// Copyright 2014 The Bazel Authors. 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; /** * Base class of exceptions thrown by {@link SkyFunction#compute} on failure. * * SkyFunctions should declare a subclass {@code C} of {@link SkyFunctionException} whose * constructors forward fine-grained exception types (e.g. {@code IOException}) to * {@link SkyFunctionException}'s constructor, and they should also declare * {@link SkyFunction#compute} to throw {@code C}. This way the type system checks that no * unexpected exceptions are thrown by the {@link SkyFunction}. * *
We took this approach over using a generic exception class since Java disallows it because of * type erasure * (see http://docs.oracle.com/javase/tutorial/java/generics/restrictions.html#cannotCatch). * *
Note that there are restrictions on what Exception types are allowed to be wrapped in this * manner. See {@link SkyFunctionException#validateExceptionType}. * *
Failures are explicitly either transient or persistent. The transience of the failure from
* {@link SkyFunction#compute} should be influenced only by the computations done, and not by the
* transience of the failures from computations requested via
* {@link SkyFunction.Environment#getValueOrThrow}.
*/
public abstract class SkyFunctionException extends Exception {
/** The transience of the error. */
public enum Transience {
// An error that may or may not occur again if the computation were re-run. If a computation
// results in a transient error and is needed on a subsequent MemoizingEvaluator#evaluate call,
// it will be re-executed.
TRANSIENT,
// An error that is completely deterministic and persistent in terms of the computation's
// inputs. Persistent errors may be cached.
PERSISTENT;
}
private final Transience transience;
@Nullable
private final SkyKey rootCause;
public SkyFunctionException(Exception cause, Transience transience) {
this(cause, transience, null);
}
/** Used to rethrow a child error that the parent cannot handle. */
public SkyFunctionException(Exception cause, SkyKey childKey) {
this(cause, Transience.PERSISTENT, childKey);
}
private SkyFunctionException(Exception cause, Transience transience, SkyKey rootCause) {
super(Preconditions.checkNotNull(cause));
SkyFunctionException.validateExceptionType(cause.getClass());
this.transience = transience;
this.rootCause = rootCause;
}
@Nullable
final SkyKey getRootCauseSkyKey() {
return rootCause;
}
final boolean isTransient() {
return transience == Transience.TRANSIENT;
}
/**
* Catastrophic failures halt the build even when in keepGoing mode.
*/
public boolean isCatastrophic() {
return false;
}
@Override
public synchronized Exception getCause() {
return (Exception) super.getCause();
}
static