feature(bottlecap): add trace context extractor

bottlecap/Cargo.toml

@@ -18,12 +18,14 @@ datadog-trace-obfuscation = { version = "12.0.0", git = "https://github.com/Data
 dogstatsd = { git = "https://github.com/DataDog/libdatadog", branch = "main" }
 figment = { version = "0.10", default-features = false, features = ["yaml", "env"] }
 hyper = { version = "0.14", default-features = false, features = ["server"] }
+lazy_static = { version = "1.5", default-features = false }
 log = { version = "0.4", default-features = false }
 protobuf = { version = "3.5", default-features = false }
 regex = { version = "1.10", default-features = false }
 reqwest = { version = "0.12", features = ["json", "http2", "rustls-tls"], default-features = false }
 serde = { version = "1.0", default-features = false, features = ["derive"] }
 serde_json = { version = "1.0", default-features = false, features = ["alloc"] }
+thiserror = { version = "1.0", default-features = false}
 tokio = { version = "1.37", default-features = false, features = ["macros", "rt-multi-thread"] }
 tokio-util = { version = "0.7", default-features = false }
 tracing = { version = "0.1", default-features = false }

bottlecap/LICENSE-3rdparty.yml

@@ -17240,7 +17240,7 @@ third_party_libraries:
   - license: Apache-2.0
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 - package_name: thiserror
-  package_version: 1.0.63
+  package_version: 1.0.64
   repository: https://github.com/dtolnay/thiserror
   license: MIT OR Apache-2.0
   licenses:
@@ -17448,7 +17448,7 @@ third_party_libraries:
 
       END OF TERMS AND CONDITIONS
 - package_name: thiserror-impl
-  package_version: 1.0.63
+  package_version: 1.0.64
   repository: https://github.com/dtolnay/thiserror
   license: MIT OR Apache-2.0
   licenses:

bottlecap/src/traces/context.rs

@@ -0,0 +1,17 @@
+use std::collections::HashMap;
+
+#[derive(Copy, Clone, Default, Debug)]
+pub struct Sampling {
+    pub priority: Option<i8>,
+    pub mechanism: Option<u8>,
+}
+
+#[derive(Clone, Default, Debug)]
+#[allow(clippy::module_name_repetitions)]
+pub struct SpanContext {
+    pub trace_id: u64,
+    pub span_id: u64,
+    pub sampling: Option<Sampling>,
+    pub origin: Option<String>,
+    pub tags: HashMap<String, String>,
+}

bottlecap/src/traces/mod.rs

@@ -1,6 +1,8 @@
 // Copyright 2023-Present Datadog, Inc. https://www.datadoghq.com/
 // SPDX-License-Identifier: Apache-2.0
 
+pub mod context;
+pub mod propagation;
 pub mod stats_flusher;
 pub mod stats_processor;
 pub mod trace_agent;

bottlecap/src/traces/propagation/carrier.rs

@@ -0,0 +1,68 @@
+/// Code inspired, and copied, by OpenTelemetry Rust project.
+/// <https://github.com/open-telemetry/opentelemetry-rust/blob/main/opentelemetry/src/propagation/mod.rs>
+///
+use std::collections::HashMap;
+
+/// Injector provides an interface for a carrier to be used
+/// with a Propagator to inject a Context into the carrier.
+///
+pub trait Injector {
+    /// Set a value in the carrier.
+    fn set(&mut self, key: &str, value: String);
+}
+
+pub trait Extractor {
+    /// Get a value from the carrier.
+    fn get(&self, key: &str) -> Option<&str>;
+
+    /// Get all keys from the carrier.
+    fn keys(&self) -> Vec<&str>;
+}
+
+impl<S: std::hash::BuildHasher> Injector for HashMap<String, String, S> {
+    /// Set a key and value in the `HashMap`.
+    fn set(&mut self, key: &str, value: String) {
+        self.insert(key.to_lowercase(), value);
+    }
+}
+
+impl<S: std::hash::BuildHasher> Extractor for HashMap<String, String, S> {
+    /// Get a value for a key from the `HashMap`.
+    fn get(&self, key: &str) -> Option<&str> {
+        self.get(&key.to_lowercase()).map(String::as_str)
+    }
+
+    /// Collect all the keys from the `HashMap`.
+    fn keys(&self) -> Vec<&str> {
+        self.keys().map(String::as_str).collect::<Vec<_>>()
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn hash_map_get() {
+        let mut carrier = HashMap::new();
+        carrier.set("headerName", "value".to_string());
+
+        assert_eq!(
+            Extractor::get(&carrier, "HEADERNAME"),
+            Some("value"),
+            "case insensitive extraction"
+        );
+    }
+
+    #[test]
+    fn hash_map_keys() {
+        let mut carrier = HashMap::new();
+        carrier.set("headerName1", "value1".to_string());
+        carrier.set("headerName2", "value2".to_string());
+
+        let got = Extractor::keys(&carrier);
+        assert_eq!(got.len(), 2);
+        assert!(got.contains(&"headername1"));
+        assert!(got.contains(&"headername2"));
+    }
+}

bottlecap/src/traces/propagation/error.rs

@@ -0,0 +1,33 @@
+use thiserror::Error;
+
+#[derive(Error, Debug, Copy, Clone)]
+#[error("Cannot {} from {}, {}", operation, message, propagator_name)]
+pub struct Error {
+    message: &'static str,
+    // which propagator this error comes from
+    propagator_name: &'static str,
+    // what operation was attempted
+    operation: &'static str,
+}
+
+impl Error {
+    /// Error when extracting a value from a carrier
+    #[must_use]
+    pub fn extract(message: &'static str, propagator_name: &'static str) -> Self {
+        Self {
+            message,
+            propagator_name,
+            operation: "extract",
+        }
+    }
+
+    /// Error when injecting a value into a carrier
+    #[allow(clippy::must_use_candidate)]
+    pub fn inject(message: &'static str, propagator_name: &'static str) -> Self {
+        Self {
+            message,
+            propagator_name,
+            operation: "inject",
+        }
+    }
+}

bottlecap/src/traces/propagation/mod.rs

@@ -0,0 +1,3 @@
+pub mod carrier;
+pub mod error;
+pub mod text_map_propagator;