fix: make shutdown &self in span processor

opentelemetry-sdk/CHANGELOG.md

@@ -26,6 +26,8 @@
  asynchronously, it should clone the log data to ensure it can be safely processed without
  lifetime issues.
 
+- **Breaking** [1836](https://github.com/open-telemetry/opentelemetry-rust/pull/1836) `SpanProcessor::shutdown` now takes an immutable reference to self. Any reference can call shutdown on the processor. After the first call to `shutdown` the processor will not process any new spans. 
+
 ## v0.23.0
 
 - Fix SimpleSpanProcessor to be consistent with log counterpart. Also removed

opentelemetry-sdk/src/trace/provider.rs

@@ -264,7 +264,7 @@ mod tests {
             }
         }
 
-        fn shutdown(&mut self) -> TraceResult<()> {
+        fn shutdown(&self) -> TraceResult<()> {
             self.force_flush()
         }
     }

opentelemetry-sdk/src/trace/span_processor.rs

@@ -91,7 +91,7 @@ pub trait SpanProcessor: Send + Sync + std::fmt::Debug {
     fn force_flush(&self) -> TraceResult<()>;
     /// Shuts down the processor. Called when SDK is shut down. This is an
     /// opportunity for processors to do any cleanup required.
-    fn shutdown(&mut self) -> TraceResult<()>;
+    fn shutdown(&self) -> TraceResult<()>;
 }
 
 /// A [SpanProcessor] that passes finished spans to the configured
@@ -137,7 +137,7 @@ impl SpanProcessor for SimpleSpanProcessor {
         Ok(())
     }
 
-    fn shutdown(&mut self) -> TraceResult<()> {
+    fn shutdown(&self) -> TraceResult<()> {
         if let Ok(mut exporter) = self.exporter.lock() {
             exporter.shutdown();
             Ok(())
@@ -249,7 +249,7 @@ impl<R: RuntimeChannel> SpanProcessor for BatchSpanProcessor<R> {
             .and_then(|identity| identity)
     }
 
-    fn shutdown(&mut self) -> TraceResult<()> {
+    fn shutdown(&self) -> TraceResult<()> {
         let (res_sender, res_receiver) = oneshot::channel();
         self.message_sender
             .try_send(BatchMessage::Shutdown(res_sender))
@@ -687,7 +687,7 @@ mod tests {
     #[test]
     fn simple_span_processor_on_end_calls_export() {
         let exporter = InMemorySpanExporterBuilder::new().build();
-        let mut processor = SimpleSpanProcessor::new(Box::new(exporter.clone()));
+        let processor = SimpleSpanProcessor::new(Box::new(exporter.clone()));
         let span_data = new_test_export_span_data();
         processor.on_end(span_data.clone());
         assert_eq!(exporter.get_finished_spans().unwrap()[0], span_data);
@@ -720,7 +720,7 @@ mod tests {
     #[test]
     fn simple_span_processor_shutdown_calls_shutdown() {
         let exporter = InMemorySpanExporterBuilder::new().build();
-        let mut processor = SimpleSpanProcessor::new(Box::new(exporter.clone()));
+        let processor = SimpleSpanProcessor::new(Box::new(exporter.clone()));
         let span_data = new_test_export_span_data();
         processor.on_end(span_data.clone());
         assert!(!exporter.get_finished_spans().unwrap().is_empty());
@@ -876,7 +876,7 @@ mod tests {
             scheduled_delay: Duration::from_secs(60 * 60 * 24), // set the tick to 24 hours so we know the span must be exported via force_flush
             ..Default::default()
         };
-        let mut processor =
+        let processor =
             BatchSpanProcessor::new(Box::new(exporter), config, runtime::TokioCurrentThread);
         let handle = tokio::spawn(async move {
             loop {
@@ -976,7 +976,7 @@ mod tests {
             delay_for: Duration::from_millis(if !time_out { 5 } else { 60 }),
             delay_fn: async_std::task::sleep,
         };
-        let mut processor = BatchSpanProcessor::new(Box::new(exporter), config, runtime::AsyncStd);
+        let processor = BatchSpanProcessor::new(Box::new(exporter), config, runtime::AsyncStd);
         processor.on_end(new_test_export_span_data());
         let flush_res = processor.force_flush();
         if time_out {
@@ -1000,7 +1000,7 @@ mod tests {
             delay_for: Duration::from_millis(if !time_out { 5 } else { 60 }),
             delay_fn: tokio::time::sleep,
         };
-        let mut processor =
+        let processor =
             BatchSpanProcessor::new(Box::new(exporter), config, runtime::TokioCurrentThread);
         tokio::time::sleep(Duration::from_secs(1)).await; // skip the first
         processor.on_end(new_test_export_span_data());

stress/src/traces.rs

@@ -42,7 +42,7 @@ impl SpanProcessor for NoOpSpanProcessor {
         Ok(())
     }
 
-    fn shutdown(&mut self) -> TraceResult<()> {
+    fn shutdown(&self) -> TraceResult<()> {
         Ok(())
     }
 }