Add logs pipeline example (#110)

The example shows how to add a custom log processor before the exporter,
which enriches the log record with attributes. In this case, it adds
exception attributes for error logs, so the exporter exports them as
exceptions to app insights.

Author: frigus02

Cargo.toml

@@ -106,6 +106,10 @@ required-features = ["live-metrics", "opentelemetry_sdk/rt-tokio", "opentelemetr
 name = "logs"
 required-features = ["logs", "opentelemetry-http/reqwest"]
 
+[[example]]
+name = "logs_pipeline"
+required-features = ["logs", "opentelemetry-http/reqwest"]
+
 [[example]]
 name = "metrics"
 required-features = ["metrics", "opentelemetry_sdk/rt-tokio"]

examples/logs_pipeline.rs

@@ -0,0 +1,66 @@
+use opentelemetry::logs::LogRecord;
+use opentelemetry_semantic_conventions as semcov;
+use std::error::Error;
+
+#[derive(Debug)]
+struct ErrorAsExceptionLogProcessor;
+
+impl opentelemetry_sdk::logs::LogProcessor for ErrorAsExceptionLogProcessor {
+    fn emit(
+        &self,
+        data: &mut opentelemetry_sdk::logs::SdkLogRecord,
+        _instrumentation: &opentelemetry::InstrumentationScope,
+    ) {
+        if let Some(severity) = data.severity_number() {
+            if severity >= opentelemetry::logs::Severity::Error {
+                // TODO: Check if exception attributes are already present
+                data.add_attribute(semcov::attribute::EXCEPTION_TYPE, "error");
+                if let Some(body) = data.body() {
+                    data.add_attribute(
+                        semcov::attribute::EXCEPTION_MESSAGE,
+                        any_value_to_string(body),
+                    );
+                }
+            }
+        }
+    }
+
+    fn force_flush(&self) -> opentelemetry_sdk::error::OTelSdkResult {
+        Ok(())
+    }
+}
+
+fn any_value_to_string(v: &opentelemetry::logs::AnyValue) -> String {
+    match v {
+        opentelemetry::logs::AnyValue::String(v) => v.to_string(),
+        _ => format!("{:?}", v).into(),
+    }
+}
+
+fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
+    let client = reqwest::blocking::Client::new();
+
+    let exporter = opentelemetry_application_insights::Exporter::new_from_env(client)?;
+
+    let logger_provider = opentelemetry_sdk::logs::SdkLoggerProvider::builder()
+        .with_log_processor(ErrorAsExceptionLogProcessor)
+        .with_batch_exporter(exporter)
+        .build();
+    let otel_log_appender =
+        opentelemetry_appender_log::OpenTelemetryLogBridge::new(&logger_provider);
+    log::set_boxed_logger(Box::new(otel_log_appender))?;
+    log::set_max_level(log::Level::Info.to_level_filter());
+
+    // Log via `log` crate.
+    let fruit = "apple";
+    let price = 2.99;
+    let colors = ("red", "green");
+    log::info!(fruit, price, colors:sval; "info! {fruit} is {price}");
+    log::warn!("warn!");
+    log::error!("error!");
+
+    // Force export before exit.
+    logger_provider.shutdown()?;
+
+    Ok(())
+}