com.netflix.fenzo.queues.QueuableTask Maven / Gradle / Ivy
/*
* Copyright 2016 Netflix, Inc.
*
* Licensed 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 com.netflix.fenzo.queues;
import com.netflix.fenzo.TaskRequest;
/**
* A queuable task extends {@link TaskRequest} with a method to get attributes for the queue.
*/
public interface QueuableTask extends TaskRequest {
/**
* Get the attributes for the queue that the task belongs to.
* @return The queue attributes for this task.
*/
QAttributes getQAttributes();
/**
* Get the time at which this task is ready for consideration for assignment. This can be compared to system's
* current time, for example, via {@link System#currentTimeMillis()}, to determine if the task is ready for being
* considered for assignment. If the returned time is less than current time, then it is not ready. A return time
* of 0 implies that the task is ready now. Tasks that are not ready in a scheduling iteration may
* be skipped to be considered in the next scheduling iteration.
* @return Time in milli seconds when this task is ready, or 0 to indicate it is ready.
*/
default long getReadyAt() {
return 0L;
}
/**
* Safely set the ready time of this task. Generally, task objects in Fenzo are immutable once added into Fenzo's
* queue. That is, the scheduling iteration will access methods from the task and expect to obtain valid results
* without being impacted by concurrent modifications. This method provides a safe mechanism to set the ready at
* time via one or both of the following:
*
* - Fenzo calls this method when it is safe to do so, for all tasks for which setting a new ready time has
* been requested via
* {@link com.netflix.fenzo.TaskSchedulingService#setTaskReadyTime(String, QAttributes, long)}
,
* - The implementation of this interface supports safe concurrent access to {@link this#getReadyAt()}
.
*
* Fenzo guarantees the first of the above two options, thereby keeping the system safe in the absence of the second
* option. That is, the implementations don't need to keep this method concurrent safe with the corresponding access
* method if they always set the ready time using
* {@link com.netflix.fenzo.TaskSchedulingService#setTaskReadyTime(String, QAttributes, long)}
* @param when The time at which this task is ready for consideration for resource assignment.
*/
default void safeSetReadyAt(long when) {
// no-op
}
}