()),
         );
+        // Histograms are running totals per node; without this a reader
+        // diffs one node's total against another's
+        obj.insert_unchecked(Property::NodeId, JmapValue::Number(node_id.into()));
     }
     value
 }

crates/utils/src/snowflake.rs

@@ -108,6 +108,12 @@ impl SnowflakeIdGenerator {
         (id >> (SEQUENCE_LEN + NODE_ID_LEN)) / 1000 + DEFAULT_EPOCH
     }
 
+    // inbuxa: the node that made the id, so per-node history (metric
+    // totals) can be told apart
+    pub fn to_node_id(id: u64) -> u64 {
+        id & NODE_ID_MASK
+    }
+
     #[inline(always)]
     pub fn past_id(&self, period: Duration) -> Option<u64> {
         self.epoch.elapsed().ok().map(|elapsed| {