Instrument KV operation timing logs

crates/edgezero-core/src/key_value_store.rs

@@ -57,6 +57,7 @@
 use bytes::Bytes;
 use serde::de::DeserializeOwned;
 use serde::{Deserialize, Serialize};
+use web_time::Instant;
 
 use crate::error::EdgeError;
 
@@ -415,7 +416,12 @@
     #[inline]
     pub async fn delete(&self, key: &str) -> Result<(), KvError> {
         Self::validate_key(key)?;
-        self.store.delete(key).await
+        let started_at = Self::kv_timing_start();
+        let result = self.store.delete(key).await;
+        Self::kv_timing_log(started_at, "delete", &result, || {
+            format!("key_len={}", key.len())
+        });
+        result
     }
 
     fn encode_list_cursor(prefix: &str, cursor: Option<String>) -> Result<Option<String>, KvError> {
@@ -437,7 +443,12 @@
     #[inline]
     pub async fn exists(&self, key: &str) -> Result<bool, KvError> {
         Self::validate_key(key)?;
-        self.store.exists(key).await
+        let started_at = Self::kv_timing_start();
+        let result = self.store.exists(key).await;
+        Self::kv_timing_log(started_at, "exists", &result, || {
+            Self::kv_exists_metadata(key.len(), &result)
+        });
+        result
     }
 
     /// Get a value by key, deserializing from JSON.
@@ -449,7 +460,13 @@
     #[inline]
     pub async fn get<T: DeserializeOwned>(&self, key: &str) -> Result<Option<T>, KvError> {
         Self::validate_key(key)?;
-        match self.store.get_bytes(key).await? {
+        let started_at = Self::kv_timing_start();
+        let result = self.store.get_bytes(key).await;
+        Self::kv_timing_log(started_at, "get", &result, || {
+            Self::kv_read_metadata(key.len(), &result)
+        });
+
+        match result? {
             Some(bytes) => {
                 let val = serde_json::from_slice(&bytes)?;
                 Ok(Some(val))
@@ -465,7 +482,12 @@
     #[inline]
     pub async fn get_bytes(&self, key: &str) -> Result<Option<Bytes>, KvError> {
         Self::validate_key(key)?;
-        self.store.get_bytes(key).await
+        let started_at = Self::kv_timing_start();
+        let result = self.store.get_bytes(key).await;
+        Self::kv_timing_log(started_at, "get_bytes", &result, || {
+            Self::kv_read_metadata(key.len(), &result)
+        });
+        result
     }
 
     /// Get a value by key, returning `default` if the key does not exist.
@@ -477,6 +499,78 @@
         Ok(self.get(key).await?.unwrap_or(default))
     }
 
