[DRAFT - DO NOT MERGE] Basic OpenTelemetry integration

dropshot/Cargo.toml

@@ -43,11 +43,21 @@ slog-async = "2.8.0"
 slog-bunyan = "2.5.0"
 slog-json = "2.6.1"
 slog-term = "2.9.1"
+tracing = { version = "0.1.40", optional = true }
+tracing-subscriber = { version = "0.3.18", features = ["env-filter"], optional = true }
 thiserror = "2.0.12"
 tokio-rustls = "0.25.0"
 toml = "0.8.23"
 waitgroup = "0.1.2"
 
+opentelemetry = { version = "0.30", optional = true }
+opentelemetry-http = { version = "0.30", features = ["hyper"], optional = true }
+opentelemetry-semantic-conventions = { version = "0.30", optional = true }
+opentelemetry-otlp = { version = "0.30", features = ["tonic"], optional = true }
+opentelemetry_sdk = { version = "0.30", features = ["rt-tokio"], optional = true }
+opentelemetry-stdout = { version = "0.30", optional = true }
+tracing-opentelemetry = { version = "0.31", optional = true }
+
 [dependencies.chrono]
 version = "0.4.41"
 features = [ "serde", "std", "clock" ]
@@ -136,6 +146,8 @@ version_check = "0.9.5"
 [features]
 usdt-probes = ["usdt/asm"]
 internal-docs = ["simple-mermaid"]
+tracing = ["dep:tracing", "dep:tracing-subscriber"]
+otel-tracing = ["tracing", "opentelemetry", "opentelemetry-http", "opentelemetry-semantic-conventions", "opentelemetry-otlp", "opentelemetry_sdk", "opentelemetry-stdout", "tracing-opentelemetry"]
 
 [package.metadata.docs.rs]
 features = ["internal-docs"]

