graph: Use slog::Level directly in log drain structs

- Replace level: String with level: Level in ElasticLog, FileLogDocument,
and LokiLogDocument
- Add shared serialize_log_level to common.rs that serializes Level
as lowercase
- Remove level_to_str() and level_str()

Author: fordN

graph/src/log/common.rs

@@ -1,6 +1,7 @@
 use std::collections::HashMap;
 use std::fmt;
 
+use serde::ser::Serializer as SerdeSerializer;
 use serde::Serialize;
 use slog::*;
 
@@ -105,16 +106,12 @@ pub struct LogMeta {
     pub column: i64,
 }
 
-/// Converts an slog Level to a string representation
-pub fn level_to_str(level: Level) -> &'static str {
-    match level {
-        Level::Critical => "critical",
-        Level::Error => "error",
-        Level::Warning => "warning",
-        Level::Info => "info",
-        Level::Debug => "debug",
-        Level::Trace => "trace",
-    }
+/// Serializes an slog Level as a lowercase string
+pub fn serialize_log_level<S>(level: &Level, serializer: S) -> std::result::Result<S::Ok, S::Error>
+where
+    S: SerdeSerializer,
+{
+    serializer.serialize_str(&level.as_str().to_ascii_lowercase())
 }
 
 /// Builder for common log entry fields across different drain implementations
@@ -205,9 +202,9 @@ impl<'a> LogEntryBuilder<'a> {
         }
     }
 
-    /// Gets the level as a string
-    pub fn level_str(&self) -> &'static str {
-        level_to_str(self.record.level())
+    /// Gets the log level
+    pub fn level(&self) -> Level {
+        self.record.level()
     }
 
     /// Gets the timestamp

graph/src/log/elastic.rs

@@ -9,7 +9,6 @@ use http::header::CONTENT_TYPE;
 use prometheus::Counter;
 use reqwest;
 use reqwest::Client;
-use serde::ser::Serializer as SerdeSerializer;
 use serde::Serialize;
 use serde_json::json;
 use slog::*;
@@ -31,14 +30,6 @@ pub struct ElasticLoggingConfig {
     pub client: Client,
 }
 
-/// Serializes an slog log level using a serde Serializer.
-fn serialize_log_level<S>(level: &str, serializer: S) -> Result<S::Ok, S::Error>
-where
-    S: SerdeSerializer,
-{
-    serializer.serialize_str(level)
-}
-
 type ElasticLogMeta = LogMeta;
 
 // Log message to be written to Elasticsearch.
@@ -51,8 +42,8 @@ struct ElasticLog {
     arguments: HashMap<String, String>,
     timestamp: String,
     text: String,
-    #[serde(serialize_with = "serialize_log_level")]
-    level: String,
+    #[serde(serialize_with = "super::common::serialize_log_level")]
+    level: Level,
     meta: ElasticLogMeta,
 }
 
@@ -260,7 +251,7 @@ impl Drain for ElasticDrain {
             arguments: builder.build_arguments_map(),
             timestamp,
             text: builder.build_text(),
-            level: builder.level_str().to_string(),
+            level: builder.level(),
             meta: builder.build_meta(),
         };
 

graph/src/log/file.rs

@@ -25,7 +25,8 @@ struct FileLogDocument {
     id: String,
     subgraph_id: String,
     timestamp: String,
-    level: String,
+    #[serde(serialize_with = "super::common::serialize_log_level")]
+    level: Level,
     text: String,
     arguments: Vec<(String, String)>,
     meta: FileLogMeta,
@@ -83,7 +84,7 @@ impl Drain for FileDrain {
             id: builder.build_id(),
             subgraph_id: builder.subgraph_id().to_string(),
             timestamp: builder.timestamp().to_string(),
-            level: builder.level_str().to_string(),
+            level: builder.level(),
             text: builder.build_text(),
             arguments: builder.build_arguments_vec(),
             meta: builder.build_meta(),
@@ -161,7 +162,7 @@ mod tests {
             id: "test-id".to_string(),
             subgraph_id: "QmTest".to_string(),
             timestamp: "2024-01-15T10:30:00Z".to_string(),
-            level: "error".to_string(),
+            level: Level::Error,
             text: "Test error message".to_string(),
             arguments,
             meta: FileLogMeta {

graph/src/log/loki.rs

@@ -34,7 +34,8 @@ struct LokiLogDocument {
     id: String,
     subgraph_id: String,
     timestamp: String,
-    level: String,
+    #[serde(serialize_with = "super::common::serialize_log_level")]
+    level: Level,
     text: String,
     arguments: HashMap<String, String>,
     meta: LokiLogMeta,
@@ -183,7 +184,7 @@ impl Drain for LokiDrain {
             id: builder.build_id(),
             subgraph_id: builder.subgraph_id().to_string(),
             timestamp,
-            level: builder.level_str().to_string(),
+            level: builder.level(),
             text: builder.build_text(),
             arguments: builder.build_arguments_map(),
             meta: builder.build_meta(),
@@ -201,7 +202,10 @@ impl Drain for LokiDrain {
         // Build labels for Loki stream
         let mut labels = HashMap::new();
         labels.insert("subgraphId".to_string(), builder.subgraph_id().to_string());
-        labels.insert("level".to_string(), builder.level_str().to_string());
+        labels.insert(
+            "level".to_string(),
+            builder.level().as_str().to_ascii_lowercase(),
+        );
 
         // Create log entry
         let entry = LokiLogEntry {
@@ -306,7 +310,7 @@ mod tests {
             id: "test-id".to_string(),
             subgraph_id: "QmTest".to_string(),
             timestamp: "2024-01-15T10:30:00Z".to_string(),
-            level: "error".to_string(),
+            level: Level::Error,
             text: "Test error".to_string(),
             arguments,
             meta: LokiLogMeta {