[
https://issues.apache.org/jira/browse/BROOKLYN-356?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15609469#comment-15609469
]
ASF GitHub Bot commented on BROOKLYN-356:
-----------------------------------------
Github user geomacy commented on a diff in the pull request:
https://github.com/apache/brooklyn-server/pull/390#discussion_r85106043
--- Diff:
core/src/main/java/org/apache/brooklyn/util/core/task/ImmediateSupplier.java ---
@@ -0,0 +1,50 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.brooklyn.util.core.task;
+
+import org.apache.brooklyn.util.guava.Maybe;
+
+/**
+ * A class that supplies objects of a single type, without blocking for
any significant length
+ * of time.
+ */
+public interface ImmediateSupplier<T> {
+
+ /**
+ * Indicates that we are unable to get the value immediately, because
that is not supported
+ * (e.g. because the supplier is composed of sub-tasks that do not
support {@link ImmediateSupplier}.
+ */
+ public static class ImmediateUnsupportedException extends
RuntimeException {
--- End diff --
Might be nice to extend `UnsupportedOperationException` rather than
RuntimeException directly
> The sensor Transformer enricher fails to resolve its targetValue
> indeterministically.
> -------------------------------------------------------------------------------------
>
> Key: BROOKLYN-356
> URL: https://issues.apache.org/jira/browse/BROOKLYN-356
> Project: Brooklyn
> Issue Type: Bug
> Reporter: Svetoslav Neykov
>
> The sensor {{Transformer}} enricher fails to resolve its {{targetValue}}
> indeterministically, especially so on loaded systems. This is especially
> problematic if sourceSensor/triggerSensors change infrequently or do not
> change ever (when using default values).
> Bueprints using the {{Transformer}} behave perfectly fine during development
> and on test setups, but will fail on production machines (i.e. under load).
> The code [doing the value
> resolving|https://github.com/apache/brooklyn-server/blob/b59e7463a9b337c2d0e7931cd420d5bac68d8549/core/src/main/java/org/apache/brooklyn/enricher/stock/Transformer.java#L90-L94]
> tries to do so in a non-blocking fashion by spinning a thread to try to
> resolve and cancelling it after a short while without guarantees it ever got
> scheduled to run. It's more likely to fail when nesting DSLs, for example
> nesting several levels of {{$brooklyn:formatString}} and ending with a
> {{$brooklyn:attributeWhenRready}}. It's a common pattern in moderately
> complex blueprints. It needs to schedule a thread for each nesting level thus
> maximizing the chance that the value will not be resolved in the allotted
> time even if resolvabe. This is especially bad for sensors which don't get
> updated, for example {{PortAttributeSensorAndConfigKey} set only when
> initializing the entity or any config values which are always resolvable.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
