Add force_flush to LogExporter

opentelemetry-sdk/src/export/logs/mod.rs

@@ -91,6 +91,25 @@ pub trait LogExporter: Send + Sync + Debug {
         // By default, all logs are enabled
         true
     }
+
+    /// This is a hint to ensure that the export of any Logs the exporter
+    /// has received prior to the call to this function SHOULD be completed
+    /// as soon as possible, preferably before returning from this method.
+    ///
+    /// This function SHOULD provide a way to let the caller know
+    /// whether it succeeded, failed or timed out.
+    ///
+    /// This function SHOULD only be called in cases where it is absolutely necessary,
+    /// such as when using some FaaS providers that may suspend the process after
+    /// an invocation, but before the exporter exports the completed logs.
+    ///
+    /// This function SHOULD complete or abort within some timeout. This function can be
+    /// implemented as a blocking API or an asynchronous API which notifies the caller via
+    /// a callback or an event. OpenTelemetry client authors can decide if they want to
+    /// make the flush timeout configurable.
+    fn force_flush(&mut self) -> ExportResult {
+        Ok(())
+    }
     /// Set the resource for the exporter.
     fn set_resource(&mut self, _resource: &Resource) {}
 }

opentelemetry-sdk/src/logs/log_processor.rs

@@ -129,7 +129,11 @@
     }
 
     fn force_flush(&self) -> LogResult<()> {
-        Ok(())
+        if let Ok(mut exporter) = self.exporter.lock() {
+            exporter.force_flush()
+        } else {
+            Err(LogError::MutexPoisoned("SimpleLogProcessor".into()))
+        }
     }
 
     fn shutdown(&self) -> LogResult<()> {
@@ -278,7 +282,8 @@
                             &timeout_runtime,
                             logs.split_off(0),
                         )
-                        .await;
+                        .await
+                        .and(exporter.as_mut().force_flush());
 
                         if let Some(channel) = res_channel {
                             if let Err(send_error) = channel.send(result) {
@@ -803,6 +808,25 @@
         let _ = provider.shutdown();
     }
 
+    #[tokio::test(flavor = "multi_thread")]
+    async fn test_batch_forceflush() {
+        let exporter = InMemoryLogExporterBuilder::default().build();
+        // TODO: Verify exporter.force_flush() is called
+
+        let processor = BatchLogProcessor::new(
+            Box::new(exporter.clone()),
+            BatchConfig::default(),
+            runtime::Tokio,
+        );
+
+        let mut record = LogRecord::default();
+        let instrumentation = InstrumentationScope::default();
+
+        processor.emit(&mut record, &instrumentation);
+        processor.force_flush().unwrap();
+        assert_eq!(1, exporter.get_emitted_logs().unwrap().len());
+    }
+
     #[tokio::test(flavor = "multi_thread")]
     async fn test_batch_shutdown() {
         // assert we will receive an error
@@ -820,7 +844,6 @@
         let instrumentation = InstrumentationScope::default();
 
         processor.emit(&mut record, &instrumentation);
-        processor.force_flush().unwrap();
         processor.shutdown().unwrap();
         // todo: expect to see errors here. How should we assert this?
         processor.emit(&mut record, &instrumentation);