feat: write metrics (#25692)

Added prometheus metrics to track lines written and bytes written per
database. The write buffer does the tracking after validation of incoming
line protocol.

Tests added to verify.

influxdb3/src/commands/serve.rs

@@ -484,6 +484,7 @@ pub async fn command(config: Config) -> Result<()> {
         executor: Arc::clone(&exec),
         wal_config,
         parquet_cache,
+        metric_registry: Arc::clone(&metrics),
     })
     .await
     .map_err(|e| Error::WriteBufferInit(e.into()))?;

influxdb3_server/src/lib.rs

@@ -815,6 +815,7 @@ mod tests {
                 executor: Arc::clone(&exec),
                 wal_config: WalConfig::test_config(),
                 parquet_cache: Some(parquet_cache),
+                metric_registry: Arc::clone(&metrics),
             },
         )
         .await

influxdb3_server/src/query_executor.rs

@@ -700,6 +700,7 @@ mod tests {
                 snapshot_size: 1,
             },
             parquet_cache: Some(parquet_cache),
+            metric_registry: Default::default(),
         })
         .await
         .unwrap();

influxdb3_write/Cargo.toml

@@ -18,6 +18,7 @@ iox_catalog.workspace = true
 iox_http.workspace = true
 iox_query.workspace = true
 iox_time.workspace = true
+metric.workspace = true
 parquet_file.workspace = true
 observability_deps.workspace = true
 schema.workspace = true
@@ -71,7 +72,6 @@ optional = true
 # Core Crates
 arrow_util.workspace = true
 insta.workspace = true
-metric.workspace = true
 pretty_assertions.workspace = true
 test_helpers.workspace = true
 test-log.workspace = true

influxdb3_write/src/write_buffer/metrics.rs

@@ -0,0 +1,94 @@
+use std::borrow::Cow;
+
+use metric::{Metric, Registry, U64Counter};
+
+#[derive(Debug)]
+pub(super) struct WriteMetrics {
+    write_lines_total: Metric<U64Counter>,
+    write_bytes_total: Metric<U64Counter>,
+}
+
+pub(super) const WRITE_LINES_TOTAL_NAME: &str = "influxdb3_write_lines_total";
+pub(super) const WRITE_BYTES_TOTAL_NAME: &str = "influxdb3_write_bytes_total";
+
+impl WriteMetrics {
+    pub(super) fn new(metric_registry: &Registry) -> Self {
+        let write_lines_total = metric_registry.register_metric::<U64Counter>(
+            WRITE_LINES_TOTAL_NAME,
+            "track total number of lines written to the database",
+        );
+        let write_bytes_total = metric_registry.register_metric::<U64Counter>(
+            WRITE_BYTES_TOTAL_NAME,
+            "track total number of bytes written to the database",
+        );
+        Self {
+            write_lines_total,
+            write_bytes_total,
+        }
+    }
+
+    pub(super) fn record_lines<D: Into<String>>(&self, db: D, lines: u64) {
+        let db: Cow<'static, str> = Cow::from(db.into());
+        self.write_lines_total.recorder([("db", db)]).inc(lines);
+    }
+
+    pub(super) fn record_bytes<D: Into<String>>(&self, db: D, bytes: u64) {
+        let db: Cow<'static, str> = Cow::from(db.into());
+        self.write_bytes_total.recorder([("db", db)]).inc(bytes);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use metric::{Attributes, Registry};
+
+    use super::WriteMetrics;
+
+    #[test]
+    fn record_lines() {
+        let metric_registry = Registry::new();
+        let metrics = WriteMetrics::new(&metric_registry);
+        metrics.record_lines("foo", 64);
+        metrics.record_lines(String::from("bar"), 256);
+        assert_eq!(
+            64,
+            metrics
+                .write_lines_total
+                .get_observer(&Attributes::from(&[("db", "foo")]))
+                .unwrap()
+                .fetch()
+        );
+        assert_eq!(
+            256,
+            metrics
+                .write_lines_total
+                .get_observer(&Attributes::from(&[("db", "bar")]))
+                .unwrap()
+                .fetch()
+        );
+    }
+
+    #[test]
+    fn record_bytes() {
+        let metric_registry = Registry::new();
+        let metrics = WriteMetrics::new(&metric_registry);
+        metrics.record_bytes("foo", 64);
+        metrics.record_bytes(String::from("bar"), 256);
+        assert_eq!(
+            64,
+            metrics
+                .write_bytes_total
+                .get_observer(&Attributes::from(&[("db", "foo")]))
+                .unwrap()
+                .fetch()
+        );
+        assert_eq!(
+            256,
+            metrics
+                .write_bytes_total
+                .get_observer(&Attributes::from(&[("db", "bar")]))
+                .unwrap()
+                .fetch()
+        );
+    }
+}