Show using tracing layer filters in examples (open-telemetry#2667)

Author: cijothomas

Cargo.toml

@@ -23,7 +23,8 @@ tracing-opentelemetry = { version = "0.29", optional = true }
 log = { workspace = true }
 opentelemetry-stdout = { path = "../opentelemetry-stdout", features = ["logs"] }
 opentelemetry_sdk = { path = "../opentelemetry-sdk", features = ["logs", "testing"]  }
-tracing-subscriber = { workspace = true, features = ["registry", "std", "env-filter"] }
+tracing = { workspace = true, features = ["std"]}
+tracing-subscriber = { workspace = true, features = ["env-filter","registry", "std", "fmt"] }
 tracing-log = "0.2"
 criterion = { workspace = true }
 tokio = { workspace = true, features = ["full"]}

examples/basic.rs

@@ -3,7 +3,7 @@
 use opentelemetry_appender_tracing::layer;
 use opentelemetry_sdk::{logs::SdkLoggerProvider, Resource};
 use tracing::error;
-use tracing_subscriber::prelude::*;
+use tracing_subscriber::{prelude::*, EnvFilter};
 
 fn main() {
     let exporter = opentelemetry_stdout::LogExporter::default();
@@ -15,8 +15,37 @@ fn main() {
         )
         .with_simple_exporter(exporter)
         .build();
-    let layer = layer::OpenTelemetryTracingBridge::new(&provider);
-    tracing_subscriber::registry().with(layer).init();
+
+    // For the OpenTelemetry layer, add a tracing filter to filter events from
+    // OpenTelemetry and its dependent crates (opentelemetry-otlp uses crates
+    // like reqwest/tonic etc.) from being sent back to OTel itself, thus
+    // preventing infinite telemetry generation. The filter levels are set as
+    // follows:
+    // - Allow `info` level and above by default.
+    // - Restrict `opentelemetry`, `hyper`, `tonic`, and `reqwest` completely.
+    // Note: This will also drop events from crates like `tonic` etc. even when
+    // they are used outside the OTLP Exporter. For more details, see:
+    // https://github.com/open-telemetry/opentelemetry-rust/issues/761
+    let filter_otel = EnvFilter::new("info")
+        .add_directive("hyper=off".parse().unwrap())
+        .add_directive("opentelemetry=off".parse().unwrap())
+        .add_directive("tonic=off".parse().unwrap())
+        .add_directive("h2=off".parse().unwrap())
+        .add_directive("reqwest=off".parse().unwrap());
+    let otel_layer = layer::OpenTelemetryTracingBridge::new(&provider).with_filter(filter_otel);
+
+    // Create a new tracing::Fmt layer to print the logs to stdout. It has a
+    // default filter of `info` level and above, and `debug` and above for logs
+    // from OpenTelemetry crates. The filter levels can be customized as needed.
+    let filter_fmt = EnvFilter::new("info").add_directive("opentelemetry=debug".parse().unwrap());
+    let fmt_layer = tracing_subscriber::fmt::layer()
+        .with_thread_names(true)
+        .with_filter(filter_fmt);
+
+    tracing_subscriber::registry()
+        .with(otel_layer)
+        .with(fmt_layer)
+        .init();
 
     error!(name: "my-event-name", target: "my-system", event_id = 20, user_name = "otel", user_email = "[email protected]", message = "This is an example message");
     let _ = provider.shutdown();