+    fn kv_exists_metadata(key_len: usize, result: &Result<bool, KvError>) -> String {
+        match result.as_ref() {
+            Ok(exists) => format!("key_len={key_len} exists={exists}"),
+            Err(_err) => format!("key_len={key_len}"),
+        }
+    }
+
+    fn kv_hit_metadata(result: &Result<Option<Bytes>, KvError>) -> String {
+        match result.as_ref() {
+            Ok(Some(bytes)) => format!("hit=true bytes={}", bytes.len()),
+            Ok(None) => "hit=false bytes=0".to_owned(),
+            Err(_err) => String::new(),
+        }
+    }
+
+    fn kv_list_metadata(
+        prefix_len: usize,
+        cursor_present: bool,
+        limit: usize,
+        result: &Result<KvPage, KvError>,
+    ) -> String {
+        match result.as_ref() {
+            Ok(page) => format!(
+                "prefix_len={prefix_len} cursor_present={cursor_present} limit={limit} count={} next_cursor_present={}",
+                page.keys.len(),
+                page.cursor.is_some()
+            ),
+            Err(_err) => {
+                format!("prefix_len={prefix_len} cursor_present={cursor_present} limit={limit}")
+            }
+        }
+    }
+
+    fn kv_read_metadata(key_len: usize, result: &Result<Option<Bytes>, KvError>) -> String {
+        match result {
+            Ok(_value) => format!("key_len={key_len} {}", Self::kv_hit_metadata(result)),
+            Err(_err) => format!("key_len={key_len}"),
+        }
+    }
+
+    fn kv_timing_log<ResultValue, Metadata>(
+        started_at: Option<Instant>,
+        operation: &str,
+        result: &Result<ResultValue, KvError>,
+        metadata: Metadata,
+    ) where
+        Metadata: FnOnce() -> String,
+    {
+        if let Some(started_at) = started_at {
+            let status = if result.is_ok() { "ok" } else { "error" };
+            log::debug!(
+                "kv operation={operation} elapsed_ms={} status={status} {}",
+                started_at.elapsed().as_millis(),
+                metadata()
+            );
+        }
+    }
+
+    fn kv_timing_start() -> Option<Instant> {
+        log::log_enabled!(log::Level::Debug).then(Instant::now)
+    }
+
+    fn kv_write_metadata(key_len: usize, bytes_len: usize, ttl: Option<Duration>) -> String {
+        match ttl {
+            Some(ttl) => format!(
+                "key_len={key_len} bytes={bytes_len} ttl_secs={}",
+                ttl.as_secs()
+            ),
+            None => format!("key_len={key_len} bytes={bytes_len}"),
+        }
+    }
+
     /// List keys in a bounded, paginated fashion.
     ///
     /// The cursor is opaque, prefix-bound, and should be passed back unchanged
@@ -496,10 +590,15 @@
         Self::validate_prefix(prefix)?;
         Self::validate_list_limit(limit)?;
         let decoded_cursor = Self::decode_list_cursor(prefix, cursor)?;
-        let page = self
+        let started_at = Self::kv_timing_start();
+        let result = self
             .store
             .list_keys_page(prefix, decoded_cursor.as_deref(), limit)
-            .await?;
+            .await;
+        Self::kv_timing_log(started_at, "list_keys_page", &result, || {
+            Self::kv_list_metadata(prefix.len(), cursor.is_some(), limit, &result)
+        });
+        let page = result?;
 
         Ok(KvPage {
             cursor: Self::encode_list_cursor(prefix, page.cursor)?,
@@ -522,7 +621,13 @@
         Self::validate_key(key)?;
         let bytes = serde_json::to_vec(value)?;
         Self::validate_value(&bytes)?;
-        self.store.put_bytes(key, Bytes::from(bytes)).await
+        let bytes_len = bytes.len();
+        let started_at = Self::kv_timing_start();
+        let result = self.store.put_bytes(key, Bytes::from(bytes)).await;
+        Self::kv_timing_log(started_at, "put", &result, || {
+            Self::kv_write_metadata(key.len(), bytes_len, None)
+        });
+        result
     }
 
     /// Put raw bytes for a key.
@@ -533,7 +638,13 @@
     pub async fn put_bytes(&self, key: &str, value: Bytes) -> Result<(), KvError> {
         Self::validate_key(key)?;
         Self::validate_value(&value)?;
-        self.store.put_bytes(key, value).await
+        let bytes_len = value.len();
+        let started_at = Self::kv_timing_start();
+        let result = self.store.put_bytes(key, value).await;
+        Self::kv_timing_log(started_at, "put_bytes", &result, || {
+            Self::kv_write_metadata(key.len(), bytes_len, None)
+        });
+        result
     }
 
     /// Put raw bytes with a TTL.
@@ -550,7 +661,13 @@
         Self::validate_key(key)?;
         Self::validate_ttl(ttl)?;
         Self::validate_value(&value)?;
-        self.store.put_bytes_with_ttl(key, value, ttl).await
+        let bytes_len = value.len();
+        let started_at = Self::kv_timing_start();
+        let result = self.store.put_bytes_with_ttl(key, value, ttl).await;
+        Self::kv_timing_log(started_at, "put_bytes_with_ttl", &result, || {
+            Self::kv_write_metadata(key.len(), bytes_len, Some(ttl))
+        });
+        result
     }
 
