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Date: Wed, 26 Oct 2016 19:44:58 +0000 (UTC)
From: "ASF GitHub Bot (JIRA)" <jira@apache.org>
To: dev@brooklyn.apache.org
Message-ID: <JIRA.13009042.1475312740000.92876.1477511098570@Atlassian.JIRA>
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Subject: [jira] [Commented] (BROOKLYN-356) The sensor Transformer enricher
 fails to resolve its targetValue indeterministically.
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archived-at: Wed, 26 Oct 2016 19:45:00 -0000


    [ 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.


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