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// 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.lib.actions;
import com.google.common.collect.ImmutableList;
/**
* An implementation of how to {@linkplain #exec execute} a {@link Spawn} instance.
*
* <p>Strategies are used during the execution phase based on how they were {@linkplain
* com.google.devtools.build.lib.runtime.BlazeModule#registerSpawnStrategies registered by a module}
* and whether they {@linkplain #canExec match a given spawn based on their abilities}.
*/
// TODO(blaze-team): If possible, merge this with AbstractSpawnStrategy and SpawnRunner. The former
// because (almost?) all implementations of this interface extend it; the latter because it forms
// a shadow hierarchy graph that looks like that of the corresponding strategies.
public interface SpawnStrategy {
/**
* Executes the given spawn and returns metadata about the execution. Implementations must
* guarantee that the first list entry represents the successful execution of the given spawn (if
* no execution was successful, the method must throw an exception instead). The list may contain
* further entries for (unsuccessful) retries as well as tree artifact management (which may
* require additional spawn executions).
*/
ImmutableList<SpawnResult> exec(Spawn spawn, ActionExecutionContext actionExecutionContext)
throws ExecException, InterruptedException;
/**
* Executes the given spawn, possibly asynchronously, and returns a SpawnContinuation to represent
* the execution. Otherwise all requirements from {@link #exec} apply.
*/
default SpawnContinuation beginExecution(
Spawn spawn, ActionExecutionContext actionExecutionContext) throws InterruptedException {
try {
return SpawnContinuation.immediate(exec(spawn, actionExecutionContext));
} catch (ExecException e) {
return SpawnContinuation.failedWithExecException(e);
}
}
/**
* Returns whether this SpawnActionContext supports executing the given Spawn. This does not allow
* using the legacy fallback to local execution controlled by the {@code
* --incompatible_legacy_local_fallback} flag.
*/
boolean canExec(Spawn spawn, ActionContext.ActionContextRegistry actionContextRegistry);
/**
* Returns true if this SpawnActionContext supports executing the given Spawn through a legacy
* fallback system. This will only be used if no SpawnActionContexts were able to execute it by
* normal means.
*/
default boolean canExecWithLegacyFallback(
Spawn spawn, ActionContext.ActionContextRegistry actionContextRegistry) {
return false;
}
/**
* Performs any actions conditional on this strategy not only being registered but triggered as
* used because its identifier was requested and it was not overridden.
*
* @param actionContextRegistry a registry containing all available contexts
*/
// TODO(katre): Remove once strategies are only instantiated if used, the callback can then be
// done upon construction.
default void usedContext(ActionContext.ActionContextRegistry actionContextRegistry) {}
}