Configure 'compute_ctl' to use OpenTelemetry exporter.

This allows tracing the startup actions e.g. with Jaeger
(https://www.jaegertracing.io/). We use the "tracing-opentelemetry"
crate, which turns tracing spans into OpenTelemetry spans, so you can
use the usual "#[instrument]" directives to add tracing.

I put the tracing initialization code to a separate crate,
`tracing-utils`, so that we can reuse it in other programs. We
probably want to set up tracing in the same way in all our programs.

Co-authored-by: Joonas Koivunen <joonas@neon.tech>

compute_tools/src/bin/compute_ctl.rs

@@ -53,7 +53,7 @@ use compute_tools::spec::*;
 use url::Url;
 
 fn main() -> Result<()> {
-    init_logger(DEFAULT_LOG_LEVEL)?;
+    init_tracing_and_logging(DEFAULT_LOG_LEVEL)?;
 
     let matches = cli().get_matches();
 
@@ -159,6 +159,10 @@ fn main() -> Result<()> {
         info!("shutting down");
     }
 
+    // Shutdown trace pipeline gracefully, so that it has a chance to send any
+    // pending traces before we exit.
+    tracing_utils::shutdown_tracing();
+
     exit(exit_code.unwrap_or(1))
 }
 

compute_tools/src/logger.rs

@@ -1,21 +1,37 @@
-use anyhow::Result;
+use tracing_opentelemetry::OpenTelemetryLayer;
 use tracing_subscriber::layer::SubscriberExt;
 use tracing_subscriber::prelude::*;
 
-/// Initialize `env_logger` using either `default_level` or
+/// Initialize logging to stderr, and OpenTelemetry tracing and exporter.
+///
+/// Logging is configured using either `default_log_level` or
 /// `RUST_LOG` environment variable as default log level.
-pub fn init_logger(default_level: &str) -> Result<()> {
+///
+/// OpenTelemetry is configured with OTLP/HTTP exporter. It picks up
+/// configuration from environment variables. For example, to change the destination,
+/// set `OTEL_EXPORTER_OTLP_ENDPOINT=http://jaeger:4318`. See
+/// `tracing-utils` package description.
+///
+pub fn init_tracing_and_logging(default_log_level: &str) -> anyhow::Result<()> {
+    // Initialize Logging
     let env_filter = tracing_subscriber::EnvFilter::try_from_default_env()
-        .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new(default_level));
+        .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new(default_log_level));
 
     let fmt_layer = tracing_subscriber::fmt::layer()
         .with_target(false)
         .with_writer(std::io::stderr);
 
+    // Initialize OpenTelemetry
+    let otlp_layer =
+        tracing_utils::init_tracing_without_runtime("compute_ctl").map(OpenTelemetryLayer::new);
+
+    // Put it all together
     tracing_subscriber::registry()
         .with(env_filter)
+        .with(otlp_layer)
         .with(fmt_layer)
         .init();
+    tracing::info!("logging and tracing started");
 
     Ok(())
 }