     /// Put a value with a TTL, serializing it to JSON.
@@ -568,9 +685,16 @@
         Self::validate_ttl(ttl)?;
         let bytes = serde_json::to_vec(value)?;
         Self::validate_value(&bytes)?;
-        self.store
+        let bytes_len = bytes.len();
+        let started_at = Self::kv_timing_start();
+        let result = self
+            .store
             .put_bytes_with_ttl(key, Bytes::from(bytes), ttl)
-            .await
+            .await;
+        Self::kv_timing_log(started_at, "put_with_ttl", &result, || {
+            Self::kv_write_metadata(key.len(), bytes_len, Some(ttl))
+        });
+        result
     }
 
     /// Read-modify-write: get the current value (or `default`),
@@ -995,6 +1119,24 @@
         });
     }
 
+    #[test]
+    fn error_metadata_omits_unknown_result_fields() {
+        let read_result = Err(KvError::Unavailable);
+        assert_eq!(KvHandle::kv_read_metadata(18, &read_result), "key_len=18");
+
+        let exists_result = Err(KvError::Unavailable);
+        assert_eq!(
+            KvHandle::kv_exists_metadata(18, &exists_result),
+            "key_len=18"
+        );
+
+        let list_result = Err(KvError::Unavailable);
+        assert_eq!(
+            KvHandle::kv_list_metadata(4, true, 100, &list_result),
+            "prefix_len=4 cursor_present=true limit=100"
+        );
+    }
+
     #[test]
     fn exists_returns_false_after_delete() {
         let kv = handle();
@@ -1204,6 +1346,43 @@
         });
     }
 
+    #[test]
+    fn read_metadata_logs_lengths_not_raw_key_or_value() {
+        let key = "super-secret-token";
+        let value = Bytes::from_static(b"super-secret-value");
+        let result = Ok(Some(value));
+
+        let metadata = KvHandle::kv_read_metadata(key.len(), &result);
+
+        assert_eq!(metadata, "key_len=18 hit=true bytes=18");
+        assert!(!metadata.contains(key));
+        assert!(!metadata.contains("super-secret-value"));
+    }
+
+    #[test]
+    fn success_metadata_keeps_stable_field_types() {
+        let read_result = Ok(Some(Bytes::from_static(b"abc")));
+        assert_eq!(
+            KvHandle::kv_read_metadata(1, &read_result),
+            "key_len=1 hit=true bytes=3"
+        );
+
+        let exists_result = Ok(false);
+        assert_eq!(
+            KvHandle::kv_exists_metadata(1, &exists_result),
+            "key_len=1 exists=false"
+        );
+
+        let list_result = Ok(KvPage {
+            cursor: Some("cursor".to_owned()),
+            keys: vec!["a".to_owned(), "b".to_owned()],
+        });
+        assert_eq!(
+            KvHandle::kv_list_metadata(4, false, 100, &list_result),
+            "prefix_len=4 cursor_present=false limit=100 count=2 next_cursor_present=true"
+        );
+    }
+
     #[test]
     fn typed_get_bad_json_returns_serialization_error() {
         let kv = handle();

docs/guide/kv.md

@@ -109,6 +109,12 @@ For strict correctness, use a transactional data store.
 
 Key listing is paginated by design. This avoids buffering an unbounded number of keys in memory and matches the underlying provider APIs. The Spin adapter materialises `Store::get_keys()` and pages client-side; a `max_list_keys` cap (configurable via `EDGEZERO__STORES__KV__<ID>__MAX_LIST_KEYS`, default `1000`) guards against runaway lists and yields `KvError::LimitExceeded` when exceeded.
 
+## Operation Timing / Observability
+
+`KvHandle` emits debug-level timing logs for backend KV operations across all adapters. Logs include safe metadata such as operation name, elapsed milliseconds, success/error status, key or prefix length, hit/miss, byte counts, TTL seconds, and list page counts.
+
+Timing logs are limited to derived metadata such as lengths, counts, booleans, and TTLs rather than raw keys, prefixes, cursors, or values. On Cloudflare Workers, `elapsed_ms` should be treated as approximate because the runtime uses a reduced-resolution monotonic clock. Typed helper timings measure only the backend call after validation/serialization and before JSON deserialization. `read_modify_write` performs separate read and write calls, so it emits separate operation logs.
+
 ## Platform Specifics
 
 ### Local Development