dropshot/examples/otel.rs

@@ -0,0 +1,316 @@
+// Copyright 2025 Oxide Computer Company
+//! Example use of Dropshot with OpenTelemetry integration.
+//!
+//! Dropshot's built-in OpenTelemetry support will automatically parse
+//! standard OTEL environment variables.
+//! If you launch an otel-collector or otel-enabled jaeger-all-in-one
+//! listening for otlp over http, then you can do:
+//!
+//! ```bash
+//! export OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318
+//! export OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf
+//! cargo run --features=otel-tracing --example otel&
+//! curl http://localhost:4000/get
+//! ```
+//!
+//! And you should see an example trace.
+
+use dropshot::endpoint;
+use dropshot::ApiDescription;
+use dropshot::ConfigDropshot;
+use dropshot::ConfigLogging;
+use dropshot::ConfigLoggingLevel;
+use dropshot::HttpError;
+use dropshot::HttpResponseOk;
+use dropshot::HttpResponseUpdatedNoContent;
+use dropshot::HttpServerStarter;
+use dropshot::RequestContext;
+use dropshot::TypedBody;
+use schemars::JsonSchema;
+use serde::Deserialize;
+use serde::Serialize;
+use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
+#[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+use tracing;
+
+#[tokio::main]
+async fn main() -> Result<(), String> {
+    let config_dropshot = ConfigDropshot {
+        bind_address: "127.0.0.1:4000".parse().unwrap(),
+        ..Default::default()
+    };
+
+    // For simplicity, we'll configure an "info"-level logger that writes to
+    // stderr assuming that it's a terminal.
+    let config_logging =
+        ConfigLogging::StderrTerminal { level: ConfigLoggingLevel::Info };
+    let log = config_logging
+        .to_logger("example-basic")
+        .map_err(|error| format!("failed to create logger: {}", error))?;
+
+    // Initialize tracing with both slog bridge and OpenTelemetry support
+    #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+    let _tracing_guard = dropshot::tracing_support::init_tracing(&log)
+        .await
+        .map_err(|e| format!("failed to initialize tracing: {}", e))?;
+
+    // Build a description of the API.
+    let mut api = ApiDescription::new();
+    api.register(example_api_get_counter).unwrap();
+    api.register(example_api_put_counter).unwrap();
+    api.register(example_api_get).unwrap();
+    api.register(example_api_error).unwrap();
+    api.register(example_api_panic).unwrap();
+    api.register(example_api_sleep).unwrap();
+    api.register(example_api_exit).unwrap();
+
+    // The functions that implement our API endpoints will share this context.
+    let api_context = ExampleContext::new();
+
+    // Set up the server.
+    let server =
+        HttpServerStarter::new(&config_dropshot, api, api_context, &log)
+            .map_err(|error| format!("failed to create server: {}", error))?
+            .start();
+
+    let shutdown = server.wait_for_shutdown();
+
+    tokio::task::spawn(async move {
+        loop {
+            if server.app_private().shutdown.load(Ordering::SeqCst) {
+                break;
+            } else {
+                tokio::time::sleep(tokio::time::Duration::from_secs(1)).await;
+            }
+        }
+        server.close().await.unwrap();
+    });
+
+    // From a separate task, wait for the server to stop.
+    shutdown.await
+}
+
+/// Application-specific example context (state shared by handler functions)
+#[derive(Debug)]
+struct ExampleContext {
+    /// counter that can be manipulated by requests to the HTTP API
+    counter: AtomicU64,
+    shutdown: AtomicBool,
+}
+
+impl ExampleContext {
+    /// Return a new ExampleContext.
+    pub fn new() -> ExampleContext {
+        ExampleContext {
+            counter: AtomicU64::new(0),
+            shutdown: AtomicBool::new(false),
+        }
+    }
+}
+
+// HTTP API interface
+
+/// `CounterValue` represents the value of the API's counter, either as the
+/// response to a GET request to fetch the counter or as the body of a PUT
+/// request to update the counter.
+#[derive(Debug, Deserialize, Serialize, JsonSchema)]
+struct CounterValue {
+    counter: u64,
+}
+
+/// Demonstrates creating child spans for internal operations using tracing instrumentation
+#[endpoint {
+    method = GET,
+    path = "/get",
+}]
+#[cfg_attr(
+any(feature = "tracing", feature = "otel-tracing"),
+tracing::instrument(skip(rqctx), fields(counter_processing = tracing::field::Empty)))]
+async fn example_api_get(
+    rqctx: RequestContext<ExampleContext>,
+) -> Result<HttpResponseOk<CounterValue>, HttpError> {
+    #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+    tracing::info!("Starting counter fetch with processing");
+
+    // Simulate some work
+    fetch_counter_with_delay().await;
+
+    let api_context = rqctx.context();
+    let counter_value = api_context.counter.load(Ordering::SeqCst);
+
+    // Do some "processing" that would benefit from being traced
+    let processed_value = process_counter_value(counter_value).await;
+
+    // Record the processing result in the span
+    #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+    tracing::Span::current().record("counter_processing", processed_value);
+
+    #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+    tracing::info!(
+        processed_value = processed_value,
+        "Counter processing completed"
+    );
+
+    Ok(HttpResponseOk(CounterValue { counter: processed_value }))
+}
+
+#[cfg_attr(
+    any(feature = "tracing", feature = "otel-tracing"),
+    tracing::instrument
+)]
+async fn fetch_counter_with_delay() {
+    #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+    tracing::debug!("Simulating work");
+    tokio::time::sleep(std::time::Duration::from_millis(10)).await;
+}
+
+#[cfg_attr(
