Add more javadocs

ts-segment-uploader/src/main/java/com/pinterest/kafka/tieredstorage/uploader/dlq/LocalFileDeadLetterQueueHandler.java

@@ -19,6 +19,9 @@
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Future;
 
+/**
+ * A {@link DeadLetterQueueHandler} that writes failed uploads to a local file with human-readable formatting.
+ */
 public class LocalFileDeadLetterQueueHandler extends DeadLetterQueueHandler {
 
     private static final Logger LOG = LogManager.getLogger(LocalFileDeadLetterQueueHandler.class);

ts-segment-uploader/src/main/java/com/pinterest/kafka/tieredstorage/uploader/dlq/S3LocalExecutableDeadLetterQueueHandler.java

@@ -19,6 +19,10 @@
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Future;
 
+/**
+ * A {@link DeadLetterQueueHandler} that writes failed uploads to a local executable file in a format
+ * that can be run as-is to retry the uploads.
+ */
 public class S3LocalExecutableDeadLetterQueueHandler extends DeadLetterQueueHandler {
 
     private static final Logger LOG = LogManager.getLogger(S3LocalExecutableDeadLetterQueueHandler.class);

ts-segment-uploader/src/test/java/com/pinterest/kafka/tieredstorage/uploader/TestDirectoryTreeWatcher.java

@@ -184,6 +184,9 @@ void testExponentialBackoffRetries() throws InterruptedException {
         }
     }
 
+    /**
+     * Test that retry exhaustion calls the DLQ handler
+     */
     @Test
     void testRetryExhaustion() throws Exception {
         // override s3AsyncClient to have a very short timeout

ts-segment-uploader/src/test/java/com/pinterest/kafka/tieredstorage/uploader/TestMultiThreadedS3FileUploader.java

@@ -148,6 +148,9 @@ public void onCompletion(DirectoryTreeWatcher.UploadTask uploadTask, long totalT
         });
     }
 
+    /**
+     * Ensure that an upload that times out returns the correct error code and exception
+     */
     @Test
     void testTimeoutUpload() throws IOException {
         // override s3AsyncClient to have a very short timeout

ts-segment-uploader/src/test/java/com/pinterest/kafka/tieredstorage/uploader/dlq/TestS3LocalExecutableDeadLetterQueueHandler.java

@@ -25,6 +25,9 @@
 
 public class TestS3LocalExecutableDeadLetterQueueHandler extends TestBase {
 
+    /**
+     * Test the handler by having it send many tasks concurrently to a local executable file.
+     */
     @Test
     void testConcurrentSend() throws IOException, ExecutionException, InterruptedException {
         String filePath = "/tmp/s3-local-executable-dlq-handler-test.sh";