Fix BatchLogProcessor (open-telemetry#2510)

Author: utpilla

opentelemetry-sdk/src/logs/log_processor.rs

@@ -199,7 +199,7 @@ impl<T: LogExporter> LogProcessor for SimpleLogProcessor<T> {
 #[allow(clippy::large_enum_variant)]
 #[derive(Debug)]
 enum BatchMessage {
-    /// This ONLY sent when the number of logs records in the data channel has reached `max_export_batch_size`.
+    /// This is ONLY sent when the number of logs records in the data channel has reached `max_export_batch_size`.
     ExportLog(Arc<AtomicBool>),
     /// ForceFlush flushes the current buffer to the exporter.
     ForceFlush(mpsc::SyncSender<ExportResult>),
@@ -457,23 +457,31 @@ impl BatchLogProcessor {
                 where
                     E: LogExporter + Send + Sync + 'static,
                 {
-                    // Get upto `max_export_batch_size` amount of logs log records from the channel and push them to the logs vec
-                    while let Ok(log) = logs_receiver.try_recv() {
-                        logs.push(log);
-                        if logs.len() == config.max_export_batch_size {
-                            break;
+                    let target = current_batch_size.load(Ordering::Relaxed); // `target` is used to determine the stopping criteria for exporting logs.
+                    let mut result = LogResult::Ok(());
+                    let mut total_exported_logs: usize = 0;
+
+                    while target > 0 && total_exported_logs < target {
+                        // Get upto `max_export_batch_size` amount of logs log records from the channel and push them to the logs vec
+                        while let Ok(log) = logs_receiver.try_recv() {
+                            logs.push(log);
+                            if logs.len() == config.max_export_batch_size {
+                                break;
+                            }
                         }
-                    }
 
-                    let count_of_logs = logs.len(); // Count of logs that will be exported
-                    let result = export_with_timeout_sync(
-                        config.max_export_timeout,
-                        exporter,
-                        logs,
-                        last_export_time,
-                    ); // This method clears the logs vec after exporting
+                        let count_of_logs = logs.len(); // Count of logs that will be exported
+                        total_exported_logs += count_of_logs;
+
+                        result = export_with_timeout_sync(
+                            config.max_export_timeout,
+                            exporter,
+                            logs,
+                            last_export_time,
+                        ); // This method clears the logs vec after exporting
 
-                    current_batch_size.fetch_sub(count_of_logs, Ordering::Relaxed);
+                        current_batch_size.fetch_sub(count_of_logs, Ordering::Relaxed);
+                    }
                     result
                 }
 
@@ -485,6 +493,9 @@ impl BatchLogProcessor {
 
                     match message_receiver.recv_timeout(remaining_time) {
                         Ok(BatchMessage::ExportLog(export_log_message_sent)) => {
+                            // Reset the export log message sent flag now it has has been processed.
+                            export_log_message_sent.store(false, Ordering::Relaxed);
+
                             otel_debug!(
                                 name: "BatchLogProcessor.ExportingDueToBatchSize",
                             );
@@ -497,9 +508,6 @@ impl BatchLogProcessor {
                                 &current_batch_size,
                                 &config,
                             );
-
-                            // Reset the export log message sent flag now it has has been processed.
-                            export_log_message_sent.store(false, Ordering::Relaxed);
                         }
                         Ok(BatchMessage::ForceFlush(sender)) => {
                             otel_debug!(name: "BatchLogProcessor.ExportingDueToForceFlush");