Use remaining timeout as rpc timeout when downloading

Make sure to use remaining timeout as rpc timeout when downloading,
otherwise client initiating download will timeout before getting
any response. Environment variable will override this if set.

filedistribution/src/main/java/com/yahoo/vespa/filedistribution/FileReferenceDownloader.java

@@ -46,7 +46,7 @@ public class FileReferenceDownloader {
     private final Downloads downloads;
     private final Duration downloadTimeout;
     private final Duration backoffInitialTime;
-    private final Duration rpcTimeout;
+    private final Optional<Duration> rpcTimeout; // Only used when overridden with env variable
     private final File downloadDirectory;
     private final AtomicBoolean shutDown = new AtomicBoolean(false);
 
@@ -61,8 +61,8 @@ public class FileReferenceDownloader {
         this.backoffInitialTime = backoffInitialTime;
         this.downloadDirectory = downloadDirectory;
         // Undocumented on purpose, might change or be removed at any time
-        String timeoutString = System.getenv("VESPA_FILE_DOWNLOAD_RPC_TIMEOUT");
-        this.rpcTimeout = Duration.ofSeconds(timeoutString == null ? 30 : Integer.parseInt(timeoutString));
+        var timeoutString = Optional.ofNullable(System.getenv("VESPA_FILE_DOWNLOAD_RPC_TIMEOUT"));
+        this.rpcTimeout = timeoutString.map(t -> Duration.ofSeconds(Integer.parseInt(t)));
     }
 
     private void waitUntilDownloadStarted(FileReferenceDownload fileReferenceDownload) {
@@ -78,7 +78,10 @@ private void waitUntilDownloadStarted(FileReferenceDownload fileReferenceDownloa
                 return;
             if (FileDownloader.fileReferenceExists(fileReference, downloadDirectory))
                 return;
-            if (startDownloadRpc(fileReferenceDownload, retryCount, connection))
+            var timeout = rpcTimeout.orElse(Duration.between(Instant.now(), end));
+            log.log(Level.FINE, "Wait until download of " + fileReference + " has started, retryCount " + retryCount +
+                    " timeout" + timeout + " (request from client " + fileReferenceDownload.client() + ")");
+            if ( ! timeout.isNegative() && startDownloadRpc(fileReferenceDownload, retryCount, connection, timeout))
                 return;
 
             retryCount++;
@@ -113,7 +116,6 @@ CompletableFuture<Optional<File>> startDownload(FileReferenceDownload fileRefere
         Optional<FileReferenceDownload> inProgress = downloads.get(fileReference);
         if (inProgress.isPresent()) return inProgress.get().future();
 
-        log.log(Level.FINE, () -> "Will download " + fileReference + " with timeout " + downloadTimeout);
         downloads.add(fileReferenceDownload);
         downloadExecutor.submit(() -> waitUntilDownloadStarted(fileReferenceDownload));
         return fileReferenceDownload.future();
@@ -129,7 +131,7 @@ void startDownloadFromSource(FileReferenceDownload fileReferenceDownload, Spec s
                 downloadExecutor.submit(() -> {
                     log.log(Level.FINE, () -> "Will download " + fileReference + " with timeout " + downloadTimeout + " from " + spec);
                     downloads.add(fileReferenceDownload);
-                    startDownloadRpc(fileReferenceDownload, 1, connection);
+                    startDownloadRpc(fileReferenceDownload, 1, connection, downloadTimeout);
                     downloads.remove(fileReference);
                 });
         }
@@ -139,10 +141,9 @@ void failedDownloading(FileReference fileReference) {
         downloads.remove(fileReference);
     }
 
-    private boolean startDownloadRpc(FileReferenceDownload fileReferenceDownload, int retryCount, Connection connection) {
+    private boolean startDownloadRpc(FileReferenceDownload fileReferenceDownload, int retryCount, Connection connection, Duration timeout) {
         Request request = createRequest(fileReferenceDownload);
-        Duration rpcTimeout = rpcTimeout(retryCount);
-        connection.invokeSync(request, rpcTimeout);
+        connection.invokeSync(request, timeout);
 
         Level logLevel = (retryCount > 3 ? Level.INFO : Level.FINE);
         FileReference fileReference = fileReferenceDownload.fileReference();
@@ -162,7 +163,7 @@ private boolean startDownloadRpc(FileReferenceDownload fileReferenceDownload, in
         } else {
             log.log(logLevel, "Downloading " + fileReference + " from " + address + " failed:" +
                     " error code " + request.errorCode() + " (" + request.errorMessage() + ")." +
-                    " (retry " + retryCount + ", rpc timeout " + rpcTimeout + ")");
+                    " (retry " + retryCount + ", rpc timeout " + timeout + ")");
             return false;
         }
     }
@@ -177,10 +178,6 @@ private Request createRequest(FileReferenceDownload fileReferenceDownload) {
         return request;
     }
 
-    private Duration rpcTimeout(int retryCount) {
-        return Duration.ofSeconds(rpcTimeout.getSeconds()).plus(Duration.ofSeconds(retryCount * 5L));
-    }
-
     private boolean validateResponse(Request request) {
         if (request.isError()) {
             return false;