feat: local prometheus sdk metrics

confidence-resolver/CLAUDE.md

@@ -38,7 +38,7 @@ The crate does NOT use `thiserror`. It has a custom error system:
 The build script compiles protos from `protos/`. Beyond standard prost generation:
 - When `json` feature is enabled, `pbjson-build` generates additional `.serde.rs` files for each module
 - Google well-known types are re-exported from `pbjson_types` (with `json`) or `prost_types` (without)
-- It also generates `telemetry_config.rs` by scanning proto annotations for histogram configs and emitting `HistogramConfig` trait impls
+- It also generates `telemetry_config.rs` with constants derived from proto descriptors (e.g. `REASON_COUNT` from the `ResolveReason` enum)
 
 ## Key Types
 

confidence-resolver/build.rs

@@ -3,7 +3,7 @@ use std::fmt::Write as _;
 use std::io::Result;
 use std::path::PathBuf;
 
-use prost_reflect::{DescriptorPool, Value};
+use prost_reflect::DescriptorPool;
 
 fn main() -> Result<()> {
     // Suppress all clippy lints in generated proto code
@@ -110,79 +110,14 @@ fn main() -> Result<()> {
     Ok(())
 }
 
-/// Scan proto descriptors for messages annotated with `(confidence.api.histogram)`
-/// and generate `HistogramConfig` trait impls for the corresponding prost types.
+/// Generate telemetry constants from proto descriptors.
 fn generate_telemetry_config(descriptor_path: &std::path::Path) -> Result<()> {
     let descriptor_bytes = std::fs::read(descriptor_path)?;
     let pool = DescriptorPool::decode(descriptor_bytes.as_ref())
         .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e))?;
 
-    let histogram_ext = pool
-        .get_extension_by_name("confidence.api.histogram")
-        .expect("confidence.api.histogram extension not found in descriptor pool");
-
     let mut code = String::new();
 
-    for msg in pool.all_messages() {
-        let opts = msg.options();
-        if !opts.has_extension(&histogram_ext) {
-            continue;
-        }
-        let val = opts.get_extension(&histogram_ext);
-
-        let histogram_msg = match val.as_ref() {
-            Value::Message(m) => m,
-            _ => continue,
-        };
-
-        let min_value = histogram_msg
-            .get_field_by_name("min_value")
-            .and_then(|v| v.as_i32())
-            .unwrap_or(0);
-        let max_value = histogram_msg
-            .get_field_by_name("max_value")
-            .and_then(|v| v.as_i32())
-            .unwrap_or(0);
-        let bucket_count = histogram_msg
-            .get_field_by_name("bucket_count")
-            .and_then(|v| v.as_i32())
-            .unwrap_or(0);
-        let unit = histogram_msg
-            .get_field_by_name("unit")
-            .and_then(|v| v.as_str().map(|s| s.to_owned()))
-            .unwrap_or_default();
-
-        assert!(
-            min_value > 0,
-            "histogram min_value must be positive, got {min_value} on {}",
-            msg.full_name()
-        );
-        assert!(
-            max_value > min_value,
-            "histogram max_value must be greater than min_value, got max={max_value} min={min_value} on {}",
-            msg.full_name()
-        );
-        assert!(
-            bucket_count >= 3,
-            "histogram bucket_count must be >= 3, got {bucket_count} on {}",
-            msg.full_name()
-        );
-
-        let rust_type = proto_name_to_rust_type(msg.full_name());
-
-        writeln!(
-            code,
-            "impl crate::telemetry::HistogramConfig for crate::proto::{rust_type} {{"
-        )
-        .unwrap();
-        writeln!(code, "    const MIN_VALUE: u32 = {min_value};").unwrap();
-        writeln!(code, "    const MAX_VALUE: u32 = {max_value};").unwrap();
-        writeln!(code, "    const BUCKET_COUNT: usize = {bucket_count};").unwrap();
-        writeln!(code, "    const UNIT: &'static str = \"{unit}\";").unwrap();
-        writeln!(code, "}}").unwrap();
-        writeln!(code).unwrap();
-    }
-
     // Generate REASON_COUNT from the ResolveReason enum
     let reason_enum = pool
         .get_enum_by_name("confidence.flags.resolver.v1.ResolveReason")
@@ -213,38 +148,3 @@ fn generate_telemetry_config(descriptor_path: &std::path::Path) -> Result<()> {
 
     Ok(())
 }
-
-/// Convert a fully-qualified proto name like
-/// `confidence.flags.resolver.v1.TelemetryData.ResolveLatency`
-/// into a Rust module path like
-/// `confidence::flags::resolver::v1::telemetry_data::ResolveLatency`.
-fn proto_name_to_rust_type(full_name: &str) -> String {
-    let parts: Vec<&str> = full_name.split('.').collect();
-    let mut result = String::new();
-    for (i, part) in parts.iter().enumerate() {
-        if i > 0 {
-            result.push_str("::");
-        }
-        // In prost, parent message names become snake_case modules,
-        // but the final type name stays PascalCase. We also need to handle
-        // package segments (all lowercase) vs message names (PascalCase).
-        if i < parts.len() - 1 && part.chars().next().is_some_and(|c| c.is_uppercase()) {
-            // This is a parent message name — prost generates a module for it in snake_case
-            result.push_str(&to_snake_case(part));
-        } else {
-            result.push_str(part);
-        }
-    }
-    result
-}
-
-fn to_snake_case(s: &str) -> String {
-    let mut result = String::new();
-    for (i, ch) in s.chars().enumerate() {
-        if ch.is_uppercase() && i > 0 {
-            result.push('_');
-        }
-        result.push(ch.to_ascii_lowercase());
-    }
-    result
-}

confidence-resolver/protos/confidence/api/annotations.proto

@@ -36,14 +36,3 @@ extend google.protobuf.FieldOptions {
   ValidationSpec validation = 4324223;
 }
 
-// Histogram configuration for metrics collection
-message HistogramSpec {
-  int32 min_value = 1;
-  int32 max_value = 2;
-  int32 bucket_count = 3;
-  string unit = 4;
-}
-
-extend google.protobuf.MessageOptions {
-  optional HistogramSpec histogram = 4399232;
-}

confidence-resolver/protos/confidence/flags/resolver/v1/internal_api.proto

@@ -129,13 +129,6 @@ message TelemetryData {
   string resolver_version = 8;
 
   message ResolveLatency {
-    option (confidence.api.histogram) = {
-      min_value: 1
-      max_value: 1000000
-      bucket_count: 100
-      unit: "microseconds"
-    };
-
     // Delta sum of observed values since the last flush.
     uint32 sum = 1;
     uint32 count = 2;