feat(logging): Emit a setup error when a restricted keys are used for logging default keys (#5185)

Co-authored-by: hyperswitch-bot[bot] <148525504+hyperswitch-bot[bot]@users.noreply.github.com>

crates/router_env/src/logger/formatter.rs

@@ -8,6 +8,7 @@ use std::{
     io::Write,
 };
 
+use config::ConfigError;
 use once_cell::sync::Lazy;
 use serde::ser::{SerializeMap, Serializer};
 use serde_json::{ser::Formatter, Value};
@@ -155,7 +156,11 @@ where
     /// let formatting_layer = router_env::FormattingLayer::new("my_service", std::io::stdout, serde_json::ser::CompactFormatter);
     /// ```
     ///
-    pub fn new(service: &str, dst_writer: W, formatter: F) -> Self {
+    pub fn new(
+        service: &str,
+        dst_writer: W,
+        formatter: F,
+    ) -> error_stack::Result<Self, ConfigError> {
         Self::new_with_implicit_entries(service, dst_writer, HashMap::new(), formatter)
     }
 
@@ -163,9 +168,9 @@ where
     pub fn new_with_implicit_entries(
         service: &str,
         dst_writer: W,
-        mut default_fields: HashMap<String, Value>,
+        default_fields: HashMap<String, Value>,
         formatter: F,
-    ) -> Self {
+    ) -> error_stack::Result<Self, ConfigError> {
         let pid = std::process::id();
         let hostname = gethostname::gethostname().to_string_lossy().into_owned();
         let service = service.to_string();
@@ -174,20 +179,16 @@ where
         #[cfg(feature = "vergen")]
         let build = crate::build!().to_string();
         let env = crate::env::which().to_string();
-        default_fields.retain(|key, value| {
-            if !IMPLICIT_KEYS.contains(key.as_str()) {
-                true
-            } else {
-                tracing::warn!(
-                    ?key,
-                    ?value,
-                    "Attempting to log a reserved entry. It won't be added to the logs"
-                );
-                false
+        for key in default_fields.keys() {
+            if IMPLICIT_KEYS.contains(key.as_str()) {
+                return Err(ConfigError::Message(format!(
+                    "A reserved key `{key}` was included in `default_fields` in the log formatting layer"
+                ))
+                .into());
             }
-        });
+        }
 
-        Self {
+        Ok(Self {
             dst_writer,
             pid,
             hostname,
@@ -199,7 +200,7 @@ where
             build,
             default_fields,
             formatter,
-        }
+        })
     }
 
     /// Serialize common for both span and event entries.

crates/router_env/src/logger/setup.rs

@@ -2,6 +2,7 @@
 
 use std::time::Duration;
 
+use ::config::ConfigError;
 use opentelemetry::{
     global, runtime,
     sdk::{
@@ -36,7 +37,7 @@ pub fn setup(
     config: &config::Log,
     service_name: &str,
     crates_to_filter: impl AsRef<[&'static str]>,
-) -> TelemetryGuard {
+) -> error_stack::Result<TelemetryGuard, ConfigError> {
     let mut guards = Vec::new();
 
     // Setup OpenTelemetry traces and metrics
@@ -69,11 +70,9 @@ pub fn setup(
             &crates_to_filter,
         );
         println!("Using file logging filter: {file_filter}");
-
-        Some(
-            FormattingLayer::new(service_name, file_writer, CompactFormatter)
-                .with_filter(file_filter),
-        )
+        let layer = FormattingLayer::new(service_name, file_writer, CompactFormatter)?
+            .with_filter(file_filter);
+        Some(layer)
     } else {
         None
     };
@@ -107,17 +106,21 @@ pub fn setup(
             }
             config::LogFormat::Json => {
                 error_stack::Report::set_color_mode(error_stack::fmt::ColorMode::None);
-                let logging_layer =
-                    FormattingLayer::new(service_name, console_writer, CompactFormatter)
-                        .with_filter(console_filter);
-                subscriber.with(logging_layer).init();
+                subscriber
+                    .with(
+                        FormattingLayer::new(service_name, console_writer, CompactFormatter)?
+                            .with_filter(console_filter),
+                    )
+                    .init();
             }
             config::LogFormat::PrettyJson => {
                 error_stack::Report::set_color_mode(error_stack::fmt::ColorMode::None);
-                let logging_layer =
-                    FormattingLayer::new(service_name, console_writer, PrettyFormatter::new())
-                        .with_filter(console_filter);
-                subscriber.with(logging_layer).init();
+                subscriber
+                    .with(
+                        FormattingLayer::new(service_name, console_writer, PrettyFormatter::new())?
+                            .with_filter(console_filter),
+                    )
+                    .init();
             }
         }
     } else {
@@ -126,10 +129,10 @@ pub fn setup(
 
     // Returning the TelemetryGuard for logs to be printed and metrics to be collected until it is
     // dropped
-    TelemetryGuard {
+    Ok(TelemetryGuard {
         _log_guards: guards,
         _metrics_controller,
-    }
+    })
 }
 
 fn get_opentelemetry_exporter(config: &config::LogTelemetry) -> TonicExporterBuilder {