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From: sjcorbett <git@git.apache.org>
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Subject: [GitHub] brooklyn-server pull request #386: Add AbstractInvokeEffectorPolicy
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Message-Id: <20161031105157.4670DE0BB1@git1-us-west.apache.org>
Date: Mon, 31 Oct 2016 10:51:57 +0000 (UTC)
archived-at: Mon, 31 Oct 2016 10:51:59 -0000

Github user sjcorbett commented on a diff in the pull request:

    https://github.com/apache/brooklyn-server/pull/386#discussion_r85716905
  
    --- Diff: core/src/main/java/org/apache/brooklyn/policy/AbstractInvokeEffectorPolicy.java ---
    @@ -0,0 +1,145 @@
    +/*
    + * 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.policy;
    +
    +import java.util.Map;
    +import java.util.concurrent.atomic.AtomicInteger;
    +import javax.annotation.Nonnull;
    +
    +import org.apache.brooklyn.api.effector.Effector;
    +import org.apache.brooklyn.api.entity.EntityLocal;
    +import org.apache.brooklyn.api.mgmt.Task;
    +import org.apache.brooklyn.api.sensor.AttributeSensor;
    +import org.apache.brooklyn.config.ConfigKey;
    +import org.apache.brooklyn.core.config.ConfigKeys;
    +import org.apache.brooklyn.core.policy.AbstractPolicy;
    +import org.apache.brooklyn.core.sensor.Sensors;
    +import org.apache.brooklyn.util.guava.Maybe;
    +import org.apache.brooklyn.util.text.Strings;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import com.google.common.base.Objects;
    +import com.google.common.util.concurrent.MoreExecutors;
    +
    +public abstract class AbstractInvokeEffectorPolicy extends AbstractPolicy {
    +
    +    private static final Logger LOG = LoggerFactory.getLogger(AbstractInvokeEffectorPolicy.class);
    +
    +    public static final ConfigKey<String> IS_BUSY_SENSOR_NAME = ConfigKeys.newStringConfigKey(
    +            "isBusySensor",
    +            "Name of the sensor to publish on the entity that indicates that this policy has incomplete effectors. " +
    +                    "If unset running tasks will not be tracked.");
    +
    +    private final AtomicInteger taskCounter = new AtomicInteger();
    +
    +    /**
    +     * Indicates that onEvent was notified of an value of is not the latest sensor value.
    +     */
    +    private boolean moreUpdatesComing;
    +    /**
    +     * The timestamp of the event that informed moreUpdatesComing. Subsequent notifications
    +     * of earlier events will not cause updates of moreUpdatesComing.
    +     */
    +    private long mostRecentUpdate = 0;
    +    /**
    +     * Guards {@link #moreUpdatesComing} and {@link #mostRecentUpdate}.
    +     */
    +    private final Object[] moreUpdatesLock = new Object[0];
    +
    +    @Override
    +    public void setEntity(EntityLocal entity) {
    +        super.setEntity(entity);
    +        if (isBusySensorEnabled()) {
    +            // Republishes when the entity rebinds.
    +            publishIsBusy();
    +        }
    +    }
    +
    +    /**
    +     * Invoke effector with parameters on the entity that the policy is attached to.
    +     */
    +    protected <T> Task<T> invoke(Effector<T> effector, Map<String, ?> parameters) {
    +        if (isBusySensorEnabled()) {
    +            getTaskCounter().incrementAndGet();
    +            publishIsBusy();
    +        }
    +        Task<T> task = entity.invoke(effector, parameters);
    +        if (isBusySensorEnabled()) {
    +            task.addListener(new EffectorListener(), MoreExecutors.sameThreadExecutor());
    +        }
    +        return task;
    +    }
    +
    +    protected boolean isBusy() {
    +        synchronized (moreUpdatesLock) {
    --- End diff --
    
    I included the synchronisation to make sure that `moreUpdatesComing` is visible to whatever thread invokes the effector's completion listener (which calls `publishIsBusy` which calls `isBusy`). At a minimum the field should be volatile then. Is it a big one for you? 


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