document throws and extend metadata sync timeout

Author: sergiitk

xds/src/main/java/io/grpc/xds/ClientXdsClient.java

@@ -122,6 +122,7 @@
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
+import java.util.concurrent.CancellationException;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
@@ -163,8 +164,8 @@ final class ClientXdsClient extends XdsClient implements XdsResponseHandler, Res
  static boolean enableRouteLookup =
  !Strings.isNullOrEmpty(System.getenv("GRPC_EXPERIMENTAL_XDS_RLS_LB"))
  && Boolean.parseBoolean(System.getenv("GRPC_EXPERIMENTAL_XDS_RLS_LB"));
-
- private static final long METADATA_SYNC_TIMEOUT_SEC = 1;
+ // Normally this shouldn't take long, but add some slack for cases like a cold JVM.
+ private static final long METADATA_SYNC_TIMEOUT_SEC = 20;
  private static final String TYPE_URL_HTTP_CONNECTION_MANAGER_V2 =
  "type.googleapis.com/envoy.config.filter.network.http_connection_manager.v2"
  + ".HttpConnectionManager";
@@ -2062,7 +2063,7 @@ public void run() {
  return future.get(METADATA_SYNC_TIMEOUT_SEC, TimeUnit.SECONDS);
  } catch (ExecutionException e) {
  throw new UncheckedExecutionException(e.getCause());
- } catch (TimeoutException e) {
+ } catch (TimeoutException | CancellationException e) {
  throw new UncheckedExecutionException(e);
  } catch (InterruptedException e) {
  logger.log(XdsLogLevel.DEBUG, "Interrupted while preparing subscribed resources snapshot", e);

xds/src/main/java/io/grpc/xds/XdsClient.java

@@ -497,6 +497,12 @@ TlsContextManager getTlsContextManager() {
  /**
  * Returns a map from the "resource type" to a map ("resource name": "resource metadata")
  * containing the snapshot of the subscribed resources as they are at the moment of the call.
+ *
+ * @throws com.google.common.util.concurrent.UncheckedExecutionException
+ * if couldn't retrieve the snapshot of the subscribed resources in a synchronous manner
+ * because the task failed, cancelled, or timed out.
+ * TODO(sergiitk): when migrated to Java 8, throw CompletionException instead.
+ * @throws InterruptedException if the current thread was interrupted while waiting.
  */
  // Must be synchronized.
  Map<ResourceType, Map<String, ResourceMetadata>> getSubscribedResourcesMetadataSnapshot()