+    any(feature = "tracing", feature = "otel-tracing"),
+    tracing::instrument
+)]
+async fn process_counter_value(counter_value: u64) -> u64 {
+    #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+    tracing::debug!(input_value = counter_value, "Processing counter value");
+    tokio::time::sleep(std::time::Duration::from_millis(5)).await;
+    let result = counter_value * 2; // Some arbitrary processing
+    #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+    tracing::debug!(output_value = result, "Counter processing complete");
+    result
+}
+
+/// Fetch the current value of the counter.
+#[endpoint {
+    method = GET,
+    path = "/counter",
+}]
+#[cfg_attr(
+    any(feature = "tracing", feature = "otel-tracing"),
+    tracing::instrument(skip(rqctx))
+)]
+async fn example_api_get_counter(
+    rqctx: RequestContext<ExampleContext>,
+) -> Result<HttpResponseOk<CounterValue>, HttpError> {
+    let api_context = rqctx.context();
+    let counter = api_context.counter.load(Ordering::SeqCst);
+
+    #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+    tracing::info!(counter_value = counter, "Retrieved counter value");
+
+    Ok(HttpResponseOk(CounterValue { counter }))
+}
+
+/// Demonstrates error tracing - errors will be marked on the span
+#[endpoint {
+    method = GET,
+    path = "/error",
+}]
+#[cfg_attr(
+    any(feature = "tracing", feature = "otel-tracing"),
+    tracing::instrument(skip(_rqctx))
+)]
+async fn example_api_error(
+    _rqctx: RequestContext<ExampleContext>,
+) -> Result<HttpResponseOk<CounterValue>, HttpError> {
+    #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+    tracing::warn!("About to return an error for demonstration");
+    let error =
+        HttpError::for_internal_error("This endpoint is broken".to_string());
+    #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+    tracing::error!(error = ?error, "Returning demonstration error");
+    Err(error)
+}
+
+/// Demonstrates panic handling - panics are converted to 500 errors and traced
+#[endpoint {
+    method = GET,
+    path = "/panic",
+}]
+#[cfg_attr(
+    any(feature = "tracing", feature = "otel-tracing"),
+    tracing::instrument(skip(_rqctx))
+)]
+async fn example_api_panic(
+    _rqctx: RequestContext<ExampleContext>,
+) -> Result<HttpResponseOk<CounterValue>, HttpError> {
+    panic!("This handler panics to demonstrate error tracing");
+}
+
+/// Takes too long so the client disconnects
+#[endpoint {
+    method = GET,
+    path = "/sleep",
+}]
+#[cfg_attr(
+    any(feature = "tracing", feature = "otel-tracing"),
+    tracing::instrument(skip(_rqctx))
+)]
+async fn example_api_sleep(
+    _rqctx: RequestContext<ExampleContext>,
+) -> Result<HttpResponseOk<CounterValue>, HttpError> {
+    tokio::time::sleep(tokio::time::Duration::from_secs(2)).await;
+    Err(HttpError::for_internal_error(
+        "This endpoint takes too long".to_string(),
+    ))
+}
+
+/// Exit shortcut
+#[endpoint {
+    method = GET,
+    path = "/exit",
+}]
+#[cfg_attr(
+    any(feature = "tracing", feature = "otel-tracing"),
+    tracing::instrument(skip(rqctx))
+)]
+async fn example_api_exit(
+    rqctx: RequestContext<ExampleContext>,
+) -> Result<HttpResponseUpdatedNoContent, HttpError> {
+    rqctx.context().shutdown.store(true, Ordering::SeqCst);
+    Ok(HttpResponseUpdatedNoContent())
+}
+
+/// Update the current value of the counter.  Note that the special value of 10
+/// is not allowed (just to demonstrate how to generate an error).
+#[endpoint {
+    method = PUT,
+    path = "/counter",
+}]
+#[cfg_attr(
+any(feature = "tracing", feature = "otel-tracing"),
+tracing::instrument(skip(rqctx, update), fields(new_value = tracing::field::Empty)))]
+async fn example_api_put_counter(
+    rqctx: RequestContext<ExampleContext>,
+    update: TypedBody<CounterValue>,
+) -> Result<HttpResponseUpdatedNoContent, HttpError> {
+    let api_context = rqctx.context();
+    let updated_value = update.into_inner();
+
+    // Record the new value in the span
+    #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+    tracing::Span::current().record("new_value", updated_value.counter);
+    #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+    tracing::info!(
+        new_counter_value = updated_value.counter,
+        "Updating counter"
+    );
+
+    if updated_value.counter == 10 {
+        #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+        tracing::warn!(
+            rejected_value = updated_value.counter,
+            "Rejecting forbidden value"
+        );
+        Err(HttpError::for_bad_request(
+            Some(String::from("BadInput")),
+            format!("do not like the number {}", updated_value.counter),
+        ))
+    } else {
+        api_context.counter.store(updated_value.counter, Ordering::SeqCst);
+        #[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+        tracing::info!(
+            updated_counter = updated_value.counter,
+            "Counter updated successfully"
+        );
+        Ok(HttpResponseUpdatedNoContent())
+    }
+}

dropshot/src/handler.rs

@@ -287,6 +287,7 @@ where
 /// This type is not exported to Dropshot consumers; it is purely an internal
 /// implementation detail of the interface between `HttpHandlerFunc` and the
 /// server.
+#[derive(Debug)]
 pub enum HandlerError {
     /// An error returned by a fallible handler function itself.
     ///

dropshot/src/lib.rs

@@ -852,11 +852,15 @@ mod from_map;
 mod handler;
 mod http_util;
 mod logging;
+#[cfg(feature = "otel-tracing")]
+pub mod otel;
 mod pagination;
 mod router;
 mod schema_util;
 mod server;
 mod to_map;
+#[cfg(any(feature = "tracing", feature = "otel-tracing"))]
+pub mod tracing_support;
 mod type_util;
 mod versioning;
 mod websocket;