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Implementation of the VM scheduler that use the Constraint Programming solver CHOCO to compute solutions.
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/*
 * Copyright  2022 The BtrPlace Authors. All rights reserved.
 * Use of this source code is governed by a LGPL-style
 * license that can be found in the LICENSE.txt file.
 */

package org.btrplace.scheduler.choco.transition;

import org.btrplace.model.Node;
import org.btrplace.model.VM;
import org.btrplace.model.VMState;
import org.btrplace.plan.ReconfigurationPlan;
import org.btrplace.scheduler.SchedulerException;
import org.btrplace.scheduler.SchedulerModelingException;
import org.btrplace.scheduler.choco.ReconfigurationProblem;
import org.btrplace.scheduler.choco.Slice;
import org.btrplace.scheduler.choco.SliceBuilder;
import org.chocosolver.solver.Cause;
import org.chocosolver.solver.Model;
import org.chocosolver.solver.Solution;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.variables.BoolVar;
import org.chocosolver.solver.variables.IntVar;

import java.util.EnumSet;


/**
 * Model a transition that allows a ready VP to be booted on a node.
 * An estimation of the action duration must be provided through a
 * {@link org.btrplace.scheduler.choco.duration.ActionDurationEvaluator} accessible from
 * {@link org.btrplace.scheduler.choco.ReconfigurationProblem#getDurationEvaluators()} with the key {@code BootVM.class}
 * 
 * If the reconfiguration problem has a solution, a {@link org.btrplace.plan.event.BootVM} action
 * is inserted into the resulting reconfiguration plan.
 *
 * @author Fabien Hermenier
 */
public class BootVM implements VMTransition {

    /**
     * The prefix to use for the variables
     */
    public static final String VAR_PREFIX = "bootVM";

  private final Slice dSlice;

  private final IntVar end;

  private final IntVar start;

  private final IntVar duration;

  private final VM vm;

  private final ReconfigurationProblem rp;

  private final BoolVar state;

    /**
     * Make a new model.
     *
     * @param p the RP to use as a basis.
     * @param e the VM managed by the action
     * @throws org.btrplace.scheduler.SchedulerException if an error occurred
     */
    public BootVM(ReconfigurationProblem p, VM e) throws SchedulerException {
        vm = e;

        Model csp = p.getModel();
        int d = p.getDurationEvaluators().evaluate(p.getSourceModel(), org.btrplace.plan.event.BootVM.class, e);
        this.rp = p;
        start = p.makeDuration(p.getEnd().getUB() - d, 0, VAR_PREFIX, "(", e, ").start");
        end = rp.getModel().intOffsetView(start, d);
        String label = "";
        if (rp.labelVariables()) {
            label = p.makeVarLabel(VAR_PREFIX, "(", e, ").duration");
        }
        duration = p.fixed(d, label);
        dSlice = new SliceBuilder(p, e, VAR_PREFIX, "(", e, ").dSlice").setStart(start)
                .setDuration(p.makeDuration(p.getEnd().getUB(), d, VAR_PREFIX, "(", e, ").dSlice_duration"))
                .build();

        try {
            p.getEnd().updateLowerBound(d, Cause.Null);
        } catch (final ContradictionException ex) {
            throw new SchedulerModelingException(rp.getSourceModel(), ex.getMessage());
        }
        state = csp.boolVar(true);
    }

    @Override
    public boolean isManaged() {
        return true;
    }

    @Override
    public boolean insertActions(Solution s, ReconfigurationPlan plan) {
        Node node = rp.getNode(s.getIntVal(dSlice.getHoster()));
        org.btrplace.plan.event.BootVM a = new org.btrplace.plan.event.BootVM(vm, node, s.getIntVal(start), s.getIntVal(end));
        plan.add(a);
        return true;
    }

    @Override
    public IntVar getStart() {
        return start;
    }

    @Override
    public IntVar getEnd() {
        return end;
    }

    @Override
    public IntVar getDuration() {
        return duration;
    }

    @Override
    public Slice getCSlice() {
        return null;
    }

    @Override
    public Slice getDSlice() {
        return dSlice;
    }

    @Override
    public BoolVar getState() {
        return state;
    }

    @Override
    public VM getVM() {
        return vm;
    }

    @Override
    public VMState getSourceState() {
        return VMState.READY;
    }

    @Override
    public VMState getFutureState() {
        return VMState.RUNNING;
    }

    /**
     * The builder devoted to a ready to running transition.
     */
    public static class Builder extends VMTransitionBuilder {

        /**
         * New builder
         */
        public Builder() {
            super("boot", EnumSet.of(VMState.READY), VMState.RUNNING);
        }

        @Override
        public VMTransition build(ReconfigurationProblem r, VM v) throws SchedulerException {
            return new BootVM(r, v);
        }
    }
}