[AN-333] Prevent infinite DRS download retries

cromwell-drs-localizer/src/main/scala/drs/localizer/downloaders/GcsUriDownloader.scala

@@ -57,33 +57,30 @@
                           downloadAttempt: Int = 0
   ): IO[DownloadResult] = {
 
-    def maybeRetryForDownloadFailure(t: Throwable): IO[DownloadResult] =
-      if (downloadAttempt < downloadRetries) {
-        backoff foreach { b => Thread.sleep(b.backoffMillis) }
-        logger.warn(s"Attempting download retry $downloadAttempt of $downloadRetries for a GCS url", t)
-        downloadWithRetries(downloadRetries,
-                            backoff map {
-                              _.next
-                            },
-                            downloadAttempt + 1
-        )
-      } else {
-        IO.raiseError(new RuntimeException(s"Exhausted $downloadRetries resolution retries to download GCS file", t))
-      }
-
-    runDownloadCommand.redeemWith(
-      recover = maybeRetryForDownloadFailure,
-      bind = {
-        case s: DownloadSuccess.type =>
-          IO.pure(s)
-        case _: RecognizedRetryableDownloadFailure =>
-          downloadWithRetries(downloadRetries, backoff, downloadAttempt + 1)
-        case _: UnrecognizedRetryableDownloadFailure =>
-          downloadWithRetries(downloadRetries, backoff, downloadAttempt + 1)
-        case _ =>
-          downloadWithRetries(downloadRetries, backoff, downloadAttempt + 1)
-      }
-    )
+    // Necessary function to handle the throwable when trying to recover a failed download
+    def handleDownloadFailure(t: Throwable): IO[DownloadResult] =
+      downloadWithRetries(downloadRetries, backoff, downloadAttempt + 1)
+
+    logger.info(s"Attempting download attempt $downloadAttempt of $downloadRetries for a GCS url")
+
+    if (downloadAttempt < downloadRetries) {
+      backoff foreach { b => Thread.sleep(b.backoffMillis) }
+      runDownloadCommand.redeemWith(
+        recover = handleDownloadFailure,
+        bind = {
+          case s: DownloadSuccess.type =>
+            IO.pure(s)
+          case _: RecognizedRetryableDownloadFailure =>
+            downloadWithRetries(downloadRetries, backoff, downloadAttempt + 1)
+          case _: UnrecognizedRetryableDownloadFailure =>
+            downloadWithRetries(downloadRetries, backoff, downloadAttempt + 1)
+          case _ =>
+            downloadWithRetries(downloadRetries, backoff, downloadAttempt + 1)
+        }
+      )
+    } else {
+      IO.raiseError(new RuntimeException(s"Exhausted $downloadRetries resolution retries to download GCS file"))
+    }
   }
 
   /**

cromwell-drs-localizer/src/test/scala/drs/localizer/downloaders/GcsUriDownloaderSpec.scala

@@ -1,6 +1,7 @@
 package drs.localizer.downloaders
 
 import common.assertion.CromwellTimeoutSpec
+import org.mockito.Mockito.{spy, times, verify}
 import org.scalatest.flatspec.AnyFlatSpec
 import org.scalatest.matchers.should.Matchers
 
@@ -96,4 +97,27 @@ class GcsUriDownloaderSpec extends AnyFlatSpec with CromwellTimeoutSpec with Mat
 
     downloader.generateDownloadScript(gcsUrl, Option(fakeSAJsonPath)) shouldBe expectedDownloadScript
   }
+
+  it should "fail to download GCS URL after 5 attempts" in {
+    val gcsUrl = "gs://foo/bar.bam"
+    val downloader = spy(
+      new GcsUriDownloader(
+        gcsUrl = gcsUrl,
+        downloadLoc = fakeDownloadLocation,
+        requesterPaysProjectIdOption = Option(fakeRequesterPaysId),
+        serviceAccountJson = None
+      )
+    )
+
+    val result = downloader.downloadWithRetries(5, None).attempt.unsafeRunSync()
+
+    result.isLeft shouldBe true
+    // attempts to download the 1st time and the 5th time, but doesn't attempt a 6th
+    verify(downloader, times(1)).downloadWithRetries(5, None, 1)
+    verify(downloader, times(1)).downloadWithRetries(5, None, 5)
+    verify(downloader, times(0)).downloadWithRetries(5, None, 6)
+    // attempts the actual download command 5 times
+    verify(downloader, times(5)).runDownloadCommand
+
+  }
 }