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// Copyright 2014 Google Inc. All rights reserved.
//
// 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.google.devtools.build.skyframe;
import com.google.common.base.Preconditions;
import javax.annotation.Nullable;
/**
* A work queue -- takes {@link Runnable}s and runs them when requested.
*/
interface Scheduler {
/**
* Schedules a new action to be eventually done.
*/
void schedule(Runnable action);
/**
* Runs the actions that have been scheduled. These actions can in turn schedule new actions,
* which will be run as well.
*
* @throw SchedulerException wrapping a scheduled action's exception.
*/
void run() throws SchedulerException;
/**
* Wrapper exception that {@link Runnable}s can throw, to be caught and handled
* by callers of {@link #run}.
*/
static class SchedulerException extends RuntimeException {
private final SkyKey failedValue;
private final ErrorInfo errorInfo;
private SchedulerException(@Nullable Throwable cause, @Nullable ErrorInfo errorInfo,
SkyKey failedValue) {
super(errorInfo != null ? errorInfo.getException() : cause);
this.errorInfo = errorInfo;
this.failedValue = Preconditions.checkNotNull(failedValue, errorInfo);
}
/**
* Returns a SchedulerException wrapping an expected error, e.g. an error describing an expected
* build failure when trying to evaluate the given value, that should cause Skyframe to produce
* useful error information to the user.
*/
static SchedulerException ofError(ErrorInfo errorInfo, SkyKey failedValue) {
Preconditions.checkNotNull(errorInfo);
return new SchedulerException(errorInfo.getException(), errorInfo, failedValue);
}
/**
* Returns a SchedulerException wrapping an InterruptedException, e.g. if the user interrupts
* the build, that should cause Skyframe to exit as soon as possible.
*/
static SchedulerException ofInterruption(InterruptedException cause, SkyKey failedValue) {
return new SchedulerException(cause, null, failedValue);
}
SkyKey getFailedValue() {
return failedValue;
}
@Nullable ErrorInfo getErrorInfo() {
return errorInfo;
}
}
}