Add force_flush to LogExporter

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

@@ -2,6 +2,7 @@
 use crate::logs::LogRecord;
 use crate::Resource;
 use async_trait::async_trait;
+use futures_util::future::BoxFuture;
 #[cfg(feature = "logs_level_enabled")]
 use opentelemetry::logs::Severity;
 use opentelemetry::logs::{LogError, LogResult};
@@ -91,6 +92,25 @@ pub trait LogExporter: Send + Sync + Debug {
         // By default, all logs are enabled
         true
     }
+
+    /// This is a hint to ensure that the export of any Spans 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 spans.
+    ///
+    /// 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) -> BoxFuture<'static, ExportResult> {
+        Box::pin(async { Ok(()) })
+    }
     /// Set the resource for the exporter.
     fn set_resource(&mut self, _resource: &Resource) {}
 }

opentelemetry-sdk/src/logs/log_processor.rs

@@ -261,7 +261,8 @@
                             &timeout_runtime,
                             logs.split_off(0),
                         )
-                        .await;
+                        .await
+                        .and(exporter.as_mut().force_flush().await);
 
                         if let Some(channel) = res_channel {
                             if let Err(send_error) = channel.send(result) {